LAUSR

Although intrathecal morphine and bupivacaine are increasingly implemented in effective postoperative pain control, there is a lack of consensus on the dosage as high doses of bupivacaine may inadvertently cause unwanted side effects. The purpose of this study was to compare the effects of intrathecal morphine injection and low-dose bupivacaine with morphine injection. In total, 90 patients were divided into 3 groups: (1) sham injection for the control group; (2) morphine 400 mcg for the morphine group (M); and (3) morphine 400 mcg and bupivacaine 5 mg for the morphine and bupivacaine group (M + B). Our primary outcome was time to first rescue analgesic. The VAS (visual analogue scale) pain score was compared until POD (postoperative day)1. Total fentanyl dose was compared until POD2. Side effects were monitored until POD3. Although time to first rescue was significantly shorter in the control group compared to group M and group M + B (p < 0.001), both groups (M and M + B) were comparable to each other. There was a significant decrease in the VAS score and total fentanyl administration in group M and group M + B compared to the control group. Pruritus and tingling were more prevalent in the M + B group (p = 0.023; p = 0.010). The addition of 5 mg bupivacaine may be insufficient in providing further analgesic benefits; however, higher doses may aggravate side effects.