The characteristics of analgesic requirements following subarachnoid diamorphine in patients undergoing total hip replacement.

BACKGROUND AND OBJECTIVES: The postoperative pain scores and analgesic requirements were assessed in 60 patients who had undergone total hip replacement under bupivacaine spinal anesthesia. METHODS: Thirty of the patients had intrathecal diamorphine injected after the bupivacaine, and the remaining 30 received saline. RESULTS: Superior postoperative pain relief was obtained in the diamorphine group, whose average postoperative morphine requirements were 12 +/- 11.4 mg compared to 31 +/- 18.7 mg (mean +/- SD) in the control group. Despite the lower doses of morphine, their pain scores over the first 24 hours postoperatively were consistently lower. No differences were seen between the groups with respect to respiratory depression, nausea, pruritus, postoperative sedation, headache, or urinary retention. CONCLUSION: Pain control after intrathecal diamorphine supplemented by intravenous morphine from a patient controlled analgesia system is superior to intravenous morphine alone.