Which assessment is most important to monitor after the administration of epidural anesthesia?

Combined Spinal-Epidural Analgesia

Combined spinal-epidural (CSE) analgesia has become increasingly popular in the past 20 years. Onset of complete analgesia is significantly faster than with epidural techniques (2 to 5 minutes versus 10 to 15 minutes, respectively).24 In a meta-analysis of the onset time of CSE compared with low-dose epidural analgesia,24 the mean difference in onset was –5.4 minutes (95% confidence interval [CI], –7.3 to –3.6). More women with spinal analgesia than with epidural analgesia had effective analgesia at 10 minutes (relative risk [RR], 1.9; 95% CI, 1.5 to 2.5). In particular, the onset of sacral analgesia is significantly slower after the initiation of lumbar epidural analgesia than with spinal analgesia. It may take several hours of lumbar epidural infusion, or several bolus injections of local anesthetic into the lumbar epidural space, to achieve sacral analgesia. Rapid onset of sacral analgesia is advantageous in the parturient in whom analgesia is initiated late in the first stage of labor or in a parous parturient with rapid progress of labor. Spinal analgesia requires significantly lower drug doses to attain effective analgesia than does epidural analgesia; therefore, the risk for local anesthetic systemic toxicity is decreased. In addition, there is less systemic absorption of spinal anesthetic agents into the maternal circulation, so maternal and fetal plasma drug concentrations are lower with spinal than with epidural analgesia.

An additional advantage of spinal analgesia is that complete analgesia for early labor can be accomplished with the intrathecal injection of a lipid-soluble opioid without the addition of a local anesthetic. Thus, motor blockade is avoided and the risk for hypotension is lower.25 This method is ideal for patients who wish to ambulate or for those with preload-dependent cardiac conditions such as stenotic heart lesions. Finally, use of the CSE technique may lower the incidence of failure of epidural analgesia (e.g., a nonfunctioning epidural catheter).26,27 The likelihood of an epidural catheter placed for labor analgesia failing to provide satisfactory anesthesia for a subsequent cesarean delivery was more than five times higher for catheters placed as part of an epidural technique than for catheters placed as part of a CSE technique.28

Several studies have described a modification of CSE analgesia in which a dural puncture is made with a small-gauge spinal needle but no drug is injected into the subarachnoid space (dural puncture epidural analgesia).29–32 Results of studies are inconsistent, but two studies found that blockade of sacral dermatomes occurred more frequently after injection of epidural local anesthetic and opioid in parturients with a dural puncture than in those without.30,32 Presumably, enhanced sacral analgesia occurs because of increased migration of anesthetic solution across the dural puncture site.

Epidural Analgesia

Epidural analgesia can be accomplished by infusing a variety of drugs (typically low-dose local anesthetics and opioids) into the epidural space. Epidural analgesia must be distinguished from epidural anesthesia, which implies dense epidural local anesthetic blockade and is generally reserved for intraoperative use. Conceptually, the provision of epidural analgesia is an attractive means of minimizing opioid requirement while providing excellent analgesia, thereby promoting recovery after surgery. Epidural opioid doses are much smaller than those required systemically (in the order of one tenth), and low-dose epidural local anesthetics, apart from producing analgesia without overt sensory/motor blockade or opioid-associated adverse effects, can have additional beneficial effects on bowel mobility. Does the evidence support the superior analgesic efficacy of epidural analgesia and its ability to promote recovery after surgery?

It is important to separate the potential benefits of intraoperative epidurals from the benefits of postoperative epidural analgesia. There are significant differences in the way epidurals are used during surgery: sometimes complete epidural anesthesia is provided, sometimes only epidural analgesia, sometimes the epidural is not used at all intraoperatively, and of course there is a range of practice in between. Some benefits are likely to pertain chiefly to the use of profound blockade during surgery (e.g., lower incidence of thromboembolic events, lower incidence of graft failure in the case of major vascular surgery, lower blood loss, lowering of the metabolic stress response, lower incidence of chronic pain). This chapter concentrates on the benefits likely to pertain specifically to postoperative epidural analgesia.

