Lumbar epidural analgesic techniques for labor are characterized by numerous variations of drug regimens, including those with and without local anesthetics, opioids, and/or epinephrine, and some that include other, more novel agents such as clonidine. Advocates and rationale for various regimens depend on many factors, including patient expectations, staffing and availability of anesthesiologists, and institutional expectations. Below are recommended techniques commonly used for the provision of lumbar epidural anesthesia.

Once labor has been well established, and the obstetrician or midwife has consulted the patient, and the patient has requested epidural analgesia for pain relief, has been evaluated, and consent obtained, a continuous epidural infusion (CEI), patient controlled epidural analgesia (PCEA), or CSE may be administered. Epidural analgesia is appropriate at any time of labor when the parturient experiences painful uterine contractions, providing there are no medical or obstetric

contraindications. In the past, epidural analgesia had been withheld until a parturient was in the active phase of labor (4 to 6 cm dilated), or was experiencing strong uterine contractions lasting 1 minute or longer at regular intervals of 3 minutes. This has been the source of considerable controversy, but there is no evidence that administering an epidural analgesic in early labor is harmful (4). Both the ASA and the American College of Obstetricians and Gynecologists (ACOG) endorse practice guidelines which advocate that neuraxial analgesia should not be withheld on the basis of achieving an arbitrary cervical dilation, and neuraxial analgesia should be offered on an individual basis and on patient request (3).

After placement of a needle or catheter in the epidural space, either a specific test dose or testing regimen (see later) must be used to help rule out accidental subarachnoid or intravenous (IV) placement (Table 9-4). Analgesia is then established by injecting a local anesthetic and/or opioid (Table 9-4). The mother is tilted to her side to prevent aortocaval compression. If unilateral analgesia occurs, the patient is turned to the opposite side and more local anesthetic (5 to 10 mL) is injected. When continuous infusion techniques are used, sufficient perineal anesthesia is usually achieved by the time of delivery and a perineal dose of local anesthetic is usually not required for spontaneous vaginal delivery. When intermittent injections are used during labor, segmental analgesia is provided during labor with repeated injections until perineal anesthesia is required. When
there is perineal distention by the fetal presenting part, 10 to 15 mL of drug can be administered; either lidocaine 1.0% to 2.0% or 2-chloproprocaine 2% or 3% will produce rapid onset of profound analgesia and muscle relaxation. Bupivacaine 0.125% or 0.25% can also be used to augment perineal analgesia.

The use of a CEI of epidural local anesthetics provides greater quality of analgesia compared with parenteral (i.e., intravenous or intramuscular) opioids (1,3). The addition of opioids to epidural local anesthetics has been shown to improve analgesia with reduced motor block and maternal side effects (e.g., hypotension) compared with higher concentrations of local anesthetics without opioids (3). The lowest concentration of local anesthetic infusion (i.e., ≤0.125% bupivacaine) with or without an opioid that provides adequate maternal analgesia and satisfaction should be administered to minimize potential side effects such as motor block and hypotension (3).

A CEI allows a stable therapeutic anesthetic level, and avoids fluctuations in pain relief often found with conventional intermittent epidural injections during labor. A number of studies have suggested significant advantages to this approach (5,6). Because of the dilute local anesthetic solutions used, the amount of motor block is minimal. This allows the parturient greater mobility in bed. Pelvic muscle tone is maintained, possibly decreasing the incidence of malposition, and the parturient is better able to make expulsive efforts during the second stage of labor.

Compared to intermittent epidural bolus injections, there are fewer hypotensive episodes during CEIs (5,6,7,8), possibly due to fewer fluctuations in sympathetic block. CEI offers advantages to the busy anesthesiologist in that without intermittent injections, there is no need for the time-consuming repeat test doses or the necessary close monitoring of the patient after a reinjection. This does not mean,
however, that the anesthesiologist can ignore the patient following establishment of the block (Table 9-6). To safely achieve optimum analgesia and patient satisfaction, the anesthesiologist should examine and interview the patient at regular intervals. At those times, he or she can make necessary adjustments in the infusion rate or concentration of local anesthetic, and detect any signs of intravascular or subarachnoid migration of the catheter. Between visits, trained labor and delivery nurses must closely monitor the patient.

A variety of infusion devices may be used for delivery of continuous epidural analgesia. However, it is important that the device used has a number of safety features. The flow rate should be accurate, adjustable, and locked so that the flow rate cannot be changed by accident. The solution reservoir and tubing should be clearly and prominently labeled, and precautions must be taken to eliminate the possibility of unintentional injection of other drugs by mistake.

