Version May 2024
INTRODUCTION — Epidural anesthesia is a type of neuraxial anesthesia; local anesthetic (LA) is injected into the epidural space to anesthetize the spinal nerve roots that traverse the space. Epidural anesthesia is used for anesthesia of abdominal, pelvic, and lower extremity procedures and, less commonly, thoracic procedures. It may be used to supplement general anesthesia for thoracic, abdominal, and pelvic procedures and for postoperative analgesia following these procedures. The usual technique involves siting a catheter in the epidural space. LA solution and adjuvants are administered through the catheter, both to initiate and maintain anesthesia for the duration of the surgical procedure.
This topic will discuss the relevant anatomy, techniques, and management of epidural and combined spinal-epidural anesthesia. The technique for spinal anesthesia is discussed separately. Indications, contraindications, preoperative evaluation, physiologic effects, and complications of epidural anesthesia are discussed separately. (See "Spinal anesthesia: Technique" and "Overview of neuraxial anesthesia".)
SPINAL VERSUS EPIDURAL ANESTHESIA — Spinal, epidural, and combined spinal-epidural (CSE) anesthesia can be used for many of the same surgical procedures. Differences among them may affect the choice of technique for a specific procedure or patient. The advantages and disadvantages of the various neuraxial anesthesia techniques are shown in a table (table 1). Spinal anesthesia is usually administered as a single shot, whereas epidural anesthesia is usually administered via a catheter (thus it is a continuous technique), and CSE anesthesia combines the two.
Catheter-based neuraxial anesthesia (ie, epidural, CSE, and continuous spinal) allows prolonged anesthesia and titration of the onset of the anesthetic. Single-shot spinal or epidural anesthesia is limited to the duration of action of the injected drug.
ANATOMY — Epidural anesthesia is performed by introducing a needle between the lumbar, thoracic, or cervical vertebrae and injecting anesthetic medication into the epidural space, via the epidural needle and/or a catheter inserted through the needle into the epidural space (figure 1). Detailed anatomy of the bony spine and vertebrae are discussed separately (figure 2 and figure 3) (see "Spinal column injuries in adults: Types, classification, and mechanisms", section on 'Anatomy'). This topic will focus on lumbar and thoracic epidural anesthesia/analgesia. Cervical epidural injections are done mostly for pain procedures and are outside the scope of this topic.
Anatomy related specifically to the performance of epidural anesthesia is discussed here.
●Boundaries – The epidural space lies between the dural sac and the inside of the bony spinal canal. It extends from the foramen magnum to the sacral hiatus. The posterior longitudinal ligament forms the anterior border, the ligamentum flavum forms the posterior border, and pedicles and intervertebral foramina form the lateral border of the epidural space.
●Vertebral level – Epidural anesthesia is most commonly performed at the lumbar or thoracic vertebral levels and occasionally at the cervical level. The vertebral level for epidural anesthesia is determined by the dermatomal levels of the surgical procedure and the required extent of surgical anesthesia.
Historically, surface landmarks have been used to estimate the vertebral level for epidural needle placement, as follows (figure 4):
•The intercristal line (ie, imaginary line between the highest point of the iliac crests) crosses the body of L4 in most patients.
•The inferior border of the scapula is at T7.
•The C7 spinous process is the most prominent among the cervical vertebrae on palpation (vertebra prominens).
Surface landmarks do not accurately predict the vertebral interspaces [1-3], and clinicians are more likely to insert the needle more cephalad than estimated. Preprocedure ultrasound is increasingly being used for vertebral-level estimation, especially in the lumbar region. Data are lacking as to whether precise determination of the interspace before initiation of epidural anesthesia results in improved outcomes and safety.
●Ligaments – Three spinal ligaments are important for the epidural anesthesia technique.
•The supraspinous ligament anchors the tips of the spinous processes in a continuous column
•The interspinous ligament stretches between the spinous processes of successive vertebrae
•The ligamentum flavum is a tough ligament that lies deep to the interspinous ligament and forms the posterior border of the epidural space (figure 5).
●Contents of the epidural space – The epidural space is a discontinuous space, roughly divided into posterior, lateral, and anterior compartments, occupied by nerves, fat, and blood vessels. The anesthetic solution is usually deposited into the posterior epidural space, but it must spread throughout the space to provide effective anesthesia.
●Nerves and dermatomes – The spinal nerves, autonomic nerves, and dermatomes relevant for neuraxial anesthesia are discussed separately. (See "Spinal anesthesia: Technique", section on 'Anatomy'.)
PREOPERATIVE EVALUATION — A medical history and anesthesia-focused physical examination should be performed for all patients who undergo any type of anesthesia; if epidural anesthesia is planned, the spine should also be examined. The preoperative evaluation should focus on medical conditions that may alter the physiologic response to epidural anesthesia or increase the risk of complications. (See "Overview of neuraxial anesthesia".)
PREPARATION FOR EPIDURAL ANESTHESIA — For epidural anesthesia, the standard and emergency anesthesia equipment and medications should be prepared as they would be for general anesthesia. (See "Induction of general anesthesia: Overview", section on 'Preparation for anesthetic induction'.)
A disposable epidural kit is usually used. The kit contains needles, an epidural catheter, drugs, labels, and other required equipment. The kit is preferably placed on a cart or table on the side of the clinician's dominant hand.
Intravenous (IV) access must be secured prior to the procedure. Standard American Society of Anesthesiologists (ASA) monitors should be applied (eg, noninvasive blood pressure [BP] monitor, electrocardiography, pulse oximetry) prior to initiation of epidural anesthesia. Additional monitoring (eg, intraarterial pressure monitoring) is dictated by the patient's medical status and the planned procedure.
A preprocedure time-out should be performed, which includes confirmation of the following:
●Patient identifiers (eg, name, medical record number, date of birth)
●Drug allergies
●Planned surgical procedure or indication for epidural anesthesia
●Surgical and anesthesia consent with site marked, if applicable
●Coagulation status (eg, anticoagulant administration, coagulation laboratory values, if applicable)
Premedication — Sedation may be titrated, if necessary, prior to epidural needle placement. Deep sedation should be avoided to allow patient cooperation with positioning and feedback (ie, the occurrence of pain or paresthesia) during the procedure.
Positioning for epidural procedure — Like spinal anesthesia, the sitting and lateral decubitus positions are commonly used (figure 4). Success rate is similar between the sitting and the lateral decubitus position, although the insertion time may be shorter in the sitting position [4]. The goal of positioning is to create a straight path for the needle insertion between the superior and inferior vertebral spinous processes (figure 6) and to avoid rotation of the spine. Commercial devices are available that are designed to support the patient in the sitting position during neuraxial block (figure 7). Positioning is discussed in detail separately. (See "Spinal anesthesia: Technique", section on 'Positioning for spinal procedure'.)
Preprocedure ultrasonography — Preprocedure ultrasound scanning of the spine may be useful in identifying the intervertebral space for needle placement and an estimation of the depth required to reach the epidural space. Ultrasound can be particularly useful in patients with obesity or patients with altered anatomy in whom the traditional surface landmarks are vague or difficult to identify [5-8]. (See "Spinal anesthesia: Technique", section on 'Preprocedure ultrasonography'.)
Aseptic technique — Strict aseptic technique must be used for all aspects of the epidural anesthesia procedure. Aseptic technique for neuraxial anesthesia is discussed separately. (See "Spinal anesthesia: Technique", section on 'Aseptic technique'.)
