Background and aims: Use of various adjuvants to spinal anaesthesia is a well-known modality to provide intra- and post-operative analgesia. This study was designed to evaluate and compare the analgesic efficacy of clonidine and magnesium when used as an additive to intrathecal 0.5% hyperbaric bupivacaine.
Methods: Ninety patients of the American Society of Anesthesiologists' physical status grade I or II, scheduled for lower abdominal surgery under spinal anaesthesia, were randomly allocated into three groups. Group B received 3 mL of 0.5% hyperbaric bupivacaine with 1 mL of normal saline, Group C received 3 mL of 0.5% hyperbaric bupivacaine with 1 mL (30 μg) of clonidine and Group M received 3 mL of 0.5% hyperbaric bupivacaine with 1 mL (50 mg) magnesium sulphate. The primary outcome variable was duration of analgesia and secondary outcome variables included onset and duration of sensory and motor block, sedation level and adverse effects. Data were analysed with ANOVA, Kruskal-Wallis and Chi-square tests.
Results: The time to first rescue analgesia was significantly (P < 0.01) longer in the Group C (330.7 ± 47.7 min) than both Groups. Group M (246.3 ± 55.9 min) showed significantly prolonged analgesia than Group B (134.4 ± 17.9 min). Group C and Group M showed significantly prolonged duration of both sensory and motor block compared to Group B.
Conclusion: Intrathecal clonidine added to bupivacaine prolongs the duration of post-operative analgesia, and hastens the onset and prolongs the duration of sensory and motor block compared to magnesium or controls.
Keywords: Bupivacaine; clonidine; magnesium; post-operative analgesia.