Potential complications of this technique are intravascular or subarachnoid migration of the catheter during the infusion, or the development of progressively higher levels of anesthesia with resulting hypotension and respiratory difficulties. It is unlikely that serious complications would occur with the

technique as outlined above. Significant systemic toxicity is usually avoided if the catheter migrates into a blood vessel because of the very low infusion rate and low concentration of local anesthetic. The principal “side effect” would be loss of pain relief. For example, bupivacaine 0.125% infused at 10 mL/h would only inject 12.5 mg of drug per hour—an amount that would not cause systemic toxicity, but which would not produce any analgesic effect.

Should the epidural catheter accidently be sited intrathecally, the onset of motor block would be slow and easily diagnosed. For example, bupivacaine 0.125% infused at 10 mL/h over a 30-minute period would deliver 6.25 mg bupivacaine into the subarachnoid space, an amount that would prevent the patient from raising her legs, thereby alerting the staff to an intrathecal injection. Even with higher infusion rates of dilute solutions, the unexpectedly and generally slowly ascending sensory level would be easily recognized. Despite the inherent safety of continuous infusion for obstetric anesthesia, mishaps can still occur. Experienced, trained, vigilant medical and nursing staff must be immediately and readily available to manage possible complications of epidural analgesia.

Gambling in 1988 was the first to describe PCEA (9). PCEA can be provided as demand dose only or in combination with a continuous background infusion. Compared to CEI, advantages of PCEA include less local anesthetic consumption (3,9,10,11), decreased anesthesia personnel work-load with fewer anesthetic interventions, equivalent or improved analgesia (3,9), increased patient satisfaction (3,9), greater patient participation, control, and autonomy over pain relief (9), and less motor blockade (3). PCEA may be used with or without a background infusion (3); however, a fixed continuous background infusion may allow for a more stable therapeutic analgesic level with improved analgesia and less need for intervention (i.e., “top-ups”) by the anesthesia provider (3,12).

Solutions used for PCEA are the same as those used for CEI analgesia. The anesthesia provider can manipulate the infusion solution (local anesthesia/opioid concentration), patient controlled bolus volume, lockout interval, background infusion rate, and maximum allowable dose per hour. It should be noted that the ideal PCEA parameters (i.e., bolus dose, lockout interval, background infusion rate) have not been determined. Recommended PCEA drug regimens and infusion parameters are presented in Table 9-5.

In a meta-analysis of nine randomized controlled trials comparing PCEA without a background infusion versus CEI, van der Vyer et al. (11) found there were fewer anesthetic interventions, less local anesthetic requirement, and less motor block, equivalent maternal satisfaction, and no differences in maternal or neonatal outcome.

In summary, PCEA offers many advantages over CEI and provides a highly effective and flexible approach for the maintenance of labor analgesia (3).

Programmed intermittent epidural bolus (PIEB) dosing compared with CEI used with or without PCEA has been studied. It seems that when larger epidural volumes are administered under high pressure, distribution of anesthetic solutions in the epidural space is more uniform. In a study on cadavers, Hogan noticed that epidural spread is much more uniform when larger volumes are given with corresponding higher injectate pressures, while low-pressure continuous infusions are associated with uneven distribution in the epidural space (13). Similarly, in comparing CEI to an intermittent hourly bolus dose of the same solution, Fettes et al. (14) found that regular intermittent epidural administration is associated with reduced need for epidural rescue medication, less epidural drug use, and equivalent pain relief when compared with CEI. Fettes concluded that intermittent boluses result in more uniform spread, giving more reliable analgesia than CEI (14).

In a clinical study, Wong et al. (15) compared automated PIEB every 30 minutes beginning 45 minutes after the intrathecal injection in multiparous patients with CEI (12 mL/h infusion) in laboring parturients, and found that PIEB combined with PCEA provided similar analgesia, but with a smaller bupivacaine dose, fewer manual rescue boluses, and better patient satisfaction compared with CEI. Likewise, Sia et al. (16) found that PIEB delivered as an automated bolus every hour combined with PCEA reduced analgesic consumption and the need for parturients’ self-bolus of analgesics compared with CEI. In both studies, the total dose of local anesthetic was smaller in the automated bolus groups than in the continuous infusion groups. In another PIEB study by Wong et al. (17), they compared PIEB alone (without the combination of PCEA) and found that extending the PIEB interval and volume from 15 to 60 minutes, and 2.5 to 10 mL decreased bupivacaine consumption without decreasing patient comfort or satisfaction.

In summary PIEB can result in less local anesthetic consumption, less breakthrough pain, and improved patient satisfaction compared with CEI or PCEA with a continuous basal infusion. However, the greatest impediment to implementation of PIEB analgesia is the lack of commercial pumps designed to deliver timed boluses or time boluses with PCEA. Further studies are needed to determine the optimal combination of bolus volume, time interval, and drug concentrations for use with this technique.

