The effect of epidural magnesium sulphate on postoperative nociception and serum B endorphin levels in high tibial osteotomy orthopedic surgery

Abstract

ABSTRACTBackground: Epidural magnesium sulphate provides better analgesia and opioid-sparing effect postoperatively. B-endorphins plasma levels are inversely related to the severity of pain. We investigated the possible relationship between epidural magnesium sulphate, postoperative analgesia and serum beta-endorphin levels in high knee osteotomy orthopedic surgery.Methods: Sixty patients of both sexes, aged between 18 and 65 years, ASA I or II scheduled for high tibial osteotomy were divided to two groups (30 patients each): control group, received epidural bupivacaine 0.5%, lidocaine 2% and saline; and (Mg group) received epidural bupivacaine, lidocaine and magnesium sulphate (50 mg/10 ml saline). Venous blood samples were withdrawn to measure serum b endorphin levels (SBE), at different time intervals. We recorded time to first analgesic requirement, pain numeric rating score (NRS) and postoperative hemodynamic variables and incidence of complications.Results: Time to first analgesic request was significantly longer in Mg group (pain score less than 5) compared to control group (P < 0.05) also the frequency and number of analgesic requests were significantly less in the Mg group than in the control group P = 0.000. B endorphins level was significantly lower in the Mg group than in the control group after 4 h of epidural insertion (P = 0.004).Conclusion: We conclude that the addition of magnesium sulphate 50 mg/10 ml saline to epidural bupivacaine/lidocaine provides better postoperative analgesia as well as reducing serum B endorphins in the postoperative period without increasing the incidence of complications in high knee osteotomy orthopedic surgery postoperatively.

Keywords

• Epidural
• magnesium sulphate
• serum B-endorphins