Epidural morphine for postoperative pain relief in anorectal surgery.

Postoperative analgesia and side effects of a single dose of 20 ml of 2% epidural prilocaine followed immediately by either morphine (3 mg in 3 ml saline) or saline (3 ml) were studied in 79 patients scheduled for anorectal surgery. Pain relief was evaluated by a linear scale for 24 hr and by an assessment of the requirement for parenteral analgesics. Of the patients given epidural morphine, 25% did not require analgesics, whereas all patients given prilocaine alone asked for additional analgesia. Remaining patients given morphine were pain-free for a mean duration of 7.6 +/- 5.1 hr (SD). Only 9% of patients given morphine required a maximum of three analgesic parenteral injections in 24 hr. Urinary retention was the most prominent side effect observed in patients given epidural morphine. No early or delayed respiratory depression was noted in our patients.