Intrathecal morphine reduces breakthrough pain during labour epidural analgesia

When using the combined spinal-epidural (CSE) technique for labour analgesia, parturients often experience breakthrough pain after the spinal medication has receded. We tested the hypothesis that a small dose of intrathecal morphine would reduce breakthrough pain.

This was a randomized, double-blind, placebo-controlled trial. Subjects were randomized to receive either 100 microg of morphine (MS) or placebo (PLCB) with the spinal injection of bupivacaine and fentanyl. Assessments included need for supplementation during labour analgesia, use of pain medications for 24 h after delivery, and side-effects. The primary end-point was the rate of breakthrough pain.

Sixty subjects were enrolled, 55 subjects completed the trial. The MS group had a significantly lower rate of breakthrough pain than the PLCB group [0.6 (0.6) vs 1.1 (0.8) episodes per patient; P < 0.01], and longer time to first episode of breakthrough pain (300 vs 180 min; P = 0.03). The MS group used 75% less opioid medications during the subsequent 24 h, but had a 17% incidence of nausea.

The addition of small dose of morphine to the spinal component of the CSE technique improved the effectiveness of epidural labour analgesia and reduced the need for pain medications over 24 h, but resulted in a small increase in nausea.