EPIDURAL ANESTHESIA TECHNIQUE
Epidural anesthesia equipment
●Epidural needles – In an adult epidural kit, the epidural needle is typically 17- or 18-gauge and 8.89 cm (3.5 inches) in length, with surface markings at 1-cm intervals. Longer needles up to 15 cm (6 inches) in length are available for patients with severe obesity. Many commercially available epidural needles, including the Hustead, Weiss, and Tuohy needles, have a curved opening at the tip to guide the catheter into the epidural space. Wings at the junction of the needle shaft and hub may allow for better control as the needle is passed through tissue, although some practitioners may prefer epidural needles without wings or with detachable wings.
●Loss of resistance – The loss-of-resistance (LOR) syringe is a special syringe that is used to identify the epidural space, with low resistance between the plunger and the inside of the needle barrel. The syringe is filled with saline, air, or a combination of the two and attached to the epidural needle when the needle tip is engaged in the interspinous ligament. As the needle is advanced with pressure on the plunger, LOR occurs once the needle tip is advanced beyond the ligamentum flavum into the epidural space. (See 'Midline approach technique' below.)
Historically, glass syringes with a ground-glass barrel and plunger have been used, but low-resistance plastic syringes are now available for this purpose, and the choice between plastic and glass is a matter of clinician preference. The authors prefer to use a glass LOR syringe.
The choice of saline, air, or both for LOR is also a matter of personal preference. A Cochrane database systematic review reported no difference between using air or saline for LOR in identifying the epidural space and no difference in rate of complications [9]. However, the studies included in the review were primarily obstetric patients so may not be applicable to the general population.
●Epidural catheter – A variety of epidural catheters are available. Distinguishing features include the degree of stiffness and tip design. Flexible designs have an embedded stainless steel wire coil (reinforced) surrounded by either a polyurethane or a nylon-blend catheter, depending on the manufacturer. Nylon catheters with or without the spring-wound inner coil tend to be stiffer [10]. Catheter tip designs differ in the number and arrangement of orifices (multi-orifice versus single end-hole) and flexibility of tip (flexible versus blunt) (figure 8).
•Stiffer catheters may be easier to thread [10], but more flexible catheters may reduce the incidence of paresthesia, catheter migration, and intravascular cannulation [11,12]. Several studies have compared ease of insertion and complications using different epidural catheters:
-In one single clinician randomized trial including 220 patients who had epidural labor analgesia, a single end hole wire-reinforced flexible tip catheter (Arrow FlexTip Plus) resulted in a lower incidence of paresthesia (3/112 versus 39/110) and intravascular catheter placement (0/112 versus 11/110) compared with a multiorifice nylon catheter (Concord/Portex) [12]. There was a trend towards easier catheter insertion with the flexible tip catheter.
-In another single institution trial, 240 patients who had epidural labor analgesia were randomly assigned to one of two epidural kits, one that included a single end hole wire-reinforced catheter (Arrow FlexTip Plus) versus a kit with a closed tip multiorifice wire-reinforced catheter (B. Braun Perifix FX Springwound) [10]. First attempt at catheter placement was more successful with the closed tip, stiffer catheter (119 of 120 versus 102 of 120). Incidences of paresthesias and vascular cannulation were similar in the two groups. However, the role of epidural needle design (which differed in the two epidural kits) in ease of epidural catheter advancement is not well studied.
•Several studies have reported reduced incidence of inadequate analgesia with multi-orifice catheters compared with single-orifice catheters [13-15]. In contrast, one randomized study that compared uniport and multiport versions of flexible, wire-reinforced catheters for labor analgesia reported no difference in the success of analgesia, breakthrough pain, or occurrence of complications [16].
•It may be easier to aspirate blood or cerebrospinal fluid (CSF) from a multi-orifice catheter that is malpositioned in a blood vessel or the intrathecal space [17,18].
•The individual orifices of a multi-orifice catheter may reside in different compartments simultaneously (eg, epidural and subarachnoid) and could theoretically result in only partial placement of the drug in the intended space.
In general, choice of epidural catheter is a matter of clinician and institutional preference. Epidural catheters are marked at 1-cm intervals, so the depth of its insertion can be easily determined.
Wire-reinforced catheters have limited magnetic resonance imaging (MRI) compatibility, which may be important if a patient requires MRI for perioperative neurologic evaluation (eg, for stroke evaluation in patients with mental status changes). Based on nonclinical testing, some catheters are considered "magnetic-resonance-conditional," which allows for use under specific conditions (ie, a static magnetic field of 3 Tesla or less, a maximum spatial gradient magnetic field of 720 Gauss/cm or less, and a transmit/receive radio frequency head coil) [19].
●Epidural catheter and syringe connectors – Most currently used commercial epidural kits use standard syringe-catheter connections with Luerlock or Luer-slip connectors. Drug errors (wrong drug injected by the wrong route) are common. The International Organization for Standardization (ISO) is developing new guidelines for small-bore catheter connectors designed to reduce the incidence of drug error. An example is the B. Braun NRFit; the connector is designed to fit specific syringes or infusion tubing designed only for use with neuraxial drugs. (See "Prevention of perioperative medication errors", section on 'Solutions for wrong route errors'.)
Approaches to the epidural space — The epidural needle can be inserted using a midline or a paramedian approach. Lumbar and lower thoracic epidural catheters are usually sited via a midline approach; the paramedian approach is more commonly used for the mid- to high-thoracic insertions. The epidural needle is advanced through skin, soft tissue, and spinal ligaments until the tip of the epidural needle enters the epidural space. This is recognized by so-called "loss of resistance" (LOR). When the needle tip is located in spinal ligaments, the contents of the syringe are difficult to inject. When the needle tip enters the epidural space, the resistance to injection is lost and the syringe contents (air and/or saline) are easily injected.
Midline approach technique — The epidural needle is inserted in the midline of the patient's back, defined by the spinous processes. The procedure is performed as follows:
●Palpate the interspace between two spinous processes at the chosen spinal level. Raise a skin wheal with 1% lidocaine using a 25-gauge needle in the midline of the spine, in the lower third to half of the interspace. Infiltrate the subcutaneous tissue with lidocaine and continue through supraspinous ligament down to the interspinous ligament.
●Insert the epidural needle with stylet at a straight or slight cephalad angle (if in the lumbar or lower thoracic spine) or at steeper cephalad angle (if in the mid-thoracic spine) (figure 3). The needle bevel is oriented cephalad whether the patient is in a supine or lateral decubitus position. Advance the needle through the supraspinous ligament and into the interspinous ligament (figure 1). A firmness in the tissue suggests that the tip of the needle is in the supraspinous or intraspinous ligament. Lack of firmness may indicate a paraspinous position of the needle tip, and the needle should be adjusted.
●Once the needle tip is anchored in the interspinous ligament, remove the stylet and attach an LOR syringe containing air, saline, or some of each. Apply intermittent or continuous gentle pressure to the plunger with the dominant thumb, while advancing the needle slowly with the nondominant hand (figure 9). The ligamentum flavum is a tougher structure than the intraspinous ligament and is identified by increased resistance to injection as the needle is advanced. Once LOR occurs, stop needle advancement to avoid an unintentional dural puncture. The tip of the epidural needle is now located in the epidural space.
