Impact of Prophylactic Weight-Based Phenylephrine Infusion on Shivering During Cesarean Delivery– A Prospective Randomized Controlled Trial

Background: Shivering during cesarean delivery under spinal anesthesia is an undesirable complication. Intravenous phenylephrine infusion, at varying doses, decreases the intensity of redistribution hypothermia with no consensus on ideal dosing regimen. We hypothesized that prophylactic infusion of phenylephrine based on maternal weight would reduce the incidence of shivering and hypothermia, along with stable hemodynamics during cesarean delivery performed under spinal anesthesia. Methods and Materials: In this prospective randomized double-blinded controlled trial, 112 patients undergoing elective cesarean section were randomly allocated to receive phenylephrine 0.25 µg/kg/min (Group P) or saline infusion (Group S) after spinal anesthesia. The primary outcome was the incidence and grade of shivering. The secondary outcome included changes in tympanic membrane temperature, mean arterial pressure, and heart rate. Results: The incidence of shivering in the phenylephrine group was 16.1% (95% CI 7.6–28.3%) compared to 30.4% (95% CI 18.8%– 44.1%) in the saline group ( P = 0.05). The intensity of shivering was Grade 2 in both groups. The mean tympanic membrane temperature was comparatively lower in the saline group throughout the intraoperative period without statistical significance. The need for phenylephrine bolus dose to maintain mean arterial pressures was lower in the phenylephrine group (7.1% vs 33.9%; P = 0.001) compared to the control group. The incidence of bradycardia was higher with phenylephrine infusion (17.9% vs 1.8%; P = 0.004). Conclusion: Prophylactic weight-based infusion of phenylephrine reduces both the incidence of shivering and hypotension simultaneously during cesarean delivery performed under spinal anesthesia.