Anesthesia for patients with diabetes mellitus and/ or hyperglycemia

INTRODUCTION — Diabetes is the most common endocrine disease, affecting 1 in 10 adults and found to be the seventh leading cause of death in the United States in 2015 [1]. When patients with diabetes require anesthesia, associated comorbidities such as cardiovascular disease, obesity, hypertension, neuropathy and nephropathy can complicate perioperative care. This topic will discuss the preoperative assessment and anesthetic considerations for patients with diabetes.

Perioperative blood glucose management in adults with diabetes is discussed separately. (See "Perioperative management of blood glucose in adults with diabetes mellitus" and "Overview of general medical care in nonpregnant adults with diabetes mellitus".)

Perioperative blood glucose management in children is also discussed separately. (See "Management of type 1 diabetes mellitus in children during illness, procedures, school, or travel", section on 'Medical procedures'.)

PREANESTHESIA EVALUATION — The preanesthesia evaluation of patients with diabetes mellitus should include a diabetes history, as well as assessment of the multiorgan system effects of diabetes that affect anesthetic care and perioperative risk.

Diabetes history — Components of the diabetes history that should be addressed during preanesthesia evaluation include the following:

Type 1 versus type 2 diabetes — The type of diabetes should be determined, since patients with type 1 diabetes are at much higher risk of diabetic ketoacidosis and must receive basal insulin at all times. Patients with type 2 diabetes are susceptible to developing hyperosmolar hyperglycemic state (also known as nonketotic hyperosmolar state) that may lead to severe volume depletion and neurologic complications, and they may develop ketoacidosis in the setting of extreme stress. (See "Diabetic ketoacidosis and hyperosmolar hyperglycemic state in adults: Clinical features, evaluation, and diagnosis".)

Level of blood glucose control — The level of blood glucose control should be assessed preoperatively, including average and range of blood glucose levels, glycated hemoglobin (A1C) levels, and the frequency of patient monitoring. (See 'Laboratory evaluation' below and 'Glycemic targets' below.)

Patients should be asked if they experience episodes of hypoglycemia, how often and at what blood glucose level it occurs, its severity, and if they are aware of being hypoglycemic. This information would be helpful when deciding whether to reduce insulin doses preoperatively and can help determine appropriate perioperative blood glucose targets.

Retrospective studies have reported an association between elevated A1C levels and adverse infectious and cardiovascular outcomes after cardiac and noncardiac surgery [2-7]. Retrospective data also suggest that preoperative hyperglycemia may be harmful in the perioperative setting [8-12].

Different societal guidelines recommend various A1C thresholds for delaying elective surgery. The American Diabetes Association does not make specific recommendations for this scenario [13], whereas the Australian Diabetes Association guidelines recommend delaying surgery for A1C ≥9 percent [14], and the Association of Anaesthetists of Great Britain and Ireland recommends delay of elective surgery for a preoperative A1C ≥8.5 percent [15]. The Joint British Societies guidelines recommend referral to a specialist for evaluation if preoperative A1C is ≥8.5 percent, but state that the decision to delay surgery must be individualized. The 2022 European Society of Cardiology guidelines on cardiovascular assessment and management of patients undergoing non-cardiac surgery recommends postponing elective non-cardiac surgery for A1C >8.5 percent, if safe and practical [16]. However, this recommendation is not supported by evidence as there are no reliable data to suggest that achieving and maintaining a specific A1C, fasting blood glucose level, or preoperative blood glucose level in the preoperative period will improve postoperative outcomes [17].

●When patients are evaluated days to weeks in advance of elective surgery and present with a preoperative fasting blood glucose >200 mg/dL or A1C >9, we consult with the clinician who manages the patient's diabetes and request a re-evaluation aimed at improving control of blood glucose prior to surgery, if feasible. The goal for preoperative management in this setting is to avoid severe perioperative hyperglycemia or hypoglycemia, and to provide an opportunity to improve the patient's overall diabetes management. In patients who do not have a diagnosis of diabetes and are found to be hyperglycemic on preoperative testing, the A1C level can help separate patients with previously undiagnosed diabetes from nondiabetic patients with stress-induced hyperglycemia or prediabetes [18].

However, we proceed with the scheduled surgery in patients with diagnosed or undiagnosed diabetes. We take this approach because, as stated above, an optimal A1C that would improve surgical outcomes has not been identified, and also because lowering A1C before surgery is not easily achievable nor practical, as it could take up to three years to achieve the desired concentration [19].

