Epidural, spinal, or combined spinal-epidural techniques are the most common methods used for pain relief during labor and delivery. In the United States in 2008, epidural analgesia was used in nearly 70 percent of mothers during labor and had a success rate of 98.8 percent. Neuraxial analgesia was used even more often in operative vaginal deliveries and supported 84 percent of forceps deliveries and 77 percent of vacuum extractions (Osterman, 2011).
Spinal (Subarachnoid) Block
Anesthetic in this block can be given as a single dose, can be partnered with an epidural catheter as combined spinal-epidural analgesia, or can be administered as a continuous infusion. Injection of a local anesthetic into the subarachnoid space to effect analgesia has long been used for delivery. Advantages include rapid analgesia onset, short duration of action, and high success rate. The subarachnoid space during pregnancy is smaller, which likely results from internal vertebral venous plexus engorgement. Thus, in parturients, the same amount of anesthetic agent in the same volume of solution produces a much higher blockade than in nonpregnant women.
The first stage of labor requires a sensory block to the level of the umbilicus (T10). During the second stage of labor and for operative vaginal delivery, a sensory block of S2 through S4 is usually adequate to cover pain from perineal stretching and/or instrumentation. Analgesic options include continuous lumbar epidural analgesia, combined spinal-epidural, continuous spinal analgesia, and other blocks such as pudendal and paracervical blocks.
Local anesthetic agents are usually given to establish a sensory block to the desired dermatome level. They are almost exclusively used in conjunction with neuraxial opioids. The mechanism of action is a function of the administration route and lipid solubility. Analgesia is induced by absorption into the vascular system (supraspinal), actions on the dorsal horns, and direct spread in the cerebrospinal fluid to the brainstem. Highly-soluble lipid opioids such as fentanyl and sufentanil have a rapid onset of action. But, because they are absorbed into lipid membranes and the epidural vasculature, their duration of action is short. Hydrophilic solutions such as morphine, on the other hand, provide extended analgesia (Lavoie, 2013). The major advantages of using such a combination are the rapid onset of pain relief, a decrease in shivering, and less dense motor blockade. Side effects are common and include pruritus and urinary retention. Nalbuphine, 2.5 to 5 mg intravenously, can be used to treat pruritis without diminishing the analgesic effect.
A level of sensory blockade extending to the T4 dermatome is desired for cesarean delivery. Depending on maternal size, 10 to 12 mg of bupivacaine in a hyperbaric solution or 50 to 75 mg of lidocaine hyperbaric solution is administered. The addition of opioid increases the rapidity of blockade onset, reduces shivering, and minimizes referred pain and other symptoms such as nausea and vomiting. The addition of a preservative-free morphine (Duramorph or Astramorph), 0.1 to 0.3 mg intrathecal or 2 to 4 mg epidural, provides pain control up to 24 hours postoperatively.
Shown in Table 25-5 are some of the more common adverse events associated with neuraxial analgesia. Importantly, obese women have significantly impaired ventilation, and thus close clinical monitoring is imperative (Vricella, 2011).
TABLE 25-5Complications of Regional Analgesia ||Download (.pdf) TABLE 25-5 Complications of Regional Analgesia
|Not infrequent |
Fever Postdural puncture headache
Inadvertant intrathecal, subdural, or intravascular injection of local anesthetic drugs
Hypotension is a common complication that may develop soon after injection of the local anesthetic agent. It is the consequence of vasodilatation from sympathetic blockade and is compounded by obstructed venous return due to uterine compression of the great vessels. In the supine position, even in the absence of maternal hypotension measured in the brachial artery, placental blood flow may still be significantly reduced. Treatment includes uterine displacement by left lateral patient positioning, intravenous crystalloid hydration, and intravenous bolus injections of ephedrine or phenylephrine.
Ephedrine is a sympathomimetic drug that binds to α- and β-receptors but also indirectly enhances norepinephrine release. It raises blood pressure by raising heart rate and cardiac output and by variably elevating peripheral vascular resistance. In early animal studies, ephedrine preserved uteroplacental blood flow during pregnancy compared with α1-receptor agonists. Accordingly, it had been the preferred vasopressor for obstetrical use. Phenylephrine is a pure α-agonist and elevates blood pressure solely through vasoconstriction. A metaanalysis of seven randomized trials by Lee (2002a) suggests that the safety profiles of ephedrine and phenylephrine are comparable. Following their systematic review of 14 reports, Lee (2002b) questioned whether routine prophylactic ephedrine is needed for elective cesarean delivery. Although fetal acidemia has been reported with prophylactic ephedrine use, this was not observed with prophylactic phenylephrine use (Ngan Kee, 2004).
