Effects of Bupivacaine Induced Motor Blockade During the Second Stage of Labor
Status:
Completed
Trial end date:
2013-07-01
Target enrollment:
Participant gender:
Summary
The aim of this study is to measure the effects of bupivacaine administered via epidural
catheters on indices of motor blockade ascertained during the second stage of labor. This is
a randomized, double-blind, controlled trial designed to address the primary research
question: Does bupivacaine lengthen the second stage of labor? The secondary research
question is: Is there other evidence of motor blockade attributable to bupivacaine during the
second stage of labor?
The investigators know from prior studies that the length of the second stage in nulliparous
women delivered at Parkland Hospital without epidural analgesia is 28 minutes. The
investigators hypothesize in this now proposed study that epidural analgesia with bupivacaine
will significantly increase this baseline from 28 minutes to 37 minutes or more (a 33%
increase) thus implicating motor blockade. Baseline data for the Bromage and Breen scores
during the second stage as well as the uterine contractility data are not available as these
indices of motor blockade have not here-to-fore been studied in this context.
Currently at Parkland Hospital, 82% of nulliparous women undergoing induction of labor at
term receive continuous epidural infusions with bupivacaine during the first and second
stages of labor. Such women will be identified when admitted for scheduled inductions at
Parkland. After informed consent is obtained standard management of labor induction will be
provided. Those consented women reaching 8 cm cervical dilation will be randomized. Group I
will receive bupivacaine plus fentanyl via epidural catheter during the second stage (i.e. 10
cm dilation) and Group II will receive only fentanyl infusion via epidural catheter (see
study procedure below). Both the patient and the caregiver will be blinded as to whether the
patient is in the bupivacaine plus fentanyl arm or the fentanyl only arm. To detect a 33%
increase (from 28 minutes to 37 minutes) in the primary outcome the investigators need a
total of 310 women enrolled in the study (or 155 per arm). Assuming a 30% consent rate and
given that approximately 1000 women meet the inclusion criteria each year at Parkland, the
investigators project that this study could be completed in 12 months.