A Comparative Study on the Effect of Placebo and Oral Clonidine as a Premedication on Onset and on the Duration of Spinal Anaesthesia with Hyperbaric Bupivacaine

Background: The utilisation of vasoconstrictors like clonidine with local anaesthetics during subarachnoid blockade is a well-established practice. Objectives: This study aims to compare the effects of oral clonidine premedication versus placebo on the onset and duration of spinal anaesthesia with hyperbaric bupivacaine. Materials and Methods: A randomised, double-blind, placebo-controlled trial was conducted with 90 patients, divided into three groups: placebo (n = 30), clonidine-A (100 µg, n = 30) and clonidine-B (150 µg, n = 30). The primary outcomes measured were the onset of sensory blockade, duration of sensory and motor blockade and two-segment regression time. Secondary outcomes included haemodynamic parameters and sedation levels. Statistical analysis was performed using analysis of variance (ANOVA) and chi-square tests, with significance set at p < .05. Results: Clonidine significantly reduced the time to achieve maximum sensory blockade compared to placebo (clonidine-A: 11.68 ± 1.860 min, clonidine-B: 9.18 ± 1.793 min, placebo: 15.55 ± 2.784 min; p < .001). Both clonidine groups demonstrated prolonged sensory blockade and two-segment regression times (clonidine-A: 107 ± 8.799 min, clonidine-B: 125.31 ± 8.372 min, placebo: 69.35 ± 6.309 min; p < .001). Motor blockade recovery was significantly longer in the clonidine groups, although no significant difference was found between clonidine-A and clonidine-B (p < .05). Haemodynamic stability was maintained, with significant reductions in heart rate and systolic blood pressure (SBP) observed in the clonidine groups. Sedation was notably higher in the clonidine groups compared to placebo (p < .001). Conclusion: Oral clonidine premedication significantly accelerates the onset and prolongs the duration of spinal anaesthesia with hyperbaric bupivacaine. The 150 µg dose exhibited a dose-dependent enhancement of effects without compromising haemodynamic stability. While clonidine offers promising benefits in improving the efficacy of spinal anaesthesia, its sedative and bradycardic effects necessitate careful monitoring in clinical practice.