Epidural and prolonged course of labor: Casual or causal

Abstract

T HE EFFECT OF epidural analgesia on 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, 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 need for oxvtocin augmentation, and a much higher cesarean section rate (25% v 2.2%) mainly caused by dystocia. They only conducted 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 Thorp et al study included several factors. First, element of bias. The obstetricians who made decision to perform cesarean section were participants in study. The obstetricians were also aware-of type of analgesia, and had previously reported that epidural anesthesia caused a higher incidence of cesarean section. Second, anesthetic management was not detailed and epidural analgesia was not a well-established technique in center where study was performed. Third. premature termination of study and possible change in statistical difference had a few cases been added, threw doubts on results. Fourth, Thorp et al did not explain why in one study, conducted by same investigators, incidence of cesarean section was 14% while in this study it was 25%. Fifth, in their study, incidence of cesarean section with or without epidural analgesia (25.0% v 2.2%) is quite different from experience of other centers. Sixth, there were no specific guidelines in protocol to follow for management of labor. Thorp et al's study, unjustifiably, stated that most of cases requiring cesarean section for dystocia were associated with 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 question whether early administration of epidural analgesia would affect 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 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 first or second stage of labor, increase dystocia, increase operative delivery, or adversely affect 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 incidence of oxytocin augmentation, prolong interval between randomization and diagnosis of complete cervical dilation, or increase incidence of malposition of vertex at delivery. Also, early administration of epidural analgesia did not result in an increased incidence of cesarean section or instrumental delivery, eg, incidence of cesarean