Prophylactic Norepinephrine and Phenylephrine Boluses for Postspinal Anesthesia Hypotension

An initial prophylactic bolus dose of phenylephrine (37.5μg) simultaneous with spinal anesthesia. If the patient did not respond adequately to the current dose (SBP decreased to \< 80% of baseline), the dose was considered to have failed and the subsequent dose for the following patient was increased to the next higher dose level. The dose administered to subsequent patients varied by increments or decrements of 12.5 μg according to the responses of previous patients according to the up-down sequential allocation.

An initial prophylactic bolus dose of norepinephrine (3μg) simultaneous with spinal anesthesia. The dose administered to subsequent patients varied by increments or decrements of 1 μg according to the responses of previous patients according to the up-down sequential allocation.