Programmed Intermittent Epidural Bolus Time Interval and Injection Volume
Condition: Labor Pain
MeSH terms: Labor Pain
Study type: Interventional

Summary: 
      Studies suggest that administration of maintenance epidural solutions as programmed or
      automated intermittent boluses, rather than continuous infusions, result in lower bupivacaine
      consumption, decreased need for manual boluses by the anesthesiologist, and greater patient
      satisfaction. In this technique, the epidural maintenance dose is administered as a bolus by
      the infusion pump at regular intervals instead of as a continuous infusion. However, the
      optimal combination of bolus volume and dosing interval has not been determined. At one end
      of the spectrum, a small volume and short bolus dose interval will likely behave like a
      continuous infusion. At the other end of the spectrum, a large volume and long bolus dose
      interval may lead to an increased incidence of breakthrough pain. The purpose of this
      randomized, double-blind trial was to determine how manipulation of the programmed
      intermittent time interval and volume influences total drug use, quality of analgesia, and
      patient satisfaction during maintenance of labor analgesia. We hypothesized that manipulation
      of the programmed intermittent bolus time interval and volume during the maintenance of
      epidural labor analgesia influences total drug use, quality of analgesia and patient
      satisfaction.
    

Detailed description: 
      Traditionally, neuraxial labor analgesia was maintained for the duration of labor with manual
      intermittent bolus injection of anesthetic by the anesthesiologist via an in-dwelling
      epidural catheter. During the last decade, there has been a transition to maintenance of
      analgesia with a continuous epidural infusion. Analgesia is maintained with fewer episodes of
      breakthrough pain and parturient satisfaction is increased. The anesthesiologists' workload
      is less. More recently, use of patient controlled epidural analgesia (PCEA) has become
      popular; usually a continuous infusion is supplemented by patient-activated bolus injections.

      Studies have compared the intermittent manual epidural bolus technique to continuous
      infusion, continuous infusion to PCEA without a background infusion, and PCEA with and
      without a background infusion. Studies vary in the epidural solution local anesthetic mass
      (volume and concentration), and lock-out intervals. The incidence and intensity of motor
      blockade is greater with continuous infusion compared to bolus administration of the same
      concentration/mass local anesthetic per unit time, whether the bolus is administered manually
      or by PCEA. Consumption of local anesthetic is less with bolus administration (manual or
      PCEA) compared to continuous infusion. Therefore, lower concentrations of local anesthetic
      are frequently used for continuous infusions.

      Current pump technology supports continuous epidural infusion, PCEA without a background
      infusion, and PCEA with a background infusion. Current pump technology does not support
      programmed intermittent bolus administration with or without supplemental PCEA. Further study
      in this area may motivate pump manufacturers to redesign their pumps to support this type of
      drug administration.

      The purpose of the study is to determine how manipulation of the programmed intermittent time
      interval and volume influences total drug use, quality of analgesia, and patient satisfaction
      during maintenance of labor analgesia.

      Eligible women were asked to participate shortly after admission to the Labor and Delivery
      Unit at Prentice Women's Hospital immediately following the routine preanesthetic interview.
      Informed, written consent was obtained. At the time of request for labor analgesia the cervix
      was examined and a baseline Visual Analog Scale (VAS) for pain (100 mm unmarked line with the
      end points labeled "no pain" and "worst pain imaginable") was determined. Labor analgesia was
      initiated with a routine combined spinal epidural (CSE) technique. The VAS for pain was
      determined 10 minutes after the intrathecal injection. If the VAS was less than 10 mm, the
      parturient was randomized (by a computer generated random number table) to one of three
      programmed intermittent epidural bolus analgesia maintenance techniques: 2.5 mL every 15
      minutes, 5 mL every 30 minutes, or 10 mL every 60 minutes. All epidural solutions consisted
      of bupivacaine 0.0625% with fentanyl 1.95 micrograms/mL. The initial programmed intermittent
      bolus dose was initiated 30 minutes after the intrathecal injection in all groups.

      Programmed intermittent epidural doses were administered via a Hospira Gemstar infusion pump.
      A commercial pump that can be programmed to administer intermittent boluses and patient
      controlled boluses does not exist. Thus two pumps were prepared for each subject with the
      same epidural solution. One pump was programmed to administer the programmed intermittent
      boluses at a rate of 300 ml/hr at regular intervals. The second pump was programmed to
      administer the patient's controlled epidural analgesia.

      VAS scores for pain were determined every 120 minutes until complete cervical dilation
      beginning 60 minutes after the intrathecal injection. A modified Bromage score was determined
      every 120 minutes during the 1st stage of labor (0=no motor paralysis; 1=inability to raise
      extended leg, but able to move knee and foot; 2=inability to raise extended leg and to move
      knee, but able to move foot; 3=inability to raise extended leg or to move knee and foot).
      Sensory threshold to a rigid von Frye filament (pressure applied with the rigid tip until the
      subject reported feeling pressure at the thoracic dermatome of T12, T10, T7, and T4) was
      determined bilaterally at initiation of epidural and 3 hours after the intrathecal injection.
      Epidural infusion was discontinued shortly after delivery. Prior to discharge from the Labor
      and Delivery Unit the parturient was asked to mark her overall satisfaction with labor
      analgesia using a 100 mm unmarked line with the left end labeled "not satisfied at all" and
      the right end labeled "extremely satisfied".
    

Intervention name(s): Programmed Intermittent Epidural Bolus (PIEB)
Intervention type(s): Procedure
Intervention description(s): A commercial pump that can be programmed to administer intermittent boluses and patient controlled boluses does not exist. Two pumps were prepared for each subject with the same epidural solution. One pump was programmed to administer the programmed intermittent epidural bolus(PIEB). The second pump was programmed to administer patient controlled epidural analgesia (PCEA)with a dose of 5 mL delivered with a lockout of every 10 minutes.
Other intervention name(s): Hospira Gemstar infusion pump
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: Patient controlled epidural analgesia; Labor analgesia; Epidural analgesia