Comparison of intravenous Magnesium Sulphate with intrathecal Magnesium Sulphate for post- operative analgesia in orthopaedic patients undergoing extracapsular hip fracture surgery

Background: Magnesium sulphate (MgSO4) N methyl D aspartate receptor antagonist has the potential to be an ideal adjuvant for postoperative analgesia via intrathecal or intravenous route. The aim of the study was, we compared the efficacy of two routes of MgSO4 (Intravenous vs intrathecal) as an adjuvant to bupivacaine in subarachnoid block (SAB).Methods: Ninety, American Society of Anesthesiologists physical status 1 or 2 patients, aged 20-60 years, scheduled for hip surgeries under SAB were recruited in department of Anaesthesia and Dept. of Orthopaedics. Patients in group 1 (n=29) received intrathecal 0.5% (H) bupivacaine 15 mg with 0.1 ml of normal saline and 250 ml 0.9% normal saline intravenous 30 minutes before giving SAB. Group 2 (n=30) patients received intrathecal 0.5% bupivacaine 15mg with 0.1 ml of normal saline and 50mg/kg of magnesium sulphate in 250 ml normal saline intravenous 30minutes before giving SAB. In Group 3 (n=30) patients received intrathecal 0.5% (H) bupivacaine 15 mg with 50mg (0.1ml) magnesium sulphate and 250 ml 0.9% normal saline intravenous 30 minutes before giving SAB. They were evaluated for block characteristics, visual analogue scale at various time intervals up to 24 hours and total rescue analgesic and duration of postoperative analgesia were noted.Results: Intravenous magnesium sulphate had maximum pain free interval, lower pain scores, longer sensory and motor blockade and less requirement of rescue analgesia as compared to the patients in intrathecal group or control group (P<0.05).Conclusions: Intravenous magnesium sulphate was more effective as compared to intrathecal route with regards to the pain scores and in providing postoperative analgesia.