●A small amount of air (1 to 2 mL) may be injected into the epidural space if air is used for the LOR technique. Avoid injecting larger amounts of air as this may contribute to patchy anesthesia [20].
●Injection of 5 to 10 mL of saline before epidural catheter insertion may reduce the risk of vascular injury [11]. This can be performed after LOR is obtained with air or saline.
Paramedian approach technique — The paramedian approach is often used for mid- to high-thoracic epidural anesthesia. The angulation of the spinous processes in the thoracic spine and the narrow interspaces make the midline approach technically difficult. This approach is also useful in patients who are unable to flex the spine for lumbar epidural anesthesia or when the midline technique is unsuccessful. It requires mental triangulation in three planes and is thus more difficult to learn.
With the paramedian approach, the needle does not traverse the interspinous ligament, so minimal resistance to injection occurs as the needle is advanced until the needle tip is engaged in the ligamentum flavum.
●Palpate the interspace between two spinous processes at the chosen spinal level. With a 25-gauge needle, raise a skin wheal with 1% lidocaine 1 cm lateral to the midline at the cephalad border of the inferior spinous process. Infiltrate the subcutaneous tissue with lidocaine.
●The following technique for paramedian needle insertion is shown in a figure (figure 10). Insert the epidural needle 1 cm lateral to the cephalad border of the inferior spinous process. Advance the needle perpendicular to the skin until the tip contacts the lamina of the vertebral body below the intended interlaminar space. This helps to estimate the depth of the epidural space. Withdraw the needle slightly, and redirect the tip approximately 15 degrees medially and 45 degrees cephalad. Advance the needle, walking the tip off the edge of the lamina. Stop needle advancement as soon as the ligamentum flavum is felt.
●Attach the LOR syringe, and gently depress the plunger. Resistance to injection indicates that the needle tip is engaged in the ligamentum flavum. Advance the needle and syringe; once LOR occurs, stop needle advancement to avoid a dural puncture.
For both the midline and paramedian approaches, the depth of the epidural space from the skin depends on body habitus, vertebral level of insertion, and the angle of the epidural needle. In the average adult, the depth ranges from 4 to 5 cm in the mid-lumbar spine and 4 to 6 cm in the mid-thoracic spine [21,22].
Confirming epidural space — Loss of resistance to saline or air is the most commonly used method to identify entry into the epidural space. However, this approach has poor specificity and has led investigators to propose adjunct modalities to confirm identification of the epidural space. These modalities include radiographic imaging, electrical stimulation, and epidural waveform analysis [23-27]. However, these techniques may require additional and/or bulky equipment. As an alternative, in one report, readily available supplies (ie, syringe, stopcock, and extension tubing) were used to assess epidural pressure variation followed by administration of the epidural anesthetic solution using gravity flow, to confirm entry into the epidural space in 100 laboring patients [28]. This technique appears promising but has not been well studied.
Epidural catheter placement — Some clinicians initiate epidural anesthesia by injecting anesthetic solution directly through the epidural needle into the epidural space (for single-shot epidural anesthesia or prior to siting the epidural catheter for continuous epidural anesthesia). However, more commonly, a catheter is inserted into the space and anesthetic solution is administered via the catheter. After LOR confirms that the tip of the epidural needle is in the epidural space, insert the epidural catheter as follows:
●Remove the LOR syringe, and count the markings on the visible shaft of the epidural needle to calculate the depth of the epidural space from the skin.
●Thread the epidural catheter through the needle until the 20 cm mark is at the needle hub. Resistance to catheter advancement may be encountered as it reaches the curve at the tip of the needle; however, applying steady pressure on the catheter will usually result in passage into the epidural space.
●Carefully remove the needle over the catheter, making sure to avoid pulling the catheter back with the needle. Note the mark on the catheter at the skin, and withdraw the catheter to leave 4 to 6 cm in the epidural space (eg, if the epidural space was 5 cm from the skin, the catheter mark at the skin should be 9 to 11 cm).
The optimal length the catheter should be inserted in the epidural space is debated among anesthesiologists. The catheter should be inserted far enough to avoid dislodgement with patient movement and to make sure that all of the catheter orifices are in the epidural space. However, inserting the catheter too far may increase the chance of threading the catheter tip out of the epidural space. In laboring obstetric patients, insertion of a lumbar epidural catheter ≤3 cm in the epidural space increases the risk of dislodgement and insufficient analgesia, whereas length ≥7 cm is associated with catheter malposition and unilateral analgesia [29-31]. In one study of thoracic epidural analgesia for thoracotomy, there were no differences in pain scores or nonfunctioning epidurals for patients who were randomly assigned to catheter-threading distances of 3, 5, and 7 cm [32].
●Attach the catheter connector; hold the catheter tip below the insertion site and confirm that there is no CSF or blood flow from the catheter, which would indicate intrathecal or intravascular catheter placement. Attach a 3-mL syringe and aspirate gently, again to confirm absence of CSF or blood return.
●Place a transparent, occlusive, sterile dressing over the catheter insertion site, and tape the catheter securely to the patient's back, usually to the shoulder. When the epidural is placed in the sitting position, it may be preferable to secure the catheter after placing the patient in the lateral decubitus position, particularly in heavier patients. Catheters may move inward into the subcutaneous tissue as the patient moves from the flexed to the extended position; as such, we wait to secure the catheter with the dressing until the back is no longer flexed. The site of catheter insertion at the skin should remain visible.
Troubleshooting — Several common problems may occur when placing an epidural needle or catheter.
●Difficulty locating the epidural space – If the needle hits bone during epidural needle placement, the clinician should first consider what part of the vertebra is in contact with tip of the epidural needle. If bony contact occurs within 1 to 2 cm of the skin, contact is likely being made with the tip of the spinous process. If contact is deeper (2 to 3 cm), the side of the spinous process is likely being contacted. If contact is made yet deeper (>4 cm), the lamina is likely being contacted. The patient may be asked whether the needle tip seems to be on the left or right side. The clinician should use this information to assess the location of the needle tip and make further adjustments. Usually, an attempt is made to "walk" the needle off the bone. The needle is withdrawn approximately 0.5 to 1.0 cm and then readvanced with the tip of the needle directed slightly more cephalad and toward the midline (if the needle is perceived by the patient to be on the left or right side).
The epidural needle may become occluded with a bony fragment or tissue due to contact with bone. LOR will not be appreciated, and unintentional dural puncture may occur if the needle is advanced. If an occluded needle is suspected, the stylet should be reinserted to clear the lumen of the needle, or the needle should be removed and flushed with saline.
●"False" LOR – False LOR (resistance to injection is lost, but the epidural needle tip is not in the epidural space) can occur when there is a loose connection between the LOR syringe and epidural needle, therefore allowing leakage of saline or air as pressure is applied to the syringe plunger. A false LOR may also occur if the epidural needle enters the interspinous ligament at an oblique angle and exits the ligament into soft tissue on the opposite side. Methods suggested for identifying a false LOR include the following:
•Add a small amount of air (0.5 mL) to the saline in the LOR syringe, and inject a small amount of saline through the needle. The air bubble will compress because of tissue resistance if the needle tip is in soft tissue, whereas it will not compress if the needle tip is in the epidural space.
•Pass a long spinal needle through the epidural needle. If dural puncture occurs (ie, CSF return into the spinal needle hub), the tip of the epidural needle is likely to be in the epidural space.