Many of the early trials of epidural analgesia (during the 1970s and early 1980s) were small, randomized studies that attempted to confirm the clinically apparent superior analgesia of postoperative epidurals compared with conventional analgesia, some also assessing aspects of postoperative recovery. These early trials (and meta-analyses) overwhelmingly supported the superior analgesic efficacy of epidural analgesia compared with conventional analgesia.9 Assessments of postoperative recovery focused on differences in minor morbidities, including pulmonary function, bowel function, and mobility.10–12

A goal of epidural analgesia is to restore normal physiologic function as rapidly as possible to avoid adverse outcomes associated with prolonged immobilization and hospital stay. As evidenced by small randomized controlled trials (RCTs) and subsequent meta-analysis (and in some cases, confirmed by the large RCTs), epidural analgesia fulfills this goal extremely well. Epidural analgesia has been shown to promote early mobilization and reduce rehabilitation time, particularly after joint surgery.13–15 In addition, it has been shown to reduce pulmonary morbidity,11,16–19reduce time to extubation of the trachea after major thoracic and vascular procedures,16–18,20–22 reduce cardiac ischemia and dysrhythmia in high-risk patients,20,23 and reduce postoperative ileus,24 thereby reducing length of hospital stay. 25–28 A meta-analysis by Beattie and colleagues23 found a reduction in the incidence of myocardial infarction associated with the use of postoperative epidural anesthesia (odds ratio [OR] 0.56; confidence interval [CI] 0.30 to 1.03).

Several clinical trials have been conducted to evaluate the impact of epidural analgesia on mortality rate and major morbidity (including major cardiac morbidity, pulmonary embolus, and stroke). Early results suggested that combined epidural and general anesthesia (GA) followed by postoperative epidural analgesia had a favorable effect on major morbidity, and possibly also on mortality rate.29,30 The findings of Yeager and colleagues30 were particularly striking because they showed remarkable decreases in surgical morbidity and mortality rates attributable to epidural analgesia in high-risk patients undergoing major surgical procedures. Interestingly, this study was stopped after the completion of 53 patients by the monitoring committee because the early results favored the epidural treatment so strongly that the committee believed it would be unethical to continue the trial. This study certainly contributed to the belief that epidural analgesia improves surgical outcome, particularly in sick patients.

However, the validity of the results of the Yeager study has been questioned,31 and this skepticism led investigators to set about assessing the possible effects of epidural analgesia on major morbidity in high-risk patients. Two large RCTs were later published. Unfortunately, neither confirmed the earlier findings that epidural analgesia has a favorable effect on major morbidity.16,17

Well-designed, large randomized trials such as those by Park and colleagues16 and Rigg and colleagues17 constitute strong evidence about the efficacy of epidural analgesia. (Meta-analysis is considered stronger evidence, but it must be carefully conducted and must select only well-designed and relatively homogeneous studies.) In terms of analgesic efficacy, these studies lend further support to the findings of earlier smaller trials and meta-analyses that confirmed the superior analgesic efficacy of epidural analgesia. However, these two large studies were designed specifically to assess the value of epidural analgesia in terms of its ability to reduce major morbidity and mortality rates in high-risk patients. In these respects, the results were disappointing for those who believed, on the basis of earlier small trials,29,30 that the treatment has a major impact on major morbidity and mortality rates.

Epidural analgesia may play an important role following abdominal surgery. In this setting, epidural analgesia has been reported to lower the incidence of myocardial infarction, stroke, and death in patients undergoing abdominal aortic surgery.16 A recent meta-analysis evaluated the impact of epidural analgesia versus systemic opioids following abdominal aortic surgery.32 This analysis included 13 studies involving 1224 patients. The epidural analgesia group showed significantly improved pain control on movement up to the third postoperative day. In addition, postoperative duration of tracheal intubation and mechanical ventilation was significantly shorter by about 20%. The overall incidence of cardiovascular complications, myocardial infarction, acute respiratory failure, gastrointestinal complications, and renal insufficiency were all significantly lower in the epidural analgesia group, especially in trials that used thoracic epidural analgesia. The incidence of mortality, however, was not reduced.