High or Total Spinal Blockade
Most often, high or total spinal blockade follows administration of an excessive dose of local anesthetic or inadvertent injection into the subdural or subarachnoid space. Subdural injection manifests as a high but patchy block even with a small dose of local anesthetic agent, whereas subarachnoid injection typically leads to complete spinal blockade with hypotension and apnea. These conditions must be immediately treated to prevent cardiac arrest. In the undelivered woman: (1) the uterus is immediately displaced laterally to minimize aortocaval compression; (2) effective ventilation is established, preferably with tracheal intubation; and (3) intravenous fluids and vasopressors are given to correct hypotension. If chest compressions are to be performed, the woman is placed in the left-lateral position to allow left uterine displacement.
Postdural Puncture Headache
Leakage of cerebrospinal fluid (CSF) from the dura mater puncture site can lead to postdural puncture or “spinal headache.” Presumably, when the woman sits or stands, the diminished CSF volume creates traction on pain-sensitive central nervous system structures. Another mechanism may be the compensatory cerebral vasodilation in response to the loss of CSF—the Monro-Kellie doctrine (Mokri, 2001).
Rates of this complication can be reduced by using a small-gauge spinal needle and avoiding multiple punctures. In a prospective, randomized study of five different spinal needles, Vallejo and associates (2000) concluded that Sprotte and Whitacre needles had the lowest risks of postdural puncture headaches. Sprigge and Harper (2008) reported that the incidence of postdural puncture headache was 1 percent in more than 5000 women undergoing spinal analgesia. Postdural puncture headaches are much less frequent with epidural blockade because the dura mater is not intentionally punctured. The incidence of inadvertent dural puncture with epidural analgesia approximates 0.2 percent (Introna, 2012; Katircioglu, 2008). There is no good evidence that placing a woman absolutely flat on her back for several hours is effective in preventing this headache.
Once headache develops, it is managed aggressively, as expectant management increases hospital-stay lengths and subsequent emergency-room visits (Angle, 2005). Conservative management, such as fluid administration and bed rest, is largely ineffective. If not effectively treated, postdural puncture headache can persist as a chronic headache (Webb, 2012).
Epidural blood patch is considered the gold standard for treatment. Typically, 10 to 20 mL of autologous blood obtained aseptically by venipuncture is injected into the epidural space. Further CSF leakage is halted by either mass effect or coagulation. Relief is almost always immediate, and complications are uncommon. The initial success rate of an epidural blood patch ranges from 61 to 73 percent (Paech, 2011). Performing a “prophylactic” blood patch is debatable and is thought not to be as effective as if performed after the headache develops (Scavone, 2004, 2015).
If a headache does not have the pathognomonic postural characteristics or persists despite treatment with a blood patch, other diagnoses are considered. Chisholm and Campbell (2001) described a case of superior sagittal sinus thrombosis that manifested as a postdural headache. Smarkusky and colleagues (2006) described pneumocephalus, which caused immediate cephalgia. Finally, intracranial and intraspinal subarachnoid hematomas have developed after spinal analgesia (Dawley, 2009; Liu, 2008).
In rare instances, postdural puncture cephalgia is associated with temporary blindness and convulsions. Shearer and associates (1995) described eight such cases associated with 19,000 regional analgesic procedures done at Parkland Hospital. It is presumed that these too are caused by CSF hypotension. Immediate treatment of seizures and a blood patch were usually effective in these cases.
With neuraxial analgesia, bladder sensation is likely to be obtunded and bladder emptying impaired for several hours after delivery. As a consequence, bladder distention is a frequent postpartum complication, especially if appreciable volumes of intravenous fluid are given. Millet and colleagues (2012) randomized 146 women with neuraxial analgesia to either intermittent or continuous bladder catheterizations and found that the intermittent method was associated with significantly higher rates of bacteriuria. That said, we do not recommend routine postpartum use of indwelling catheters following uncomplicated vaginal delivery.
