Effect of Timing on Efficacy of Morphine Analgesia After 2-chloroprocaine Anesthesia
Status:
Completed
Trial end date:
2008-09-01
Target enrollment:
Participant gender:
Summary
Epidural chloroprocaine is often used in obstetrical anesthesia because of its fast onset and
short duration. These properties make it an ideal drug to use for epidural anesthesia in
patients undergoing postpartum tubal ligation. When epidural morphine is given after
chloroprocaine, there is a decreased efficacy of analgesia as compared to lidocaine (1).
Several studies have hypothesized a specific opioid receptor mediated antagonism of
chloroprocaine (2,3). Karambelkar raised the question whether this decreased efficacy is due
to a disparity between the time the chloroprocaine anesthesia resolves and the onset of
epidural morphine analgesia, resulting in a time window of pain (2). The duration of action
of epidural 2-CP anesthesia is 30-45 minutes and the onset of epidural morphine analgesia is
60-70 minutes, therefore the regression of sensory blockade before the onset of the morphine
analgesia could result in a window of pain (2). Hess and colleagues studied epidural morphine
analgesia and women who had a Cesarean delivery under spinal bupivacaine anesthesia (3).
Subjects were randomized to receive epidural 2-CP and morphine or epidural saline and
morphine. There was no difference in postoperative analgesia between the two groups (3 and
personal communication, Dr. Philip Hess). A literature search cross referencing epidural
chloroprocaine, using Pub Med, did not produce any articles comparing epidural morphine given
before the procedure (in an attempt to time the onset of analgesia with the resolution of
chloroprocaine anesthesia) to the standard administration time after the procedure.