ﺑﺎﺯﮔﺸﺖ ﺑﻪ ﺻﻔﺤﻪ ﻗﺒﻠﯽ
خرید پکیج
تعداد ایتم قابل مشاهده باقیمانده : 4 مورد

Prevention of venous thromboembolic disease in adult nonorthopedic surgical patients

Prevention of venous thromboembolic disease in adult nonorthopedic surgical patients
Authors:
Menaka Pai, MD, FRCPC
James D Douketis, MD, FRCPC, FACP, FCCP
Section Editors:
Lawrence LK Leung, MD
Jess Mandel, MD
Deputy Editors:
Geraldine Finlay, MD
Kathryn A Collins, MD, PhD, FACS
Literature review current through: Aug 2021. | This topic last updated: Apr 09, 2021.

INTRODUCTION — Venous thromboembolism (VTE; deep venous thrombosis and pulmonary embolism [PE]) is common in the postoperative setting with over half of this population at moderate risk for VTE [1-3]. PE is one of the most common preventable causes of in-hospital deaths following surgery [4-8].

Nonorthopedic surgeries include surgery of the skin and soft tissues of the trunk or extremities; surgery involving the chest, abdomen, or pelvic organs; and surgery of the head (including brain) and neck. Our approach to the prevention of VTE in nonorthopedic surgical patients will be reviewed here. Our approach is, for the most part, in keeping with the American College of Chest Physicians (ACCP) and the American Society of hematology (ASH) [9,10]. Prevention of VTE in patients undergoing orthopedic procedures (eg, joint repair/replacement) and in hospitalized medical patients are presented separately. (See "Prevention of venous thromboembolism in adult orthopedic surgical patients" and "Prevention of venous thromboembolic disease in acutely ill hospitalized medical adults".)  

ASSESS RISK FOR THROMBOSIS — The risk of postoperative VTE should be assessed prior to surgery and the patient stratified into very low, low, moderate, or high risk groups so that an appropriate method of VTE prevention can be selected [11]. (See 'Baseline thrombosis risk' below and 'Thrombosis risk model (Caprini)' below.)

VTE risk largely depends upon the procedure but patient-related factors also play a role:

Procedure-related – Many procedure-related factors contribute to the risk of VTE in nonorthopedic patients including the extent and duration of surgery, intraoperative positioning, the type of anesthesia, and postoperative mobility. In general, the highest risk is in those undergoing major surgery (defined as surgery lasting longer than 45 minutes [12]), abdominal and thoracic cavity surgery (eg, major abdominal/pelvic or surgery for malignancy), prolonged surgery (≥2 hours), emergency rather than elective surgery, postoperative immobilization for ≥4 days, as well as critically ill patients who are confined to bed (eg, extensive burns, multiple trauma, brain/spine injury) [12-15]. The risk is generally low for patients undergoing minor, typically ambulatory procedures (eg, elective hernia repair, thyroid surgery, minor skin excision, carotid endarterectomy).

Patient-related – Patient-related VTE risk factors are discussed separately. (See "Overview of the causes of venous thrombosis".)  

Baseline thrombosis risk — The baseline risk of VTE associated with individual surgeries is highly variable reflecting the wide range of surgeries within each specialty [11,16]. Importantly, estimates of baseline risk are imperfect since they use data from studies in populations not on VTE prophylaxis and populations on prophylaxis, or use extrapolated data from related populations.

General, abdominal/pelvic, bariatric, vascular, plastic surgery — The risk categories (very low, low, moderate, high) correspond to the Caprini model (table 1) discussed below, although in practice many experts use clinical gestalt to estimate the risk. (See 'Thrombosis risk model (Caprini)' below.)  

General/abdominal pelvic (low to high Caprini score) – Rates of symptomatic VTE derived from untreated groups in randomized trials [17-29] have ranged from 0.5 to 1.6 percent, higher among those undergoing surgery for malignancy (up to 3.7 percent) [6,17]. However, several studies report that VTE risk is wide in this population since it encompasses a broad range of surgeries from laparoscopic appendectomy to open pelvic surgery for cancer.

Bariatric surgery (low to high Caprini score) – Observational data suggest that while in the past rates were between 1.9 and 5.4 percent [30,31], advances in less extensive bariatric surgery may be associated with lower rates (0.5 percent) according to data from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) [32].  

Noncardiac vascular surgery (low to high Caprini score) – Baseline risk in the absence of prophylaxis is extrapolated from the population of patients undergoing abdominal/pelvic operations since vascular procedures were commonly included in those studies. Small observational studies comparing pharmacologic prophylaxis with no prophylaxis in only vascular surgery patients report variable rates for open abdominal vascular surgery (up to 10 percent) [33-40], peripheral artery surgery (1.8 to 9 percent) [41-45], venous ablation procedures (<1 percent) [46-56], and lower extremity amputation (2 to 15 percent, higher for above knee compared with below-knee [36,57-61].

Plastic and reconstructive (low to high Caprini score) – In the absence of pharmacologic prophylaxis, the baseline risk as estimated by the American College of Chest Physicians (ACCP) is between 0.5 to 1.8 percent based upon three observational studies [11,62-64]. However, extrapolating from related surgical populations (breast surgery, lower extremity bypass surgery), the estimated baseline VTE risk ranges from low (eg, outpatient cosmetic procedures) to high (eg, reconstructive surgeries).

Cardiac, thoracic, neurosurgery, major trauma — The ACCP has provided rough estimates of the baseline risk for VTE, in the absence of prophylaxis, for the other nonorthopedic surgical specialties [11]. The risk categories in parenthesis below correspond to the Caprini model, although this scoring system (table 1) has not been validated in these populations, and most experts use gestalt assessment. (See 'Thrombosis risk model (Caprini)' below.)

Cardiac surgery (moderate to high Caprini score) – Several studies have identified rates of VTE up to 1 percent in this population (prophylaxis unknown) [6,65,66] but older studies suggest higher rates (up to 25 percent) in the absence of prophylaxis [67-69].

Noncardiac thoracic surgery (moderate to high Caprini score) – Several studies reported that the incidence of symptomatic VTE ranges from 0.18 to 7.4 percent (highest in pneumonectomy, esophagectomy, extended resection) [6,65,70-72].

Neurosurgery (moderate to high Caprini score) – Meta-analyses report a pooled incidence of VTE in untreated patients between 16 and 29 percent, highest in those undergoing craniotomy [28,29]. In studies limited to spinal surgery, the incidence of deep vein thrombosis (DVT) ranges from 0 to 15 percent (with and without prophylaxis) [73-79]. Limited spine surgeries for benign conditions and cervical spine surgery are associated with less risk [73,74].

Major trauma (moderate to high Caprini score) – While studies report an incidence of DVT as high as 58 percent among those not receiving prophylaxis [80], these rates may reflect the most seriously ill patients with multiple other injuries (eg, traumatic brain and spinal injury) [81-86]. However, a 2013 systematic review, reported lower incidences of DVT and PE in patients who received either no prophylaxis (8.7 percent) or only mechanical prophylaxis (3.7 percent) [87]. Accurate estimates have been hampered by a baseline risk that varies widely in this population since these patients often undergo abdominal, vascular, neurologic, and/or orthopedic surgeries [80-86,88-90].

Thrombosis risk model (Caprini) — Although there have been many attempts to quantitate VTE risks, no one method has been found to be universally acceptable and many physicians use a gestalt assessment [11-13,91-93]. Nonetheless, the most widely used model is the Modified Caprini Risk Assessment Model (ie, Caprini score modified by The ACCP (table 1) [11]). The Rogers score is less frequently used and has not been externally validated [13].

Using the Caprini score, patients undergoing surgical procedures are classified according to their estimated baseline risk (EBR) for VTE in the absence of thromboprophylaxis as (see 'Baseline thrombosis risk' above):

Very low risk: Caprini score 0; corresponding to an EBR <0.5 percent (see 'Very low thrombosis risk: Early ambulation' below)

Low risk: Caprini score 1 to 2; corresponding to an EBR of about 1.5 percent (see 'Low VTE risk: Mechanical methods' below)

Moderate risk: Caprini score 3 to 4; corresponding to an EBR of about 3 percent (see 'Moderate or high VTE risk' below)

High risk: Caprini score ≥5; corresponding to an EBR of at least 6 percent (see 'Moderate or high VTE risk' below)

The caveat of this model is that it has been validated, and is therefore, only applicable to patients undergoing general (eg, breast, thyroid, parathyroid) and abdominal/pelvic surgery (eg, gastrointestinal, urologic, gynecologic), including those who are critically ill [11,91,93-95]. Although not validated in other populations, it is considered by most experts as acceptable for use in those undergoing bariatric and vascular surgery. In addition, this model underwent further modification for patients undergoing plastic/reconstructive surgery since a validation study reported a lower risk of VTE for a given Caprini score in this population (0.6 percent among those with a score of 3 to 4, 1.3 percent with a score of 5 to 6, 2.7 percent with a score 7 to 8, and 11.3 percent with a score of >8).

ASSESS RISK FOR MAJOR BLEEDING — For patients in whom pharmacologic VTE prophylaxis is indicated, a full history and examination should be obtained to assess the risk for major bleeding. Major bleeding is defined as fatal bleeding, and/or symptomatic bleeding in a critical area or organ (perhaps requiring re-exploration), and/or bleeding causing a fall in hemoglobin of ≥2 g/dL or leading to transfusion of two or more units of whole blood or red cells [96]. When assessing the risk, we prefer that the baseline risk be assessed first and then modified according to the potential consequences of bleeding and individual risk factors discussed below. (See 'Estimates of baseline bleeding risk' below and 'Individual risk factors for bleeding' below and 'Bleeding risk categories' below.)

The rate of bleeding associated with pharmacologic prophylaxis varies among patients groups. One meta-analysis of 51 randomized trials of pharmacologic VTE prophylaxis in general surgery patients reported that minor bleeding was common and included injection site bruising (7 percent), wound hematoma (6 percent), drain site bleeding (2 percent), and hematuria (2 percent) [97]. Major bleeding complications were uncommon and included including gastrointestinal tract (0.2 percent) or retroperitoneal (<0.1%) bleeding. Discontinuation of prophylaxis occurred in 2 percent of patients and subsequent re-operation for bleeding occurred in less than 1 percent.

Estimates of baseline bleeding risk — Baseline bleeding risk has been poorly studied in nonorthopedic surgical patients. Although several studies have attempted to elucidate bleeding risk, risk stratification for major bleeding has been estimated by the American College of Chest Physicians (ACCP) in the following patient groups as [11]:

General/abdominal/ pelvic surgery – 1 percent

Bariatric surgery – <1 percent

Plastic and reconstructive surgery – 0.5 to 1.8 percent

Vascular surgery – 0.3 to 1.8 percent

Cardiac surgery – 5 percent (high risk)

Thoracic surgery – 1 percent

Neurosurgery – Craniotomy: 1 to 1.5 percent; spinal surgery: <0.5 percent

Major trauma – 3.4 to 4.7 percent (high risk)

Individual risk factors for bleeding — Patients with individual risk factors for bleeding include those with active bleeding as an indication for surgery (eg, gastrointestinal bleeding, trauma, ruptured aneurysm), patients with intracranial hemorrhage, patients who develop a moderate or severe coagulopathy (eg, patients with liver disease), and patients with an underlying bleeding disorder or thrombocytopenia (eg, platelet count <50,000/microL, or < 100,000/microL plus additional risk factors for bleeding). Patients with relative contraindications include those with recurrent bleeding from multiple gastrointestinal telangiectasias. Epistaxis and menstrual bleeding are not contraindications to pharmacologic thromboprophylaxis. (See "Prevention of venous thromboembolic disease in acutely ill hospitalized medical adults", section on 'Bleeding risk assessment'.)

Bleeding risk categories — Following the above assessment, bleeding risk can be categorized as either low or high.

Low bleeding risk – In general, patients undergoing general, abdominal-pelvic, bariatric, vascular, and thoracic surgery that is uncomplicated tend to have lower rates of bleeding (<2 percent) when compared with other patients.

High bleeding risk – Patients undergoing cardiac surgery and patients with major trauma, especially involving the brain and spine [79], are at highest risk of bleeding (>3 percent). Patients in this category also include those in whom the consequences of bleeding are considered potentially devastating; for example patients undergoing neurosurgical procedures where thromboprophylaxis may result in spinal or intracranial hemorrhage, and patients undergoing plastic/reconstructive surgery where thromboprophylaxis may result in failed reconstruction. Similarly, patients with one or more individual risk factors for bleeding are considered at high risk of bleeding postoperatively. Prophylaxis in this population is discussed below. (See 'With high bleeding risk: Mechanical methods' below.)

SELECTING THROMBOPROPHYLAXIS — Options for primary VTE prophylaxis include early ambulation, pharmacologic and/or mechanical methods. VTE prevention strategies should be individualized according to the risk of VTE (very low, low, moderate, and high) as well as the risk and consequences of major bleeding. (See 'Assess risk for thrombosis' above and 'Assess risk for major bleeding' above.).

The approach outlined in the sections below is, in general, consistent with international guidelines including the American College of Chest Physicians (ACCP), the Asian Venous Thrombosis Forum, Korean guidelines for the Prevention of Venous Thromboembolism, European guidelines on perioperative venous thromboembolism prophylaxis: Executive summary, and the International Consensus Statement on the Prevention and Treatment of Venous Thromboembolism [11,98-104]. Importantly, the approach assumes that patients are at low risk for bleeding. In addition, the decision is fluid such that individual circumstances before, during, and after surgery may alter the decision regarding method selection. In addition, individualizing the approach according to individual factors is also prudent. Clinicians should also be aware that in general, thromboprophylaxis reduces but does not eliminate VTE events and VTE-related mortality [25,65,105,106].

Noteworthy, methods of secondary prophylaxis (eg, surveillance imaging) and inferior vena cava filters are not recommended for VTE prevention in this population.

