Low-dose intrathecal morphine for postoperative pain control in patients undergoing transurethral resection of the prostate

Abstract

Thirty patients undergoing lidocaine spinal anesthesia for transurethral resection of the prostate (TURP) were studied to evaluate the effectiveness of low-dose intrathecal morphine (ITM) for postoperative analgesia. In a double-blinded fashion, groups of ten patients received either 0.1 mg morphine, 0.2 mg morphine, or placebo (control group) intrathecally with lidocaine 75 mg. Standard postoperative analgesics were available to all patients. Patients receiving 0.1 mg or 0.2 mg morphine reported significantly less postoperative pain as assessed by an inverse numerical visual pain scale and required significantly fewer postoperative analgesic interventions than the control group. There was no difference between the 0.1 mg ITM and 0.2 mg ITM groups with regard to severity of postoperative pain or analgesic requirements. The incidence of nausea and vomiting was significantly higher in the group receiving 0.2 mg ITM than in the control group. Six patients (60%) in the 0.2 mg ITM group, two patients (20%) in the 0.1 mg ITM group, and one patient (10%) in the control group experienced nausea and vomiting. No clinically evident respiratory depression occurred in any of the subjects. The authors conclude that administration of 0.1 mg or 0.2 mg of morphine intrathecally is effective in reducing postoperative pain following TURP and that 0.1 mg ITM is not associated with nausea and vomiting.