●When patients present to the preoperative area immediately before surgery with poor preoperative glycemic control, we individualize the decision to delay surgery based on the patient's overall physical status and urgency of surgery. We assess for the presence of ketoacidosis or hyperosmolar hyperglycemic non-ketotic (HHNK) state. If either exist, nonemergency surgery should be postponed, and patients admitted for appropriate treatment. (See "Diabetic ketoacidosis and hyperosmolar hyperglycemic state in adults: Treatment".)

For patients without ketoacidosis or HHNK, or for urgent surgery, we initiate treatment of hyperglycemia with insulin (usually, intravenous insulin infusion and boluses for severe hyperglycemia), fluids and electrolytes' (K) monitoring as indicated, and proceed with the planned surgery. Hyperglycemia management is continued throughout surgery, with a postoperative consult to the endocrinology service in certain cases, to ensure optimal management.

Medication regimen — Assessment of the patient's medication regimen is part of every preanesthesia evaluation. For diabetic patients, insulin type, dose and timing, and oral diabetes medications must be determined to allow for appropriate preoperative management. Outpatient management of blood glucose in patients with type 1 and type 2 diabetes, including choice of oral agents and choice of insulin type and delivery are discussed separately. (See "Management of blood glucose in adults with type 1 diabetes mellitus" and "Initial management of hyperglycemia in adults with type 2 diabetes mellitus".)

Perioperative management of diabetes medications is also discussed in detail separately. (See "Perioperative management of blood glucose in adults with diabetes mellitus".)

Glucagon-like peptide-1 (GLP-1) agonists are increasingly used for the management of diabetes and weight loss. These medications can have gastrointestinal adverse effects including nausea, vomiting, bloating and abdominal pain. One of the mechanisms of action of this class of medications is delayed gastric emptying which could potentially increase the risk of regurgitation and aspiration of gastric contents during general anesthesia despite proper preoperative fasting [20]. The American Society of Anesthesiologists (ASA) task force on preoperative fasting has put forth consensus based guidance on the preoperative management of patients on GLP-1 receptor agonists [21]. Their recommendations, regardless of the indication for receiving this class of medications, are as follows:

●For patients on daily dosing – Hold medication on the day of surgery

●For patients on weekly dosing – Hold medication a week prior to surgery

●For patients with gastrointestinal symptoms (severe nausea/vomiting/retching/abdominal pain) – Consider delaying elective procedures

●For patients without gastrointestinal symptoms who did not hold the GLP-1 agonist as recommended – Proceed with "full stomach" precautions (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Patients taking GLP-1 receptor agonists'.)

Hyperglycemia without the diagnosis of diabetes — Patients with hyperglycemia without a known diagnosis of diabetes may be at greater risk for perioperative morbidity and mortality than patients with known diabetes. Patients with hyperglycemia without known diabetes present for surgery with varying degrees of hyperglycemia, and may have microvascular and macrovascular complications that have not been optimized. We approach preoperative blood glucose control in these patients similarly to patients with diabetes, as discussed above. (See 'Level of blood glucose control' above.)

Undiagnosed diabetes is common; the Centers for Disease Control and Prevention in the United States estimated that approximately 23.8 percent of the patients with diabetes in the United States in 2015 were undiagnosed [1]. Worldwide, the incidence of undiagnosed diabetes may be higher. A 2014 global review of data across 74 countries estimated that a little less than one-half of all the patients who have diabetes were undiagnosed [22]. In a retrospective single center review of approximately 40,000 patients who underwent noncardiac surgery, 10 percent had suspected diabetes (ie, preoperative fasting blood glucose >126 mg/dL), and those patients had significantly higher preoperative glucose levels than patients with known diabetes [23].

Several studies have found that adverse events are more common in patients with hyperglycemia without known diabetes than in patients with diabetes [8,24,25]. In a retrospective review of approximately 7300 cardiac surgical patients, patients with preoperative hyperglycemia (ie, fasting blood glucose >126 mg/dL without a diagnosis of diabetes), were at increased risks of prolonged mechanical ventilation, reintubation, the need for resuscitation, and mortality, compared with known diabetic patients and with patients without preoperative hyperglycemia [24]. Similarly, a single center retrospective review of approximately 61,500 noncardiac surgery patients found that preoperative hyperglycemia without a diagnosis of diabetes was associated with higher one-year-mortality than the same level of hyperglycemia in diabetic patients [8]. Studies of patients in intensive care [26], and of patients undergoing coronary bypass surgery [27] have reported that nondiabetic patients with hyperglycemia benefited more from tight control of blood glucose than diabetic patients.