Another study provided indirect evidence that epidural analgesia may lower mortality rate following major surgery. 33 This study examined a cohort of 3501 patients who underwent lung resection. These patients represented a 5% random sample of patients who underwent lung resection procedures between 1997 and 2001, and who were listed in the Medicare claims database. Multivariate regression analysis showed that the presence of epidural analgesia was associated with a significantly lower odds of death at 7 days (OR 0.39; 95% CI 0.19 to 0.80; p = 0.001) and 30 days (OR 0.53; 95% CI 0.35 to 0.78; p = 0.002). Interestingly, this study reported no difference in major morbidity.

It is easy to forget that the evolution of epidural analgesia has occurred alongside the evolution of postoperative management in general, and that differences in serious morbidity and mortality rates that might be expected to emanate from the benefits outlined earlier may not be obvious because of improvements in postoperative care in general. A policy of early oral fluid administration, early nasogastric tube removal, and forced early mobilization, in combination with optimized pain management, has resulted in earlier hospital discharge and a decrease in postoperative mortality rate when compared with that 20 years ago. It may be impossible to show the benefit of postoperative epidural analgesia in isolation, whereas studies of this mode of analgesia used with regard to its specific effects on certain outcomes (e.g., postoperative ileus); with attention to appropriate level of catheter placement, drug choice, and drug dose in order to achieve the desired outcome; and its combination with other aspects of postoperative care are needed before we can discount the value of epidural analgesia in terms of major morbidity and mortality rates.34 At the same time, major morbidity and mortality rates have become so low that even larger trials or patient numbers in meta-analyses may be required to show a difference.17

In summary, the superior analgesic efficacy of epidural analgesia compared with conventional analgesia seems absolutely clear, and benefits in terms of morbidity and length of hospital stay (by contributing to an accelerated return to normal physiologic function) have been demonstrated. The evidence is even stronger for thoracic epidural catheters. It remains unclear whether epidural analgesia has a role in reducing mortality.

Epidural Analgesia and Anesthesia

Epidural anesthesia is being used with increasing frequency, especially in hospitals where anesthesiologists are available to patients in labor 24 hours a day. In experienced hands, epidural anesthesia has an excellent safety record.391 Although it is the most difficult form of anesthesia to administer, it has the advantage of providing excellent pain relief for the first and second stages of labor and for delivery without altering the consciousness of the mother. Bupivacaine and chloroprocaine are the drugs most commonly used, the former providing more prolonged anesthesia but with a greater delay in onset. Combinations of local anesthetics and narcotics also provide excellent analgesia with less motor blockade.392

Continuous lumbar epidural anesthesia has been associated with late decelerations in fetal heart rate suggestive of decreased uteroplacental perfusion in as many as 20% of cases. This is more common with bupivacaine than with chloroprocaine or lidocaine.393 Also, the use of oxytocin to augment labor in women given continuous epidural anesthesia has been reported to increase the frequency of late decelerations noted on fetal monitoring.394 When uterine hypertonus or maternal hypotension is associated with the augmentation of contractions in patients with epidural anesthesia, fetal heart rate patterns indicating uteroplacental insufficiency occur in as many as 70% of cases.395 Prehydration of the mother and avoidance of the supine position396 can reduce the incidence of uteroplacental insufficiency with epidural anesthesia. Drug mixtures of local anesthetics and analgesics results in less motor block; this allows women who have epidural anesthesia to be more mobile during labor, and they are less likely to be confined to the supine position.

Thorp and Breedlove397 reviewed the benefits and risks of epidural analgesia for labor and delivery. Both retrospective and prospective controlled trials have demonstrated that epidural analgesia results in longer labors and a higher incidence of operative vaginal delivery and cesarean delivery than intravenous analgesia. Some studies have suggested that the untoward effect of epidural analgesia on labor occurs primarily in patients in whom the epidural block is placed when the cervix is dilated less than 5 cm398; however, controlled trials by Chestnut and coauthors399,400 established that the time of onset of epidural analgesia did not affect length of labor or method of delivery. In a retrospective, case-controlled study, Thompson and colleagues401 showed that those patients who had abnormal labor progress after epidural analgesia often had abnormal labor curves before placement of the epidural block.