●Difficulty threading the epidural catheter into the epidural space – If resistance is encountered when advancing the catheter into the epidural space, it may indicate that the epidural needle tip is not in the epidural space, and the needle should be removed and repositioned.
•If the clinician is convinced that the needle tip is in the epidural space and the catheter does not advance beyond the needle tip, we do not recommend rotating the needle, as this increases the risk of unintentional dural puncture. Several maneuvers have been described to overcome the problem.
-The simplest is to ask the patient to take a deep breath while the clinician maintains gentle pressure on the epidural catheter. In one study, epiduroscopy demonstrated that this maneuver "opened" the space at the needle tip [33].
-Reinsertion of the epidural needle at a steeper angle may facilitate advancement of the catheter [34]. This is best achieved by withdrawing the epidural needle 0.5 to 1.0 cm, reattaching the LOR syringe, and re-advancing at a steeper angle by applying downward pressure to the hub of the needle.
-Alternatively, approximately 5 mL of saline may be injected through the needle into the epidural space and the catheter reinserted.
•If resistance to threading the epidural catheter occurs after advancing the catheter beyond the tip of the epidural needle (indicated by the centimeter calibration on the catheter), the catheter and the needle must be withdrawn together and the procedure started anew. There is a risk of shearing off the catheter tip if it is withdrawn through the needle.
●Paresthesias during needle or catheter placement – If the patient complains of paresthesias during needle or catheter advancement, further advancement should stop.
•If paresthesias occur during needle placement, the needle should be withdrawn and repositioned at a different angle towards the midline, away from the side of the paresthesia.
•Transient paresthesias are common during epidural catheter placement. If a paresthesia resolves, the catheter can be advanced. If the paresthesia recurs, the needle and catheter should be withdrawn and the procedure repeated.
●Blood in the epidural needle or catheter – The epidural needle may puncture a blood vessel either in the soft tissue or in the epidural space as it is advanced. The needle should be removed, flushed with saline, and readvanced at a different angle through the same or a different puncture site. Clotted blood may occlude the epidural needle, prevent LOR, and increase the risk of unintentional dural puncture.
●Unintentional dural puncture – Unintentional dural puncture may be recognized at the time of epidural needle advancement or after threading the epidural catheter. CSF can flow into the LOR syringe from the hub of the epidural needle or from the proximal end of the catheter.
Further management after unintentional dural puncture depends on the clinical situation and provider preference. There are two management options for neuraxial anesthesia after unintentional dural puncture:
•Remove and replace the epidural needle and catheter at a different interspace, or
•For lumbar neuraxial anesthesia, place or leave the catheter in the subarachnoid space and proceed with continuous spinal anesthesia. An intrathecal catheter should not be left in place after unintentional dural puncture in the thoracic spine.
Advantages and disadvantages of these options are shown in a table (table 2). If postoperative neuraxial analgesia is planned, the epidural should be replaced at another interspace. Although continuous spinal analgesia is possible, it is generally not advised because of the risk of drug-dosing errors.
●Unintentional subdural catheter placement – The subdural space is a potential space between the dura mater and arachnoid membrane. Unintentional placement of an epidural catheter in the subdural space is often not recognized and diagnosis maybe delayed or made in retrospect. A catheter in the subdural space may result in unpredictable sensory or motor blockade and serious complications (eg, cardiovascular or respiratory depression). The true incidence of subdural catheter placement is not known, but a study in patients having thoracic epidural catheters placed under fluoroscopic guidance predicted an incidence of 2.8 to 9.0/1000 [35].
Epidural test dose — The rationale for administering an epidural test dose is to determine whether the epidural catheter has been unintentionally placed in an epidural vein or the subarachnoid space. The unintentional subarachnoid injection of an epidural dose of local anesthetic (LA) could result in high or total spinal anesthesia, while an unintentional intravenous (IV) injection could cause LA systemic toxicity. (See "Local anesthetic systemic toxicity", section on 'Local anesthetic dose'.)
While a negative epidural test dose does not eliminate the possibility that the epidural catheter is malpositioned in a vein or the subarachnoid space, it improves the safety of epidural anesthesia.
The most commonly used test dose (and the one used by the authors) consists of 3 mL of 1.5% lidocaine with epinephrine (1:200,000). The onset of acute tachycardia within one minute (indicating intravascular placement of the epidural catheter) or dense motor block within five minutes (indicating intrathecal placement) constitutes a "positive" test dose. The LA dose used should be adequate to cause spinal anesthesia if injected in the subarachnoid space but not so large as to cause high or total spinal anesthesia. An increase in heart rate of 20 to 30 beats per minute is usually observed after 20 to 40 seconds following an intravenous injection of epinephrine 15 mcg [36,37]. The heart rate response to epinephrine may be less or abolished in patients receiving chronic beta-adrenergic blocker therapy; an increase in systolic blood pressure (15 to 20 mmHg) may occur without tachycardia after a positive test dose [37,38].
Chloroprocaine is the only LA that can be used alone (without epinephrine) as a single test dose to rule out both intravascular and intrathecal injection. Intravascular chloroprocaine 90 mg will cause subtoxic symptoms of LA systemic toxicity (eg, tinnitus, circumoral paresthesias) in the unpremedicated patient, and intrathecal injection will result in spinal anesthesia [39].
The use of an epidural test dose in obstetrics is discussed separately. (See "Neuraxial analgesia for labor and delivery (including instrumental delivery)", section on 'The epidural test dose in obstetrics'.)
COMBINED SPINAL-EPIDURAL ANESTHESIA — The combined spinal-epidural (CSE) technique combines the rapid onset and dense block of spinal anesthesia with the flexibility to prolong anesthesia/analgesia using the epidural catheter. The most common CSE technique is a needle-through-needle technique, which involves siting the tip of an epidural needle in the epidural space, followed by insertion of a long spinal needle through the epidural needle to inject spinal drugs, followed by removal of the spinal needle and threading of the epidural catheter in the normal fashion. Alternatively, an epidural catheter may be placed, after which a spinal anesthetic is performed at a more caudal interspace. The technique for needle-through-needle CSE is described here.
CSE equipment — Combined spinal-epidural (CSE) is usually performed with a standard epidural needle and a long spinal needle. Specialized equipment is also available, including a double-lumen epidural needle, an epidural needle with a separate parallel bore for the spinal needle [40], and epidural/spinal needle sets with hubs that lock together.
Typically, an approximately 4.7- to 5-inch (119- to 127-mm), small-gauge, pencil-point spinal needle (ie, 25- to 27-gauge) is used with a standard 8.89-cm (3.5-inch) epidural needle. In the rare instance in which a longer epidural needle is used, an even longer spinal needle is required. When the spinal needle hub is inserted up to the epidural needle hub, the spinal needle should protrude beyond the tip of the epidural needle 12 to 15 mm. A standard epidural catheter is threaded.
CSE technique — As for single-shot spinal anesthesia, combined spinal-epidural (CSE) is performed below the L2 to L3 interspace to avoid needle trauma to the spinal cord. (See "Spinal anesthesia: Technique", section on 'Midline approach technique'.)
●Position the epidural needle tip in the epidural space, as for epidural anesthesia at or below the L2 to L3 interspace. (See 'Approaches to the epidural space' above.)
●Insert a long (119- to 127-mm), 25- to 27-gauge, pencil-point spinal needle through the epidural needle. Slight resistance may be felt as a 25-gauge spinal needle exits the epidural needle. Advance the needle several millimeters, stopping if a pop or give is felt as the spinal needle punctures the dura and arachnoid membranes.
