Comparison of a Modified Regimen of Prophylactic Phenylephrine Boluses Versus Variable Rate Infusion During Elective Cesarean Delivery Under Spinal Anesthesia: A Noninferiority Randomized Double-Blind Study.

BACKGROUND

Prophylactic phenylephrine boluses have been found to be as effective as variable rate infusions during elective cesarean delivery but require a higher number of physician interventions to maintain blood pressure near baseline values. Therefore, there is a need to find a feasible regimen of bolus administration that is equally efficacious to the infusion regimen while at the same time requires a comparable number of physician interventions and is thus non-inferior to the infusion regimen.

METHODS

Healthy pregnant women with term, uncomplicated, singleton pregnancies undergoing elective cesarean delivery under spinal anesthesia were randomly divided into two groups. The Bolus group received a phenylephrine bolus 100 μg immediately after spinal anesthesia and then at every systolic blood pressure value <90% of the baseline. The infusion group received a prophylactic variable-rate infusion of phenylephrine beginning at 50 μg/min and titrated to maintain systolic blood pressure at 90-99% of baseline. The primary outcome was the number of physician interventions needed to maintain the target systolic blood pressure; the secondary outcomes included phenylephrine requirements, incidence of hypotension/hypertension/bradycardia, umbilical arterial and venous blood gas analysis, Apgar scores, and maternal complications. The primary outcome was analyzed in terms of non-inferiority using a non-inferiority margin of two interventions.

RESULTS

Eighty patients were included in the study. The median (interquartile range [IQR]) number of physician interventions was 6 (5-8) in the infusion group and 3 (2-4) in the bolus group (P < .001). The difference of medians (95% confidence interval [CI]) between the two groups was -3 (-4 to -2). Phenylephrine requirements were higher in the infusion group (630 [426-765] μg) compared to the bolus group (300 [200-400] μg; P < .001). Blood pressure was higher at certain time points in the infusion group, but overall accuracy of blood pressure control was not different between the groups. Incidence of hypotension, hypertension, and bradycardia, neonatal outcomes, and maternal complications did not differ between the groups.

CONCLUSIONS

The modified regimen of prophylactic boluses is non-inferior to variable rate prophylactic phenylephrine infusion in terms of physician interventions needed to maintain systolic blood pressure within the target range and maternal and neonatal outcomes.