Spinal anesthesia, also referred to as a saddle block, is often administered when a patient is in advanced labor. It can provide immediate analgesia when there is not enough time for placement of an epidural catheter. For a true saddle block, a small dose of hyperbaric local anesthetic (e.g., bupivacaine 4 to 5 mg, lidocaine 15 to 20 mg, or tetracaine 3 mg, with
or without fentanyl 10 to 25 μg, or sufentanil 2.5 to 5 μg) is injected into the subarachnoid space with the patient in the sitting position, to accomplish sacral-only anesthesia.

More commonly, however, a wider dermatomal anesthetic distribution (T10 to S5) is desired and can be accomplished with slightly larger doses of bupivacaine (7.5 mg), lidocaine (30 mg), or tetracaine (4 mg) with or without an opioid (fentanyl 10 to 25 μg, or sufentanil 2.5 to 5 μg). Small-bore, pencil-point spinal needles will decrease the incidence of postdural puncture headache (PDPH) (18,19,20).

The degree to which spinal anesthesia can be confined to sacral, or even to low thoracic dermatomes is limited and not directly related to the dose of subarachnoid local anesthetic (21). Hyperbaric solutions tend to ascend to mid- or upper thoracic dermatomes regardless of dose. One-shot spinal anesthesia is therefore rarely used in modern practice.

Passing a catheter into the subarachnoid space has several potential advantages: (1) Provision of rapid analgesia or anesthesia, (2) allows flexibility in medication dosing of small amounts of local anesthetic or opioid, perhaps limiting the degree of sympathectomy and hypotension, which can be particularly useful for high-risk patients in whom an unplanned high block may produce serious cardiovascular or respiratory problems, (3) the morbidly obese parturient in whom placement of an epidural is technically difficult or impossible (22), and (4) placing an epidural catheter into the subarachnoid space following an accidental dural puncture during a planned epidural (“wet tap”). When this situation occurs, the anesthesiologist may choose to insert the epidural catheter into the subarachnoid space proceed with intermittent or continuous spinal anesthesia. After delivery, the intrathecal catheter can be left in place for 24 hours before removal, which has been shown in some but not all studies to decrease the incidence of PDPH (19).

Disadvantages of the technique include the increased risk for infection (meningitis, arachnoiditis) and nerve trauma, which have not proven to be a significant problem in clinical practice. Concern regarding the use of a large-bore needle commonly used for continuous techniques producing an unacceptably high incidence of PDPH also has not been consistently supported by clinical studies in nonpregnant patients (23,24,25). However, many obstetric anesthesiologists find the rate of PDPH when unintentional dural puncture occurs and is managed with an intrathecal (epidural) catheter to be too high to allow for routine elective use.

Spinal microcatheters that pass through a standard 25 or 26 gauge spinal needle have been investigated in the past, and are not currently marketed in the United States. In 1992, the US Food and Drug Administration removed intrathecal microcatheters (27 to 32 gauge) from clinical use after reports of neurologic injury in nonobstetric patients (26,27,28,29,30). Larger gauge spinal catheters have been investigated (31). Alonso studied continuous spinal anesthesia using an over-the-needle 22 or 2-gauge spinal catheter and found an unacceptably high block failure rate and PDPH rate (31).

More recently, in a prospective, randomized, multicenter trial, Arkoosh et al. (32) examined the safety and efficacy of a 28 gauge intrathecal catheter for labor analgesia using bupivacaine and sufentanil compared to conventional epidural analgesia and found that the intrathecal technique was associated with increased technical difficulties (more difficult to remove) and catheter failures compared with traditional epidural analgesia. Importantly, there were zero cases of adverse neurologic sequelae. Nonetheless, spinal microcatheters have not found a market in the United States after the earlier failures. Novel devices for continuous spinal anesthesia have been explored, including the Wiley spinal device (an over-the-needle system utilizing a small-bore pencil-point needle for the dural puncture) and may be promising alternatives (33).

CSE analgesia in labor has become a popular technique in many obstetric centers. The CSE technique combines the benefits of spinal anesthesia including rapid onset of analgesia and confirmation of correct needle placement (CSF flow) with the benefits of epidural anesthesia (34,35,36). After the spinal anesthesia wears off, the epidural catheter can be dosed in the usual fashion and used for labor analgesia or anesthesia. The CSE technique can also be used to provide anesthesia for cesarean delivery and other surgical procedures (37).

