Comparative evaluation of two different doses of intravenous dexmedetomidine infusion for sedation in patients undergoing lower abdominal general surgical procedures under spinal anesthesia

BACKGROUND: Spinal anesthesia is the most popular regional anesthesia technique for lower abdominal surgeries. The failure of many spinal anesthesia techniques is more due to inadequate sedation and anxiolysis than technically faulty blocks. This study was designed to determine the appropriate dose of intravenous dexmedetomidine maintainance infusion to provide adequate sedation for spinal anesthesia. METHODS: A prospective, randomized, controlled double-blind study was carried out on 75 patients aged 18-60 years with ASA I and ASA II physical status who were scheduled for elective lower abdominal surgery under spinal anesthesia. Before the spinal anesthesia, all study participants were given an initial loading dose of 0.5 µg/kg dexmedetomidine infusion. Participants were randomly divided into three groups for maintenance drug infusion, Group A (to receive dexmedetomidine infusion at 0.2 µg/kg/hr), Group B (to receive dexmedetomidine infusion at 0.4 µg/kg/hr) and Group C to receive an intravenous infusion of normal saline during surgery. The Ramsay Sedation Scale (RSS) score, duration of analgesia, hemodynamic variables and occurrence of adverse events were monitored in all patients. RESULTS: Dexmedetomidine group had increased RSS score in intraoperative period and upto first 30 minutes in postoperative period compared to control group . Time to request for first analgesic was prolonged and incidence of shivering and PONV in postoperative period was less in group B than group A. The hemodynamic parameters, Respiratory parameters were not statistically significant among group A and group B. CONCLUSION: We conclude that intravenous administration of dexmedetomidine0.5 µg/kg loading dose followed by 0.4 µg/kg/hr as maintenance infusion is the optimum dose to produce sedation during spinal anesthesia with an additional advantage of increased duration of analgesia and reduced postoperative sideeffects .