●Grasp the spinal and epidural needle hubs securely in the nondominant hand to prevent spinal needle movement, and remove the spinal needle stylet with the dominant hand to check for cerebrospinal fluid (CSF) flow. If there is no flow, replace the stylet and continue to advance the spinal needle, stopping again when a pop is felt. If neither a "dural pop" nor CSF is appreciated, then the epidural needle is most likely in the lateral epidural space, left or right of midline, or not in the epidural space at all. Alternatively, the spinal needle may not protrude far enough beyond the epidural needle to reach the dura, although this is unlikely. In either case, the epidural and spinal needle can be withdrawn and the procedure can be repeated at the same or at a different interspace, or the spinal portion can be abandoned and the epidural catheter can be inserted. If the catheter does not thread easily into the epidural space, the epidural needle should be removed and the procedure attempted from a different angle or at a different interspace.
●If CSF flows freely from the spinal needle, attach the spinal syringe and inject the intrathecal medication.
We do not routinely aspirate for CSF before injection through the spinal needle during a labor CSE analgesia, but practice varies, and it may be helpful in certain situations. Considerations regarding aspiration through the spinal needle in this setting include the following:
•Aspiration may increase the risk of spinal needle dislodgement but can also re-confirm correct spinal needle location if dislodgement is suspected.
•Aspiration prior to injection can help confirm that drugs are deposited in the subarachnoid space; however, some clinicians omit this step because the sited epidural catheter can be used to "rescue" failed spinal anesthesia.
•CSF flow may be slow if a 27-gauge spinal needle is used or if the procedure is performed in the lateral position. In some cases, CSF cannot be aspirated, despite the spinal needle tip being sited correctly in the subarachnoid space. As long as CSF drips from the spinal needle, spinal drug solution can be injected.
●Once the spinal injection is complete, repeat aspiration may be helpful to confirm that the entire spinal dose was deposited in the subarachnoid space.
●Remove the spinal needle and syringe together, leaving the epidural needle in place.
●Insert the epidural catheter, attach the catheter connector, aspirate to confirm the absence of CSF or blood return, and apply a dressing.
Dose of spinal drugs — There are various options for management of CSE anesthesia initiated for surgery, including administration of a full dose of spinal drug (table 3), followed by epidural medication as necessary, or administration of a partial spinal dose (ie, sequential CSE) with epidural administration to achieve adequate surgical anesthesia. The authors typically use a full-dose spinal technique for CSE. The choice of drugs for spinal anesthesia is discussed separately. (See "Spinal anesthesia: Technique", section on 'Choice of spinal drugs'.)
●Full spinal dose CSE – In most cases, the same doses and combinations of spinal drugs are administered as for single-shot spinal anesthesia, such that the spinal injection results in adequate surgical anesthesia.
The first dose of epidural medication is typically administered at the lower end of the range of duration of anesthesia for the spinal anesthetic (table 3). The epidural catheter is aspirated, checking for blood or CSF return. If blood or CSF is not aspirated, we administer a test dose of 3 mL of 1.5 or 2% lidocaine with epinephrine 1:200,000. In this setting, this bolus acts as a test dose for intravascular injection (ie, tachycardia occurs with intravascular injection of epinephrine). Because the patient already has a spinal block with motor block, the bolus does not test for intrathecal injection.
If the test dose is negative, an additional dose of epidural local anesthetic (LA) is injected, usually 5 to 10 mL in 3 to 5 mL increments.
●Sequential CSE – CSE anesthesia may be managed by injection of a portion of the usual single-shot spinal LA dose (table 3), usually half, followed by subsequent epidural injections (eg, 3 to 5 mL LA), titrated to achieve adequate surgical anesthesia. A full spinal dose of opioids is included with the spinal injection.
Sequential techniques result in less hypotension than single-shot or full-dose spinal CSE [41-44]. Thus, the technique may be particularly useful for patients at high risk for hypotension or at high risk for complications of hypotension. Epidural dosing or injection of even small volumes (eg, test dose) should not commence within the first 30 to 60 minutes after a full spinal dose was administered, given the increased risk of high spinal [45].
INITIATION OF EPIDURAL ANESTHESIA — Local anesthetics (LAs) should be injected slowly and preferably in increments of 3 to 5 mL every two to three minutes. Using this technique, every incremental dose acts as a test dose. Although the speed of injection of LA has been shown to increase the initial spread of sensory block, there is no difference in the final extent of the block [46,47]. A rapid injection of large doses of local anesthetic exposes the patient to the risk of LA systemic toxicity if the total dose is unintentionally injected into an epidural vein or total spinal anesthesia if unintentionally injected into the subarachnoid space.
Choice of epidural drugs — Multiple variables affect the dermatomal spread and duration of epidural anesthesia. The required dermatomal levels of sensory anesthesia vary for specific surgical procedures (table 4).
●The volume and the total LA dose (mg) are the two most important drug-related factors that influence the dermatomal extent and density of sensory and motor blockade. At the extremes, a small volume of highly concentrated LA solution will result in a dense block of limited dermatomal spread (ie, dense anesthesia limited to several dermatomes surrounding the spinal level of the drug injection). In contrast, the injection of the same dose of drug in a high-volume, low-concentration solution will result in widespread dermatomal sensory blockade of low density.
●Dense block is required for surgical anesthesia; less dense block is adequate and desired for analgesia. The required density of block also depends on the surgical stimulus and requirement for muscle relaxation. For example, manipulation of viscera may be more stimulating than skin incision. Dense anesthesia is associated with complete motor blockade, whereas less dense anesthesia/analgesia allows retention of some or all motor function.
In most cases, motor block is undesirable during postoperative epidural analgesia.
●Onset and duration of anesthesia is dependent on the physical characteristics of the individual LAs.
●The addition of adjuvants to LA solutions influences latency, density, and duration of nerve blockade.
Similar to spinal anesthesia, only preservative-free preparations of local anesthetics and other adjuvant drugs should be used for epidural anesthesia.
Local anesthetics — The local anesthetics (LAs) commonly used for epidural anesthesia include lidocaine, bupivacaine, and ropivacaine. Outside the United States, levobupivacaine is also used. 2-chloroprocaine is sometimes used for rapid onset of epidural anesthesia for emergency cesarean delivery (table 5).
●Bupivacaine – Bupivacaine is a long-acting amide LA that is commonly used for intraoperative and postoperative analgesia. Similar to other LAs, it causes a dose-dependent neuro- and cardiotoxicity. The drug is absorbed from the epidural space; therefore, the maximum recommended dose is 2 mg/kg injected into the epidural space over a short period of time. 0.75% bupivacaine is contraindicated for obstetric anesthesia because of reports of fatal LA systemic toxicity associated with its use. (See "Local anesthetic systemic toxicity".)
•Available formulations – 0.25, 0.5, and 0.75%
•Onset – 15 to 25 minutes
•Duration of surgical anesthesia – Two to four hours, depending on the dose and age [48]
•The commonly used concentrations for postoperative analgesia are 0.05, 0.0625, 0.1, and 0.125%. These must be prepared locally (off-label concentrations).
