Effect Of Intravenous Dexmedetomidine On Subarachnoid Block Characteristics, Using 0.5% Hyperbaric Bupivacaine, In Patients Undergoing Unilateral Knee Arthroscopy - A Prospective Randomized Double Blinded Placebo Controlled Study

Abstract

Introduction: Many techniques and drug regimens, with partial or greater success, have been tried from time to time to eliminate the anxiety component, to improve the quality of regional anesthesia and prolong the postoperative analgesia. Alpha 2-adrenergic agonists have both analgesic and sedative properties, when used as an adjuvant to regional anesthesia. They potentiate the effect of local anesthetics and prolong the duration of motor and sensory spinal blockade and postoperative analgesia. Dexmedetomidine is a selective alpha 2-adrenoreceptor agonist; it has a alpha 2/alpha 1 selectivity ratio which is ten times higher than that of clonidine. So we hypothesised that a premedication with intravenous dexmedetomidine 0.5mcg/kg will prolong sensory and motor block with hyperbaric bupivacaine and significant postoperative analgesia with minimal side effects. Material and Methods: In our study, 70 patients undergoing elective unilateral knee arthroscopic surgeries were randomly allocated into two groups A and B. Group A received intravenous dexmedetomidine 0.5mcg/kg bolus over 10 minutes prior to subarachnoid block and group B received similar volume of normal saline. The time of onset of sensory block, duration of sensory block, peak sensory level attained, time to reach peak sensory level, time of onset of motor block, duration of motor block, hemodynamic characteristics, duration of postoperative analgesia, sedation, side effects and other outcomes were recorded and compared between the two groups. We presumed that premedication with dexmedetomidine will prolong the quality of spinal block without significant hemodynamic alterations and side effects. Results: We concluded that intravenous dexmedetomidine 0.5 mcg/kg administered 30 minutes before subarachnoid block as loading dose alone will shorten the onset of both sensory and motor block of subarachnoid block with hyperbaric 3 ml 0.5% bupivacaine and provide adequate intraoperative sedation without significant hemodynamic alterations and harmful side effects.