Various strategies to improve the use of thromboprophylaxis methods have been demonstrated to be effective, including computerized order sets with electronic alerts, or pre-printed orders and quality improvement in the form of clinician education programs, audit, and feedback [3,107-113]. Further efforts are required to improve the use of thromboprophylaxis in clinical practice.

Very low thrombosis risk: Early ambulation — The risk of VTE is considered very low when the baseline risk in the absence of prophylaxis is estimated to be less than 0.5 percent (table 1). Very low risk group surgeries generally include patients undergoing general or abdominal/pelvic surgery with a Caprini score of zero or patients undergoing plastic/reconstructive surgeries with a Caprini score of zero to two. Examples include healthy young patients undergoing minor outpatient procedure (eg, LASIK surgery, cataract removal, skin biopsy, benign breast biopsy, diagnostic endoscopy, nasal polyp removal, dilatation and curettage, colposcopy, fluid removal from joint effusion).

For nonorthopedic surgical patients at very low risk of VTE, we recommend early and frequent ambulation rather than pharmacologic or mechanical methods of prophylaxis. Most very low risk patients are able to ambulate easily after surgery. Mechanical methods may be employed in the unusual circumstance where unexpected issues occur during the procedure (eg, bleeding, more extensive surgery, which intrinsically change the risk category) or the patient has a complication and requires admission.    

Since there are no randomized trials comparing ambulation with other methods, this approach is largely based upon the rationale that the baseline rate of VTE in this population is too low (<0.5 percent) to warrant prophylaxis. In addition, indirect data from studies evaluating the risk of VTE in orthopedic patients have also suggested that the risk of VTE is lowered by 70 percent in those who ambulate on or before the second postoperative day [114]. (See "Prevention of venous thromboembolism in adult orthopedic surgical patients", section on 'Assessing the risk of thrombosis'.)

Low VTE risk: Mechanical methods — The risk of VTE is considered low when the baseline risk in the absence of prophylaxis is estimated to be 1.5 percent (table 1). Patients in this category include those undergoing general or abdominal/pelvic surgery with a Caprini score of 1 to 2 or patients undergoing plastic/reconstructive surgery with a Caprini score of 3 to 4. Examples include those undergoing minor elective abdominal-pelvic surgery (eg, appendectomy, laparoscopic cholecystectomy) or minor thoracic surgery (eg, diagnostic thoracoscopy, video-assisted biopsy). Other examples include patients undergoing minor vascular procedures (eg, vein ablation), and elective spine surgery (eg, spinal fusion [115]). (See 'Baseline thrombosis risk' above.)

For nonorthopedic surgical patients at low risk for VTE, we suggest mechanical methods of VTE prophylaxis rather than pharmacologic prophylaxis or no prophylaxis. The rationale for this approach is that the risk of VTE is high enough to justify thromboprophylaxis but does not warrant the risk of bleeding associated with pharmacologic methods. Switching to pharmacologic methods may be appropriate in this with individual risk factors for VTE (eg, history of recurrent VTE or cancer).

Mechanical methods of thromboprophylaxis include intermittent pneumatic compression (IPC), graduated compression stockings (GCS, also known as elastic stockings), and the venous foot pump (VFP). Although IPC devices may be superior and are preferred by the ACCP, experts generally choose IPC or GCS since the data comparing one device over the other is fundamentally flawed [11,116-118].

Intermittent pneumatic compression and venous foot pump — Data supporting the use of IPC for the prevention of VTE in nonorthopedic surgical patients are limited. However, of the mechanical devices (IPC, GCS, VFP), efficacy appears best with IPC use (picture 1) [116,118-120]. Meta-analyses of small randomized trials of mixed surgical populations (including general, abdominal, urologic, neurosurgery, oncologic, orthopedic) report that IPC use is superior to no prophylaxis and to GCS, and may offer additive benefit to surgical patients on low molecular weight (LMW) heparin [11,119,121-125]. (See 'With low bleeding risk: Combined prophylaxis' below.)

As an example, the largest meta-analysis, which included data on 16,164 patients (mostly surgical) enrolled in 70 trials, reported that IPC was more effective than no prophylaxis in reducing deep venous thrombosis (DVT; 7.3 versus 16.7 percent) and pulmonary embolism (PE; 1.2 versus 2.8 percent) without any effect on mortality [121]. Although the addition of pharmacologic prophylaxis to IPC further reduced the risk of DVT (relative risk [RR] 0.54; 95% CI 0.32-0.91), it had no effect on the incidence of PE. In another meta-analysis of eight studies that compared mechanical prophylaxis with LMW heparin, the risk of DVT (symptomatic and asymptomatic) was 80 percent higher in those who had mechanical methods of prophylaxis (RR, 1.80; 95% CI, 1.16-2.79) [120] with a 57 percent decrease in the risk of major bleeding. However, patients in these studies had a range of VTE risk and many were of moderate to high risk.

Randomized studies showing efficacy of VFP devices (picture 2) in surgical patients are lacking but, similar to IPC devices, they prevent thrombosis by stimulating lower limb venous flow [126,127].

Compliance, proper fit, and discomfort are major issues with IPC devices. Devices may be removed while the patient is ambulating, but should be put back on when the patient returns to a seated or supine position. However, reflective of practice, observational studies report frequent errors in IPC application [128-130]. This suggests that frequent interference with the device is common and may potentially interfere with efficacy. Battery-operated devices may improve compliance in the future.  

IPC is contraindicated in patients with evidence of leg ischemia (eg, peripheral artery disease). Although there are no data available on skin complications of IPC use, skin breakdown is a known complication, especially in frail, older adults, although some clinicians use loose stockinettes underneath the device to counteract this phenomenon. In addition, practical considerations for amputees or patients with burns or extensive skin lesions (eg, Stevens Johnson’s syndrome) may limit IPC application. In this context, although one device can be applied to any extremity, its efficacy in the prevention of VTE is not assured and likely limited. There is also a hypothetical concern that patients who have been immobilized for a period of ≥72 hours without any form of prophylaxis may be at risk of dislodging recently formed venous clot in the lower extremities. The value of clinical examination or ultrasound in determining risk of clot dislodgement following the application of IPC in this setting is unknown.  

Optimal timing of IPC in surgical patients is poorly studied. However, one study suggested that IPC should be started as soon as possible, preferably just before surgery or in the operating room and continued with few interruptions until discharge [131]. (See 'Timing of initiation' below.)

IPC devices are thought to prevent VTE by enhancing blood flow in the deep veins of the legs, thereby preventing venous stasis [132]. IPC also reduces plasminogen activator inhibitor-1 (PAI-1), thereby increasing endogenous fibrinolytic activity [133]. (See "Thrombotic and hemorrhagic disorders due to abnormal fibrinolysis", section on 'PAI-1'.)

Graduated compression stockings — There is a paucity of high quality randomized trials that have studied the efficacy of GCS for preventing VTE in the surgical population [118,134-138]. GCS alone are effective at preventing DVT but may be less effective than pharmacologic agents. However, GCS when combined with other prophylactic methods appears to improve rates of DVT prevention. Of note, GCS refer to prescription-style stockings and not anti- embolism stockings, which are widely available in most facilities. (See 'With low bleeding risk: Combined prophylaxis' below.)

As examples:

One meta-analysis of 20 randomized trials mostly surgical and orthopedic patients(mixed populations) reported that the use of GCS alone was more effective than no prophylaxis in the prevention of DVT (21 versus 9 percent; odds ratio 0.35 95% CI 0.28-0.43) [139].

In another meta-analysis of eight studies (mostly hospitalized general surgical and orthopedic patients), the incidence of proximal DVT and PE was lower in patients treated with GCS compared with patients without GCS (1 versus 5 percent, 2 versus 5 percent, respectively) [138]. However, addition of a second method of prophylaxis in some of the included trials may have biased the favorable outcome associated with GCS in this analysis.

Trials reporting the efficacy of GCS when combined with pharmacologic prophylaxis are discussed below. (See 'With low bleeding risk: Combined prophylaxis' below.)

The efficacy and safety of thigh- versus knee-length stockings has not been studied in surgical patients.

Optimal timing of GCS in surgical patients is unstudied. However, in general, GCS should be started as soon as possible, preferably before surgery, or in the operating room and continued with few interruptions until discharge. (See 'Timing of initiation' below.)

Contraindications against their use and local skin breakdown complications are similar to those for IPC. (See 'Intermittent pneumatic compression and venous foot pump' above.)

Moderate or high VTE risk — The risk of VTE is considered moderate when the baseline risk in the absence of prophylaxis is estimated to 3 percent and high if it is at least 6 percent (table 1). (See 'Baseline thrombosis risk' above.)

Moderate risk surgical patients have been defined as patients undergoing general or abdomen/pelvic surgery with a Caprini score of 3 to 4 or patients undergoing plastic/reconstructive surgery with a Caprini score of 5 to 6 (table 1). Patients undergoing major gynecologic and urologic surgery usually fall into the moderate risk category [140]. In addition, patients undergoing major cardiac or thoracic surgery, bariatric surgery, and neurosurgical procedures, and patients with nonextensive trauma not involving the brain or spine are, at minimum, also considered moderate risk for VTE.

High risk surgical patients have been defined as patients undergoing general or abdominal/pelvic surgery with a Caprini score of 5 or more (table 1) or patients undergoing plastic/reconstructive surgery with a Caprini score of 7 to 8. Examples of patients in the high risk group are those undergoing extensive thoracic or abdominal-pelvic surgery (eg, distal colorectal surgery, extensive pelvic surgery), major trauma (particularly if involving the brain or spinal cord), acute spinal cord injury, or cancer surgery [141,142].

With low bleeding risk: Pharmacologic alone — In nonorthopedic surgical patients at moderate risk for VTE and in whom the risk of bleeding is low, we suggest pharmacologic prophylaxis, rather than mechanical methods, while in those at high risk we recommend pharmacologic prophylaxis rather than mechanical methods. The rationale for this approach is based upon randomized trials and meta-analyses with data for patients at moderate risk being weaker than for those at high risk. For select patients in whom the risk of VTE is considered to be particularly high, we suggest the addition of mechanical to pharmacologic methods (eg, multiple risk factors, surgery for cancer). (See 'With low bleeding risk: Combined prophylaxis' below and 'Pharmacologic dosing' below.)

Among the available agents, low molecular weight (LMW) heparin is generally the preferred anticoagulant based upon randomized trials that report superior or similar efficacy with unfractionated heparin (UFH) or fondaparinux, although most data show no appreciable effect on mortality and limited effect on clinically relevant bleeding. For those with renal insufficiency (creatinine clearance <20 to 30 mL/min) or for those in whom cost is an issue, UFH is appropriate (table 2). For patients in whom UFH or LMW heparin is contraindicated (eg, heparin-induced thrombocytopenia [HIT]) or unavailable, fondaparinux or mechanical methods are preferred. Timing of initiation and dosing of these agents are discussed below. (See 'Administration' below.)  

Many experts administer more aggressive prophylaxis in very high risk populations in the form of increased intensity of a pharmacologic agent (eg, three times a day UFH, twice daily enoxaparin) and/or the addition of a mechanical device (usually IPC). Patients in this category include those undergoing abdominal pelvic surgery with a Caprini score >8, patients with multiple risk factors, patients undergoing craniotomy or spinal surgery for cancer, and patients with major trauma, especially that involving the brain or spine. (See 'With low bleeding risk: Combined prophylaxis' below.)

The efficacy of pharmacologic therapy in comparison with mechanical methods, and specifically for LMW heparin compared with other anticoagulants is summarized below:

Pharmacologic versus no prophylaxis or mechanical methods – In general, randomized trials and meta-analyses have shown that pharmacologic prophylaxis with LMW heparin, low dose UFH, and fondaparinux are superior to placebo or mechanical devices. However, in general, the level of support from data in patients at moderate risk is weaker than for those at high risk.

LMW heparin – In a meta-analysis of eight trials of five different preparations of LMW heparin that included >48,000 general and abdominal surgery patients, compared with no prophylaxis, LMW heparin reduced the risk of symptomatic VTE by 70 percent but resulted in a doubling of the risk of major bleeding and wound hematomas [17].

Similar results were obtained from another meta-analysis that also included gastrointestinal, urologic, gynecologic, and thoracic surgery patients [143].

Trials reporting the efficacy of LMW heparin combined with compression stockings in nonorthopedic patients including those undergoing neurosurgery are discussed below. (See 'With low bleeding risk: Combined prophylaxis' below.)  

Low dose UFH – An early trial involving over 4000 patients established the efficacy of low dose UFH for reducing the incidence of fatal PE in patients undergoing major surgical procedures compared with controls (0.7 versus 0.1 percent) [105]. Pooled data from meta-analyses subsequently confirmed that low dose UFH reduced the incidence of all DVT, proximal DVT, and all PE including fatal PE, when compared with placebo [25,97,144,145].

LMW heparin versus other agents – Our preference for LMW heparin is based upon direct data derived from nonorthopedic surgical populations that included randomized trials and meta-analyses, most of which show similar or superior efficacy compared with UFH as well as indirect data that show similar benefits in orthopedic and medical populations. However, the quality of data is limited by the heterogeneity of study populations eg, (wide range in risk, different surgery types) and the failure to distinguish symptomatic from asymptomatic VTE. (See "Prevention of venous thromboembolism in adult orthopedic surgical patients" and "Prevention of venous thromboembolic disease in acutely ill hospitalized medical adults", section on 'Low molecular weight heparin'.)