Liposomal bupivacaine is a preparation that incorporates the bupivacaine into a liposome capsule (DepoFoam). This permits bupivacaine release over an extended period, thereby prolonging the duration of analgesia. Liposome bupivacaine is approved by the US Food and Drug Administration (FDA) for surgical wound infiltration, field block, and for several peripheral nerve blocks for postsurgical pain, but not for epidural use. In a phase I trial, an epidural bolus of liposome bupivacaine resulted in a longer duration of analgesia compared with plain bupivacaine [49]. (See "Clinical use of local anesthetics in anesthesia", section on 'Sustained release bupivacaine'.)
●Lidocaine – Lidocaine is a short-acting amide LA. In contrast with intrathecal administration of lidocaine, epidural injection of lidocaine has not been associated with transient neurologic symptoms. (See "Spinal anesthesia: Technique", section on 'Local anesthetics'.)
•Available formulations – 1, 1.5, and 2%
•Onset – 5 to 15 minutes
•Duration of surgical anesthesia – 90 to 120 minutes, addition of epinephrine can extend surgical anesthesia by 30 to 45 minutes [50]
•Solutions less than 1.5% concentration (usually 1%) can be used for postoperative analgesia. However, the shorter duration of action compared with bupivacaine limits its use for this indication, as shorter acting LAs may be associated with tachyphylaxis [51].
●Ropivacaine – Ropivacaine is a pure L-enantiomer amide LA. It is 40 percent less potent than bupivacaine when used for epidural anesthesia [52,53]. Ropivacaine may cause less motor block than bupivacaine, at equivalent levels of sensory block. Animal studies show that ropivacaine may have a superior safety profile compared with an equal dose of bupivacaine [53-55], but human studies investigating the cardiac and central nervous system (CNS) toxicity of equipotent doses of ropivacaine compared with bupivacaine have found ropivacaine to be slightly less toxic than bupivacaine or not different [56,57]. The slight safety margin for ropivacaine is likely clinically relevant only when high doses are used.
•Available formulations – 0.2, 0.5, 0.75, and 1.0%
•Onset – 15 to 20 minutes
•Duration of surgical anesthesia – 1.5 to 3 hours
•The concentrations commonly used for analgesia are 0.08, 0.1, and 0.2%.
●Levobupivacaine – Levobupivacaine is the L-enantiomer of racemic bupivacaine. Levobupivacaine has similar characteristics to bupivacaine; however, it is less cardiotoxic compared with an equipotent dose of bupivacaine [52,58]. It is not available in the United States.
•Available formulations, outside the United States – 0.25, 0.5, and 0.75%
•Onset – 15 to 20 minutes
•Duration of surgical anesthesia – Two to four hours
●2-Chloroprocaine – 2-Chloroprocaine is an ester LA, with rapid onset and short duration of action. It is often used for urgent surgery, particularly in obstetrics. Systemic toxicity is rare with epidural 2-chloroprocaine because it is rapidly metabolized by plasma esterases. There is some evidence that epidural chloroprocaine reduces the efficacy of subsequently administered epidural bupivacaine and opioids [59,60], though this issue is controversial.
•Available preparations – 2 and 3%
•Onset – 10 to 15 minutes
•Duration of surgical anesthesia – 45 to 60 minutes
Adjuvants — Several classes of medications may be added to the LA solution. The addition of adjuvant medications may shorten latency, prolong the duration of anesthesia, and increase the density of sensory and motor blockade.
Opioids — Opioids improve the analgesic effect of LAs via a synergistic mechanism. Epidural opioids cross the dura and arachnoid membranes to reach the cerebrospinal fluid (CSF) and bind to opioid receptors in the dorsal horn of the spinal cord. Lipophilic opioids such as fentanyl and sufentanil readily distribute into the epidural fat and, therefore, CSF concentrations are lower compared with hydrophilic opioids such as morphine and hydromorphone.
Hydrophilic opioids can also be administered alone for analgesia, to avoid the sympathectomy and hemodynamic effects associated with epidural LAs.
There may be an analgesic ceiling effect with increasing doses of neuraxial opioids, such that there is an increase in side effects without improved analgesia [61]. Common dose-dependent adverse side effects of epidural opioids include pruritus, nausea and vomiting, and urinary retention [62,63].
●Fentanyl – Fentanyl is a lipid-soluble opioid with an onset of 5 to 15 minutes and a short duration of analgesia (one to two hours). It is usually administered in combination with LAs in bolus doses of 50 to 100 mcg to optimize intraoperative anesthesia/analgesia. The rapid onset and short duration of action of fentanyl are desirable characteristics for continuous epidural infusion. It is commonly combined with a low-concentration, long-acting LA in doses of 1.5 to 2 mcg/mL for continuous epidural labor analgesia or 2 to 5 mcg/mL for postoperative analgesia.
Use of fentanyl for epidural labor analgesia is discussed separately. (See "Neuraxial analgesia for labor and delivery (including instrumental delivery)", section on 'Epidural analgesia drug choice'.)
●Sufentanil – Sufentanil is a lipid-soluble opioid with a rapid onset and duration of analgesia similar to fentanyl, with potency approximately five times greater than fentanyl [64]. Sufentanil is usually administered in combination with LAs in bolus doses of 5 to 15 mcg to optimize intraoperative anesthesia/analgesia.
●Morphine – Morphine is a hydrophilic opioid that is usually administered for postoperative analgesia. It is administered as a bolus dose of 1 to 5 mg; onset of analgesia occurs within 30 to 60 minutes, and duration of analgesia is up to 24 hours. The ideal epidural morphine dose that will provide analgesia while minimizing adverse effects is 2.5 to 3.75 mg [61,62]. Morphine can also be administered as a continuous epidural infusion at a dose of 0.1 to 0.4 mg/hour.
Neuraxial morphine is associated with delayed respiratory depression (6 to 18 hours after administration). The use of neuraxial morphine and patient monitoring are discussed in more detail separately. (See "Continuous epidural analgesia for postoperative pain: Technique and management", section on 'Monitoring during epidural analgesia' and "Post-cesarean delivery analgesia", section on 'Side effects and complications'.)
Morphine is commercially available in preservative-free formulations intended for neuraxial use (0.5 mg/mL).
●Hydromorphone – Hydromorphone is more lipophilic than morphine. It may be administered with an LA for both intraoperative and postoperative analgesia in a bolus dose of 0.4 to 1.5 mg; onset of analgesia occurs within 15 to 30 minutes, and duration of analgesia is up to 18 hours.
Quality of analgesia and side effects of hydromorphone are similar to morphine.
Hydromorphone is commercially available in a preservative-free formulation intended for neuraxial use (2 mg/mL).
Alpha-adrenergic agonists — Alpha-adrenergic agonists may be added to epidural LA solutions to prolong the duration of action, improve analgesia, and, in the case of epinephrine, decrease systemic absorption of coadministered LAs.
●Epinephrine – The vasoconstriction associated with epinephrine reduces vascular absorption of LAs from the epidural space, thereby prolonging the anesthetic effect, reducing LA blood levels, and decreasing the risk of LA systemic toxicity. Epinephrine may also augment epidural anesthesia by direct activity on alpha-adrenergic receptors in the dorsal horn of the spinal cord [65].
Epinephrine is most effective as an adjunct and prolongs duration of anesthesia when administered in combination with the short-acting LAs lidocaine and chloroprocaine [66,67]. Epinephrine does not prolong the block with bupivacaine, levobupivacaine, or ropivacaine, because the LA effect outlasts the epinephrine effect. However, despite the intrinsic vasoconstrictive properties of bupivacaine and ropivacaine, epinephrine may reduce the vascular absorption and peak serum concentrations of these drugs [68,69].