Laboratory evaluation — Preoperative testing should be performed selectively, based on the patient's medical status, the planned procedure, and the likelihood that test results will change management or help with risk assessment (table 1). For patients with diabetes who undergo moderate- or high-risk surgery, we order an A1C if not performed in the past three months and renal function tests. (See "Perioperative management of blood glucose in adults with diabetes mellitus", section on 'Laboratory'.)

Many patients with diabetes have comorbidities that require further preoperative testing (eg, electrocardiogram [ECG]) in anticipation of moderate- or high-risk surgery. We order preoperative ECGs in all patients with long standing diabetes who undergo moderate- or high-risk surgery. Preoperative testing, including cardiac testing, is discussed in more depth separately. (See "Preoperative evaluation for anesthesia for noncardiac surgery", section on 'Preoperative testing' and "Evaluation of cardiac risk prior to noncardiac surgery".)

MULTIORGAN SYSTEM EFFECTS OF DIABETES — Diabetes is a multiorgan disease associated with multiple conditions that may affect anesthetic care and perioperative risk. Diabetes is a risk factor for macrovascular disease (ie, coronary heart disease [CHD], cerebrovascular disease [CVD], and peripheral vascular disease) and microvascular disease (ie, retinopathy, nephropathy, neuropathy). Organ system effects of diabetes that are of particular importance for anesthesia and perioperative care are discussed here.

Coronary heart disease — Type 2 diabetes is an independent risk factor for CHD, with an overall risk of CHD and cardiac death twice that of patients without diabetes. (See "Prevalence of and risk factors for coronary heart disease in patients with diabetes mellitus".)

Diabetic patients are at increased risk of atherosclerosis due to the frequent presence of risk factors other than diabetes itself (ie, hypertension, hyperlipidemia, obesity, and uncontrolled hyperglycemia) [28,29]. Furthermore, diabetic patients with CHD are more likely to be asymptomatic or have atypical symptoms than nondiabetic patients with CHD. Patients with diabetes are also at increased risk of heart failure, poor perioperative cardiac outcomes, and death compared with nondiabetic patients [30,31].

Diabetes or insulin dependence is a risk factor in a number of the commonly used tools for assessment of cardiac risk prior to noncardiac surgery (eg, the Revised Cardiac Risk Index [RCRI], the Vascular Study Group of New England [VSGNE] risk index, the American College of Surgeons National Surgical Quality Improvement Program [NSQIP] calculator). Preoperative assessment of cardiac risk and anesthesia for patients with ischemic heart disease are discussed in detail separately. (See "Evaluation of cardiac risk prior to noncardiac surgery" and "Anesthesia for noncardiac surgery in patients with ischemic heart disease".)

Cerebrovascular disease — CVD is an important cause of mortality and morbidity in patients with diabetes mellitus. Diabetes is an independent major risk factor for stroke; diabetic patients have approximately twice the risk of ischemic stroke compared with patients without diabetes. Comorbidities associated with diabetes (eg, hypertension, dyslipidemia, obesity) may also increase the risk for CVD and stroke. Risk factors for ischemic stroke in the general population and the risk factors and strategies for risk reduction for perioperative stroke are discussed separately. (See "Overview of secondary prevention of ischemic stroke" and "Perioperative stroke following noncardiac, noncarotid, and nonneurologic surgery".)

Peripheral vascular disease — Diabetes and associated comorbidities are risk factors for peripheral vascular disease. Epidemiology, risk factors for peripheral artery disease in diabetic patients, and anesthetic management for lower extremity revascularization are discussed separately. (See "Overview of peripheral artery disease in patients with diabetes mellitus" and "Anesthesia for infrainguinal revascularization".)

Diabetic neuropathy — Neuropathy is probably the most common complication of diabetes, and occurs in both type 1 and type 2 diabetes. Approximately 50 percent of patients with diabetes will eventually develop neuropathy, and most patients with type 2 diabetes have abnormal nerve conduction, with or without clinical manifestations (see "Epidemiology and classification of diabetic neuropathy", section on 'Epidemiology'). Diabetic neuropathy may have implications for perioperative management, including cardiovascular instability, delayed gastric emptying, risks of injury related to positioning for surgery, and increased sensitivity to local anesthetics (LAs).