LMW heparin versus low dose UFH – Low dose UFH is generally considered an alternative to LMW heparin, when, for example, cost or renal insufficiency is an issue. While early meta-analyses comparing low dose UFH and LMW heparin found similar efficacy and safety for both agents [146,147], newer analyses suggest that LMW heparin is superior. As an example, compared with low dose UFH, one meta-analysis of 51 randomized trials of general surgery patients reported that the rate of VTE events was 30 percent lower in patients receiving LMW heparin without any effect on death or bleeding [17]. However, the same efficacy was not apparent when the analysis was confined to placebo-controlled trials. Most of the patients in these trials underwent abdominal (particularly for gastrointestinal disease) or thoracic surgery, but some patients underwent gynecologic or urologic surgery, mastectomy, or vascular procedures [25,144].

Similar results of superior or similar efficacy were reported in other meta-analyses and randomized trials that included patients undergoing gynecologic and urologic surgery [17,143,146-149], and cancer surgery [150-156].

For patients admitted with major trauma, LMW heparin was also reported to be superior to UFH in the prevention of both total and proximal DVTs [26,157-159].

Fondaparinux versus UFH or LMW heparin – Fondaparinux is an alternative to LMW heparin and UFH in patients with contraindications to heparin (eg, HIT) or when these agents are not available. In a randomized trial (PEGASUS) of 2408 patients undergoing major abdominal surgery, fondaparinux and the LMW heparin, dalteparin, had a similar efficacy in reducing the rate of VTE (4.4 versus 6.1 percent) without any increased rate of major bleeding (3.4 versus 2.4 percent) [149]. In a meta-analysis that pooled the results from this study with studies including orthopedic patients, when compared with LMW heparin, fondaparinux did not reduce VTE events but resulted in an increased risk of bleeding [9]. (See "Prevention of venous thromboembolism in adult orthopedic surgical patients".)

Oral agents (warfarin, aspirin, direct oral anticoagulants) – Although oral agents including warfarin, aspirin, direct thrombin inhibitors (eg, dabigatran) and factor Xa inhibitors (eg, rivaroxaban, edoxaban, and apixaban) are sometimes administered in orthopedic patients for VTE prevention, they are unstudied and are not typically administered in nonorthopedic surgical patients. Occasionally, for patients undergoing general or abdominal/pelvic surgery considered at high risk for VTE in whom LMW heparin or UFH is contraindicated or unavailable, some experts administer aspirin as an alternative to fondaparinux or mechanical methods, although the data to support this strategy is indirect and derived from patients undergoing major orthopedic surgery [11]. (See "Prevention of venous thromboembolism in adult orthopedic surgical patients".)

With low bleeding risk: Combined prophylaxis — Combining pharmacologic and mechanical methods of prophylaxis are generally reserved for those considered to be at the highest risk of VTE. Although there are a paucity of high quality studies comparing combined methods to pharmacologic prophylaxis alone, data in general suggest that combining methods of thromboprophylaxis offers additional protective benefit against the development of VTE. However, the contributions of each method is unclear and most studies are limited by incomplete blinding, small sample size, uncertain concealment, and measurement of surrogate outcomes. No convincing data report further benefits in efficacy when two mechanical methods are combined or added to pharmacologic agents.  

As examples:

In a large meta-analysis of 70 trials, which included data on 16,164 patients (mostly surgical), the addition of pharmacologic prophylaxis to IPC further reduced the risk of DVT (RR 0.54), but had no effect on the incidence of PE [121].

In a meta-analysis of 25 randomized trials in mixed surgical populations, adding pharmacologic agents to GCS almost halved the rate of postoperative DVT (RR 0.56) while the risk of bleeding almost doubled (RR 1.74) compared with GCS alone [137]. In another meta-analysis, rates of DVT were lower in those treated with GCS plus any other prophylactic method compared with GCS alone (4 versus 13 percent) [136].

Several randomized trials of patients undergoing neurosurgical procedures reported LMW heparin, when added to GCS, prevented more venographic DVT than GCS alone (17 to 19 percent versus 26 to 32 percent ) without an increased risk of bleeding [160,161].

In a randomized trial (APOLLO) of patients undergoing major abdominal surgery (gastrointestinal, urologic), fondaparinux combined with IPC significantly reduced the rate of VTE when compared with IPC alone (1.7 versus 5.3 percent) [162]. Major bleeding was more frequent after fondaparinux (1.6 versus 0.2 percent), although none of the bleeding events were fatal or involved a critical organ.

With high bleeding risk: Mechanical methods — For patients with contraindications to pharmacologic prophylaxis (eg, active bleeding, intracranial hemorrhage, bleeding diathesis (table 3)), patients at high risk of bleeding, or patients in whom the consequences of bleeding are thought to be potentially catastrophic (eg, neurosurgical procedures), we suggest mechanical methods rather than no thromboprophylaxis. Among the options, IPC is the typical method used but data to support their use over graduated compression stockings or VFP devices are limited. Vena cava filters should not be routinely used for VTE prevention. (See 'Intermittent pneumatic compression and venous foot pump' above and 'Methods not recommended' below.)

Switching to or adding a pharmacologic agent, such as LMW heparin, should be done as soon as the bleeding risk becomes acceptably low (eg, 48 to 72 hours following neurosurgery) or the bleeding diathesis has been reversed. (See 'Assess risk for major bleeding' above.)

SPECIFIC SURGICAL POPULATIONS — Additional data that support VTE prophylaxis in special surgical populations are discussed separately in the followings topics:

General and abdominal/pelvic surgery

Bariatric surgery (table 4) (see "Bariatric surgery: Postoperative and long-term management of the uncomplicated patient", section on 'Venous thromboembolism')

Colon surgery (see "Overview of colon resection", section on 'Thromboprophylaxis')

Abdominal aortic aneurysm repair (See "Open surgical repair of abdominal aortic aneurysm", section on 'Thromboprophylaxis' and "Endovascular repair of abdominal aortic aneurysm", section on 'Thromboprophylaxis'.)

Extremity amputation (see "Lower extremity amputation", section on 'Thromboprophylaxis' and "Upper extremity amputation", section on 'Evaluation and preparation')

Gynecologic surgery (see "Overview of preoperative evaluation and preparation for gynecologic surgery", section on 'Thromboprophylaxis')

Neurosurgery including neurotrauma

Traumatic brain injury (See "Management of acute moderate and severe traumatic brain injury", section on 'Venous thromboembolism prophylaxis'.)

Spinal cord injury (see "Respiratory complications in the adult patient with chronic spinal cord injury", section on 'Venous thromboembolism')

Surgery for brain tumors (see "Treatment and prevention of venous thromboembolism in patients with brain tumors", section on 'Primary prevention (VTE prophylaxis)')

Anesthesia and perioperative care

Patients undergoing neuraxial anesthesia or analgesia (see "Neuraxial anesthesia/analgesia techniques in the patient receiving anticoagulant or antiplatelet medication" and "Perioperative management of patients receiving anticoagulants", section on 'Neuraxial anesthesia')

Critically ill patients including postoperative surgical patients (see "Prevention of venous thromboembolic disease in acutely ill hospitalized medical adults", section on 'Selection of method of prophylaxis')

Trauma patients (see "Thromboembolism and prevention in the severely injured trauma patient", section on 'Thromboprophylaxis')

Patients with stroke (see "Prevention and treatment of venous thromboembolism in patients with acute stroke")

Patients with cancer (table 5) (see "Risk and prevention of venous thromboembolism in adults with cancer")

Patients who are pregnant (see "Deep vein thrombosis and pulmonary embolism in pregnancy: Prevention")

ADMINISTRATION

Timing of initiation — The optimal timing for initiation of mechanical and/or pharmacologic thromboprophylaxis in nonorthopedic patients is unknown and should be individualized according to factors including timing of surgery (elective or emergency), type and duration of surgery, the estimated risk of bleeding, and baseline risk of VTE. (See 'Assess risk for thrombosis' above and 'Assess risk for major bleeding' above.)

Studies that specifically examine timing of pharmacologic dosing are limited. However, the approach below is in accordance with studies that proved efficacy of pharmacologic agents (see 'Pharmacologic dosing' below), as well as data derived from observational studies in trauma patients (ie, patients with the highest risk of VTE and bleeding). (See "Thromboembolism and prevention in the severely injured trauma patient", section on 'Specific trauma populations'.)

For most patients in whom thromboprophylaxis is indicated and the risk of bleeding is low, experts agree that mechanical methods may commence just before surgery and that pharmacologic agents should ideally commence within 2 to 12 hours preoperatively. The exception to this rule is fondaparinux, which is typically started six to eight hours after skin closure. In patients not considered suitable candidates for preoperative pharmacologic thromboprophylaxis due to a contraindication to anticoagulants, a high risk of bleeding, or potential catastrophic effect of bleeding, mechanical methods should be employed (typically just before surgery) and pharmacologic agents started or added postoperatively, as soon as hemostasis is achieved and it is considered safe (eg, 2 to 72 hours).

All anticoagulants have a boxed warning regarding the risk of spinal or epidural hematoma in patients receiving neuraxial anesthesia or undergoing spinal puncture. The risk is increased in those with indwelling epidural catheters, other drugs that impair hemostasis (eg, anti-platelet agents), traumatic or repeated epidural or spinal puncture, or a history of spinal surgery. Evidence-based guidelines from the American Society of Regional Anesthesia (ASRA) suggest not administering preoperative pharmacologic agents and waiting at least six to eight hours after catheter removal before administering prophylactic anticoagulant. (See "Neuraxial anesthesia/analgesia techniques in the patient receiving anticoagulant or antiplatelet medication" and "Perioperative management of patients receiving anticoagulants", section on 'Neuraxial anesthesia' and "Overview of neuraxial anesthesia", section on 'Spinal-epidural hematoma (SEH)'.)

Perioperative management of anticoagulants for patients who are therapeutically anticoagulated is discussed separately. (See "Perioperative management of patients receiving anticoagulants".)

Duration — In most cases VTE prophylaxis is continued until the patient becomes fully ambulatory or until hospital discharge (typically up to 10 days). Once patients become fully ambulatory, pharmacologic and mechanical methods of prophylaxis are generally stopped. However, the definition of ambulatory is highly subjective such that patients who have prolonged periods of immobility in between ambulatory periods should probably receive continued or additional methods of prophylaxis, particularly in light of the fact that the risk of VTE does not drop to zero upon ambulation but rather may be sustained for weeks beyond the day of surgery [163]. In addition, 10 to 14 days of thromboprophylaxis may be indicated in high risk surgical patients, including those with cancer. (See "Risk and prevention of venous thromboembolism in adults with cancer", section on 'Surgical patients'.)

Extended pharmacologic VTE prophylaxis beyond discharge is not routinely recommended in most nonorthopedic surgical patients except for those who undergo major abdominal and/or pelvic surgery for cancer. Extended pharmacologic VTE prophylaxis, typically with low molecular weight (LMW) heparin, is offered to this population who are at very high risk for VTE up to 12 weeks post discharge. The optimal duration of extended prophylaxis is unknown but is typically recommended beyond 10 days and for a period of three to four weeks for high-risk patients who undergo major abdominal and/or pelvic surgery for cancer [11,150-152,164-166]. (See "Risk and prevention of venous thromboembolism in adults with cancer", section on 'Surgical patients'.)

Several meta-analyses of randomized and non-randomized trials have demonstrated benefit associated with extended prophylaxis in major abdominal/pelvic surgery, particularly for cancer [27,150,152,164,167-169]. As an example, in a meta-analysis of seven randomized trials of patients undergoing major abdominal or pelvic surgery, extended prophylaxis with low molecular weight heparin resulted in a reduction in the overall rate of VTE (5 versus 13 percent) and rate of symptomatic VTE (1 versus 0.1 percent) without an increased risk of bleeding (4 versus 3 percent) [169].

Pharmacologic dosing — Pharmacologic prophylaxis is the method of choice for surgical patients at moderate or high risk for VTE (Caprini score ≥3) (table 1). Efficacy is discussed above. (See 'Moderate or high VTE risk' above.)

Low molecular weight heparin — In general, LMW heparin is pharmacologic agent of choice for preventing VTE in nonorthopedic surgical patients. (See 'With low bleeding risk: Pharmacologic alone' above.)

A number of LMW heparin preparations are available (enoxaparin, dalteparin, tinzaparin, nadroparin) none of which have proven superiority over the others when administered as agents to prevent VTE. These regimens differ in detail from product label recommendations but are generally consistent with 2012 American College of Chest Physicians guidelines on antithrombotic therapy and 2013 guidelines of the American Society of Clinical Oncology on VTE prophylaxis and treatment in patients with cancer [11,165].

Typical regimens commonly used in nonorthopedic surgical patients (assuming no renal insufficiency at any point) are listed below. Considerations for individualizing therapy, including adjustments required for neuraxial (ie, epidural or spinal) anesthesia, are reviewed elsewhere. (See 'Timing of initiation' above and 'Duration' above.)

Enoxaparin:

Patients without cancer: 40 mg subcutaneously once daily started two hours before abdominal surgery or about 12 hours before other surgery and 40 mg once daily thereafter. Alternatively, 40 mg once daily started 2 to 72 hours after surgery once hemostasis is achieved and initiation is considered safe.  

Patients with cancer: 40 mg 10 to 12 hours before surgery and 40 mg once daily thereafter [165]. Alternatively, 40 mg once daily started approximately 6 to 12 hours after surgery. There is variation in clinical practice especially with regards to the administration of enoxaparin before surgery in patients with cancer. (See "Risk and prevention of venous thromboembolism in adults with cancer", section on 'Surgical patients'.)

Both once daily and twice daily regimens of enoxaparin have been shown to be effective but direct comparison of these regimens are poorly studied [157]. More aggressive prophylaxis (eg, twice daily enoxaparin and/or the addition of a mechanical device) may be considered in very high risk populations (eg, patients with cancer).

Dalteparin:

Including patients with cancer: 5000 units subcutaneously started about 12 hours (or evening) before surgery and 5000 units once daily thereafter.

Although labeling in some countries recommends reduced doses in lower thrombotic risk general surgeries (2500 units subcutaneously started 1 to 2 hours before surgery and 2500 units daily thereafter), we use full dosing listed above when LMW prophylaxis is indicated.