CSE kits can be purchased individually from several manufacturers. The CSE technique can also be performed by placing a standard epidural needle in the usual manner at L3–L4 or L4–L5, and then placing a long spinal needle (24 gauge or smaller and 124 mm or longer) through the epidural needle to enter the subarachnoid space. For labor analgesia, an opioid such as fentanyl (10 to 25 μg) or sufentanil (2.5 to 10 μg) may be injected alone or in combination with a local anesthetic such as plain bupivacaine (1 to 2.5 mg) to provide pain relief for approximately 90 minutes (range: 20 to 245 minutes) (34,35,36).

In many institutions, intrathecal fentanyl alone is a common choice for CSE. In one study, the median effective dose was 14 μg (95% confidence interval, 13 to 15 μg), and there was no benefit shown in increasing the dose beyond 25 μg (35). In another study, the mean duration of intrathecal sufentanil (10 μg) for labor analgesia was 102 ± 49.8 minutes (36), though lower doses (5 μg) may be sufficient. After the intrathecal dose is administered, an epidural catheter is then placed for further administration of local anesthetic for labor analgesia or instrumental surgical delivery as needed. For labor, an epidural infusion initiated with a bolus of bupivacaine 0.0625% to 0.125% with 0.0002% fentanyl (2 μg/mL) or an equivalent dose of ropivacaine or levobupivacaine. Alternatively, a continuous infusion or PCEA may be initiated without a bolus
immediately following the intrathecal injection and insertion of the epidural catheter. The transition from intrathecal to epidural analgesia is typically nearly seamless.

When the CSE technique is used for labor, it has the benefit of allowing maternal ambulation if desired, and is often referred to as the walking epidural. While walking itself with CSE (38), or without neuraxial analgesia (39), may not offer any real advantages with respect to labor duration, augmentation with oxytocin, delivery outcome, maternal, or fetal complications, walking using the CSE technique can be safely done and may be appealing to some parturients (40,41). However, specific criteria to allow walking must be developed and followed if accidents are to be avoided (42). Even if ambulation is not encouraged, establishing analgesia promptly with minimal initial motor blockade is not only satisfying to the patient, but to the obstetricians and nurses as well.

In comparing labor analgesia using epidural anesthesia or CSE in nulliparous and parous women, no significant differences were observed in duration of labor, mode of delivery, local anesthetic consumed, or maternal or fetal complications (42,43,44).

The side effects of the CSE technique are similar to those encountered with epidural or intrathecal opioids combined with those of spinal anesthesia. They include pruritus, nausea, vomiting, hypotension, respiratory depression, PDPH, urinary retention, and fetal heart rate (FHR) abnormalities (Table 9-9) (45). The most common side effect of the CSE is pruritus, which has been reported to occur in 80% of patients receiving intrathecal sufentanil (45,46); however, few of these patients require treatment. Hypotension occurs in 5% to 10% of patients who receive intrathecal fentanyl or sufentanil (47,48). The incidence of hypotension is similar to that seen with routine labor epidural analgesia and is treated in the same manner. Nausea and vomiting (2% to 3%), respiratory depression (very rare), and PDPH (1% or less) are not common and can be managed fairly easily (Table 9-9).

However, FHR abnormalities with the CSE technique are more common (47,49,50). Three nonrandomized studies have reported that the risk of fetal bradycardia is similar after intrathecal sufentanil or epidural bupivacaine (51–53). Meta-analysis of multiple randomized trials comparing intrathecal and epidural analgesia found a modest increase in FHR abnormalities (odds ratio 1.8 [95% confidence interval 1.0 to 3.1], number-needed-to-harm 28) but not in adverse fetal outcomes or emergency cesarean delivery (54). FHR abnormalities occur commonly during labor and have been reported to occur with IV meperidine, paracervical blocks, epidural local anesthetics, and intrathecal opioids (55). It has also been suggested that women in severe pain, or with induced labor may be at a greater risk for FHR changes (53), and that a selection bias may be created by administering CSE to these women (55). Management of FHR changes can include treatment of maternal hypotension, maternal position change (left uterine displacement [LUD]), supplemental oxygen administration, IV fluid bolus, and treatment of uterine hyperstimulation. Uterine hyperstimulation has been postulated as a possible mechanism for fetal bradycardia associated with the CSE technique (see Chapter 9) (50,55). Terbutaline (1.25 to 2.5 mg IV or subcutaneously) or nitroglycerin (50 to 200 μg IV or 400 to 800 g [two puffs]
sublingual) can be useful for treatment of uterine hyperstimulation. An alternative hypothesis is transient uterine vascular constriction following changes in maternal catecholamines (56). FHR abnormalities usually respond to this management and in a large retrospective review the incidence of emergency cesarean sections was no different in women receiving CSE for labor analgesia compared with either no regional technique or systemic medication (1.3% vs. 1.4%) (57). As noted earlier, the rate of emergency cesarean delivery also did not differ in a meta-analysis of RCTs comparing CSE to conventional epidural analgesia (54).