Diabetic neuropathy is classified into distinct clinical syndromes, including distal symmetric polyneuropathy (most common), autonomic neuropathy, polyradiculopathy, focal mononeuropathies, and mononeuropathy multiplex (see "Epidemiology and classification of diabetic neuropathy", section on 'Classification'). These syndromes, including the pathogenesis, are discussed in detail separately (see "Pathogenesis of diabetic polyneuropathy"). The anesthetic implications of several of them are discussed here.

Diabetic peripheral neuropathy — Distal symmetric polyneuropathy is often considered synonymous with diabetic neuropathy. Whether symmetric or not, peripheral neuropathies are often characterized by progressive loss of sensation, classically in a stocking-glove distribution, which can result in tissue ulceration and ultimately limb amputation.

Diabetic neuropathy may also cause neuropathic pain; treatment may include medications (eg, antidepressants or anticonvulsants) that can interact with other drugs used for anesthesia. (See "Management of diabetic neuropathy", section on 'Pain management'.)

Implications for regional anesthesia — The nerve abnormalities that accompany diabetic neuropathy may have implications for regional anesthesia (ie, peripheral nerve blocks and neuraxial block).

●Increased nerve stimulation threshold – Ultrasound guidance is preferred for most peripheral nerve blocks, rather than nerve stimulator guidance, and this may be particularly important for patients with diabetic neuropathy. The nerve electrical stimulation threshold is markedly increased in patients with diabetic neuropathy, and varies widely [32-34]. Thus, the safe stimulation threshold for stimulator guided peripheral nerve block may be unpredictable in patients with neuropathy, and the risk for nerve injury may be increased. (See "Overview of peripheral nerve blocks", section on 'Nerve stimulator guidance'.)

●Increased sensitivity to local anesthetics – Sensitivity of nerves to LA may be increased in patients with diabetes. Thus, diabetic patients may be at increased risk of nerve damage with regional anesthesia, and duration of peripheral nerve block may be prolonged.

•The incidence of nerve damage after regional anesthesia in patients with diabetes, with or without evidence of neuropathy, is unknown. Most of the relevant literature involves animal studies [35,36]. There are very few reports of neurologic injury after neuraxial anesthesia or peripheral nerve blocks in diabetic patients [37,38]. For patients with known diabetic neuropathy, we agree with experts who recommend minimizing LA dose, volume, and/or concentration as appropriate, and avoiding vasoconstrictive additives to LA solutions if regional anesthesia is thought to be appropriate [39].

•Several studies have reported increased duration of peripheral nerve block in patients with diabetes [40-42]. In one prospective observational study including 72 patients who had sciatic nerve block with ropivacaine for lower limb surgery, block duration was greater in patients with type 2 diabetes, compared with non-diabetic patients (median duration 21 versus 17 hours) [40]. Similarly, a prospective observational study of 67 patients who had axillary brachial plexus block with combined lidocaine and bupivacaine for upper extremity surgery found that patients with type 2 diabetes had increased duration of sensory and motor block (mean sensory duration 774 versus 375 minutes, mean motor duration 523 versus 500 minutes) compared with non-diabetic patients [41].

The mechanisms for increased sensitivity to LA in diabetes and whether the degree of hyperglycemia affects sensitivity are unknown.

Diabetic autonomic neuropathy — Diabetic autonomic neuropathy (DAN) is one of the microvascular complications of diabetes mellitus, affecting multiple organ systems, including the cardiovascular, gastrointestinal (GI), genitourinary, pupillary, sudomotor, vasomotor, and neuroendocrine systems (table 2). The risk factors, associated outcomes, and diagnostic testing for DAN are discussed in detail separately (see "Diabetic autonomic neuropathy"). The manifestations of most concern for anesthesia care are discussed here.

During the preoperative visit, diabetic patients should be questioned about the presence of symptoms of DAN, including early satiety, alternating constipation and diarrhea, resting tachycardia, poor exercise tolerance, or erectile dysfunction [43-45]. The American Diabetes Association recommends screening for DAN at the time of diagnosis of type 2 diabetes and five years after the diagnosis of type 1 diabetes, and a history and physical examination for signs of autonomic dysfunction annually. The results of such screening should be requested during preanesthesia evaluation.