Fever

Epidural analgesia during labor is associated with an increase in maternal temperature compared with women who receive no analgesia or systemic opioids alone.76 In a well-designed study with a low crossover rate (6%), Sharma and colleagues75 reported a 33% rate of intrapartum fever greater than 37.5° C in nulliparous patients randomized to epidural analgesia compared with 7% in those who received parenteral opioids. The more than fourfold increased risk of fever occurred despite relatively minor prolongations in the mean duration of labor (50 minutes). Similarly, Yancey and colleagues77 also described an eighteenfold increase in the rate of intrapartum fever in nulliparous patients (from 0.6% to 11%) in a single year following the introduction of an epidural analgesia service in their hospital.

The etiology of this febrile response is not well understood; possible mechanisms include noninfectious inflammatory activation, changes in thermoregulation, and acquired intrapartum infection. Intrapartum fever after epidural analgesia is associated with increased serum levels of inflammatory cytokines in the mother and fetus, but no mechanism in which epidural blockade might cause inflammation has been elucidated. Thermoregulation may be altered because epidural analgesia leads to decreased sweating (by providing sympathetic blockade) and less hyperventilation after relief of pain in labor. Both sweating and hyperventilation would otherwise provide heat dissipation. No study has found an increased rate of infection associated with epidural analgesia for labor.

Acetaminophen, the standard therapy used to ameliorate hyperthermia, is not effective in preventing fever secondary to epidural analgesia. High-dose maternal corticosteroids given to parturients with epidural analgesia blocks the febrile response but also substantially increases the risk of bacteremia in exposed babies.78 A randomized trial of prophylactic cefoxitin versus placebo did not prevent fever in nulliparous women who requested epidural analgesia.79

Despite the lack of infectious morbidity, intrapartum exposure to hyperthermia may not be benign for the neonate. A retrospective review of low-risk women who received epidural analgesia found maternal temperature greater than 99.5° F was associated with adverse neonatal outcomes such as hypotonia, assisted ventilation, low Apgar scores, and early-onset seizures.80 Without temperature elevation, epidural use was not associated with adverse neonatal outcomes, but the rate of adverse outcomes increased directly with maximum maternal temperature. An animal study indicates that the presence of hyperthermia during an ischemic event increases susceptibility to hypoxic-ischemic insult.81 Although the absolute risk is low, maternal temperature greater than 38° C is associated with 9.3-fold increased risk of cerebral palsy in term infants (95% CI, 2.7 to 31). It is important to clarify that no evidence suggests that epidural analgesia is associated with infection, encephalopathy, or cerebral palsy. Active cooling measures such as decreasing room temperature, removing blankets from the mother, and use of cool IV fluids should be used for all febrile parturients.

Lumbar Epidural Analgesia/Anesthesia

Epidural blockade is a neuraxial anesthetic used to provideanalgesia during labor or surgicalanesthesia for instrumented vaginal or cesarean delivery.31Epidural analgesia offers the most effective form of pain relief.1,32 In 2011, overall rates of neuraxial labor analgesia ranged from 66% in hospitals with fewer than 500 births per year to 82% in hospitals with more than 1500 annual births.2 In most obstetric patients, the primary indication for epidural analgesia is the patient's desire for pain relief. Medical indications for epidural analgesia during labor may include anticipated difficult intubation (if cesarean delivery is required) due to morbid obesity or other causes, a history of malignant hyperthermia, selected forms of cardiovascular and respiratory disease, and prevention or treatment of autonomic hyperreflexia in parturients with a high spinal cord lesion. The technique uses a large-bore needle (16, 17, or 18 gauge) to locate the epidural space. Next, a catheter is inserted through the needle, and the needle is removed over the catheter. After aspirating the catheter, a test dose of local anesthetic with a “marker” such as epinephrine may be given first to be certain the catheter has not been unintentionally placed in the subarachnoid (spinal) space or in a blood vessel. Intravascular placement will lead to maternal tachycardia because of the epinephrine, and rapid onset of sensory and motor block will occur if the local anesthetic is injected into the spinal fluid. Once intravascular and intrathecal placement have been ruled out, local anesthetic is injected through the catheter, which remains taped in place to the mother's back to enable subsequent injections throughout labor (Fig. 16.5; see alsoFig. 16.1). It is often calledcontinuous epidural analgesia (Fig. 16.6). The patient should be able to move about in bed and perceive the impact of the presenting part on the perineum.

