Spinal morphine for post-operative analgesia after lumbar laminectomy with fusion

Abstract

Background: Intrathecal administration of preservative free morphine (spinal morphine) provides excellent post-operative analgesia. Since the dura is readily accessible by the surgeon during lumbar spinal surgery, it would be convenient and attractive to administer morphine into the spinal space to provide adequate post-operative analgesia in these patients.

Method: A prospective randomized controlled study evaluated the post-operative analgesic effect of spinal morphine after lumbar laminectomy with fusion. Forty patients were randomly allocated to two groups, morphine (MO) or normal saline (NSS). Morphine 0.3 mg in normal saline 0.3 ml or normal saline 0.3 ml was injected into the dural sac under direct visualization before closing the wound. An intravenous PCA morphine device was provided for post-operative pain relief.

Results: Median visual analog scale (VAS) pain scores were lower in the MO group at 2, 4, 24 and 48 h after surgery (1, 1, 2.75 and 1.5 cm in the MO group vs 4.25, 4.25, 5 and 4 cm in the NSS group) (p < 0.05). The time to first patient control analgesia (PCA) demand was delayed in the MO group (131.7 min vs 29.6 min) (p < 0.05). The cumulative doses of PCA morphine consumption were lower in the MO group in the first 24 h and 24-48 h (13.7 and 15.9 mg vs 41.3 mg and 27.1 mg) (p < 0.001). The incidence of pruritus was higher in the MO group in 24 h and 24-48 h (45%, and 45% vs 5% and 10%) (p < 0.05). The incidence and severity of nausea, vomiting and sedation were not different. No patient developed respiratory depression or postdural puncture headache (PDPH). The patients' satisfaction with post-operative pain management was 100 per cent in the MO group and 85 per cent in the NSS group.

Conclusion: Spinal morphine improved post-operative pain relief after lumbar laminectomy.