Less commonly used agents are:

Tinzaparin (not available in the United States):

Including patients with cancer: 4500 units subcutaneously started 12 hours before surgery and once daily thereafter. An alternative weight-based regimen is listed in the drug information monograph.

Although labeling in some countries recommends reduced doses in lower thrombotic risk general surgeries (3500 units subcutaneously started one to two hours before surgery and 3500 units daily thereafter), we use full dosing listed above when LMW prophylaxis is indicated.

Nadroparin (not available in the United States):

High VTE risk including patients with cancer: 38 units/kg (maximum 3800 units) subcutaneously once daily started 12 hours before surgery; on postoperative day 4 increase dose to 57 units/kg (maximum 5700 units once daily).

Although labeling in some countries recommends reduced doses in lower thrombotic risk general surgeries (2850 units subcutaneously started one to two hours before surgery and 2850 units daily thereafter), we use full dosing listed above when LMW prophylaxis is indicated.

The platelet count should be monitored regularly (eg, day 5, 7, and 9) in all patients receiving LMW heparin to detect the development of heparin-induced thrombocytopenia (HIT). All heparin agents are contraindicated in patients with active HIT or a history of HIT, the details of which are discussed separately. (See "Management of heparin-induced thrombocytopenia".)

The ideal dose for obese patients is unknown. In patients with a BMI ≥40 kg/m2, some experts empirically increase the standard LMW heparin dose by approximately 30 percent [170]. Suggested doses for obese patients and patients undergoing bariatric surgery are presented in the table (table 4) and discussed separately. (See "Bariatric surgery: Postoperative and long-term management of the uncomplicated patient", section on 'Venous thromboembolism'.)

Based upon data extrapolated from patients receiving therapeutic doses of LMW heparin, we prefer the avoidance of these agents in patients with severe renal insufficiency (eg, creatinine clearance 20 to 30 mL/min and end stage renal failure requiring dialysis) should it be present upon admission. For those with mild renal insufficiency dose-adjustments can be made according to the creatinine clearance and agent chosen, as outlined in the table (table 2). For those who develop severe renal insufficiency during hospitalization, it is prudent that the LMW heparin agent be discontinued and replaced with unfractionated heparin (UFH). (See "Heparin and LMW heparin: Dosing and adverse effects".)

Low dose unfractionated heparin — Low dose UFH is generally considered an alternative to LMW heparin, when, for example, cost or renal insufficiency (creatinine clearance <20 to 30 mL/min) is an issue.

Low dose subcutaneous UFH for VTE prophylaxis is usually given as 5000 units every 12 hours starting two or more hours before surgery.

Occasionally, if the risk is assessed as particularly high, the frequency is increased to three times daily, although data to support this dosing is lacking. In patients with cancer, 5000 units every eight hours starting two to four hours before surgery is suggested by American Society of Clinical Oncology 2013 guidelines [165]. Factors including cost, institutional policy, body weight, and risk of bleeding may be used to help the clinician make the decision to choose the frequency of dosing.  

The ideal dose for obese patients is unknown such that dosing should be individualized on a case-by-case basis. We generally prefer to empirically treat with UFH 5000 to 7500 units twice daily; alterations in the dosing and frequency (eg, three times per day dosing) should be tailored to individual patients [171-173].

The dose of UFH does not need to be adjusted for patients with renal insufficiency. However, similar to LMW heparin, the platelet count should be monitored regularly (eg, day 5, 7, and 9) to detect the development of HIT, in which case UFH should be discontinued. (See "Heparin and LMW heparin: Dosing and adverse effects", section on 'Platelet count monitoring'.)

Fondaparinux — Fondaparinux is an alternative to LMW heparin and UFH in patients with contraindications to heparin (eg, HIT) or when these agents are not available.

Unlike LMW heparin agents, which are often administered pre and postoperatively, in accordance with trials that have shown benefit, fondaparinux is typically given as 2.5 mg once daily, starting at least six to eight hours postoperatively (after skin closure). Although in Europe, a 1.5 mg dose is suggested for individuals with creatinine clearance of 20 to 50 mL/min, the safety and efficacy of this dose has not been well-studied. One systematic review of 17 trials reported superior efficacy of fondaparinux compared with LMW heparin (odds ratio [OR] 0.49; 95% CI 0.38-0.64) but at the expense of an increased risk of major bleeding (OR 1.48 95% CI 1.15-1.9) [174]. Dosing and adverse effects of fondaparinux are discussed separately. (See "Fondaparinux: Dosing and adverse effects".)

METHODS NOT RECOMMENDED

Screening — Secondary prevention with screening tests targeted at the early detection of thrombosis (eg, ultrasonography) is not recommended but can be reserved for rare patients in whom primary prophylaxis is not suitable (eg, patients with active minor bleeding); in such cases, resumption of primary prophylaxis should be performed as soon as is feasible [175,176]. (See "Prevention of venous thromboembolic disease in acutely ill hospitalized medical adults", section on 'Definition of VTE prophylaxis' and "Overview of inpatient management of the adult trauma patient", section on 'Screening for venous thromboembolism'.)

Prophylactic vena cava filters — Inferior vena cava (IVC) filters should generally be avoided as prophylaxis against postoperative VTE. This approach is best supported by indirect evidence from large populations of medical and surgical patients (PREPIC) in whom IVC filters were placed (mostly for therapy) that reported a reduction in pulmonary embolism (PE) but an increase in the rate of lower extremity deep venous thrombosis (DVT). These data are discussed separately. (See "Overview of the treatment of lower extremity deep vein thrombosis (DVT)", section on 'Inferior vena cava filter'.)

Smaller observational studies have confirmed similar outcomes in surgical patients:  

One retrospective study of over 6000 bariatric patients reported that compared with those who did not receive an IVC filter, filter placement did not reduce the rate of VTE and may be associated with an increased risk of death or serious disability [177].

Systematic reviews and observational studies in trauma patients reported a reduction in the rate of PE but increased rate of DVT and IVC filter complications (eg, migration) without an effect on mortality in those treated with an IVC filter compared with those in whom a filter was not placed [178-180]. (See "Thromboembolism and prevention in the severely injured trauma patient".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Superficial vein thrombosis, deep vein thrombosis, and pulmonary embolism".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)

Beyond the Basics topics (see "Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)" and "Patient education: Warfarin (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

Postoperative venous thromboembolism (VTE) is common among patients undergoing nonorthopedic surgery. This population includes patients undergoing general and abdominal-pelvic surgery, bariatric, vascular, plastic/reconstructive, cardiac, and thoracic surgery as well as patients undergoing neurosurgery and patients admitted with major trauma. (See 'Introduction' above.)

The risk of postoperative VTE depends upon procedure-related factors (eg, anatomic location, degree of invasiveness, type and duration of anesthesia, requirement for postoperative immobilization) and patient-related risk factors (eg, increasing age, prior VTE, presence of malignancy) all of which need to be assessed prior to surgery so that a risk category can be assigned and method appropriately selected. (See 'Assess risk for thrombosis' above.)

For patients undergoing general (eg, breast, thyroid, parathyroid) and abdominal-pelvic (gastrointestinal, urologic, gynecologic) surgery as well as patients undergoing bariatric, vascular, and plastic/reconstructive surgery, the modified Caprini risk assessment score is used to classify patient into very low risk, low risk, moderate risk, and high risk (table 1). Patients undergoing major cardiac, thoracic, brain and spinal surgery, or patients with major trauma are, at minimum, moderate risk for VTE (eg, uncomplicated cardiac, bariatric, minor thoracic or spinal surgery) and many are at high risk for VTE (eg, craniotomy, extensive cardiac or thoracic surgery, spinal surgery for malignancy, trauma involving brain or spine). (See 'Assess risk for thrombosis' above.)  

In nonorthopedic patients, assuming the risk of bleeding is low, we suggest the following approach (table 1):

For most patients at very low risk of VTE, pharmacologic or mechanical methods of thromboprophylaxis are typically not necessary since most are fully ambulatory; thus, early and frequent ambulation is the preferred method in this population. (See 'Very low thrombosis risk: Early ambulation' above.)

For patients at low risk of VTE, we suggest mechanical methods of VTE prophylaxis, rather than pharmacologic or no thromboprophylaxis (Grade 2C). Choosing among mechanical methods is individualized but intermittent pneumatic compression (IPC) devices or graduated compression stockings (GCS) are frequently chosen. (See 'Low VTE risk: Mechanical methods' above.)

For patients at moderate risk of VTE, we suggest pharmacologic prophylaxis, preferably with low molecular weight (LMW) heparin, rather than no thromboprophylaxis (Grade 2B). (See 'Moderate or high VTE risk' above and 'Pharmacologic dosing' above.)

For patients at high risk of VTE, we recommend, at minimum, pharmacologic prophylaxis, preferably with LMW heparin, rather than mechanical methods or no prophylaxis (Grade 1B). Combining pharmacologic with mechanical methods of thromboprophylaxis is frequently performed in this population especially in those at greatest risk (eg, multiple risk factors or cancer). (See 'Moderate or high VTE risk' above.)

Screening with surveillance ultrasonography and inferior venal cava filters are not recommended.

For nonorthopedic surgical patients with contraindications to pharmacologic prophylaxis and in whom thromboprophylaxis other than ambulation is indicated (table 3), patients with active or at high risk of bleeding or patients in whom the consequences of bleeding are thought to be potentially catastrophic (eg, neurosurgical procedures), mechanical methods rather than no thromboprophylaxis are preferred. IPC devices are commonly used but GCS or venous foot pump devices are also appropriate. Switching to or adding a pharmacologic agent, such as LMW heparin, should be done as soon as the bleeding risk becomes acceptably low (eg, 48 to 72 hours following neurosurgery) or the bleeding diathesis has been reversed.

For most patients without renal insufficiency (eg, creatinine clearance >30 mL/min) in whom pharmacologic prophylaxis is indicated, we suggest LMW heparin rather than unfractionated heparin (UFH) (Grade 2C). UFH is preferred in those with severe renal insufficiency (eg, creatinine clearance <20 to 30 mL/min), while fondaparinux is preferred in those with heparin-induced thrombocytopenia. Oral agents including warfarin, aspirin, and direct oral anticoagulants are unstudied and are not typically administered in nonorthopedic surgical patients. (See 'With low bleeding risk: Pharmacologic alone' above.)

The optimal timing for initiation of thromboprophylaxis is unknown and should be individualized. For most patients in whom the bleeding risk is low, mechanical methods are ideally started just before surgery, and pharmacologic agents administered within 2 to 12 hours before surgery, with the exception of fondaparinux which is typically initiated six to eight hours after skin closure. However, in patients with a contraindication to anticoagulants, a high risk of bleeding, or potential catastrophic effect of bleeding, mechanical methods should be employed preoperatively and pharmacologic agents started or added postoperatively, when adequate hemostasis is achieved and it is assessed as safe (eg, 2 to 72 hours). (See 'Timing of initiation' above.)

In most patients, we suggest that VTE prophylaxis be continued until the patient becomes fully ambulatory or until hospital discharge. Extended pharmacologic VTE prophylaxis beyond discharge is not routinely recommended in this population except for patients who undergo major abdominal and/or pelvic surgery for cancer in whom thromboprophylaxis should be continued for a period of four weeks. (See 'Duration' above.)

