Effect of Timing on Efficacy of Morphine Analgesia After 2-chloroprocaine Anesthesia
Condition: Labor; Analgesia, Epidural
MeSH terms: Agnosia
Study type: Interventional

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.
    

Detailed description: 
      Women undergoing post partum tubal ligation with an epidural in-situ will be randomly double
      blindedly selected into one of three groups for pain control. The groups are epidural 1)
      epidural morphine-chloroprocaine 2) epidural chloroprocaine-morphine 3) epidural
      morphine-lidocaine. Groups 1 and 3 will receive morphine 30 minutes prior to local anesthetic
      dosing followed by saline placebo after local dosing. Group 2 will receive placebo 30 minutes
      prior to local anesthetic dosing followed by epidural morphine. Pain scores and supplemental
      analgesic requirements will be evaluated 30 minutes, 1hr, 2hr, 4hr and every 4 hrs for the
      first 24hrs.
    

Intervention name(s): Morphine-CP-saline (MCS); saline-2CP-morphine (SCM); saline-lidocaine-morphine (SLM)
Intervention type(s): Drug; Drug; Drug
Intervention description(s): 3mg of preservative free morphine will be administered epidurally 30 min prior to epidural anesthesia. Epidural 3% 2CP will be used to achieve a T4 dermatomal level for surgical anesthesia for PPTL. 6ml of epidural saline will be administered at skin incision; 6ml of saline will be administered epidurally 30 min prior to epidural anesthesia. Epidural 3% 2CP will be used to achieve a T4 dermatomal level for surgical anesthesia for PPTL. 3mg of preservative free morphine will be administered at skin incision; 3mg of preservative free morphine will be administered epidurally 30 min prior to epidural anesthesia. Epidural 2% lidocaine with epinephrine 1:200,000 will be used to achieve a T4 dermatomal level for surgical anesthesia for PPTL. 6ml of epidural saline will be administered at skin incision
Intervention MeSH terms: Lidocaine; Morphine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: analgesia; tubal ligation; chloroprocaine