Arachnoiditis and Meningitis
Local anesthetics are no longer preserved in alcohol, formalin, or other toxic solutes, and disposable equipment is usually used. These practices, coupled with aseptic technique, have made meningitis and arachnoiditis rare (Centers for Disease Control and Prevention, 2010).
Contraindications to Neuraxial Analgesia
Shown in Table 25-6 are absolute contraindications. Obstetrical complications that are associated with maternal hypovolemia and hypotension—for example, severe hemorrhage—are contraindications (Kennedy, 1968).
TABLE 25-6Absolute Contraindications to Neuraxial Analgesia ||Download (.pdf) TABLE 25-6 Absolute Contraindications to Neuraxial Analgesia
|Refractory maternal hypotension |
|Maternal coagulopathy |
|Thrombocytopenia (variously defined) |
|Low-molecular-weight heparin within 12 hours |
|Untreated maternal bacteremia |
|Skin infection over site of needle placement |
|Increased intracranial pressure caused by a mass lesion |
Disorders of coagulation and defective hemostasis also preclude neuraxial analgesia use. Although no randomized studies guide the management of anticoagulation at the time of delivery, consensus opinion suggests that women given subcutaneous unfractionated heparin or low-molecular-weight heparin should be instructed to stop therapy when labor begins (Krivak, 2007). Subarachnoid puncture is also contraindicated if cellulitis involves the planned needle entry site. Many consider neurological disorders to be a contraindication, if for no other reason than that exacerbation of the neurological disease might be erroneously attributed to the anesthetic agent. Other maternal conditions, such as aortic stenosis or pulmonary hypertension, are also relative contraindications (Chap. 49, Physiological Considerations in Pregnancy).
Severe preeclampsia is another comorbid condition in which markedly decreased blood pressure can be predicted when neuraxial analgesia is used. Wallace and associates (1995) randomly assigned 80 women with severe preeclampsia undergoing cesarean delivery at Parkland Hospital to receive general anesthesia or either epidural or combined spinal-epidural analgesia. Maternal and neonatal outcomes did not differ. Still, 30 percent of women given epidural analgesia and 22 percent of those given spinal-epidural blockade developed hypotension. The average reduction in mean arterial pressure ranges between 15 and 25 percent.
Relief of labor and childbirth pain, including cesarean delivery, can be accomplished by injection of a local anesthetic agent into the epidural or peridural space (Fig. 25-3). This potential space contains areolar tissue, fat, lymphatics, and the internal vertebral venous plexus. This plexus becomes engorged during pregnancy such that the volume of the epidural space is appreciably reduced. Entry for obstetrical analgesia is usually through a lumbar intervertebral space. Although only one injection may be elected, usually an indwelling catheter is placed for subsequent agent boluses or infusion via a volumetric pump. The American College of Obstetricians and Gynecologists (2017a) concludes that under appropriate physician supervision, labor and delivery nursing personnel who have been specifically trained in the management of epidural infusions should be able to adjust dosage and also discontinue infusions.
Neuraxial analgesia: A. Combined spinal-epidural analgesia. B. Epidural analgesia.
Continuous Lumbar Epidural Block
Complete analgesia for the pain of labor and vaginal delivery necessitates a block from the T10 to the S5 dermatomes (see Fig. 25-1). For cesarean delivery, a block extending from the T4 to the S1 dermatomes is desired. The effective spread of anesthetic depends on the catheter tip location; the dose, concentration, and volume of anesthetic agent used; and whether the mother is head-down, horizontal, or head-up (Setayesh, 2001). Individual variations in anatomy or presence of synechiae may preclude a completely satisfactory block. Finally, the catheter tip may migrate from its original location during labor.
One example of the sequential steps and techniques for performance of epidural analgesia is detailed in Table 25-7. Before injection of the local anesthetic therapeutic dose, a test dose is given. The woman is observed for features of toxicity from intravascular injection and for signs of high or total blockade from subdural or subarachnoid injection. If these are absent, only then is a full dose given. Analgesia is maintained by intermittent boluses of similar volume or by small volumes delivered continuously by infusion pump (Halpern, 2009). Current pumps used for epidural analgesia offer a programmed intermittent epidural bolus (PIEB) mode, which reduces the required concentration of local anesthetics, the degree of lower extremity motor blockade, and rates of operative vaginal delivery (Capogna, 2011). The addition of small doses of a short-acting narcotic—fentanyl or sufentanil—has been shown to improve analgesic efficacy while avoiding motor blockade (Chestnut, 1988). As with spinal blockade, close monitoring, including the level of analgesia, is imperative and must be performed by trained personnel. Appropriate resuscitation equipment and drugs must be available during administration of epidural analgesia.