REFERENCES

  1. Anderson FA Jr, Zayaruzny M, Heit JA, et al. Estimated annual numbers of US acute-care hospital patients at risk for venous thromboembolism. Am J Hematol 2007; 82:777.
  2. Lobastov K, Barinov V, Schastlivtsev I, et al. Validation of the Caprini risk assessment model for venous thromboembolism in high-risk surgical patients in the background of standard prophylaxis. J Vasc Surg Venous Lymphat Disord 2016; 4:153.
  3. Ramanathan R, Lee N, Duane TM, et al. Correlation of venous thromboembolism prophylaxis and electronic medical record alerts with incidence among surgical patients. Surgery 2016; 160:1202.
  4. Lindblad B, Eriksson A, Bergqvist D. Autopsy-verified pulmonary embolism in a surgical department: analysis of the period from 1951 to 1988. Br J Surg 1991; 78:849.
  5. Stein PD, Henry JW. Prevalence of acute pulmonary embolism among patients in a general hospital and at autopsy. Chest 1995; 108:978.
  6. White RH, Zhou H, Romano PS. Incidence of symptomatic venous thromboembolism after different elective or urgent surgical procedures. Thromb Haemost 2003; 90:446.
  7. Sandler DA, Martin JF. Autopsy proven pulmonary embolism in hospital patients: are we detecting enough deep vein thrombosis? J R Soc Med 1989; 82:203.
  8. Martino MA, Borges E, Williamson E, et al. Pulmonary embolism after major abdominal surgery in gynecologic oncology. Obstet Gynecol 2006; 107:666.
  9. Falck-Ytter Y, Francis CW, Johanson NA, et al. Prevention of VTE in orthopedic surgery patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141:e278S.
  10. Anderson DR, Morgano GP, Bennett C, et al. American Society of Hematology 2019 guidelines for management of venous thromboembolism: prevention of venous thromboembolism in surgical hospitalized patients. Blood Adv 2019; 3:3898.
  11. Gould MK, Garcia DA, Wren SM, et al. Prevention of VTE in nonorthopedic surgical patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141:e227S.
  12. Bahl V, Hu HM, Henke PK, et al. A validation study of a retrospective venous thromboembolism risk scoring method. Ann Surg 2010; 251:344.
  13. Rogers SO Jr, Kilaru RK, Hosokawa P, et al. Multivariable predictors of postoperative venous thromboembolic events after general and vascular surgery: results from the patient safety in surgery study. J Am Coll Surg 2007; 204:1211.
  14. Alcalay A, Wun T, Khatri V, et al. Venous thromboembolism in patients with colorectal cancer: incidence and effect on survival. J Clin Oncol 2006; 24:1112.
  15. Clarke-Pearson DL, Dodge RK, Synan I, et al. Venous thromboembolism prophylaxis: patients at high risk to fail intermittent pneumatic compression. Obstet Gynecol 2003; 101:157.
  16. http://www.absurgery.org/default.jsp?aboutsurgerydefined (Accessed on December 20, 2016).
  17. Mismetti P, Laporte S, Darmon JY, et al. Meta-analysis of low molecular weight heparin in the prevention of venous thromboembolism in general surgery. Br J Surg 2001; 88:913.
  18. Pezzuoli G, Neri Serneri GG, Settembrini P, et al. Prophylaxis of fatal pulmonary embolism in general surgery using low-molecular weight heparin Cy 216: a multicentre, double-blind, randomized, controlled, clinical trial versus placebo (STEP). STEP-Study Group. Int Surg 1989; 74:205.
  19. Pezzuoli G, Neri Serneri GG, Settembrini PG, et al. Effectiveness and safety of the low-molecular-weight heparin CY 216 in the prevention of fatal pulmonary embolism and thromboembolic death in general surgery. A multicentre, double-blind, randomized, controlled clinical trial versus placebo (STEP). STEP Study Group. Haemostasis 1990; 20 Suppl 1:193.
  20. Valle I, Sola G, Origone A. Controlled clinical study of the efficacy of a new low molecular weight heparin administered subcutaneously to prevent post-operative deep venous thrombosis. Curr Med Res Opin 1988; 11:80.
  21. Abstracts of the 12th International Congress on Thrombosis. Florence, May 18-23, 1992. Thromb Res 1992; 65 Suppl 1:S1.
  22. Marassi A, Balzano G, Mari G, et al. Prevention of postoperative deep vein thrombosis in cancer patients. A randomized trial with low molecular weight heparin (CY 216). Int Surg 1993; 78:166.
  23. Bergqvist D, Flordal PA, Friberg B, et al. Thromboprophylaxis with a low molecular weight heparin (tinzaparin) in emergency abdominal surgery. A double-blind multicenter trial. Vasa 1996; 25:156.
  24. Ho YH, Seow-Choen F, Leong A, et al. Randomized, controlled trial of low molecular weight heparin vs. no deep vein thrombosis prophylaxis for major colon and rectal surgery in Asian patients. Dis Colon Rectum 1999; 42:196.
  25. Collins R, Scrimgeour A, Yusuf S, Peto R. Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin. Overview of results of randomized trials in general, orthopedic, and urologic surgery. N Engl J Med 1988; 318:1162.
  26. Geerts WH, Jay RM, Code KI, et al. A comparison of low-dose heparin with low-molecular-weight heparin as prophylaxis against venous thromboembolism after major trauma. N Engl J Med 1996; 335:701.
  27. Akl EA, Terrenato I, Barba M, et al. Extended perioperative thromboprophylaxis in patients with cancer. A systematic review. Thromb Haemost 2008; 100:1176.
  28. Collen JF, Jackson JL, Shorr AF, Moores LK. Prevention of venous thromboembolism in neurosurgery: a metaanalysis. Chest 2008; 134:237.
  29. Iorio A, Agnelli G. Low-molecular-weight and unfractionated heparin for prevention of venous thromboembolism in neurosurgery: a meta-analysis. Arch Intern Med 2000; 160:2327.
  30. Rocha AT, de Vasconcellos AG, da Luz Neto ER, et al. Risk of venous thromboembolism and efficacy of thromboprophylaxis in hospitalized obese medical patients and in obese patients undergoing bariatric surgery. Obes Surg 2006; 16:1645.
  31. Parker SG, McGlone ER, Knight WR, et al. Enoxaparin venous thromboembolism prophylaxis in bariatric surgery: A best evidence topic. Int J Surg 2015; 23:52.
  32. Helm MC, Simon K, Higgins R, et al. Perioperative complications increase the risk of venous thromboembolism following bariatric surgery. Am J Surg 2017; 214:1135.
  33. Farkas JC, Chapuis C, Combe S, et al. A randomised controlled trial of a low-molecular-weight heparin (Enoxaparin) to prevent deep-vein thrombosis in patients undergoing vascular surgery. Eur J Vasc Surg 1993; 7:554.
  34. Harjola P, Meurala H, Frick MH. Prevention of deep venous thrombosis and thrombo-embolism by dipyridamole and acetylsalicylic acid after reconstructive arterial surgery. J Cardiovasc Surg (Torino) 1980; 21:451.
  35. Speziale F, Verardi S, Taurino M, et al. Low molecular weight heparin prevention of post-operative deep vein thrombosis in vascular surgery. Pharmatherapeutica 1988; 5:261.
  36. Lastória S, Rollo HA, Yoshida WB, et al. Prophylaxis of deep-vein thrombosis after lower extremity amputation: comparison of low molecular weight heparin with unfractionated heparin. Acta Cir Bras 2006; 21:184.
  37. de Maistre E, Terriat B, Lesne-Padieu AS, et al. High incidence of venous thrombosis after surgery for abdominal aortic aneurysm. J Vasc Surg 2009; 49:596.
  38. Scarborough JE, Cox MW, Mureebe L, et al. A novel scoring system for predicting postoperative venous thromboembolic complications in patients after open aortic surgery. J Am Coll Surg 2012; 214:620.
  39. Bush RL, Lumsden AB, Dodson TF, et al. Mid-term results after endovascular repair of the abdominal aortic aneurysm. J Vasc Surg 2001; 33:S70.
  40. Eagleton MJ, Grigoryants V, Peterson DA, et al. Endovascular treatment of abdominal aortic aneurysm is associated with a low incidence of deep venous thrombosis. J Vasc Surg 2002; 36:912.
  41. AbuRahma AF, Woodruff BA, Lucente FC. Edema after femoropopliteal bypass surgery: lymphatic and venous theories of causation. J Vasc Surg 1990; 11:461.
  42. Fletcher JP, Batiste P. Incidence of deep vein thrombosis following vascular surgery. Int Angiol 1997; 16:65.
  43. Hollyoak M, Woodruff P, Muller M, et al. Deep venous thrombosis in postoperative vascular surgical patients: a frequent finding without prophylaxis. J Vasc Surg 2001; 34:656.
  44. Hamer JD. Investigation of oedema of the lower limb following successful femoropopliteal by-pass surgery: the role of phlebography in demonstrating venous thrombosis. Br J Surg 1972; 59:979.
  45. Myhre HO, Storen EJ, Ongre A. The incidence of deep venous thrombosis in patients with leg oedema after arterial reconstruction. Scand J Thorac Cardiovasc Surg 1974; 8:73.
  46. Proebstle TM, Herdemann S. Early results and feasibility of incompetent perforator vein ablation by endovenous laser treatment. Dermatol Surg 2007; 33:162.
  47. Puggioni A, Kalra M, Carmo M, et al. Endovenous laser therapy and radiofrequency ablation of the great saphenous vein: analysis of early efficacy and complications. J Vasc Surg 2005; 42:488.
  48. Marsh P, Price BA, Holdstock J, et al. Deep vein thrombosis (DVT) after venous thermoablation techniques: rates of endovenous heat-induced thrombosis (EHIT) and classical DVT after radiofrequency and endovenous laser ablation in a single centre. Eur J Vasc Endovasc Surg 2010; 40:521.
  49. Lawrence PF, Chandra A, Wu M, et al. Classification of proximal endovenous closure levels and treatment algorithm. J Vasc Surg 2010; 52:388.
  50. de Medeiros CA, Luccas GC. Comparison of endovenous treatment with an 810 nm laser versus conventional stripping of the great saphenous vein in patients with primary varicose veins. Dermatol Surg 2005; 31:1685.
  51. Desmyttère J, Grard C, Wassmer B, Mordon S. Endovenous 980-nm laser treatment of saphenous veins in a series of 500 patients. J Vasc Surg 2007; 46:1242.
  52. Kalteis M, Berger I, Messie-Werndl S, et al. High ligation combined with stripping and endovenous laser ablation of the great saphenous vein: early results of a randomized controlled study. J Vasc Surg 2008; 47:822.
  53. Nwaejike N, Srodon PD, Kyriakides C. 5-years of endovenous laser ablation (EVLA) for the treatment of varicose veins--a prospective study. Int J Surg 2009; 7:347.
  54. Mozes G, Kalra M, Carmo M, et al. Extension of saphenous thrombus into the femoral vein: a potential complication of new endovenous ablation techniques. J Vasc Surg 2005; 41:130.
  55. Merchant R Jr, Kistner RL, Kabnick LS. Is there an increased risk for DVT with the VNUS closure procedure? J Vasc Surg 2003; 38:628.
  56. Hingorani AP, Ascher E, Markevich N, et al. Deep venous thrombosis after radiofrequency ablation of greater saphenous vein: a word of caution. J Vasc Surg 2004; 40:500.
  57. Burke B, Kumar R, Vickers V, et al. Deep vein thrombosis after lower limb amputation. Am J Phys Med Rehabil 2000; 79:145.
  58. Harper DR, Dhall DP, Woodruff PW. Prophylaxis in iliofemoral venous thrombosis. The major amputee as a clinical research model. Br J Surg 1973; 60:831.
  59. Huang ME, Johns JS, White J, Sanford K. Venous thromboembolism in a rehabilitation setting after major lower-extremity amputation. Arch Phys Med Rehabil 2005; 86:73.
  60. Yeager RA, Moneta GL, Edwards JM, et al. Deep vein thrombosis associated with lower extremity amputation. J Vasc Surg 1995; 22:612.
  61. Matielo MF, Presti C, Casella IB, et al. Incidence of ipsilateral postoperative deep venous thrombosis in the amputated lower extremity of patients with peripheral obstructive arterial disease. J Vasc Surg 2008; 48:1514.
  62. Liao EC, Taghinia AH, Nguyen LP, et al. Incidence of hematoma complication with heparin venous thrombosis prophylaxis after TRAM flap breast reconstruction. Plast Reconstr Surg 2008; 121:1101.
  63. Hatef DA, Kenkel JM, Nguyen MQ, et al. Thromboembolic risk assessment and the efficacy of enoxaparin prophylaxis in excisional body contouring surgery. Plast Reconstr Surg 2008; 122:269.
  64. Kim EK, Eom JS, Ahn SH, et al. The efficacy of prophylactic low-molecular-weight heparin to prevent pulmonary thromboembolism in immediate breast reconstruction using the TRAM flap. Plast Reconstr Surg 2009; 123:9.
  65. Di Nisio M, Peinemann F, Porreca E, Rutjes AW. Primary prophylaxis for venous thromboembolism in patients undergoing cardiac or thoracic surgery. Cochrane Database Syst Rev 2015; :CD009658.
  66. Kulik A, Rassen JA, Myers J, et al. Comparative effectiveness of preventative therapy for venous thromboembolism after coronary artery bypass graft surgery. Circ Cardiovasc Interv 2012; 5:590.
  67. Kolluri R, Plessa AL, Sanders MC, et al. A randomized study of the safety and efficacy of fondaparinux versus placebo in the prevention of venous thromboembolism after coronary artery bypass graft surgery. Am Heart J 2016; 171:1.
  68. Viana VB, Melo ER, Terra-Filho M, et al. Frequency of Deep Vein Thrombosis and/or Pulmonary Embolism After Coronary Artery Bypass Grafting Investigation Regardless of Clinical Suspicion. Am J Cardiol 2017; 119:237.
  69. Goldhaber SZ, Hirsch DR, MacDougall RC, et al. Prevention of venous thrombosis after coronary artery bypass surgery (a randomized trial comparing two mechanical prophylaxis strategies). Am J Cardiol 1995; 76:993.
  70. Kalweit G, Huwer H, Volkmer I, et al. Pulmonary embolism: a frequent cause of acute fatality after lung resection. Eur J Cardiothorac Surg 1996; 10:242.
  71. Nagahiro I, Andou A, Aoe M, et al. Intermittent pneumatic compression is effective in preventing symptomatic pulmonary embolism after thoracic surgery. Surg Today 2004; 34:6.
  72. Gómez-Hernández MT, Rodríguez-Pérez M, Novoa-Valentín N, et al. Prevalence of venous thromboembolism in elective thoracic surgery. Arch Bronconeumol 2013; 49:297.
  73. Yoshioka K, Murakami H, Demura S, et al. Comparative study of the prevalence of venous thromboembolism after elective spinal surgery. Orthopedics 2013; 36:e223.
  74. Yoshioka K, Murakami H, Demura S, et al. Prevalence and risk factors for development of venous thromboembolism after degenerative spinal surgery. Spine (Phila Pa 1976) 2015; 40:E301.
  75. Gruber UF, Rem J, Meisner C, Gratzl O. Prevention of thromboembolic complications with miniheparin-dihydroergotamine in patients undergoing lumbar disc operations. Eur Arch Psychiatry Neurol Sci 1984; 234:157.
  76. Rokito SE, Schwartz MC, Neuwirth MG. Deep vein thrombosis after major reconstructive spinal surgery. Spine (Phila Pa 1976) 1996; 21:853.
  77. Nelson LD Jr, Montgomery SP, Dameron TB Jr, Nelson RB. Deep vein thrombosis in lumbar spinal fusion: a prospective study of antiembolic and pneumatic compression stockings. J South Orthop Assoc 1996; 5:181.
  78. Wood KB, Kos PB, Abnet JK, Ista C. Prevention of deep-vein thrombosis after major spinal surgery: a comparison study of external devices. J Spinal Disord 1997; 10:209.
  79. Fiasconaro M, Poeran J, Liu J, et al. Venous thromboembolism and prophylaxis therapy after elective spine surgery: a population-based study. Can J Anaesth 2021; 68:345.
  80. Geerts WH, Code KI, Jay RM, et al. A prospective study of venous thromboembolism after major trauma. N Engl J Med 1994; 331:1601.
  81. Jones T, Ugalde V, Franks P, et al. Venous thromboembolism after spinal cord injury: incidence, time course, and associated risk factors in 16,240 adults and children. Arch Phys Med Rehabil 2005; 86:2240.
  82. Chen D, Apple DF Jr, Hudson LM, Bode R. Medical complications during acute rehabilitation following spinal cord injury--current experience of the Model Systems. Arch Phys Med Rehabil 1999; 80:1397.
  83. Green D, Hartwig D, Chen D, et al. Spinal Cord Injury Risk Assessment for Thromboembolism (SPIRATE Study). Am J Phys Med Rehabil 2003; 82:950.
  84. Denson K, Morgan D, Cunningham R, et al. Incidence of venous thromboembolism in patients with traumatic brain injury. Am J Surg 2007; 193:380.
  85. Kim KS, Brophy GM. Symptomatic venous thromboembolism: incidence and risk factors in patients with spontaneous or traumatic intracranial hemorrhage. Neurocrit Care 2009; 11:28.
  86. Reiff DA, Haricharan RN, Bullington NM, et al. Traumatic brain injury is associated with the development of deep vein thrombosis independent of pharmacological prophylaxis. J Trauma 2009; 66:1436.
  87. Barrera LM, Perel P, Ker K, et al. Thromboprophylaxis for trauma patients. Cochrane Database Syst Rev 2013; :CD008303.
  88. Cipolle MD, Wojcik R, Seislove E, et al. The role of surveillance duplex scanning in preventing venous thromboembolism in trauma patients. J Trauma 2002; 52:453.
  89. Hemmila MR, Jakubus JL, Maggio PM, et al. Real money: complications and hospital costs in trauma patients. Surgery 2008; 144:307.
  90. Platzer P, Thalhammer G, Jaindl M, et al. Thromboembolic complications after spinal surgery in trauma patients. Acta Orthop 2006; 77:755.
  91. Caprini JA. Risk assessment as a guide for the prevention of the many faces of venous thromboembolism. Am J Surg 2010; 199:S3.
  92. Pannucci CJ, Laird S, Dimick JB, et al. A validated risk model to predict 90-day VTE events in postsurgical patients. Chest 2014; 145:567.
  93. Spyropoulos AC, McGinn T, Khorana AA. The use of weighted and scored risk assessment models for venous thromboembolism. Thromb Haemost 2012; 108:1072.
  94. Obi AT, Pannucci CJ, Nackashi A, et al. Validation of the Caprini Venous Thromboembolism Risk Assessment Model in Critically Ill Surgical Patients. JAMA Surg 2015; 150:941.
  95. Pannucci CJ, Bailey SH, Dreszer G, et al. Validation of the Caprini risk assessment model in plastic and reconstructive surgery patients. J Am Coll Surg 2011; 212:105.