●Cardiovascular autonomic neuropathy – Cardiovascular autonomic neuropathy (CAN) is associated with resting tachycardia, exercise intolerance, orthostatic hypotension, supine hypertension, syncope, intraoperative cardiovascular instability, silent myocardial infarction and ischemia, and increased mortality. (See "Diabetic autonomic neuropathy", section on 'Cardiovascular autonomic neuropathy'.)

During anesthesia, CAN can result in hypotension on induction of anesthesia or with changes in patient position, and labile blood pressure during maintenance of general anesthesia. The literature on the incidence of hemodynamic instability during general anesthesia in patients with diabetes and CAN is conflicting, with some studies reporting increased variability in intraoperative blood pressure in patients with diabetes and/or autonomic dysfunction [46-48], and others reporting no difference [49]. In several of these studies, patients with CAN have required more vasopressors for blood pressure support than patients without CAN. Patients with CAN may be at increased risk of hypotension during neuraxial anesthesia, particularly with changes in position (eg, reverse Trendelenburg), though this has not been studied.

●Diabetic autonomic neuropathy of the gastrointestinal tract – DAN of the GI tract can result in gastroesophageal reflux disease (GERD) and/or delayed gastric emptying [50], either of which can increase the risk of aspiration during induction of anesthesia (see "Diabetic autonomic neuropathy of the gastrointestinal tract"). Acute gastroparesis has been reported in the setting of a diabetic ketoacidosis episode [51].

During preanesthesia evaluation all patients should be questioned about symptoms of GERD and delayed gastric emptying, including heart burn, regurgitation, early satiety, bloating, nausea, vomiting, or abdominal pain. Patient with such symptoms may require longer fasting duration preoperatively, and many clinicians utilize rapid sequence induction and intubation (RSII) to minimize the risk of aspiration. (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'General indications'.)

Patients with severe gastroparesis may even require awake intubation for general anesthesia as an aspiration prevention strategy, particularly in patients with predictors for difficulty with airway management (algorithm 1 and figure 1) [52,53]. The decision to intubate awake is discussed in detail separately. (See "Management of the difficult airway for general anesthesia in adults", section on 'Awake intubation'.)

Patients who have constipation as a result of DAN of the GI tract may benefit from multimodal postoperative analgesia that minimizes the use of opioids.

●Association of diabetic autonomic neuropathy with sleep apnea – DAN is associated with an increased risk of obstructive sleep apnea (OSA) and/or central sleep apnea. (See "Diabetic autonomic neuropathy", section on 'Role of comorbid risk factors'.)

Sleep apnea increases the risks of perioperative complications and should be suspected, recognized, and managed in the perioperative period to minimize postoperative morbidity and mortality. Screening for OSA and perioperative management of patients with OSA are discussed separately. (See "Surgical risk and the preoperative evaluation and management of adults with obstructive sleep apnea" and "Intraoperative management of adults with obstructive sleep apnea" and "Postoperative management of adults with obstructive sleep apnea".)

Diabetic nephropathy — We test for creatinine and estimated glomerular filtration (eGFR) rate prior to anesthesia for patients with diabetes. Diabetic nephropathy occurs in both type 1 and type 2 diabetes, and routine screening for patients with known diabetes includes annual testing for urinary albumin excretion. Diabetic nephropathy is the leading cause of end-stage kidney disease in the United States along with hypertension, with approximately 50 percent of the patients with chronic kidney disease (CKD) carrying the diagnosis of diabetes [54,55]. The incidence of diabetic nephropathy, risk factors, pathogenesis, screening, and treatment of diabetic nephropathy are discussed separately. (See "Diabetic kidney disease: Pathogenesis and epidemiology" and "Diabetic kidney disease: Manifestations, evaluation, and diagnosis" and "Overview of general medical care in nonpregnant adults with diabetes mellitus", section on 'Monitoring for increased urinary albumin excretion' and "Treatment of diabetic kidney disease".)

CKD has been identified as an independent predictor of cardiovascular events and mortality in the general population and in postoperative noncardiac and cardiac surgical patients [56-58]. Renal dysfunction (independent of diabetes) is one of the risk factors in the commonly used preoperative cardiac risk assessment tools (ie, RCRI, VSGNE, NSQIP calculator). (See "Evaluation of cardiac risk prior to noncardiac surgery".)

