A randomized controlled trial of spinal morphine with an enhanced recovery pathway and its effect on duration of analgesia after cesarean delivery.

Background: Intrathecal morphine is frequently administered after cesarean delivery to provide pain relief lasting up to 24 h. An enhanced recovery after cesarean pathways reduces the amount of postoperative opioids needed. The ideal dose of intrathecal morphine when combined with a pathway has not been determined.

Methods: This was a non-inferiority trial in 72 healthy women undergoing a scheduled cesarean delivery. Women were randomized to receive either 50 mcg, 150 mcg, or 250 mcg of intrathecal morphine during spinal anesthesia, with a standardized postoperative enhanced recovery pathway. The time to request supplemental opioids was the primary outcome. Secondary outcomes included pain scores, side effects, and quality of recovery at 24 h.

Results: The duration of analgesia with 50 mcg of morphine (median 24.5 h [IQR: 3.5-34.4]) was inferior to 150 mcg (29.4 h [24.5-72]), and both doses were inferior to 250 mcg (32 h [30.5-72]). Women who received 50 mcg morphine had higher pain scores than the other doses, received more supplemental opioids, and had lower quality recovery scores. The secondary outcomes between 150 mcg and 250 mcg were similar. Side effects were similar among all groups. 63% of women who received 250 mcg remained opioid-free at 72 h, compared to 150 mcg (52%) and 50 mcg (30%).

Conclusions: The duration of analgesia using intrathecal morphine with an enhanced recovery pathway was longer with 250 mcg than with lower doses, and side effects were similar. 50 mcg provided inferior pain relief over 24 h. More than half of our patients avoided additional opioids for up to 72 h with either 150 mcg or 250 mcg doses.

Registration: Clinical trial number NCT05069012.