  96. Schulman S, Kearon C, Subcommittee on Control of Anticoagulation of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis. Definition of major bleeding in clinical investigations of antihemostatic medicinal products in non-surgical patients. J Thromb Haemost 2005; 3:692.
  97. Leonardi MJ, McGory ML, Ko CY. The rate of bleeding complications after pharmacologic deep venous thrombosis prophylaxis: a systematic review of 33 randomized controlled trials. Arch Surg 2006; 141:790.
  98. Masoomi H, Paydar KZ, Wirth GA, et al. Predictive risk factors of venous thromboembolism in autologous breast reconstruction surgery. Ann Plast Surg 2014; 72:30.
  99. Liew NC, Alemany GV, Angchaisuksiri P, et al. Asian venous thromboembolism guidelines: updated recommendations for the prevention of venous thromboembolism. Int Angiol 2017; 36:1.
  100. Nicolaides AN, Fareed J, Kakkar AK, et al. Prevention and treatment of venous thromboembolism--International Consensus Statement. Int Angiol 2013; 32:111.
  101. Bang SM, Jang MJ, Kim KH, et al. Prevention of venous thromboembolism, 2nd edition: Korean Society of Thrombosis and Hemostasis Evidence-based Clinical Practice Guidelines. J Korean Med Sci 2014; 29:164.
  102. Chana-Rodríguez F, Mañanes RP, Rojo-Manaute J, et al. Methods and Guidelines for Venous Thromboembolism Prevention in Polytrauma Patients with Pelvic and Acetabular Fractures. Open Orthop J 2015; 9:313.
  103. Robson A, Sturman J, Williamson P, et al. Pre-treatment clinical assessment in head and neck cancer: United Kingdom National Multidisciplinary Guidelines. J Laryngol Otol 2016; 130:S13.
  104. Afshari A, Ageno W, Ahmed A, et al. European Guidelines on perioperative venous thromboembolism prophylaxis: Executive summary. Eur J Anaesthesiol 2018; 35:77.
  105. Prevention of fatal postoperative pulmonary embolism by low doses of heparin. An international multicentre trial. Lancet 1975; 2:45.
  106. Durinka JB, Hecht TE, Layne AJ, et al. Aggressive venous thromboembolism prophylaxis reduces VTE events in vascular surgery patients. Vascular 2016; 24:233.
  107. Kucher N, Koo S, Quiroz R, et al. Electronic alerts to prevent venous thromboembolism among hospitalized patients. N Engl J Med 2005; 352:969.
  108. Tooher R, Middleton P, Pham C, et al. A systematic review of strategies to improve prophylaxis for venous thromboembolism in hospitals. Ann Surg 2005; 241:397.
  109. Stinnett JM, Pendleton R, Skordos L, et al. Venous thromboembolism prophylaxis in medically ill patients and the development of strategies to improve prophylaxis rates. Am J Hematol 2005; 78:167.
  110. Yu HT, Dylan ML, Lin J, Dubois RW. Hospitals' compliance with prophylaxis guidelines for venous thromboembolism. Am J Health Syst Pharm 2007; 64:69.
  111. Piazza G, Rosenbaum EJ, Pendergast W, et al. Physician alerts to prevent symptomatic venous thromboembolism in hospitalized patients. Circulation 2009; 119:2196.
  112. Boddi M, Barbani F, Abbate R, et al. Reduction in deep vein thrombosis incidence in intensive care after a clinician education program. J Thromb Haemost 2010; 8:121.
  113. Baglin T. Defining the population in need of thromboprophylaxis - making hospitals safer. Br J Haematol 2010; 149:805.
  114. Sadeghi B, Romano PS, Maynard G, et al. Mechanical and suboptimal pharmacologic prophylaxis and delayed mobilization but not morbid obesity are associated with venous thromboembolism after total knee arthroplasty: a case-control study. J Hosp Med 2012; 7:665.
  115. Fang MC, Maselli J, Lurie JD, et al. Use and outcomes of venous thromboembolism prophylaxis after spinal fusion surgery. J Thromb Haemost 2011; 9:1318.
  116. Kakkos SK, Caprini JA, Geroulakos G, et al. Combined intermittent pneumatic leg compression and pharmacological prophylaxis for prevention of venous thromboembolism in high-risk patients. Cochrane Database Syst Rev 2008; :CD005258.
  117. Hull R, Delmore TJ, Hirsh J, et al. Effectiveness of intermittent pulsatile elastic stockings for the prevention of calf and thigh vein thrombosis in patients undergoing elective knee surgery. Thromb Res 1979; 16:37.
  118. Morris RJ, Woodcock JP. Intermittent pneumatic compression or graduated compression stockings for deep vein thrombosis prophylaxis? A systematic review of direct clinical comparisons. Ann Surg 2010; 251:393.
  119. Arabi YM, Khedr M, Dara SI, et al. Use of intermittent pneumatic compression and not graduated compression stockings is associated with lower incident VTE in critically ill patients: a multiple propensity scores adjusted analysis. Chest 2013; 144:152.
  120. Eppsteiner RW, Shin JJ, Johnson J, van Dam RM. Mechanical compression versus subcutaneous heparin therapy in postoperative and posttrauma patients: a systematic review and meta-analysis. World J Surg 2010; 34:10.
  121. Ho KM, Tan JA. Stratified meta-analysis of intermittent pneumatic compression of the lower limbs to prevent venous thromboembolism in hospitalized patients. Circulation 2013; 128:1003.
  122. Kakkos SK, Caprini JA, Geroulakos G, et al. Combined intermittent pneumatic leg compression and pharmacological prophylaxis for prevention of venous thromboembolism. Cochrane Database Syst Rev 2016; 9:CD005258.
  123. Vanek VW. Meta-analysis of effectiveness of intermittent pneumatic compression devices with a comparison of thigh-high to knee-high sleeves. Am Surg 1998; 64:1050.
  124. Roderick P, Ferris G, Wilson K, et al. Towards evidence-based guidelines for the prevention of venous thromboembolism: systematic reviews of mechanical methods, oral anticoagulation, dextran and regional anaesthesia as thromboprophylaxis. Health Technol Assess 2005; 9:iii.
  125. Urbankova J, Quiroz R, Kucher N, Goldhaber SZ. Intermittent pneumatic compression and deep vein thrombosis prevention. A meta-analysis in postoperative patients. Thromb Haemost 2005; 94:1181.
  126. Pour AE, Keshavarzi NR, Purtill JJ, et al. Is venous foot pump effective in prevention of thromboembolic disease after joint arthroplasty: a meta-analysis. J Arthroplasty 2013; 28:410.
  127. Corley GJ, Broderick BJ, Nestor SM, et al. The anatomy and physiology of the venous foot pump. Anat Rec (Hoboken) 2010; 293:370.
  128. Elpern E, Killeen K, Patel G, Senecal PA. The application of intermittent pneumatic compression devices for thromboprophylaxis: AN observational study found frequent errors in the application of these mechanical devices in ICUs. Am J Nurs 2013; 113:30.
  129. Spinal Cord Injury Thromboprophylaxis Investigators. Prevention of venous thromboembolism in the acute treatment phase after spinal cord injury: a randomized, multicenter trial comparing low-dose heparin plus intermittent pneumatic compression with enoxaparin. J Trauma 2003; 54:1116.
  130. Cornwell EE 3rd, Chang D, Velmahos G, et al. Compliance with sequential compression device prophylaxis in at-risk trauma patients: a prospective analysis. Am Surg 2002; 68:470.
  131. Clements RH, Yellumahanthi K, Ballem N, et al. Pharmacologic prophylaxis against venous thromboembolic complications is not mandatory for all laparoscopic Roux-en-Y gastric bypass procedures. J Am Coll Surg 2009; 208:917.
  132. Roberts VC, Sabri S, Beeley AH, Cotton LT. The effect of intermittently applied external pressure on the haemodynamics of the lower limb in man. Br J Surg 1972; 59:223.
  133. Comerota AJ, Chouhan V, Harada RN, et al. The fibrinolytic effects of intermittent pneumatic compression: mechanism of enhanced fibrinolysis. Ann Surg 1997; 226:306.
  134. Camporese G, Bernardi E, Prandoni P, et al. Low-molecular-weight heparin versus compression stockings for thromboprophylaxis after knee arthroscopy: a randomized trial. Ann Intern Med 2008; 149:73.
  135. Cohen AT, Skinner JA, Warwick D, Brenkel I. The use of graduated compression stockings in association with fondaparinux in surgery of the hip. A multicentre, multinational, randomised, open-label, parallel-group comparative study. J Bone Joint Surg Br 2007; 89:887.
  136. Sachdeva A, Dalton M, Amaragiri SV, Lees T. Elastic compression stockings for prevention of deep vein thrombosis. Cochrane Database Syst Rev 2010; :CD001484.
  137. Zareba P, Wu C, Agzarian J, et al. Meta-analysis of randomized trials comparing combined compression and anticoagulation with either modality alone for prevention of venous thromboembolism after surgery. Br J Surg 2014; 101:1053.
  138. Sachdeva A, Dalton M, Amaragiri SV, Lees T. Graduated compression stockings for prevention of deep vein thrombosis. Cochrane Database Syst Rev 2014; :CD001484.
  139. Sachdeva A, Dalton M, Lees T. Graduated compression stockings for prevention of deep vein thrombosis. Cochrane Database Syst Rev 2018; 11:CD001484.
  140. Ho KM, Bham E, Pavey W. Incidence of Venous Thromboembolism and Benefits and Risks of Thromboprophylaxis After Cardiac Surgery: A Systematic Review and Meta-Analysis. J Am Heart Assoc 2015; 4:e002652.
  141. Johanson NA, Lachiewicz PF, Lieberman JR, et al. American academy of orthopaedic surgeons clinical practice guideline on. Prevention of symptomatic pulmonary embolism in patients undergoing total hip or knee arthroplasty. J Bone Joint Surg Am 2009; 91:1756.
  142. Kwon S, Meissner M, Symons R, et al. Perioperative pharmacologic prophylaxis for venous thromboembolism in colorectal surgery. J Am Coll Surg 2011; 213:596.
  143. National Collaborating Center for Acute Care. Venous Thromboembolism: Reducing the Risk of Venous Thromboembolism (Deep Venous Thrombosis and Pulmonary Embolism) in Patients Admitted to Hospital. NICE, London, England, 2010.
  144. Clagett GP, Reisch JS. Prevention of venous thromboembolism in general surgical patients. Results of meta-analysis. Ann Surg 1988; 208:227.
  145. Bergqvist D. Low molecular weight heparin and unfractionated heparin in thrombosis prophylaxis after major surgical intervention: update of previous meta-analyses. Br J Surg 1998; 85:872.
  146. Leizorovicz A, Haugh MC, Chapuis FR, et al. Low molecular weight heparin in prevention of perioperative thrombosis. BMJ 1992; 305:913.
  147. Nurmohamed MT, Rosendaal FR, Büller HR, et al. Low-molecular-weight heparin versus standard heparin in general and orthopaedic surgery: a meta-analysis. Lancet 1992; 340:152.
  148. Kakkar VV, Cohen AT, Edmonson RA, et al. Low molecular weight versus standard heparin for prevention of venous thromboembolism after major abdominal surgery. The Thromboprophylaxis Collaborative Group. Lancet 1993; 341:259.
  149. Agnelli G, Bergqvist D, Cohen AT, et al. Randomized clinical trial of postoperative fondaparinux versus perioperative dalteparin for prevention of venous thromboembolism in high-risk abdominal surgery. Br J Surg 2005; 92:1212.
  150. Bergqvist D, Agnelli G, Cohen AT, et al. Duration of prophylaxis against venous thromboembolism with enoxaparin after surgery for cancer. N Engl J Med 2002; 346:975.
  151. Rasmussen MS. Preventing thromboembolic complications in cancer patients after surgery: a role for prolonged thromboprophylaxis. Cancer Treat Rev 2002; 28:141.
  152. Rasmussen MS, Jorgensen LN, Wille-Jørgensen P, et al. Prolonged prophylaxis with dalteparin to prevent late thromboembolic complications in patients undergoing major abdominal surgery: a multicenter randomized open-label study. J Thromb Haemost 2006; 4:2384.
  153. Akl EA, Terrenato I, Barba M, et al. Low-molecular-weight heparin vs unfractionated heparin for perioperative thromboprophylaxis in patients with cancer: a systematic review and meta-analysis. Arch Intern Med 2008; 168:1261.
  154. Efficacy and safety of enoxaparin versus unfractionated heparin for prevention of deep vein thrombosis in elective cancer surgery: a double-blind randomized multicentre trial with venographic assessment. ENOXACAN Study Group. Br J Surg 1997; 84:1099.
  155. Andtbacka RH, Babiera G, Singletary SE, et al. Incidence and prevention of venous thromboembolism in patients undergoing breast cancer surgery and treated according to clinical pathways. Ann Surg 2006; 243:96.
  156. McLeod RS, Geerts WH, Sniderman KW, et al. Subcutaneous heparin versus low-molecular-weight heparin as thromboprophylaxis in patients undergoing colorectal surgery: results of the canadian colorectal DVT prophylaxis trial: a randomized, double-blind trial. Ann Surg 2001; 233:438.
  157. Bush S, LeClaire A, Hampp C, Lottenberg L. Review of a large clinical series: once- versus twice-daily enoxaparin for venous thromboembolism prophylaxis in high-risk trauma patients. J Intensive Care Med 2011; 26:111.
  158. Jacobs BN, Cain-Nielsen AH, Jakubus JL, et al. Unfractionated heparin versus low-molecular-weight heparin for venous thromboembolism prophylaxis in trauma. J Trauma Acute Care Surg 2017; 83:151.
  159. Byrne JP, Geerts W, Mason SA, et al. Effectiveness of low-molecular-weight heparin versus unfractionated heparin to prevent pulmonary embolism following major trauma: A propensity-matched analysis. J Trauma Acute Care Surg 2017; 82:252.
  160. Agnelli G, Piovella F, Buoncristiani P, et al. Enoxaparin plus compression stockings compared with compression stockings alone in the prevention of venous thromboembolism after elective neurosurgery. N Engl J Med 1998; 339:80.
  161. Nurmohamed MT, van Riel AM, Henkens CM, et al. Low molecular weight heparin and compression stockings in the prevention of venous thromboembolism in neurosurgery. Thromb Haemost 1996; 75:233.
  162. Turpie AG, Bauer KA, Caprini JA, et al. Fondaparinux combined with intermittent pneumatic compression vs. intermittent pneumatic compression alone for prevention of venous thromboembolism after abdominal surgery: a randomized, double-blind comparison. J Thromb Haemost 2007; 5:1854.
  163. Amin AN, Girard F, Samama MM. Does ambulation modify venous thromboembolism risk in acutely ill medical patients? Thromb Haemost 2010; 104:955.
  164. Kakkar VV, Balibrea JL, Martínez-González J, et al. Extended prophylaxis with bemiparin for the prevention of venous thromboembolism after abdominal or pelvic surgery for cancer: the CANBESURE randomized study. J Thromb Haemost 2010; 8:1223.
  165. Lyman GH, Khorana AA, Kuderer NM, et al. Venous thromboembolism prophylaxis and treatment in patients with cancer: American Society of Clinical Oncology clinical practice guideline update. J Clin Oncol 2013; 31:2189.
  166. Streiff MB, Bockenstedt PL, Cataland SR, et al. Venous thromboembolic disease. J Natl Compr Canc Netw 2011; 9:714.
  167. Bottaro FJ, Elizondo MC, Doti C, et al. Efficacy of extended thrombo-prophylaxis in major abdominal surgery: what does the evidence show? A meta-analysis. Thromb Haemost 2008; 99:1104.
  168. Rausa E, Kelly ME, Asti E, et al. Extended versus conventional thromboprophylaxis after major abdominal and pelvic surgery: Systematic review and meta-analysis of randomized clinical trials. Surgery 2018; 164:1234.
  169. Felder S, Rasmussen MS, King R, et al. Prolonged thromboprophylaxis with low molecular weight heparin for abdominal or pelvic surgery. Cochrane Database Syst Rev 2019; 3:CD004318.
  170. Nutescu EA, Spinler SA, Wittkowsky A, Dager WE. Low-molecular-weight heparins in renal impairment and obesity: available evidence and clinical practice recommendations across medical and surgical settings. Ann Pharmacother 2009; 43:1064.
  171. Joy M, Tharp E, Hartman H, et al. Safety and Efficacy of High-Dose Unfractionated Heparin for Prevention of Venous Thromboembolism in Overweight and Obese Patients. Pharmacotherapy 2016; 36:740.
  172. Wang TF, Milligan PE, Wong CA, et al. Efficacy and safety of high-dose thromboprophylaxis in morbidly obese inpatients. Thromb Haemost 2014; 111:88.
  173. Samuel S, Iluonakhamhe EK, Adair E, et al. High dose subcutaneous unfractionated heparin for prevention of venous thromboembolism in overweight neurocritical care patients. J Thromb Thrombolysis 2015; 40:302.
  174. Kumar A, Talwar A, Farley JF, et al. Fondaparinux Sodium Compared With Low-Molecular-Weight Heparins for Perioperative Surgical Thromboprophylaxis: A Systematic Review and Meta-analysis. J Am Heart Assoc 2019; 8:e012184.
  175. Meyer CS, Blebea J, Davis K Jr, et al. Surveillance venous scans for deep venous thrombosis in multiple trauma patients. Ann Vasc Surg 1995; 9:109.
  176. Schellong SM, Beyer J, Kakkar AK, et al. Ultrasound screening for asymptomatic deep vein thrombosis after major orthopaedic surgery: the VENUS study. J Thromb Haemost 2007; 5:1431.
  177. Birkmeyer NJ, Share D, Baser O, et al. Preoperative placement of inferior vena cava filters and outcomes after gastric bypass surgery. Ann Surg 2010; 252:313.
  178. Girard TD, Philbrick JT, Fritz Angle J, Becker DM. Prophylactic vena cava filters for trauma patients: a systematic review of the literature. Thromb Res 2003; 112:261.
  179. Rajasekhar A, Lottenberg R, Lottenberg L, et al. Pulmonary embolism prophylaxis with inferior vena cava filters in trauma patients: a systematic review using the meta-analysis of observational studies in epidemiology (MOOSE) guidelines. J Thromb Thrombolysis 2011; 32:40.
  180. Hemmila MR, Osborne NH, Henke PK, et al. Prophylactic Inferior Vena Cava Filter Placement Does Not Result in a Survival Benefit for Trauma Patients. Ann Surg 2015; 262:577.
Topic 1339 Version 100.0

