Effects of Bupivacaine Induced Motor Blockade During the Second Stage of Labor
Condition: Pregnancy
Study type: Interventional
Phase: Phase 4

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.
    

Detailed description: 
      Nulliparous women scheduled for labor inductions on Monday through Friday and who have
      consented to this study will be randomized to one of two arms: bupivacaine plus fentanyl
      epidural analgesia throughout labor and delivery (including the second stage) or epidural
      bupivacaine plus fentanyl until 8 cm cervical dilation and only fentanyl thereafter. From
      activation of epidural analgesia to 8 cm cervical dilation the prevailing standard epidural
      technique in use at Parkland Hospital will be used. Briefly, 19-ga multi-orifice epidural
      catheter is placed using 17-ga 3 ½cm Tuohy needle into the L3-L4 lumbar interspace. Lactated
      Ringers solution, 500-1000mL will be infused during placement of the epidural catheter to
      mitigate hypotension. A test dose using 1.5% lidocaine with 1:200,000 epinephrine, 3mL, will
      be given via the epidural catheter. If the test dose is negative, then an initial bolus of
      0.25% bupivacaine, 4-8mL, with fentanyl 100mcg is given via the catheter. After securing the
      epidural catheter the patient will be placed in the supine position and the anesthetic
      sensory level measured with the desired level of T6-T8. Once a T6-T8 sensory block is secured
      the epidural infusion using 0.125% bupivacaine with 2mcg/mL fentanyl at 10mL/hr will be
      started.

      At any time during epidural infusion the epidural catheter may be replaced at the discretion
      of the anesthesia provider for inadequate analgesia. Ephedrine or phenylephrine will be given
      intravenously for maternal hypotension defined as systolic blood pressure ≤ 90 mmHg or a
      decrease of 20% systolic blood pressure from patient's baseline.

      Randomization will occur when the woman reaches 8 cm cervical dilation. Envelopes containing
      cassettes will be sequentially randomized by Dr. McIntire and given to the attending
      obstetrical anesthesiologist containing one of two medications. Group I will receive a 100mL
      epidural cassette of 0.125% bupivacaine with fentanyl 2mcg/mL to be infused at 10mL/hr. Group
      II will receive a 100mL cassette of fentanyl 10mcg/mL (to be infused at 10mL/hr. Both groups
      will have the same rate of epidural infusion such that the patient, nurse, obstetrician, and
      anesthesia providers will be blinded to the randomized treatment group. The Parkland
      Investigational Drug Service (IDS) will provide the study drugs.

      The patient may request a 5mL bolus from the epidural infusion every 30 minutes if pain
      relief is inadequate. The obstetrician can also give patients in either study group 25mg of
      intravenous meperidine every hour for up to two doses if pain relief is unsatisfactory. The
      study regimen will continue until spontaneous delivery of the infant or until which time
      operative vaginal delivery or cesarean delivery is planned. At this point the study will be
      over and routine anesthesia care resumed.

      The standard of care for management of labor induction at Parkland requires continuous
      electronic fetal heart rate monitoring (EFM) as well as uterine contraction monitoring. The
      standard is to apply EFM internal transducers when the membranes are ruptured. Standard fetal
      monitors equipped with laptop computers will be used to electronically store the fetal heart
      rate and uterine contraction data during this study. This will permit qualification of
      uterine contractility during the second stage of labor. The Bromage and Breen scores for
      motor blockade will be assessed at complete cervical dilation and at 30, 60, and 90 minutes
      thereafter. The scoring system is as follows:

      Score Criteria

        1. Unable to move feet or knees (complete block)

        2. Able to move feet only

        3. Just able to move knees

        4. Detectable weakness of hip flexion while supine

        5. No weakness of hip flexion

        6. Able to perform partial knee bend

      Visual analog pain (VAS) scores for the adequacy of epidural analgesia from 1-10 will also be
      assessed at each time point used for the Bromage and Breen scores.

      Data collection will include maternal demographic characteristics as well as antepartum and
      intrapartum obstetrical features. Condition of the infant at birth based on Apgar scores and
      umbilical artery blood pH, as well as neonatal outcomes will be ascertained.
    

Intervention name(s): Epidural Bupivacaine plus fentanyl; Epidural fentanyl
Intervention type(s): Drug; Drug
Intervention description(s): The subjects will receive 0.125% bupivacaine with fentanyl 2 mcg/mL at a rate of 10 mL/hr.; The subjects will receive epidural fentanyl 10 mcg/mL with the rate of 10mL/hr.
Other intervention name(s): Epidural continous infusion of bupivacaine and fentanyl; Epidural continous infusion of fentanyl
Intervention MeSH terms: Fentanyl; Bupivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: double-blinded 2 arm
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: Bupivacaine; Fentanyl; Epidural; Second Stage of Labor; Randomized Controlled Trial