Effects of intrathecal morphine, injected with bupivacaine, on pain after orthopaedic surgery.

Morphine hydrochloride 0.4 mg was administered with isobaric 0.5% bupivacaine intrathecally for orthopaedic surgery and produced good analgesia for about 24 h after operation in both elderly (60-80 yr) and middle-aged patients (30-50 yr). Morphine 0.2 mg (older patients only) was not as effective in preventing pain after operation, but even this dose postponed the requirement for analgesia. Morphine did not change the quality of spinal anaesthesia. In the older groups the capillary PCO2 was increased in two patients receiving morphine 0.2 mg and in one patient receiving 0.4 mg. Severe delayed respiratory depression was not noted. Urinary retention and minor voiding difficulties were the most disturbing side-effects. This complication did not appear to be dose-dependent, and also occurred in patients not receiving morphine.