Effect of Continuous Prophylactic Administration of Phenylephrine on Hypotension during Cesarean Section under Spinal Anesthesia

Hypotension frequently occurs during the induction of spinal anesthesia for cesarean section and can cause adverse maternal and fetal effects. Phenylephrine has been used as a vasopressor to prevent and treat hypotension following spinal anesthesia. We retrospectively investigated the effects of continuous prophylactic infusion of phenylephrine, compared with only bolus group. In the former group, the phenylephrine infusion was commenced at a rate of 1 mg/h immediately after spinal anesthesia, and a bolus of the vasopressor was administered when required. Continuous prophylactic administration of phenylephrine significantly reduced the incidence of hypotension and requirement of bolus vasopressor. The combination of a low-dose phenylephrine infusion and a small dose of vasopressor bolus is preferable, as it reduces the incidence of hypotension while avoiding reactive hypertension and bradycardia.