Hypotensive anesthesia for the correction of scoliosis under total intravenous anesthesia: comparison between dexmedetomidine and magnesium sulfate

Context This study was designed to compare dexmedetomidine with magnesium sulfate as an adjunctive to total intravenous anesthesia (TIVA) as regards the efficacy and safety as hypotensive agents in scoliosis correction surgery. Patients and methods This prospective randomized double-blinded study included 40 patients of American Society of Anesthesiology II who were scheduled for the correction of scoliosis under TIVA and divided into two groups of 20 patients each. The first group was the Dex group, which was administered dexmedetomidine infusion at a rate of 0.5 μg/kg/h, and the second group was the Mg group, which was administered magnesium sulfate infusion at a rate of 15 mg/kg/h. The target mean arterial pressure (MAP) was 60–70 mmHg. The two groups were compared as regards MAP, heart rate (HR), intraoperative blood loss, blood transfusion, quality of surgical field, need for vasodilators and analgesics, time to extubation, time to recover the hypotension, time to recover the full conscious level, and perioperative serum levels of calcium and magnesium. Results Both groups could achieve the target MAP before skin incision. The Dex group showed more HR stability, less intraoperative blood loss, and less intraoperative blood transfusion with better surgical field quality. Moreover, the need for vasodilators was lesser in this group. However, the Mg group showed faster extubation time, faster reversibility of hypotension, and faster recovery of full conscious level. Need for intraoperative analgesia was comparable between the two groups. Intraoperative and postoperative serum magnesium were higher in the Mg group and intraoperative and postoperative serum calcium levels showed gradual drop in the Mg group compared with the Dex group and the preoperative level in the Mg group. Both electrolytes showed recovery to normal preoperative level 24 h postoperatively without interference. Conclusion TIVA with both dexmedetomidine and magnesium sulfate could achieve the target MAP for hypotensive anesthesia. Dexmedetomidine can control MAP with lesser need for vasodilators and with better control of HR. It provided lesser blood loss and better quality of surgical field. Magnesium sulfate showed faster extubation and recovery of conscious level with faster reversibility of hypotensive state but with the risk for perioperative hypocalcemia.