Comparison of the Hemodynamic Effect of Three Positions During Induction of Anesthesia

Overview

The most common methods for prevention of post-induction hypotension are preoperative fluid loading and vasopressors. Leg elevation induces an intrinsic transfusion of 150 mL blood from the lower limbs to the central fluid compartment. Leg elevation was previously reported by our group to decrease the incidence of maternal hypotension after spinal anesthesia for caesarean delivery. Passive leg raising was also reported to provide a stable hemodynamic profile during induction of anesthesia for cardiac surgery. Head-down position was previously reported as a useful measure for management of hypovolemia in various patient groups. No studies to the best of our knowledge had evaluated the compare both positions (leg elevation position and head-down position) during induction of anesthesia in non-cardiac surgery

Upon arrival to the operating room, routine monitors (ECG, pulse oximetry, and non-invasive blood pressure monitor) will be applied; intravenous line will be secured, and routine pre-medications (ranitidine 50 mg and midazolam 3-5 mg) will be administrated. Before induction of anesthesia, patients will be randomly allocated into:supine group, head-down group or leg elevation group Baseline mean arterial blood pressure will be obtained as average of 3 reading before induction of anesthesia at supine position. Induction of anesthesia will be achieved using fentanyl (2 mcg/Kg), propofol (2 mg/Kg), and atracurium (0.5 mg/Kg). Endotracheal tube will be inserted after 3 minutes of mask ventilation. Anesthesia will be maintained by isoflurane (1-1.5%) and atracurium 10 mg increments every 20 minutes. Ringer lactate solution will be infused at a rate of 2 mL/Kg/hour. Any episode of hypotension (defined as mean arterial pressure \< 80% of the baseline reading) will be managed by 5 mcg norepinephrine. If the hypotensive episode persisted for 2 minutes, another bolus of norepinephrine will be administered.