A dilute local anesthetic combined with an opioid such as fentanyl is administered for maintenance of epidural analgesia. Administration may be by continuous infusion at a rate of 5 to 15 mL/h, patient controlled epidural analgesia (PCEA) or programmed intermittent epidural bolus (PIEB). Patient-controlled epidural boluses are combined with a continuous infusion to allow patients to vary their responses to local anesthetics (e.g., lower infusion rate or concentration if the patient develops excessive motor block). More recently, PIEB has been used to deliver automated mandatory boluses instead of traditional continuous basal infusions.33 Data suggest that when PIEB is compared with continuous basal infusions, PIEB may improve maternal satisfaction, reduce the risk of breakthrough pain (relative risk [RR], 0.60; 95% CI, 0.39 to 0.92; 10 studies, 797 women), and decrease the amount of local anesthetic needed (median dose, −1.08 mg/h; 95% CI, −1.78 to −0.38; 12 studies, 1121 women).33 If perineal anesthesia is needed for delivery, a larger volume of local anesthetic can be administered at that time through the catheter (seeFig. 16.6). Alternatively, for perineal anesthesia, the obstetrician can perform a pudendal block or provide local infiltration of the perineum.

Thoracic Epidural Analgesia

TEA has long been considered the gold standard for thoracic surgical pain relief. There have been some studies evaluating the effectiveness of various analgesia techniques on long-term postthoracotomy pain. Based on these studies, it appears important not only whether the patient received epidural analgesia, but also how the epidural was managed.41 This is particularly relevant in the prevention of PTPS. However, thoracic epidural injections are also commonly performed for the treatment of PTPS.

There are two practiced approaches to performing a thoracic epidural with the most important determinant between the use of either one being practitioner level of expertise and comfort. However, it is of the opinion that a paramedian approach permits a markedly less angled trajectory with thoracic vertebral segments, enabling an approach to the epidural space at a predictable depth in most patients, especially above T11 vertebral level.50

On the other hand, besides the risks and complications, some studies have shown a rate of TEA failure owing to various causes between 10% and 15% to as high as 32%.51,52 Over the decades, the relative benefits of TEA in reducing postoperative pulmonary complications have decreased in studies, likely because of improved surgical techniques, prophylactic antibiotics, improved postoperative care (i.e., the avoidance of nasogastric tubes), improved pulmonary physiotherapy, and early mobilization.

EFFICACY

Epidural analgesia has earned a place among mechanisms of postoperative pain control.6 Block and associates—in a meta-analysis of 100 controlled trials with numerous surgeries (representing thoracic, abdominal, pelvic, and lower extremities) comparing IV PCA opioids, parenteral opioids, and epidural opioids (with or without local anesthetics)—demonstrated that epidurals provided better postoperative analgesia.7 Epidurals were also associated with lower than expected complications such as nausea, vomiting, and pruritus. Furthermore, patients receiving a combination of epidural local anesthetic and opioid as opposed to opioid alone exhibited greater improvements in analgesia.

The following sections review specific procedures and discuss data supportive for epidural analgesia. Table 11–3 provides recommended sites for catheter placement based on surgical procedure.

INTRODUCTION

Postoperative epidural analgesia is a relatively safe and efficacious method of controlling postoperative pain. Systematic analysis of available randomized and nonrandomized data indicates that compared with systemic opioids epidural analgesia provides significantly superior analgesia in the postoperative period [1, 2] (Table 18-1). In addition, perioperative epidural analgesia may confer some physiologic benefits. Some data suggest that epidural analgesia may be associated with improvements in postoperative morbidity and mortality, [3–6] although the effect on outcomes may vary depending on many factors, including the congruency of the catheter placement in relationship to the incisional site, the analgesic agent (opioid versus local anesthetic) administered, and duration of epidural analgesia [7]. Postoperative epidural analgesia may also be associated with improvements in patient-oriented outcomes such as patient satisfaction and quality of life [8, 9].

