• Ronald B George, Dolores M McKeen, Jennifer E Dominguez, Terrence K Allen, Patricia A Doyle, and Ashraf S Habib.
• Department of Women's & Obstetric Anesthesia, IWK Health Centre, Dalhousie University, 5850/5980 University Avenue, P.O. Box 9700, Halifax, NS, B3K 6R8, Canada. rbgeorge@dal.ca.
• Can J Anaesth. 2018 Mar 1; 65 (3): 254-262.

PurposeHypotension is common after spinal anesthesia for Cesarean delivery. It is associated with nausea, vomiting, and fetal acidosis. Previous research on phenylephrine excluded obese subjects. We compared the incidence of intraoperative nausea and vomiting (IONV) in obese patients who received a prophylactic phenylephrine infusion vs those who received bolus dosing for the treatment of spinal-induced hypotension.MethodsIn this multicentre, double-blinded randomized controlled trial, 160 obese women undergoing elective Cesarean delivery under spinal anesthesia were randomized to receive a prophylactic phenylephrine infusion initiated at 50 μg·min-1 (and titrated according to a predefined algorithm) or 100 μg phenylephrine boluses to treat hypotension. Maternal systolic blood pressure was maintained within 20% of baseline. The primary study outcome was the incidence of IONV.ResultsIntraoperative nausea and vomiting were significantly reduced in the infusion group compared to the bolus group (46% vs 75%, respectively; relative risk [RR], 0.61; 95% confidence interval [CI], 0.47 to 0.80; P < 0.001). This was associated with significantly reduced need for intraoperative rescue antiemetics (26% vs 42%, respectively; RR, 0.62; 95% CI, 0.40 to 0.97; P = 0.04), but no difference in the incidence of vomiting. Postoperative vomiting at two hours was reduced in the infusion group (11% vs 25%; RR, 0.44; 95% CI, 0.21 to 0.90; P = 0.02);however, there were no differences in the incidence or severity of postoperative nausea, need for rescue antiemetics at two hours and 24 hr, or the incidence of postoperative vomiting at 24 hr.ConclusionIn obese women undergoing Cesarean delivery with spinal anesthesia, prophylactic phenylephrine infusion was associated with less intraoperative nausea, less need for rescue antiemetics, and reduced early postoperative vomiting.Trial Registrationwww.clinicaltrials.gov (NCT01481740). Registered 22 July 2011.

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