Effect of Timing on Efficacy of Morphine Analgesia After 2-chloroprocaine Anesthesia

Not Applicable

Completed

Conditions: Labor
Analgesia, Epidural

Interventions: Drug: Morphine-CP-saline (MCS)
Drug: saline-2CP-morphine (SCM)
Drug: saline-lidocaine-morphine (SLM)

Registration Number: NCT00487084

Lead Sponsor: Northwestern University

Brief 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.

Recruitment & Eligibility

Status: COMPLETED

Sex: Female

Target Recruitment: 136

Inclusion Criteria

All patients with an epidural catheter in situ for labor analgesia, status post a vaginal delivery, and scheduled for a postpartum tubal ligation under epidural anesthesia will be eligible

Exclusion Criteria

Allergy/hypersensitivity to morphine
Allergy/hypersensitivity to ester-linked local anesthetics or para-amino benzoic acid (PABA)
Body Mass Index >40 kg/m2
Patients using chronic opioids
History of obstructive sleep apnea
Any contraindication to epidural anesthesia

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
morphine - 2CP-saline (MCS)	Morphine-CP-saline (MCS)	morphine will be administered 30 min prior to epidural anesthesia; 2CP will be used to achieve a T4 level; saline will be administered at skin incision
saline-2CP-morphine (SCM)	saline-2CP-morphine (SCM)	saline will be administered 30 min prior to epidural anesthesia; 2CP will be used to achieve a T4 level;morphine will be administered at skin incision
saline-lidocaine-morphine (SLM)	saline-lidocaine-morphine (SLM)	Saline will be administered 30 min prior to epidural anesthesia; lidocaine will be used to achieve a T4 level; morphine will be administered at skin incision

Primary Outcome Measures

Name	Time	Method
Duration of Continuing Analgesia	48 hours	Time to first request for supplemental analgesia
Supplemental Analgesia in First 90 Minutes	90 min	Participants requesting supplemental analgesia in the first 90 minutes following study drug

Secondary Outcome Measures

Name	Time	Method
Verbal Rating Score (0 to 10) for Pain (VRPS)	At recovery room entry	Verbal Rating Pain Score (VRPS) at time of post-anesthesia recovery room entry, where 0 = no pain and 10 = worst pain imaginable
Supplemental Analgesia in First 48 Hours	48 hours	Participants requesting supplemental analgesia in first 48 hours