Despite the potential benefits of continuous epidural analgesia for postoperative pain management, there are risks and complications associated with the use of this technique. The majority of these complications (e.g., nausea, vomiting, itching, urinary retention, motor block, catheter failure) are not life threatening but may be bothersome for the patient, decrease the patient's satisfaction and quality of recovery, or even delay postoperative convalescence. Other complications are much less common (e.g., intravascular or intrathecal migration) or may result in permanent and devastating injuries (e.g., epidural hematoma or abscess).

In general, complications from continuous epidural analgesia can be categorized as medication related or catheter related. Medication-related complications include nausea, vomiting, pruritus, motor block, hypotension, and respiratory depression. Catheter-related complications include catheter failure/dislodgement, intrathecal or intravascular migration, and epidural hematoma or abscess. Many of the rare but devastating complications that may be associated with continuous epidural analgesia are described in greater detail in other chapters (Chapter 3, bleeding complications; Chapter 4, infectious complications; Chapter 6, local anesthetic systemic toxicity; and Chapter 10, local anesthetic neurotoxicity and cauda equina). In this chapter we will focus on some of the more common medication- and catheter-related side effects and complications associated with continuous epidural analgesia.

Epidural Analgesia

Epidural analgesia (EA) is a highly effective and widely-used method for pain relief, with approximately 60% of laboring women in the US reporting use of EA in labor.79 A recent Cochrane review (2005) assessed the effects of EA compared with non-epidural analgesia or no pain relief during labor by studying 21 randomized controlled trials involving 6,664 women.80 The results showed that the use of EA was not associated with increased risk of cesarean section (RR 1.07, 95% CI 0.93–1.23) or low neonatal Apgar score at 5 minutes (RR 0.70, 95% CI 0.44–1.10). Its use was associated with an increased risk of instrumental vaginal delivery (RR 1.38, 95% CI 1.24–1.53), longer second stage of labor duration (weighted mean difference of 15.55 minutes, 95% CI 7.46–23.63), as well as increased oxytocin use, urinary retention, maternal fever, and maternal hypotension. However, the generalizability of the results from this review has been questioned, as some of the included studies recruited only high-risk women (with severe pre-eclampsia), or included women of mixed parity in settings with low baseline cesarean section rates.

Delayed pushing is an approach that can reduce operative vaginal delivery for women with epidural anesthesia. Women are advised to avoid voluntary expulsive efforts until an irresistible urge to push is felt, or until the presenting part has descended to the perineum under the force of uterine contractions. Its goal is to conserve the woman’s physical and psychological energies until the presenting part has descended beyond the mid-pelvis. A multicenter trial of a policy of delayed pushing for women with epidural anesthesia was conducted in Canada. The primary outcome for the trial was ‘difficult delivery’, defined as any of the following methods of delivery: cesarean section; mid-pelvic delivery; or low pelvic delivery with rotation of the fetal head more than 45 degrees.81 Delayed pushing reduced the risk of difficult delivery (RR 0.79, 95% CI 0.66–0.95), mainly owing to a reduction in mid-pelvic procedures. While there was an increase in abnormal umbilical cord blood pH results among babies in the delayed pushing group, there was no clinical evidence of adverse neonatal outcomes in the intervention groups.

