Magnesium Versus Bupivacaine Infiltration in Controlling Postoperative Pain in Inguinal Hernia Repair

BACKGROUND Postoperative pain is one of the most common problems after hernia repair. Decrease in postoperative pain accelerates functional recovery, decreases duration of hospital stay and postoperative morbidity. OBJECTIVES To compare postoperative analgesic effect of infiltration of magnesium versus bupivacaine into incision of inguinal hernia repair. PATIENTS AND METHODS In a double blind clinical trial, 80 patients' candidates for elective inguinal hernia repair were enrolled. Right before closure of incision, in Bupivacaine group 5 mL Bupivacaine 0.5% added to 5 mL normal saline and in Magnesium group, 10 mL Magnesium sulfate 20% was infused subcutaneously. Pain score was measured using numeric rating score (NRS) at 1, 3, 6, 12 and 24 hours postoperatively. If NRS was above 3, 1 mg morphine was administered as rescue analgesic until patient felt comfortable or NRS < 3. RESULTS Postoperative pain scores at 1 and 3 hours were not significantly different between bupivacaine and magnesium groups (P = 0.21, 0.224; respectively). However, at 6 (P = 0.003), 12 (P = 0.028) and 24 (P = 0.022) hours postoperative, pain score (NRS) was significantly lower in bupivacaine group. Number of patients needed at least 1 dose of rescue morphine (P = 0.001), mean number of episodes asked for morphine during next 24 hours (P = 0.001) and total dose of morphine requirement (P = 0.01) were significantly lower in bupivacaine group. CONCLUSIONS Magnesium infiltration did not decrease total dose and number of episodes needed for morphine rescue analgesic. Bupivacaine infiltration into surgical site was more effective than magnesium sulfate infiltration in postoperative pain control.