Purpose
Hypotension 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 versus those who received phenylephrine boluses for the treatment of spinal-induced hypotension.
Methods
In this multi-centre, 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 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.
Results
IONV was significantly reduced in the infusion group compared to the bolus group, 46% vs 75%; relative risk 0.61 (95% CI 0.47 to 0.80); P < 0.001. This was associated with significantly reduced need for intraoperative rescue antiemetics, 26% vs 42%; relative risk 0.62 (95% CI 0.40 to 0.97); P = 0.04, but no difference in the incidence of vomiting. Postoperative vomiting at 2h was reduced in the infusion group, 11% vs 25%; relative risk 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 2h and 24h or the incidence of postoperative vomiting at 24h. The infusion group had a significantly lower incidence of hypotension but greater incidence of reactive hypertension.
Conclusion
In 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 Registry Number
NCT01481740 https://clinicaltrials.gov/ct2/show/NCT01481740?term=NCT01481740&rank=1