We apply general principles for avoidance of perioperative kidney injury for diabetic patients with diabetic nephropathy, including maintenance of renal perfusion pressure and avoidance of nephrotoxins. Nonsteroidal antiinflammatory drugs (NSAIDs), which are often administered as part of multimodal postoperative analgesia, should be used cautiously or avoided in patients with diabetic nephropathy.

Many patients with diabetic nephropathy are treated with angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) to reduce progression of diabetic nephropathy. However, ACE inhibitors and ARBs may be prescribed for other conditions (eg, heart failure or hypertension). Whether to hold or continue these medications the morning of surgery is controversial. Continuation of these medications may result in intraoperative hypotension, whereas holding the medication can result in perioperative hypertension. We individualize the decision to continue or discontinue ACE inhibitors and ARBs based on the indications for the drug, the patient's blood pressure, and the type of surgery and anesthesia planned. For most patients, we usually withhold them on the morning of surgery. However, when the indication is for heart failure or poorly controlled hypertension, we continue them to avoid further exacerbation of these conditions. These issues are discussed in detail separately. (See "Perioperative medication management", section on 'ACE inhibitors and angiotensin II receptor blockers'.)

Diabetic retinopathy — Diabetic retinopathy (DR) is a common complication of diabetes, and is an important cause of blindness worldwide. In patients with known DR who undergo surgery associated with an increased risk of postoperative visual loss (eg, prone spinal fusion, bilateral head and neck procedures, prolonged procedures in the head down position), we document preoperative visual acuity and visual fields. The pathogenesis and clinical features of DR are discussed separately. (See "Diabetic retinopathy: Classification and clinical features" and "Diabetic retinopathy: Pathogenesis".)

Musculoskeletal abnormalities — Diabetes is associated with several musculoskeletal abnormalities that may increase the risk of difficulty with airway management, or may require particular attention during patient positioning. (See "Overview of the musculoskeletal complications of diabetes mellitus".)

Difficulty with airway management — Several studies have reported an increase in difficult laryngoscopy in patients with diabetes [59-62]. Thus, we maintain a heightened suspicion of difficultly with airway management, particularly in patients with longstanding diabetes and in diabetic patients with other indicators of difficulty with airway management (eg, obesity, increased neck circumference) (table 3 and table 4 and table 5 and table 6).

Postulated mechanisms for difficult laryngoscopy include diabetes-related cervical spine, atlanto-occipital joint, or temporomandibular joint disease [63]. Limited range of motion of the head and neck can result from the syndrome of limited joint mobility (previously known as cheiroarthropathy), which most commonly affects the joints of the hands but can affect the axial spine as well. Limited joint mobility can occur in patients with either type 1 or type 2 diabetes. (See "Limited joint mobility in diabetes mellitus".)

One test of limited joint mobility is a positive "prayer sign," which refers to the inability to completely flatten the hands together as in prayer. In some studies, a palm print test has been used as a more objective measure of limited joint mobility. The literature regarding the ability of these tests to predict difficult laryngoscopy is conflicting [62,64-66].

The incidence of limited joint mobility in diabetes, pathogenesis, and association with other diabetic complications are discussed separately. (See "Limited joint mobility in diabetes mellitus".)

Positioning concerns — Patients with diabetes-related joint disease or limitations should be assessed preoperatively for problems with positioning for surgery. As an example, patients with adhesive capsulitis of the shoulder, which is particularly common in diabetics, may be unable to lie on the affected shoulder for surgery performed in the lateral position. When possible, the position during surgery should be one that would be comfortable with the patient fully awake. If questions arise, the patient should be placed in the anticipated position as a trial before sedation or induction of anesthesia.

Diabetes is a risk factor for positioning-related tissue and nerve injury in the perioperative period. Measures to reduce the risk of injury are discussed separately. (See "Patient positioning for surgery and anesthesia in adults", section on 'Prevention of skin and tissue injury' and "Patient positioning for surgery and anesthesia in adults", section on 'Prevention of nerve injury'.)

ANESTHETIC MANAGEMENT

Monitoring during anesthesia

Physiologic monitors — Standard physiologic monitors (pulse oximeter, electrocardiography, noninvasive blood pressure device, and a temperature monitor) should be used for all patients who have anesthesia. Advanced monitoring should be determined by patient and surgical factors. (See "Basic patient monitoring during anesthesia".)

