Amitha P. Rao1 , Krishna Sagar Sriram2
BACKGROUND To improve the quality and duration of subarachnoid block various adjuncts have been used. But they exhibit side effects like nausea, vomiting, pruritis, respiratory depression, urinary retention and haemodynamic instability. Magnesium does not cause adverse effects when used as an adjuvant in therapeutic doses. METHODS This was a prospective, randomized, double blind, controlled study. 50 patients belonging to ASA physical status I and II posted for infraumbilical surgery were randomized into two groups. Group I patients received Inj. bupivacaine 0.5% heavy 2.5 mL (12.5 mg) with Inj. normal saline 0.2 mL intrathecally. Group II patients received Inj. bupivacaine 0.5% heavy 2.5 mL (12.5 mg) with Inj. magnesium sulphate 25% 0.2 mL (50 mg) intrathecally. The onset and duration of sensory blockade, the onset and duration of motor blockade, haemodynamic parameters, Ramsay sedation score and Visual Analogue Scale were assessed. Rescue analgesia was given when VAS score was >3. Statistical analysis was performed by student’s t-test for nominal data, Chi-square test or Fisher’s exact probability test for categorical data. RESULTS When 50 mg of magnesium sulphate was added intrathecally, the duration of motor blockade was prolonged (p value of <0.001); the onset of motor blockade was significantly slower, and the duration of analgesia was prolonged (p value <0.001). The prolonged analgesia in magnesium sulphate group was accompanied by an average 24-hour postoperative visual analogue scale of 1 to 2 when compared to 3 to 4 in saline group (p ≤ 0.001). CONCLUSIONS Intrathecal magnesium sulphate as an adjunct to bupivacaine in spinal anaesthesia prolongs the duration of spinal anaesthesia and postoperative analgesia, without adverse effects.
