Abstract :
Background: This study was conducted to compare the effects of intrathecal magnesium and intravenous infusion of
magnesium sulphate as adjuvants to bupivacaine for intrathecal anaesthesia. Methods: A prospective, randomized,
double-blinded, placebo controlled study was planned in 90 patients of physical status ASA I and II, aged between 18 to 55
years, scheduled to undergo elective surgery below the level of umbilicus. Patients were randomly assigned into three
equal groups A,B & C (n=30 per group) according to a computer generated list. Group A received 15mg of 0.5%
bupivacaine + 0.15ml of 50% magnesium sulphate (75mg) + 0.35ml of sterile water, Group B received 15mg of 0.5%
bupivacaine + 0.5ml sterile water + a bolus dose of magnesium sulphate 50mg/kg in 100ml saline over 10 minutes followed
by a continuous infusion of 15mg/kg/hr until the end of the surgery and group C received 15mg of 0.5% bupivacaine +
0.5ml sterile water (Placebo). Preoperative serum magnesium levels were checked, and repeated at 6h and 24hrs
postoperatively. Results: Time to 2 segment regression of sensory block, duration of spinal anaesthesia as well as
duration of effective analgesia were significantly prolonged in intrathecal as well as intravenous magnesium as compared
to placebo. Intrathecal or intravenous magnesium were not associated with significant side effects.Conclusion: Coadministration
of intravenous or intrathecal Mg given to patients undergoing spinal anesthesia for elective infraumbilical
surgeries could improve pain control for the first 24 h after surgery. Intrathecal as well as intravenous magnesium sulphate
significantly prolonged the time for the first analgesic request, thus substantiating their use in postoperative analgesia.
Keyword :
Analgesia, Intrathecal, Magnesium Sulphate