Monitoring blood glucose — The need for and frequency of blood glucose monitoring during anesthesia depends on the length and timing of surgery, preoperative blood glucose level, and pre- and intraoperative pharmacotherapy utilized. Because sedation and/or general anesthesia may mask the signs and symptoms of hypoglycemia, frequent blood glucose monitoring is required during anesthesia. Medications necessary to treat hypoglycemia, including 50% dextrose and glucagon, should be readily available.

●For patients who have received insulin of any type, check blood glucose by fingerstick or laboratory method every hour, or more frequently if blood glucose is <100 mg/dL or if blood glucose is falling rapidly. (See "Perioperative management of blood glucose in adults with diabetes mellitus", section on 'Type 1 or insulin-treated type 2 diabetes'.)

●For diabetic patients who have not received insulin (type 2 diabetic patients treated with diet alone, or oral hypoglycemic agents/noninsulin injectables), check blood glucose by fingerstick or laboratory method every two hours. (See "Perioperative management of blood glucose in adults with diabetes mellitus", section on 'Type 2 diabetes treated with oral hypoglycemic agents/noninsulin injectables'.)

●In patients who are critically ill, are on ≥2 vasopressor agents [67], or hypotensive [68], venous or arterial blood should be used instead of fingerstick samples, as changes in capillary perfusion may underestimate or overestimate blood glucose [68].

●Continuous glucose monitoring (CGM) may be beneficial for self-monitoring for patients with diabetes (see "Glucose monitoring in the ambulatory management of nonpregnant adults with diabetes mellitus", section on 'Benefits of CGM'). However, the role of continuous glucose monitors during anesthesia has not been established, and literature is limited.

Whereas CGM may provide early detection and intervention for perioperative dysglycemia, there are concerns about accuracy in the presence of edema or fluid shifts, during hypoxia or hypotension, and at the extremes of blood glucose [69-71], and there are reported cases of electromagnetic interference from electrocautery in the operating room [72]. There are several studies that have reported acceptable accuracy of some CGM systems in the ICU [73,74]. However, intraoperative data is limited, and some experts recommend against using these devices in the operating room [71]. There are logistical challenges with the perioperative use of devices programmed to communicate with the patient’s own CGM reader or personal phone.

The available CGM technologies include intravascular, subcutaneous (interstitial), and transdermal devices. They transmit glucose concentration to a receiver carried by the patient or their personal phone [75]. During the COVID-19 pandemic the FDA "did not object" to the use of two of these, the FreeStyle Libre and the DexCom system, in the hospital as part of efforts to save personal protective equipment and supplies [76,77]. This was a situational limited approval due to the pandemic. The DexCom hospital CGM system has since received a Breakthrough Device Designation from the FDA allowing for further assessment of its utility in hospitals.

Glycemic targets — Beyond avoidance of marked hyperglycemia and hypoglycemia, the optimal perioperative glucose targets are unclear. In our practice, we aim to keep glucose readings between 140 and 180 mg/dL (7.8 to 10 mmol/L). However, tighter targets, ie, extending the lower end to 110, can be used and are beneficial for certain patients, such as nondiabetics and baseline tightly controlled diabetics, hence the importance of the determination of the preoperative average and range blood glucose levels and A1C. Perioperative glycemic targets are discussed in more detail separately. (See "Perioperative management of blood glucose in adults with diabetes mellitus", section on 'Glycemic targets'.)

Choice of anesthetic technique — The choice of anesthetic technique (general anesthesia, regional anesthesia, or monitored anesthesia care) should be based on the surgical procedure, patient factors, and patient and provider preferences. Neuraxial anesthesia or analgesia may reduce the stress response to surgery, either by a direct sympathectomy, or by reducing pain, and may therefore reduce postoperative insulin resistance and hyperglycemia [78,79]. However, there is no evidence that regional anesthesia alone or in combination with general anesthesia reduces mortality or major complications in diabetic patients.

The risk of infection related to regional anesthesia techniques may be increased in patients with diabetes, particularly for catheter-related procedures (ie, epidural analgesia, continuous peripheral nerve block). Epidural abscess occurs more commonly in patients with diabetes than in nondiabetic patients. (See "Spinal epidural abscess", section on 'Epidemiology'.)