TABLE 25-7Technique for Labor Epidural Analgesia ||Download (.pdf) TABLE 25-7 Technique for Labor Epidural Analgesia
|Informed consent is obtained, and the obstetrician consulted |
|Monitoring includes the following: |
| Blood pressure every 1 to 2 minutes for 15 minutes after giving a bolus of local anesthetic |
| Continuous maternal heart rate monitoring during analgesia induction |
| Continuous maternal pulse oximetry |
| Continuous fetal heart rate monitoring |
| Continual verbal communication |
|Hydration with 500 to 1000 mL of lactated Ringer solution |
|The woman assumes a lateral decubitus or sitting position |
|The epidural space is identified with a loss-of-resistance technique |
|The epidural catheter is threaded 3 to 5 cm into the epidural space |
|A test dose of 3 mL of 1.5% lidocaine with 1:200,000 epinephrine or 3 mL of 0.25% bupivacaine with 1:200,000 epinephrine is injected after careful aspiration to avert intravascular injection and after a uterine contraction. This minimizes the chance of confusing tachycardia that results from labor pain with tachycardia from intravenous injection of the test dose. |
|If the test dose is negative, 10–15 mL of 0.0625–0.125% bupivacaine are injected to achieve a sensory T10 level. |
|After 15 to 20 minutes, the block is assessed using loss of sensation to cold or pinprick. If no block is evident, the catheter is replaced. If the block is asymmetrical, the epidural catheter is withdrawn 0.5 to 1.0 cm and an additional 5 to 10 mL of 0.0625–0.125% bupivacaine is injected. If the block remains inadequate, the catheter is replaced. |
|The woman is positioned in the lateral or semilateral position to avoid aortocaval compression. |
|Subsequently, maternal blood pressure is recorded every 5 to 15 minutes. The fetal heart rate is monitored continuously. |
|The level of analgesia and intensity of motor blockade are assessed at least hourly. |
Higher or Total Spinal Blockade
In general, complications with epidural analgesia are similar to those with spinal analgesia (see Table 25-5). Dural puncture with inadvertent subarachnoid injection may cause total spinal blockade. Sprigge and Harper (2008) cited an incidence of 0.91 percent recognized accidental dural punctures at the time of epidural analgesia in more than 18,000 women. Personnel and facilities must be immediately available to manage this complication as described earlier (Cesarean Delivery). In other aspects, however, complications are unique and inherent to epidural analgesia use.
Using currently popular continuous epidural infusion regimens such as 0.125-percent bupivacaine with 2-μg/mL fentanyl, 90 percent of women rate their pain relief as good to excellent (Sharma, 1997). Alternatively, a few women find epidural analgesia to be inadequate for labor. In a study of almost 2000 parturients, Hess and associates (2001) found that approximately 12 percent complained of three or more episodes of pain or pressure. Risk factors for such breakthrough pain included nulliparity and heavier fetal weights. Dresner and colleagues (2006) also reported that epidural analgesia was more likely to fail as body mass index increased. If epidural analgesia is allowed to dissipate before another injection of anesthetic drug, subsequent pain relief may be delayed, incomplete, or both.
In some women, epidural analgesia is insufficient for cesarean delivery. For example, in a Maternal Fetal Medicine Units (MFMU) Network study, 4 percent of women initially given epidural analgesia required a general anesthetic for cesarean delivery (Bloom, 2005). Also at times, perineal analgesia for delivery is difficult to obtain, especially with the lumbar epidural technique. When this situation is encountered, pudendal block or systemic analgesia or rarely general anesthesia may be added.
Sympathetic blockade from epidurally injected analgesic agents can cause hypotension and decreased cardiac output. Despite precautions, hypotension is the most frequent side effect and is severe enough to require treatment in a third of women (Sharma, 1997). According to Miller and coworkers (2013), hypotension is more common—20 percent—in women with an admission pulse pressure <45 mm Hg, compared with 6 percent in those whose pulse pressure is >45 mm Hg. In normal gravidas, hypotension induced by epidural analgesia usually can be prevented by rapid infusion of 500 to 1000 mL of crystalloid solution as described for spinal analgesia. Maintaining a lateral position also minimizes hypotension.