References

1 : Estimated annual numbers of US acute-care hospital patients at risk for venous thromboembolism.

2 : Validation of the Caprini risk assessment model for venous thromboembolism in high-risk surgical patients in the background of standard prophylaxis.

3 : Correlation of venous thromboembolism prophylaxis and electronic medical record alerts with incidence among surgical patients.

4 : Autopsy-verified pulmonary embolism in a surgical department: analysis of the period from 1951 to 1988.

5 : Prevalence of acute pulmonary embolism among patients in a general hospital and at autopsy.

6 : Incidence of symptomatic venous thromboembolism after different elective or urgent surgical procedures.

7 : Autopsy proven pulmonary embolism in hospital patients: are we detecting enough deep vein thrombosis?

8 : Pulmonary embolism after major abdominal surgery in gynecologic oncology.

9 : Prevention of VTE in orthopedic surgery patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

10 : American Society of Hematology 2019 guidelines for management of venous thromboembolism: prevention of venous thromboembolism in surgical hospitalized patients.

11 : Prevention of VTE in nonorthopedic surgical patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

12 : A validation study of a retrospective venous thromboembolism risk scoring method.

13 : Multivariable predictors of postoperative venous thromboembolic events after general and vascular surgery: results from the patient safety in surgery study.

14 : Venous thromboembolism in patients with colorectal cancer: incidence and effect on survival.

15 : Venous thromboembolism prophylaxis: patients at high risk to fail intermittent pneumatic compression.

16 : Venous thromboembolism prophylaxis: patients at high risk to fail intermittent pneumatic compression.

17 : Meta-analysis of low molecular weight heparin in the prevention of venous thromboembolism in general surgery.

18 : Prophylaxis of fatal pulmonary embolism in general surgery using low-molecular weight heparin Cy 216: a multicentre, double-blind, randomized, controlled, clinical trial versus placebo (STEP). STEP-Study Group.

19 : Effectiveness and safety of the low-molecular-weight heparin CY 216 in the prevention of fatal pulmonary embolism and thromboembolic death in general surgery. A multicentre, double-blind, randomized, controlled clinical trial versus placebo (STEP). STEP Study Group.

20 : Controlled clinical study of the efficacy of a new low molecular weight heparin administered subcutaneously to prevent post-operative deep venous thrombosis.

21 : Abstracts of the 12th International Congress on Thrombosis. Florence, May 18-23, 1992.

22 : Prevention of postoperative deep vein thrombosis in cancer patients. A randomized trial with low molecular weight heparin (CY 216).

23 : Thromboprophylaxis with a low molecular weight heparin (tinzaparin) in emergency abdominal surgery. A double-blind multicenter trial.

24 : Randomized, controlled trial of low molecular weight heparin vs. no deep vein thrombosis prophylaxis for major colon and rectal surgery in Asian patients.

25 : Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin. Overview of results of randomized trials in general, orthopedic, and urologic surgery.

26 : A comparison of low-dose heparin with low-molecular-weight heparin as prophylaxis against venous thromboembolism after major trauma.

27 : Extended perioperative thromboprophylaxis in patients with cancer. A systematic review.

28 : Prevention of venous thromboembolism in neurosurgery: a metaanalysis.

29 : Low-molecular-weight and unfractionated heparin for prevention of venous thromboembolism in neurosurgery: a meta-analysis.

30 : Risk of venous thromboembolism and efficacy of thromboprophylaxis in hospitalized obese medical patients and in obese patients undergoing bariatric surgery.

31 : Enoxaparin venous thromboembolism prophylaxis in bariatric surgery: A best evidence topic.

32 : Perioperative complications increase the risk of venous thromboembolism following bariatric surgery.

33 : A randomised controlled trial of a low-molecular-weight heparin (Enoxaparin) to prevent deep-vein thrombosis in patients undergoing vascular surgery.

34 : Prevention of deep venous thrombosis and thrombo-embolism by dipyridamole and acetylsalicylic acid after reconstructive arterial surgery.

35 : Low molecular weight heparin prevention of post-operative deep vein thrombosis in vascular surgery.

36 : Prophylaxis of deep-vein thrombosis after lower extremity amputation: comparison of low molecular weight heparin with unfractionated heparin.

37 : High incidence of venous thrombosis after surgery for abdominal aortic aneurysm.

38 : A novel scoring system for predicting postoperative venous thromboembolic complications in patients after open aortic surgery.

39 : Mid-term results after endovascular repair of the abdominal aortic aneurysm.

40 : Endovascular treatment of abdominal aortic aneurysm is associated with a low incidence of deep venous thrombosis.

41 : Edema after femoropopliteal bypass surgery: lymphatic and venous theories of causation.

42 : Incidence of deep vein thrombosis following vascular surgery.

43 : Deep venous thrombosis in postoperative vascular surgical patients: a frequent finding without prophylaxis.

44 : Investigation of oedema of the lower limb following successful femoropopliteal by-pass surgery: the role of phlebography in demonstrating venous thrombosis.

45 : The incidence of deep venous thrombosis in patients with leg oedema after arterial reconstruction.

46 : Early results and feasibility of incompetent perforator vein ablation by endovenous laser treatment.

47 : Endovenous laser therapy and radiofrequency ablation of the great saphenous vein: analysis of early efficacy and complications.

48 : Deep vein thrombosis (DVT) after venous thermoablation techniques: rates of endovenous heat-induced thrombosis (EHIT) and classical DVT after radiofrequency and endovenous laser ablation in a single centre.

49 : Classification of proximal endovenous closure levels and treatment algorithm.

50 : Comparison of endovenous treatment with an 810 nm laser versus conventional stripping of the great saphenous vein in patients with primary varicose veins.

51 : Endovenous 980-nm laser treatment of saphenous veins in a series of 500 patients.

52 : High ligation combined with stripping and endovenous laser ablation of the great saphenous vein: early results of a randomized controlled study.

53 : 5-years of endovenous laser ablation (EVLA) for the treatment of varicose veins--a prospective study.

54 : Extension of saphenous thrombus into the femoral vein: a potential complication of new endovenous ablation techniques.

55 : Is there an increased risk for DVT with the VNUS closure procedure?

56 : Deep venous thrombosis after radiofrequency ablation of greater saphenous vein: a word of caution.

57 : Deep vein thrombosis after lower limb amputation.