The effects of regional anesthesia in patients with diabetic neuropathy are discussed above. (See 'Implications for regional anesthesia' above.)

Induction of anesthesia — The choice of anesthesia induction agents and technique should be based on patient factors, including comorbidities, predictors of difficulty with airway management, the likelihood of aspiration during induction of anesthesia, and clinician judgment. (See 'Diabetic autonomic neuropathy' above and 'Difficulty with airway management' above and 'Coronary heart disease' above.)

Maintenance of anesthesia — There is no evidence that particular anesthetic agents should be used for patients with diabetes. Maintenance of anesthesia is discussed in detail separately. (See "Maintenance of general anesthesia: Overview".)

Positioning — The plan for surgical positioning should take into account coexisting neuropathy and arthropathy. When possible, the position during surgery should be one that would be comfortable with the patient fully awake. Patients should be questioned about limited range of motion, and if necessary, trial positioning should be performed prior to sedation or induction of anesthesia. Pressure points should be carefully padded. (See "Patient positioning for surgery and anesthesia in adults", section on 'General considerations'.)

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: Diabetes mellitus in adults".)

SUMMARY AND RECOMMENDATIONS

●Preoperative evaluation

•The preanesthesia evaluation of diabetic patient should include assessment of patient's type of diabetes (ie, type 1 or type 2), the baseline level of blood glucose control, and the patient's medication regimen. (See 'Diabetes history' above.)

•For patients with diabetes who undergo moderate- or high-risk surgery, we order a preoperative A1C if not performed in the past three months and renal function tests. Many patients with diabetes have comorbidities that require further preoperative testing (eg, electrocardiogram [ECG]) in anticipation of moderate- or high-risk surgery. (See 'Laboratory evaluation' above.)

•Diabetes is a risk factor for macrovascular disease (ie, coronary heart disease [CHD], cerebrovascular disease [CVD], and peripheral vascular disease) and microvascular disease (ie, retinopathy, nephropathy, neuropathy), all of which may have implications for perioperative care. (See 'Multiorgan system effects of diabetes' above.)

●Choice of anesthetic technique – The choice of anesthetic technique (general anesthesia, regional anesthesia, or monitored anesthesia care) should be based on the surgical procedure, patient factors, and patient and provider preferences. Neuraxial anesthesia/analgesia may reduce postoperative insulin resistance and hyperglycemia by reducing the stress response to surgery. However, there is no evidence that regional anesthesia alone or in combination with general anesthesia reduces mortality or major complications in diabetic patients. (See 'Choice of anesthetic technique' above.)

●Anesthetic management

•There is no evidence that particular anesthetic agents should be used for induction or maintenance of anesthesia in patients with diabetes. (See 'Induction of anesthesia' above and 'Maintenance of anesthesia' above.)

•Patients with diabetes-associated musculoskeletal abnormalities may be at increased risk of difficulty with airway management. (See 'Difficulty with airway management' above.)

•Diabetes-associated cardiovascular autonomic neuropathy can result in perioperative hemodynamic instability. Autonomic neuropathy of the gastrointestinal (GI) tract may increase the risk of aspiration during anesthesia. (See 'Diabetic neuropathy' above.)

•For patients with diabetic nephropathy, we apply general principles for avoidance of perioperative kidney injury, including maintenance of renal perfusion and avoidance of nephrotoxins. (See 'Diabetic nephropathy' above.)

•The optimal perioperative glucose targets are unclear. In our practice, we aim to keep glucose readings between 140 and 180 mg/dL (7.8 to 10 mmol/L), and modify these targets based on the patient's preoperative blood glucose control. We monitor blood glucose every hour for patients who have received insulin (more frequently if blood glucose is <100 mg/dL or falling rapidly), and every two hours for diabetic patients who have not received insulin. (See 'Monitoring blood glucose' above.)

●Regional anesthesia – For most peripheral nerve blocks in patients with diabetic neuropathy, ultrasound guidance is preferred rather than nerve stimulator guidance. The nerve stimulation threshold is unpredictable and markedly increased in patients with diabetic neuropathy. Patients with diabetic neuropathy may be at increased risk of nerve injury from regional anesthesia, and duration of block may be prolonged. The risk of infection related to regional anesthesia techniques may be increased in patients with diabetes. (See 'Implications for regional anesthesia' above and 'Choice of anesthetic technique' above.)