Effects of intravenous dexmedetomidine on 0.5% hyperbaric bupivacaine spinal anesthesia - a placebo controlled randomized trial

Introduction and Aim: Dexmedetomidine, a neuraxial adjuvant, when given intrathecally with hyperbaric bupivacaine provides stable hemodynamic conditions, good quality of intraoperative and prolonged postoperative analgesia with minimal side effects. When intravenous dexmedetomidine is used in conjunction with neuraxial anesthesia, few studies have shown that it prolongs the sensory-motor blockade and provides better intraoperative and postoperative analgesia. We formulated this hypothesis that intravenous (IV) dexmedetomidine bolus followed by infusion would prolong the duration of subarachnoid block (SAB) with 0.5% heavy bupivacaine. Our aim was to assess the onset and duration of sensory and motor blockade following IV dexmedetomidine supplementation after SAB. Materials and Methods: Sixty American Society of Anesthesiologists Grade I and II patients undergoing elective surgeries under spinal anesthesia were randomized into two groups of 30 each. Immediately after subarachnoid block with 3 ml of 0.5% hyperbaric bupivacaine, patients in group II received a loading dose of 1 µg/kg of dexmedetomidine intravenously by infusion pump over 10 min followed by a maintenance dose of 0.5 µg/kg/hr till the end of surgery, whereas patients in group I received an equivalent quantity of normal saline. The time to reach peak sensory block level, time taken for two segment regression and maximum motor block, total duration of sensory and motor blockade, Ramsay sedation score and modified Bromage score were statistically analyzed using Statistical Package for Social Sciences (SPSS Inc. Chicago, IL, USA) Windows-based version 16.0. Results: Two segment regression time of sensory blockade was more in the dexmedetomidine group (130.33±14.49 mins) as compared to the normal saline group (94.67±15.02 mins) which was statistically significant (P< 0> Conclusion: The results of the present study shows that, intravenous dexmedetomidine given as a loading dose followed by maintenance dose prolonged the duration of sensory and motor blockade of bupivacaine-induced spinal anesthesia. It also provided conscious sedation without respiratory depression while maintaining good hemodynamic stability.