Phenylephrine is the drug of choice to treat hypotension seen after spinal anesthesia for cesarean delivery. If a phenylephrine infusion is used rather than intermittent boluses, is there a reduction in the number of physician interventions? Dr. Marie T. Aouad, Department of Anesthesiology, American University of Beirut-Medical Center, Beirut, Lebanon, and colleagues randomized patients who received spinal anesthesia for caesarean delivery to receive a crystalloid solution bolus and either a phenylephrine infusion, started initially at 0.75 μg/kg/min, or only rescue phenylephrine boluses. The results of their study appear in next month’s issue of Anesthesia & Analgesia in the article titled “A Randomized Controlled Trial of Variable Rate Phenylephrine Infusion With Rescue Phenylephrine Boluses Versus Rescue Boluses Alone on Physician Interventions During Spinal Anesthesia for Elective Cesarean Delivery.”
For the procedure, the drugs used for spinal anesthesia included 0.75% hyperbaric bupivacaine, 12.75 mg, and morphine 0.2 mg followed by an infusion of 15 mL/kg lactated Ringer’s solution administered over 10-15 min. A phenylephrine or saline infusion was started. If systolic blood pressure increased to more than 20% of baseline, the infusion (phenylephrine or saline) was reduced by 0.25 μg/kg/min. If blood pressure decreased to less than 80% of baseline, phenylephrine 100 µg was administered and the infusion was increased by 0.25 μg/kg/min.
Eighty patients were included in the study. Both the number of interventions and incidence of hypotension were lower in the group that received a phenylephrine infusion, though the phenylephrine infusion group also had a higher incidence of hypertension. Overall, systolic blood pressure was higher and heart rate was slower over time for patients who received a phenylephrine infusion. Nausea/vomiting episodes coincided with hypotension and correcting hypotension treated nausea/vomiting.
Perhaps we need to lower our threshold for using phenylephrine infusions in parturients undergoing Cesarean section spinal anesthesia.