Solutions of LA combined with epinephrine are commercially available for neuraxial use. LA solutions with epinephrine are manufactured with a low pH, to stabilize the epinephrine and prolong shelf life. As a result, a substantial portion of the LA is in the ionized form, and the latency of block with these solutions is prolonged. Therefore, some clinicians prefer to add epinephrine to plain epidural LA solutions (which generally have a higher pH than LA with epinephrine) just prior to administration. Other clinicians add sodium bicarbonate to the premixed LA/epinephrine solution to increase the pH.
The usual concentration of epinephrine for epidural injection is 5 mcg/mL (1:200,000). At the authors' institution, the practice is to draw 0.1 mL of epinephrine (1:1000) into a 1-mL syringe and add it to 20 mL of lidocaine.
●Clonidine – The addition of clonidine, an alpha2-adrenergic agonist, to epidural LA solutions may prolong the duration of sensory block [70,71] and reduce postoperative opioid requirements [70]. However, adverse effects, including hypotension, bradycardia, sedation, and dry mouth, have limited the use of clonidine for neuraxial anesthesia and analgesia in the United States.
The epidural bolus dose of clonidine is 75 to 150 mcg. Infusion for postoperative pain is started at 40 mcg/hour.
Clonidine is commercially available for neuraxial injection in concentrations of 100 and 500 mcg/mL, which must be diluted before use.
Sodium bicarbonate — Sodium bicarbonate added to LAs increases the pH of the solution so that it is closer to the pKa of the LA. This alkalinization increases the proportion of LA that is unionized and available to enter the nerve sheath and cross membranes, resulting in an increased speed of onset. (See "Clinical use of local anesthetics in anesthesia", section on 'Speed of onset'.)
The addition of sodium bicarbonate to lidocaine, chloroprocaine, and bupivacaine is reported to increase the speed of onset of epidural anesthesia by up to 10 minutes [72-74]. The effect is particularly relevant when using commercially prepared, epinephrine-containing LA solutions because of the low pH (3.2 to 4.9) of these solutions [75]. Alkalinization does not influence the speed of onset of ropivacaine, but it has been shown to increase the duration of anesthesia and extent of sensory spread [76]. Typically, 1-mL 8.4% sodium bicarbonate is added to each 10 mL of lidocaine, chloroprocaine, or lidocaine with epinephrine, just prior to use, to achieve a 0.1 mEq/mL concentration of bicarbonate [67,77].
Bicarbonate is rarely added to solutions of bupivacaine in clinical practice since other LAs would be chosen if rapid onset is desirable. Bupivacaine can easily precipitate when alkalinized, and a smaller amount of sodium bicarbonate should be added if it is used (ie, 0.1 mL per 10 mL) [78].
Management after initiation of epidural anesthesia — After the initiation of epidural anesthesia, patients require the same standard of monitoring required for general anesthesia. The adequacy of the epidural block should also be assessed prior to surgical incision. (See 'Assessment of level of block' below.)
Hemodynamic management — The hemodynamic changes that occur after initiation of epidural anesthesia are similar to the changes that occur with spinal anesthesia, although the onset of these changes is slower. The blood pressure (BP) and heart rate must be closely monitored, and clinically significant aberrations should be treated promptly.
Blood pressure
●Monitoring – BP should be measured frequently after initiation of epidural anesthesia to facilitate rapid treatment of hypotension with fluids and vasopressors as needed. We measure BP every 2.5 minutes for the first 20 minutes and every five minutes thereafter, depending on hemodynamic stability and vasopressor requirement.
●Goal BP – The target BP depends on the patient's clinical status and the clinical scenario. As examples, in women undergoing cesarean delivery with epidural anesthesia, we aim to maintain systolic BP close to baseline because of concern for uteroplacental perfusion. A similar goal applies to patients with significant cardiovascular disease. However, in young, healthy patients undergoing lower extremity surgery, a systolic BP change 20 percent below the baseline would likely be safe and well tolerated.
●Prophylaxis for hypotension – Intravenous (IV) fluids mitigate the severity of epidural anesthesia-induced hypotension. The optimal timing of fluid administration (preload versus co-load) has not been studied in patients having epidural anesthesia [79]. We administer a rapid bolus of IV crystalloid solution at the time of epidural catheter placement/induction of anesthesia (co-load) [79], modified for patient factors (eg, reduced volume or speed of administration of IV fluid in patients at risk for pulmonary edema). Since the onset of hypotension is slower for epidural as compared with spinal anesthesia, prophylactic administration of vasopressors is not typically warranted.
●Treatment of hypotension – Hypotension can be treated with rapid IV fluid administration and vasopressor administration (eg, ephedrine 5 to 10 mg IV bolus, phenylephrine 50 to 100 mcg IV bolus, or phenylephrine infusion 0.20 to 0.75/mcg/kg/minute IV).
Heart rate — Bradycardia, although uncommon following epidural anesthesia, should be treated promptly with atropine (0.4 to 0.6 mg IV) or glycopyrrolate (0.2 to 0.4 mg IV), and ephedrine (5 to 10 mg IV, repeated as needed up to 25 to 50 mg IV). If bradycardia is associated with hypotension, epinephrine (5 to 10 mcg IV) should be administered and repeated as required.
For severe bradycardia or cardiac arrest, advanced cardiac life support protocols should be initiated.
Hemodynamic management during epidural anesthesia for cesarean delivery is discussed in more detail separately. (See "Anesthesia for cesarean delivery", section on 'Hemodynamic management'.)
Assessment of level of block — A sensory level may be detected 10 to 15 minutes after epidural injection of local anesthetic. The same method for testing spinal anesthesia level is employed for assessment of sensory level following epidural anesthesia and is discussed separately. (See "Spinal anesthesia: Technique", section on 'Assessment of level of block'.)
Troubleshooting inadequate anesthesia — Several factors may contribute to inadequate anesthesia or "patchy" block. These include inadequate dermatomal extent of sensory blockade, "missed" dermatomal segments although there is adequate cephalad and caudad spread, and inadequate density of block. In particular, visceral stimulation during pelvic or abdominal surgery requires dense nerve block for adequate anesthesia. The following strategies may be used for inadequate epidural anesthesia:
●If the extent of dermatomal coverage is inadequate in either the cephalad or caudad direction, administer additional LA in 3- to 5-mL increments.
●If there are missed segments, or the block density is inadequate, inject 20 to 25 percent of the initial dose 20 to 25 minutes after the initial dose (so-called "repainting the fence") or add adjuvants (eg, fentanyl, sufentanil, epinephrine) if not already used.
●Unilateral block may result from the epidural catheter tip migrating into the lateral epidural space or into an intervertebral foramen, especially when longer lengths of catheter are advanced into the epidural space. The management options include injecting additional LA solution (usually 5 to 10 mL, injected in 3- to 5-mL increments) or withdrawing the epidural catheter 1 cm and then administering the additional LA bolus. One study in parturients with inadequate labor analgesia reported that pulling the catheter back did not reliably improve the quality of analgesia when using multi-orifice epidural catheters [80].
●If the suggested maneuvers fail to improve the quality of the block, alternatives include replacing the epidural catheter as part of an epidural or combined spinal-epidural (CSE) technique, spinal anesthesia, or abandoning the neuraxial technique. Spinal anesthesia should be induced with care after failed epidural anesthesia because of an increased risk of high or total spinal anesthesia [81].
