When 1.5 mg epidural morphine was compared with 3 mg, patients’ pain relief was equivalent but the lower dose was associated with fewer side effects.  Illustrated is "Opium poppy, Papaver somniferum" (Image source: Thinkstock)
When 1.5 mg epidural morphine was compared with 3 mg, patients’ pain relief was equivalent but the lower dose was associated with fewer side effects. Illustrated is “Opium poppy, Papaver somniferum” (Image source: Thinkstock)

For patients experiencing pain after cesarean delivery, pain is better relieved after administration of epidural morphine rather than parenteral opioids. How much epidural morphine is appropriate?

The question is addressed in “The Efficacy of 2 Doses of Epidural Morphine for Postcesarean Delivery Analgesia: A Randomized Noninferiority Trial” by Dr. Sudha I. Singh and colleagues from the Department of Anesthesia & Perioperative Medicine, St. Joseph’s Hospital, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Canada. In this paper, published in the current issue of Anesthesia & Analgesia, the authors compared two doses of epidural morphine for patients who were laboring with epidural analgesia and who then required intrapartum cesarean delivery where epidural anesthesia was used.

The study included 87 parturients requiring cesarean delivery. Subjects did not receive combined spinal-epidural anesthesia. When the skin was closed, patients received either 3 mg or 1.5 mg epidural morphine. All patients received ketorolac intraoperatively and for 24 hours postoperatively. Subjects also received acetaminophen in the PACU and for 24 hours. If patents were in pain, they could receive oxycodone. Patients received ondansetron and metoclopramide if they had PONV. Patients received diphenhydramine for moderate pruritus and naloxone if pruritus was severe.

Differences in 24-hour opioid consumption were noninferior. Specifically, there were no differences in median 24- to 48-hour opioid consumption or median total opioid consumption within 48 hours. There was no difference between groups in the proportion of patients not consuming opioids during the first 48 hours after cesarean delivery. Pain scores at rest or with movement were not different during the 48-hour study period or at 24 hours or 12 weeks.

However, fewer side effects were observed with the lower dose of morphine: pruritus incidence at 6 and 12 hours; nausea and vomiting incidence at 6 hours; and number of patients who consumed ondansetron were all lower after 1.5 mg epidural morphine versus 3 mg.

Might even lower doses of epidural morphine be as effective? This is unclear. Certainly, though, with a background of NSAID analgesic therapy, 1.5 mg epidural morphine is not inferior to 3 mg, and is associated with fewer side effects.