Fusi and colleagues (1989) observed that the mean temperature rose in laboring women given epidural analgesia. Subsequently, several randomized and retrospective cohort studies have confirmed that some women develop intrapartum fever following this procedure. Many studies are limited by inability to control for other risk factors such as labor length, duration of ruptured membranes, and number of vaginal examinations. With this in mind, the frequency of intrapartum fever associated with epidural analgesia was found by Lieberman and O’Donoghue (2002) to be 10 to 15 percent above the baseline rate.
The two general theories concerning the etiology of maternal hyperthermia are maternal-fetal infection or dysregulation of body temperature. Dashe and coworkers (1999) studied placental histopathology in laboring women given epidural analgesia and identified intrapartum fever only when there was placental inflammation. This suggests that fever is due to infection. The other proposed mechanisms include alteration of the hypothalamic thermoregulatory set point; impairment of peripheral thermoreceptor input to the central nervous system, with selective blockage of warm stimuli; or imbalance between heat production and heat loss. Sharma (2014) randomized 400 nulliparas with labor epidural analgesia to receive cefoxitin 2 g prophylactically versus placebo. It was hypothesized that epidural-related fever was due to infection and that prophylactic antimicrobial use should significantly reduce the rate of fever. Approximately equal proportions—about 40 percent—of women developed fever >38°C during labor. This suggests that infection is unlikely to be the cause of fever.
An association between epidural analgesia and subsequent back pain has been reported by some but not all. In a prospective cohort study, Butler and Fuller (1998) reported that back pain after delivery was common with epidural analgesia, however, persistent pain was uncommon. Based on their systematic review, Lieberman and O’Donoghue (2002) concluded that available data do not support an association between epidural analgesia and development of de novo, long-term backache.
A spinal or epidural hematoma is a rare complication of an epidural catheter (Grant, 2007). Epidural abscesses are equally infrequent (Darouiche, 2006). And uncommonly, the plastic epidural catheter can be sheared off (Noblett, 2007).
Most studies, including the five from Parkland Hospital, report that epidural analgesia prolongs labor and increases the use of oxytocin stimulation (Table 25-8). Alexander and associates (2002) examined the effects of epidural analgesia on the Friedman (1955) labor curve described in Chapter 22 (First Stage of Labor). Compared with original Friedman criteria, epidural analgesia prolonged the active phase of labor by 1 hour. As further shown in Table 25-8, epidural analgesia also increased the need for operative vaginal delivery because of prolonged second-stage labor. But importantly, this led to no greater rates of adverse neonatal effects.
TABLE 25-8Selected Labor Events in 2703 Nulliparous Women Randomized to Epidural Analgesia or Intravenous Meperidine Analgesia ||Download (.pdf) TABLE 25-8 Selected Labor Events in 2703 Nulliparous Women Randomized to Epidural Analgesia or Intravenous Meperidine Analgesia
|Eventa ||Epidural Analgesia n = 1339 ||Intravenous Meperidine n = 1364 ||p value |
|Labor outcomes || || || |
|First-stage duration (hr)b ||8.1 ± 5 ||7.5 ± 5 ||0.011 |
|Second-stage duration (min) ||60 ± 56 ||47 ± 57 ||<0.001 |
|Oxytocin after analgesia ||641 (48) ||546 (40) ||<0.001 |
|Type of delivery || || || |
|SVD ||1027 (77) ||1122 (82) ||<0.001 |
|Forceps ||172 (13) ||101 (7) ||<0.001 |
|Cesarean ||140 (10.5) ||141 (10.3) ||0.92 |
This association among epidural analgesia and prolonged second-stage labor and operative vaginal delivery has been attributed to anesthesia-induced motor blockade and resultant impaired maternal expulsive efforts. Craig and colleagues (2015) randomized 310 nulliparous women with labor epidural analgesia to bupivacaine plus fentanyl or fentanyl alone during second-stage labor. Epidural bupivacaine analgesia did cause motor blockade during the second stage, however, the duration of the second stage was not increased.
