Epidural and Prolonged Course of Labor: Casual or Causal

T HE EFFECT OF epidural analgesia on the course of labor is a controversial issue that has been of concern for many decades. However, recent reports by Thorp et al 1 tried to implicate epidural analgesia as an important cause of dystocia and cesarean section. In their 1991 study, they reported an associated cesarean section of 14.1% (11.4% for dystocia). Later in 1993, the investigators intended to study 200 parturients in a randomized fashion either to receive intravenous opioids (75 mg meperidine and 25 mg promethazine) or epidural analgesia (0.25 % bupivacaine followed up by a continuous infusion of 0.125%). 2 Thorp et al stated that patients receiving epidural analgesia experienced prolongation of first and second stages of labor, had twice the need for oxvtocin augmentation, and a much higher cesarean section rate (25% v 2.2%) mainly caused by dystocia. They only conducted the study on 93 patients and terminated it prematurely because of "the unacceptable" high incidence of cesarean section. However, their study was criticized for many reasons. 3 The criticism of the Thorp et al study included several factors. First, the element of bias. The obstetricians who made the decision to perform cesarean section were the participants in the study. The obstetricians were also aware-of the type of analgesia, and had previously reported that epidural anesthesia caused a higher incidence of cesarean section. Second, the anesthetic management was not detailed and epidural analgesia was not a well-established technique in the center where the study was performed. Third. the premature termination of the study and the possible change in statistical difference had a few cases been added, threw doubts on the results. Fourth, Thorp et al did not explain why in one study, conducted by the same investigators, the incidence of cesarean section was 14% while in this study it was 25%. Fifth, in their study, the incidence of cesarean section with or without epidural analgesia (25.0% v 2.2%) is quite different from the experience of other centers. Sixth, there were no specific guidelines in the protocol to follow for the management of labor. Thorp et al's study, unjustifiably, stated that most of the cases requiring cesarean section for dystocia were associated with the administration of epidural analgesia when cervical dilatation was less than 5 cm. Thus. their conclusion that epidural analgesia should not be used before that stage of cervical dilatation has led to unnecessary suffering of parturients, particularly those with induced labor and oxytocin augmentation. To answer the question whether early administration of epidural analgesia would affect the obstetrical outcome. Chestnut et al4,s conducted 2 studies in nulliparous women. Their first study included 149 parturients receiving intravenous (IV) oxytocin divided into 2 groups. 4 In one group, epidural analgesia was started after 3-cm cervical dilatation and before 5-cm dilatation. In the other group, epidural analgesia was initiated when cervical dilatation reached at least 5 cm, and control of pain was attempted by IV nalbuphine between 3and 5-cm dilatation. These investigators found that early administration of epidural analgesia did not prolong the first or second stage of labor, increase dystocia, increase operative delivery, or adversely affect the fetus or neonate. Moreover, patient satisfaction was much higher with early epidural analgesia. In Chestnut et al's s second study, labor spontaneously occun'ed. Three hundred forty-four parturients were divided into 2 similar groups. They found that early administration of epidural analgesia did not increase the incidence of oxytocin augmentation, prolong the interval between randomization and the diagnosis of complete cervical dilation, or increase the incidence of malposition of the vertex at delivery. Also, early administration of epidural analgesia did not result in an increased incidence of cesarean section or instrumental delivery, eg, the incidence of cesarean