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

: 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.
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 Venous blood samples were withdrawn to measure serum b endorphin levels (SBE), at different time intervals.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.
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).
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.