A recent systematic review of randomized controlled trials assessed the effects of delayed pushing in women with epidural analgesia on pregnancy outcomes.82 The results showed that a policy of delayed pushing in second stage labor when epidural analgesia was used was associated with a significant reduction in rotational or mid-pelvic deliveries without evidence of increase in second stage cesarean section deliveries. Delayed pushing was associated with a reduced rate of instrumental deliveries and an increase in the duration of second stage of labor.81

F. Complications of Epidural Anesthesia

Epidural analgesia (EA) has been implicated as a risk factor for operative vaginal delivery and possibly also for cesarean section [3,4]. Clinical trials comparing EA to other forms of analgesia have shown EA to be associated with malpositions of the fetal head (OR = 5.42, 95% CI 1.33–22.04) [101]. The wider diameter of the fetal head in the OP (occipito-posterior) position can impede descent [102,103]. The OP position is associated with an increased risk of operative delivery and particularly with procedures requiring rotation of the fetal head. A meta-analysis comparing EA to other forms of pain relief in labor demonstrated that if EA was maintained in the second stage, there was a marked increase in operative vaginal delivery (OR = 2.59, 95% CI 1.29–5.19) [101]. Others have estimated that EA increases the risk of rotational forceps 20-fold [102].

Second stage duration is increased with EA [104], in part as the result of motor block. While several observational studies have found EA to be associated with an increased cesarean section risk [3,105], the few randomized trials that have compared epidural with nonepidural analgesia have yielded divergent results [4,106–108]. It appears that if epidural is indeed a risk factor for cesarean section, the effect likely depends on a number of context-specific factors, including the degree of motor block produced by the epidural agent and the threshold for intervention of the delivery obstetrician.

The routine administration of oxytocin in the second stage of labor has been advocated as a possible approach to the reduction of second stage operative deliveries for women with EA. This approach is based on two observations: the absence of the normal physiologic increase in circulating oxytocin [109] and the reduction in uterine contractility [110] among women in second stage with EA. A single randomized clinical trial comparing routine oxytocin administration to an attempt to avoid oxytocin in the second stage for women with EA has been published [111]. An increase in the rate of spontaneous delivery (50 versus 40%) and a reduction in the rate of nonrotational forceps and vacuum (31 versus 47%) was observed in the group receiving oxytocin. However, a statistically significant increase in the frequency of rotational forceps was noted in the group treated with oxytocin (18 versus 9%). Because of the potential of rotational forceps to cause adverse maternal and neonatal sequelae, the routine augmentation of second stage of labor with oxytocin cannot be recommended at present. Further studies are required to address this question.

A number of clinical trials have assessed variations in the method of epidural administration, including the types, timing, and concentrations of medications used. It has been suggested that simply by terminating the epidural at the end of the first stage, second-stage operative interventions can be reduced. However, the two trials evaluating this approach have yielded divergent results [112,113]. Pain rapidly increased to preepidural levels among women deprived of continuous infusion [114].

The addition of narcotics (fentanyl, sufentanil) to the epidural solution provides the same degree of sensory blockade at lower concentrations of local anaesthetic agent, thus reducing motor blockade [115–118]. One randomized trial [119] found that women receiving a sufentanil-bupivacaine (0.125%) combination had a statistically significant decrease in the incidence of instrumental delivery (24 versus 36%) compared to those receiving bupivacaine alone.

Delayed pushing is an approach that can reduce operative vaginal delivery for women with epidural anesthesia. Women are advised to avoid voluntary expulsive efforts until an irresistible urge to push is felt or until the presenting part has descended to the perineum under the force of uterine contractions. Its goal is to conserve the woman's physical and psychological energies until the presenting part has descended beyond the midpelvis. We completed a multicenter trial of a policy of delayed pushing for women with epidural anesthesia [120]. Women in the delayed pushing group had a median waiting period of 110 minutes after full dilatation, compared with 5 minutes among those in the early pushing group. The primary outcome for the trial was “difficult delivery,” defined as any of the following methods of delivery: cesarean section, midpelvic delivery, or low pelvic delivery with rotation of the fetal head more than 45 degrees. Delayed pushing reduced the risk of difficult delivery (RR = 0.79, 95% CI 0.66–0.95), mainly owing to a reduction in mid-pelvic procedures. While there was an increase in abnormal umbilical cord blood pH results among babies in the delayed pushing group, there was no clinical evidence of a difference in the frequency of adverse neonatal events in the two groups. The reduction in difficult delivery was most marked when the fetal head was in the transverse to posterior position at full dilatation [120].