Hill and associates (2003) examined the effects of epidural analgesia with 0.25-percent bupivacaine on fetal heart rate patterns. Compared with intravenous meperidine, no deleterious effects were identified. Reduced beat-to-beat variability and fewer accelerations were more frequent sequelae in fetuses whose mothers received meperidine (Chap. 24, Cardiac Arrhythmia). Based on their systematic review, Reynolds and coworkers (2002) reported that epidural analgesia was associated with improved neonatal acid-base status compared with meperidine.
A contentious issue in the past was whether epidural analgesia increased the risk for cesarean delivery. Supporting evidence for this view came from the era when dense blocks of local anesthetic agents were used that impaired motor function and therefore likely did contribute to higher cesarean delivery rates. As techniques were refined, however, many investigators came to believe that epidural administration of dilute anesthetic solutions did not increase cesarean delivery rates.
Several studies conducted at Parkland Hospital were designed to answer this and related questions. From 1995 to 2002, a total of 2703 nulliparas at term and in spontaneous labor were enrolled in five trials to evaluate epidural analgesia techniques compared with methods of intravenous meperidine administration. The results from these are summarized in Figure 25-4 and show that epidural analgesia does not significantly raise cesarean delivery rates.
Results of five studies comparing the incidence of cesarean delivery in women given either epidural analgesia or intravenous meperidine. The individual odds ratios (ORs) with 95-percent confidence intervals (CIs) for each randomized study, as well as overall crude and adjusted ORs with 95-percent CIs, are shown. An OR <1.0 favored epidural over meperidine analgesia. (Reproduced with permission from Sharma SK, McIntire DD, Wiley J, et al: Labor analgesia and cesarean delivery. An individual patient meta-analysis of nulliparous women, Anesthesiology. 2004 Jan;100(1):142–148.)
Local anesthetic block for cesarean delivery. The first injection site is halfway between the costal margin and iliac crest in the midaxillary line to block the 10th, 11th, and 12th intercostal nerves. A second injection at the external inguinal ring blocks branches of the genitofemoral and ilioinguinal nerves. These two sites are infiltrated bilaterally. The fifth and final site is along the line of proposed skin incision.
Timing of Epidural Placement
In several retrospective studies, epidural placement in early labor was linked to an increased risk of cesarean delivery (Lieberman, 1996; Rogers, 1999; Seyb, 1999). These observations prompted at least five randomized trials, which showed that timing of epidural placement has no effect on the risk of cesarean birth, forceps delivery, or fetal malposition (Chestnut, 1994a,b; Ohel, 2006; Wong, 2005, 2009). Thus, withholding epidural placement until some arbitrary cervical dilation has been attained is unsupportable and serves only to deny women maximal labor pain relief.
The relative safety of epidural analgesia is reflected by the extraordinary earlier experiences reported by Crawford (1985) from the Birmingham Maternity Hospital in England. Similarly, there were no anesthesia-related maternal deaths among nearly 20,000 women who received epidural analgesia in the MFMU Network study cited earlier (Bloom, 2005). And, Ruppen and associates (2006) reviewed data from 27 studies involving 1.4 million pregnant women who received epidural analgesia. They calculated risks of 1:145,000 for deep epidural infection, 1:168,000 for epidural hematoma, and 1:240,000 for persistent neurological injury.
For epidural analgesia, contraindications are similar to those with spinal analgesia (see Table 25-6). Although low platelet counts are intuitively worrisome, the level at which epidural bleeding might develop is unknown according to the American Society of Anesthesiologists Task Force on Obstetrical Anesthesia (2016). Epidural hematomas are rare, and incidence of nerve damage from a hematoma is estimated to be 1 in 150,000 (Grant, 2007). The American College of Obstetricians and Gynecologists (2016b) has concluded that selected women with platelet counts of 80,000 to 100,000/μL may be candidates for regional analgesia. Caveats include a stable platelet count, no acquired or congenital coagulopathy, normal platelet function, no antiplatelet-specific drugs, and anticoagulation parameters, described next, that are met. Counts between 50,000 and 80,000 require an individualized decision on risks and benefits (van Veen, 2010). Single-shot spinal anesthesia with a 25-gauge needle is less traumatic than epidural or combined spinal-epidural anesthesia with a 17- or 18-gauge epidural needle and thus may be safer for patients with platelets in this range.