58 : Prophylaxis in iliofemoral venous thrombosis. The major amputee as a clinical research model.

59 : Venous thromboembolism in a rehabilitation setting after major lower-extremity amputation.

60 : Deep vein thrombosis associated with lower extremity amputation.

61 : Incidence of ipsilateral postoperative deep venous thrombosis in the amputated lower extremity of patients with peripheral obstructive arterial disease.

62 : Incidence of hematoma complication with heparin venous thrombosis prophylaxis after TRAM flap breast reconstruction.

63 : Thromboembolic risk assessment and the efficacy of enoxaparin prophylaxis in excisional body contouring surgery.

64 : The efficacy of prophylactic low-molecular-weight heparin to prevent pulmonary thromboembolism in immediate breast reconstruction using the TRAM flap.

65 : Primary prophylaxis for venous thromboembolism in patients undergoing cardiac or thoracic surgery.

66 : Comparative effectiveness of preventative therapy for venous thromboembolism after coronary artery bypass graft surgery.

67 : A randomized study of the safety and efficacy of fondaparinux versus placebo in the prevention of venous thromboembolism after coronary artery bypass graft surgery.

68 : Frequency of Deep Vein Thrombosis and/or Pulmonary Embolism After Coronary Artery Bypass Grafting Investigation Regardless of Clinical Suspicion.

69 : Prevention of venous thrombosis after coronary artery bypass surgery (a randomized trial comparing two mechanical prophylaxis strategies).

70 : Pulmonary embolism: a frequent cause of acute fatality after lung resection.

71 : Intermittent pneumatic compression is effective in preventing symptomatic pulmonary embolism after thoracic surgery.

72 : Prevalence of venous thromboembolism in elective thoracic surgery.

73 : Comparative study of the prevalence of venous thromboembolism after elective spinal surgery.

74 : Prevalence and risk factors for development of venous thromboembolism after degenerative spinal surgery.

75 : Prevention of thromboembolic complications with miniheparin-dihydroergotamine in patients undergoing lumbar disc operations.

76 : Deep vein thrombosis after major reconstructive spinal surgery.

77 : Deep vein thrombosis in lumbar spinal fusion: a prospective study of antiembolic and pneumatic compression stockings.

78 : Prevention of deep-vein thrombosis after major spinal surgery: a comparison study of external devices.

79 : Venous thromboembolism and prophylaxis therapy after elective spine surgery: a population-based study.

80 : A prospective study of venous thromboembolism after major trauma.

81 : Venous thromboembolism after spinal cord injury: incidence, time course, and associated risk factors in 16,240 adults and children.

82 : Medical complications during acute rehabilitation following spinal cord injury--current experience of the Model Systems.

83 : Spinal Cord Injury Risk Assessment for Thromboembolism (SPIRATE Study).

84 : Incidence of venous thromboembolism in patients with traumatic brain injury.

85 : Symptomatic venous thromboembolism: incidence and risk factors in patients with spontaneous or traumatic intracranial hemorrhage.

86 : Traumatic brain injury is associated with the development of deep vein thrombosis independent of pharmacological prophylaxis.

87 : Thromboprophylaxis for trauma patients.

88 : The role of surveillance duplex scanning in preventing venous thromboembolism in trauma patients.

89 : Real money: complications and hospital costs in trauma patients.

90 : Thromboembolic complications after spinal surgery in trauma patients.

91 : Risk assessment as a guide for the prevention of the many faces of venous thromboembolism.

92 : A validated risk model to predict 90-day VTE events in postsurgical patients.

93 : The use of weighted and scored risk assessment models for venous thromboembolism.

94 : Validation of the Caprini Venous Thromboembolism Risk Assessment Model in Critically Ill Surgical Patients.

95 : Validation of the Caprini risk assessment model in plastic and reconstructive surgery patients.

96 : Definition of major bleeding in clinical investigations of antihemostatic medicinal products in non-surgical patients.

97 : The rate of bleeding complications after pharmacologic deep venous thrombosis prophylaxis: a systematic review of 33 randomized controlled trials.

98 : Predictive risk factors of venous thromboembolism in autologous breast reconstruction surgery.

99 : Asian venous thromboembolism guidelines: updated recommendations for the prevention of venous thromboembolism.

100 : Prevention and treatment of venous thromboembolism--International Consensus Statement.

101 : Prevention of venous thromboembolism, 2nd edition: Korean Society of Thrombosis and Hemostasis Evidence-based Clinical Practice Guidelines.

102 : Methods and Guidelines for Venous Thromboembolism Prevention in Polytrauma Patients with Pelvic and Acetabular Fractures.

103 : Pre-treatment clinical assessment in head and neck cancer: United Kingdom National Multidisciplinary Guidelines.

104 : European Guidelines on perioperative venous thromboembolism prophylaxis: Executive summary.

105 : Prevention of fatal postoperative pulmonary embolism by low doses of heparin. An international multicentre trial.

106 : Aggressive venous thromboembolism prophylaxis reduces VTE events in vascular surgery patients.

107 : Electronic alerts to prevent venous thromboembolism among hospitalized patients.

108 : A systematic review of strategies to improve prophylaxis for venous thromboembolism in hospitals.

109 : Venous thromboembolism prophylaxis in medically ill patients and the development of strategies to improve prophylaxis rates.

110 : Hospitals' compliance with prophylaxis guidelines for venous thromboembolism.

111 : Physician alerts to prevent symptomatic venous thromboembolism in hospitalized patients.

112 : Reduction in deep vein thrombosis incidence in intensive care after a clinician education program.

113 : Defining the population in need of thromboprophylaxis - making hospitals safer.

114 : Mechanical and suboptimal pharmacologic prophylaxis and delayed mobilization but not morbid obesity are associated with venous thromboembolism after total knee arthroplasty: a case-control study.

115 : Use and outcomes of venous thromboembolism prophylaxis after spinal fusion surgery.

116 : Combined intermittent pneumatic leg compression and pharmacological prophylaxis for prevention of venous thromboembolism in high-risk patients.

117 : Effectiveness of intermittent pulsatile elastic stockings for the prevention of calf and thigh vein thrombosis in patients undergoing elective knee surgery.

118 : Intermittent pneumatic compression or graduated compression stockings for deep vein thrombosis prophylaxis? A systematic review of direct clinical comparisons.

119 : Use of intermittent pneumatic compression and not graduated compression stockings is associated with lower incident VTE in critically ill patients: a multiple propensity scores adjusted analysis.

120 : Mechanical compression versus subcutaneous heparin therapy in postoperative and posttrauma patients: a systematic review and meta-analysis.

121 : Stratified meta-analysis of intermittent pneumatic compression of the lower limbs to prevent venous thromboembolism in hospitalized patients.

122 : Combined intermittent pneumatic leg compression and pharmacological prophylaxis for prevention of venous thromboembolism.

123 : Meta-analysis of effectiveness of intermittent pneumatic compression devices with a comparison of thigh-high to knee-high sleeves.

124 : Towards evidence-based guidelines for the prevention of venous thromboembolism: systematic reviews of mechanical methods, oral anticoagulation, dextran and regional anaesthesia as thromboprophylaxis.

125 : Intermittent pneumatic compression and deep vein thrombosis prevention. A meta-analysis in postoperative patients.

126 : Is venous foot pump effective in prevention of thromboembolic disease after joint arthroplasty: a meta-analysis.

127 : The anatomy and physiology of the venous foot pump.

128 : The application of intermittent pneumatic compression devices for thromboprophylaxis: AN observational study found frequent errors in the application of these mechanical devices in ICUs.

129 : Prevention of venous thromboembolism in the acute treatment phase after spinal cord injury: a randomized, multicenter trial comparing low-dose heparin plus intermittent pneumatic compression with enoxaparin.

130 : Compliance with sequential compression device prophylaxis in at-risk trauma patients: a prospective analysis.

131 : Pharmacologic prophylaxis against venous thromboembolic complications is not mandatory for all laparoscopic Roux-en-Y gastric bypass procedures.

132 : The effect of intermittently applied external pressure on the haemodynamics of the lower limb in man.

133 : The fibrinolytic effects of intermittent pneumatic compression: mechanism of enhanced fibrinolysis.

134 : Low-molecular-weight heparin versus compression stockings for thromboprophylaxis after knee arthroscopy: a randomized trial.

135 : The use of graduated compression stockings in association with fondaparinux in surgery of the hip. A multicentre, multinational, randomised, open-label, parallel-group comparative study.

136 : Elastic compression stockings for prevention of deep vein thrombosis.

137 : Meta-analysis of randomized trials comparing combined compression and anticoagulation with either modality alone for prevention of venous thromboembolism after surgery.

138 : Graduated compression stockings for prevention of deep vein thrombosis.

139 : Graduated compression stockings for prevention of deep vein thrombosis.

140 : Incidence of Venous Thromboembolism and Benefits and Risks of Thromboprophylaxis After Cardiac Surgery: A Systematic Review and Meta-Analysis.

141 : American academy of orthopaedic surgeons clinical practice guideline on. Prevention of symptomatic pulmonary embolism in patients undergoing total hip or knee arthroplasty.

142 : Perioperative pharmacologic prophylaxis for venous thromboembolism in colorectal surgery.

143 : Perioperative pharmacologic prophylaxis for venous thromboembolism in colorectal surgery.

144 : Prevention of venous thromboembolism in general surgical patients. Results of meta-analysis.

145 : Low molecular weight heparin and unfractionated heparin in thrombosis prophylaxis after major surgical intervention: update of previous meta-analyses.

146 : Low molecular weight heparin in prevention of perioperative thrombosis.

147 : Low-molecular-weight heparin versus standard heparin in general and orthopaedic surgery: a meta-analysis.

148 : Low molecular weight versus standard heparin for prevention of venous thromboembolism after major abdominal surgery. The Thromboprophylaxis Collaborative Group.

149 : Randomized clinical trial of postoperative fondaparinux versus perioperative dalteparin for prevention of venous thromboembolism in high-risk abdominal surgery.

150 : Duration of prophylaxis against venous thromboembolism with enoxaparin after surgery for cancer.

151 : Preventing thromboembolic complications in cancer patients after surgery: a role for prolonged thromboprophylaxis.

152 : Prolonged prophylaxis with dalteparin to prevent late thromboembolic complications in patients undergoing major abdominal surgery: a multicenter randomized open-label study.

153 : Low-molecular-weight heparin vs unfractionated heparin for perioperative thromboprophylaxis in patients with cancer: a systematic review and meta-analysis.

154 : Efficacy and safety of enoxaparin versus unfractionated heparin for prevention of deep vein thrombosis in elective cancer surgery: a double-blind randomized multicentre trial with venographic assessment. ENOXACAN Study Group.

155 : Incidence and prevention of venous thromboembolism in patients undergoing breast cancer surgery and treated according to clinical pathways.

156 : Subcutaneous heparin versus low-molecular-weight heparin as thromboprophylaxis in patients undergoing colorectal surgery: results of the canadian colorectal DVT prophylaxis trial: a randomized, double-blind trial.

157 : Review of a large clinical series: once- versus twice-daily enoxaparin for venous thromboembolism prophylaxis in high-risk trauma patients.

158 : Unfractionated heparin versus low-molecular-weight heparin for venous thromboembolism prophylaxis in trauma.

159 : Effectiveness of low-molecular-weight heparin versus unfractionated heparin to prevent pulmonary embolism following major trauma: A propensity-matched analysis.

160 : Enoxaparin plus compression stockings compared with compression stockings alone in the prevention of venous thromboembolism after elective neurosurgery.

161 : Low molecular weight heparin and compression stockings in the prevention of venous thromboembolism in neurosurgery.

162 : Fondaparinux combined with intermittent pneumatic compression vs. intermittent pneumatic compression alone for prevention of venous thromboembolism after abdominal surgery: a randomized, double-blind comparison.

163 : Does ambulation modify venous thromboembolism risk in acutely ill medical patients?

164 : Extended prophylaxis with bemiparin for the prevention of venous thromboembolism after abdominal or pelvic surgery for cancer: the CANBESURE randomized study.

165 : Venous thromboembolism prophylaxis and treatment in patients with cancer: American Society of Clinical Oncology clinical practice guideline update.

166 : Venous thromboembolic disease.

167 : Efficacy of extended thrombo-prophylaxis in major abdominal surgery: what does the evidence show? A meta-analysis.

168 : Extended versus conventional thromboprophylaxis after major abdominal and pelvic surgery: Systematic review and meta-analysis of randomized clinical trials.

169 : Prolonged thromboprophylaxis with low molecular weight heparin for abdominal or pelvic surgery.

170 : Low-molecular-weight heparins in renal impairment and obesity: available evidence and clinical practice recommendations across medical and surgical settings.

171 : Safety and Efficacy of High-Dose Unfractionated Heparin for Prevention of Venous Thromboembolism in Overweight and Obese Patients.

172 : Efficacy and safety of high-dose thromboprophylaxis in morbidly obese inpatients.

173 : High dose subcutaneous unfractionated heparin for prevention of venous thromboembolism in overweight neurocritical care patients.

174 : Fondaparinux Sodium Compared With Low-Molecular-Weight Heparins for Perioperative Surgical Thromboprophylaxis: A Systematic Review and Meta-analysis.

175 : Surveillance venous scans for deep venous thrombosis in multiple trauma patients.

176 : Ultrasound screening for asymptomatic deep vein thrombosis after major orthopaedic surgery: the VENUS study.

177 : Preoperative placement of inferior vena cava filters and outcomes after gastric bypass surgery.

178 : Prophylactic vena cava filters for trauma patients: a systematic review of the literature.

179 : Pulmonary embolism prophylaxis with inferior vena cava filters in trauma patients: a systematic review using the meta-analysis of observational studies in epidemiology (MOOSE) guidelines.

180 : Prophylactic Inferior Vena Cava Filter Placement Does Not Result in a Survival Benefit for Trauma Patients.