Until recently, at Mount Sinai Hospital (MSH), epidural analgesia for labor pain was
delivered with a pump that could only provide continuous infusion of the freezing medication
in combination of pushes of medication activated by the patient, a technique called patient
controlled epidural analgesia (PCEA). In the last decade or so, the literature has suggested
that this continuous infusion of medication is not as effective as previously thought, and
suggested that instead of continuous infusion we should use intermittent programmed pushes.
The investigators now have devices that are able to do that. Programmed intermittent epidural
bolus (PIEB) is a new technological advance based on the concept that boluses of freezing
medication in the epidural space are superior to continuous epidural infusion (CEI). Recently
the epidural pumps at MSH were reprogrammed to deliver bolus of medication at regular
intervals (PIEB), in addition to what the patient can deliver herself (PCEA). Studies have
shown that delivering analgesia in this manner prolong the duration of analgesia, reduce
motor block, lower the incidence of breakthrough pain, improve maternal satisfaction and
decrease local anesthetic consumption. The investigators have recently concluded a study at
MSH using PIEB where excellent results were observed. However, in that study, some patients
exhibited higher than necessary sensory blocks. The investigators believe that the technique
can be optimized by using the same interval of the previous study with smaller volumes of the
intermittent boluses. Optimizing the technique, may allow the investigators to be able to
reduce even further the amount of medication used by each patient.
The hypothesis of this study is that there is an optimal volume of the PIEB bolus at a fixed
interval of 40 minutes of 0.0625% bupivacaine plus fentanyl 2mcg/ml that will provide 90% of
women the necessary drug requirements during first stage of labor (EV90), thus avoiding
breakthrough pain and need for PCEA or physician intervention. We hypothesize that this
effective volume will be between 7 and 12 mL (6.6 mg/hr to 11.3 mg/hr of bupivacaine).