Women receiving anticoagulation therapy who are given regional analgesia are at increased risk for spinal cord hematoma and subsequent cord compression (Chap. 52, Labor and Delivery). Our practice pattern includes the following:
Women receiving unfractionated heparin therapy should be able to receive regional analgesia if they have a normal activated partial thromboplastin time (aPTT).
Women receiving prophylactic doses of unfractionated heparin or low-dose aspirin are not at increased risk and can be offered regional analgesia.
For women receiving once-daily, low-dose low-molecular-weight heparin, regional analgesia should not be placed until 12 hours after the last injection.
Low-molecular-weight heparin should be withheld for at least 2 hours after epidural catheter removal.
The safety of regional analgesia in women receiving twice-daily low-molecular-weight heparin has not been studied sufficiently. It is not known whether delaying regional analgesia for 24 hours after the last injection is adequate.
Potential concerns with epidural analgesia in women with severe preeclampsia include hypotension as well as hypertension from pressor agents given to correct hypotension. Additionally, pulmonary edema following infusion of large volumes of crystalloid is a potential risk. These are outweighed by disadvantages of general anesthesia. Tracheal intubation may be difficult because of upper airway edema. Moreover, general anesthesia can lead to severe, sudden hypertension that can cause pulmonary or cerebral edema or intracranial hemorrhage.
With improved techniques for infusion of dilute local anesthetics into the epidural space, most obstetricians and obstetrical anesthesiologists have come to favor epidural blockade for labor and delivery in women with severe preeclampsia. There seems to be no argument that epidural analgesia for women with severe preeclampsia-eclampsia can be safely used when implemented by trained anesthesiologists and obstetricians (Lucas, 2001).
Women with severe preeclampsia have remarkably diminished intravascular volumes compared with unaffected gravidas (Zeeman, 2009). Conversely, extravascular volume is increased because of the capillary leak caused by endothelial cell activation (Chap. 40, Pathophysiology). This imbalance is manifested as pathological peripheral edema, proteinuria, ascites, and total lung water. For all of these reasons, aggressive volume replacement increases the risk for pulmonary edema, especially in the first 72 hours postpartum. In one study, Hogg and associates (1999) reported that 3.5 percent of women with severe preeclampsia developed pulmonary edema when preloaded without a protocol limitation to volume. Importantly, this risk can be reduced or obviated with judicious prehydration—usually with 500 to 1000 mL of crystalloid solution. Specifically, in the study by Lucas and colleagues (2001), there were no instances of pulmonary edema among the women in whom the crystalloid preload was limited to 500 mL. Moreover, vasodilation produced by epidural blockade is less abrupt if the analgesia level is achieved slowly with dilute solutions of local anesthetic agents. This allows maintenance of blood pressure while simultaneously avoiding infusion of large crystalloid volumes.
Combined Spinal–Epidural Analgesia
The combination of spinal and epidural techniques has increased in popularity and may provide rapid and effective analgesia for labor and for cesarean delivery. An introducer needle is first placed in the epidural space. A small-gauge spinal needle is then introduced through the epidural needle into the subarachnoid space—this is called the needle-through-needle technique (see Fig. 25-3). A single bolus of an opioid, sometimes in combination with a local anesthetic, is injected into the subarachnoid space. The spinal needle is withdrawn, and an epidural catheter is then placed through the introducer needle. A subarachnoid opioid bolus results in the rapid onset of profound pain relief with virtually no motor blockade. The epidural catheter permits repeated analgesia dosing. Miro and associates (2008) compared epidural analgesia with combined spinal-epidural analgesia for labor in 6497 women and found the overall outcomes and complications to be similar for the two techniques. In a randomized comparison, however, Abrão and colleagues (2009) reported that combined spinal-epidural analgesia was associated with a greater incidence of fetal heart rate abnormalities related to uterine hypertonus. Beamon and coworkers (2014) reported similar results.
Continuous Spinal Analgesia During Labor
There is emerging interest in continuous spinal analgesia for relief of labor pain. Arkoosh (2008) randomized 429 laboring women to either continuous spinal or conventional epidural analgesia. Complication rates between these two neuraxial techniques did not differ. Tao and colleagues (2015) reported their experiences with 113 women. With a dilute bupivacaine solution for analgesia, they found no cases of peripheral nerve injury and a headache rate of 2.6 percent. The utility of continuous spinal analgesia in labor and delivery remains to be further studied.