MAINTENANCE OF ANESTHESIA — Epidural anesthesia may be maintained with intermittent bolus injections, continuous infusion, or a combination of both, depending on the clinical setting. If using bolus injections, administration of maintenance doses should be given at regular intervals. The initial dose, block height, time to two dermatome segment regression, and top up intervals for commonly used local anesthetics (LAs) are shown in a table (table 6). Waiting until sensory blockade begins to regress will result in breakthrough pain and is typically avoided.
●Bolus dosing – Typically, approximately one-half the original epidural dose of LA is injected incrementally (ie, 3 to 5 mL increments) at regular intervals (45 to 60 minutes for lidocaine and 90 to 120 minutes for bupivacaine and ropivacaine) to maintain anesthesia.
●Infusion – Epidural anesthesia may be maintained with a continuous infusion, typically a solution of a long-acting LA (bupivacaine 0.5%, ropivacaine 0.75%, or levobupivacaine 0.75%) or lidocaine 1.5% to 2%, with or without an opioid (fentanyl 2 to 5 mcg/mL or hydromorphone 5 to 10 mcg/mL) at 4 to 7 mL/hour.
If the patient experiences breakthrough pain during the surgical procedure, additional LA (and appropriate adjuvants) should be immediately injected through the epidural catheter to reestablish anesthesia.
Patients who receive intraoperative sedation may not complain of impending LA systemic toxicity, and unintentional intrathecal injection may not be recognized in patients with established neuraxial anesthesia. Therefore, epidural drugs should be injected slowly, incrementally, and cautiously while observing for signs of toxicity.
Sedation during epidural anesthesia — Sedation is administered as required and depending on the clinical setting. This is discussed separately. (See "Spinal anesthesia: Technique", section on 'Sedation during spinal anesthesia'.)
Recovery — Patients should recover in the post-anesthesia care unit (PACU) or recovery room after epidural anesthesia. In most cases after a surgical level of epidural anesthesia, the anesthetic is still in effect when the patient arrives in the PACU; BP must be measured frequently until stabilization and must be again increased in frequency after epidural bolus injection or significant increase in infusion rate. In stable patients, discharge from the PACU is safe after the sensory level of anesthesia has begun to regress.
When the epidural catheter is removed, the tip should be checked to make sure that it is intact and the catheter has been completely removed. If the catheter does not slide out with gentle traction, repositioning the patient as for epidural placement may help. A second option is to tape the epidural catheter to the skin under tension (without stretching the catheter). In the experience of the authors, this almost always results in the easy removal of the catheter several hours later. Excessive force should never be exerted while attempting to remove the epidural catheter, as the catheter may break and the distal portion will be retained in the patient.
EPIDURAL ANALGESIA FOR POSTOPERATIVE PAIN — Epidural analgesia is often used for postoperative analgesia in patients who have had epidural anesthesia. Typically, the patient is transported to the post-anesthesia care unit (PACU), and the epidural catheter is connected to an epidural infusion pump (eg, patient-controlled epidural analgesia [PCEA] pump) containing a low-concentration local anesthetic (LA)/opioid solution. A bolus dose is usually not necessary in patients with already established epidural block. The PCEA protocol is initiated as soon as the patient is stable.
Technique, benefits, and adverse effects of continuous epidural analgesia are discussed in detail separately. (See "Continuous epidural analgesia for postoperative pain: Technique and management" and "Continuous epidural analgesia for postoperative pain: Benefits, adverse effects, and outcomes".)
PATIENTS WITH SUSPECTED OR CONFIRMED COVID-19 — Regional anesthesia is not contraindicated in patients with COVID-19. Regional anesthesia may avoid the need for general anesthesia and airway management, with associated aerosolization of airway secretions and viral spread. The American Society of Regional Anesthesia and Pain Medicine and the European Society of Regional Anesthesia and Pain Therapy have published practice recommendations for neuraxial anesthesia and peripheral nerve blocks for patients with COVID-19. (See "Overview of neuraxial anesthesia", section on 'Patients with suspected or confirmed COVID-19'.)
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: Post dural puncture headache" and "Society guideline links: Local and regional anesthesia" and "Society guideline links: Local anesthetic systemic toxicity".)
SUMMARY AND RECOMMENDATIONS
●Definition and use of epidural anesthesia – Epidural anesthesia is a type of neuraxial anesthesia that is used for anesthesia and analgesia for thoracic, abdominal, pelvic, and lower extremity procedures (table 4). (See 'Anatomy' above.)
An epidural needle is used to locate the epidural space. A catheter is then inserted into the epidural space through the needle, and anesthetic solutions are injected through the catheter. (See 'Epidural anesthesia technique' above.)
●Patient positioning – Epidural anesthesia is commonly performed in the sitting or lateral decubitus position, with the spine flexed to open the space between the spinous processes and to create a straight path between the bones of the spine (figure 4 and figure 6). (See 'Positioning for epidural procedure' above.)
●Insertion technique – Epidural anesthesia can be performed either using a midline or a paramedian approach. A midline approach is commonly used for lumbar and low thoracic epidural placement. A paramedian approach is commonly used for mid- to high-thoracic epidural placement and when lumbar epidural placement fails (figure 1 and figure 10). (See 'Approaches to the epidural space' above.)
After an epidural needle is inserted and engaged in a spinal ligament, the epidural space is located by finding loss of resistance (LOR) to injection of air or saline when the needle tip is advanced out of the ligament and into the epidural space. The epidural catheter is inserted through the needle, the needle is removed, and the catheter is secured with a sterile dressing (figure 5). (See 'Approaches to the epidural space' above.)
●Epidural drugs – The volume and the dose of the injected drug are the two most important drug-related factors that influence the extent (dermatomal spread) of the epidural blockade. Lidocaine, bupivacaine, and ropivacaine are the most commonly used local anesthetics (LAs) for epidural anesthesia and analgesia (table 5). (See 'Choice of epidural drugs' above.)
Adjuvants, including opioids, epinephrine, and sodium bicarbonate, may be added to the epidural LA solution to shorten the onset time, improve anesthesia and analgesia, prolong the duration of anesthesia, and/or decrease vascular absorption. (See 'Adjuvants' above.)
●Combined spinal epidural (CSE) technique – CSE anesthesia involves injection of a spinal drug, followed by placement of an epidural catheter. A needle-through-needle technique is the most common; following epidural needle placement, a long spinal needle is inserted through the epidural needle to inject spinal drugs. An epidural catheter is then inserted to continue with epidural anesthesia. (See 'Combined spinal-epidural anesthesia' above.)
CSE can be performed with a full dose of a spinal drug, with the epidural catheter used if necessary later during surgery; or with a partial spinal dose with the full anesthetic achieved by injecting epidural drugs (sequential CSE). Epidural dosing or injection of even small volumes (eg, test dose) should not commence within the first 30 to 60 minutes after a full spinal dose was administered, due to the risk of high spinal. (See 'Dose of spinal drugs' above.)
●Monitoring during epidural or CSE anesthesia – After the initiation of epidural or CSE anesthesia, patients should be monitored as for general anesthesia, with close attention to blood pressure (BP) and heart rate. The level of sensory block should be assessed prior to incision. (See 'Maintenance of anesthesia' above.)
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