The aim of our study was to evaluate the effects of fixed rate phenylephrine infusion versus variable rate phenylephrine infusion on maternal hemodynamics and fetal pH.
Patients and methods: We included 60 women aged 20 to 35 years, ASA status 1, scheduled
for caesarean section. Patients had the same anesthetic protocol. Then, they were randomized into two groups:
• Group 1: receives a fixed rate phenylephrine infusion at 50μg / min
• Group 2: receives a variable rate phenyephrine infusion. Intravenous phenylephrine was started at 25μg / min and the perfusion rate was titred according to the variation in the systolic blood pressure compared to the initial systolic blood pressure.
Results: Demographic data (age, weight, height, gestity and parity) were comparable between the two groups. The total dose of phenylephrine consumed was 336 ± 120 mg in group 1 versus 161 ± 49 mg in group 2, p <0.001.
The systolic and diastolic blood pressures were also comparable as well as the number of boluses of ephedrine.
We did not reveal any bradycardia episode requiring administration of atropine in both groups. However, we noted a higher FC in Group 2 at four minutes and five minutes after the cesarean section
Conclusion:
Phenylephrine is widely used in the prevention of spinal anesthesia-induced hypotension during cesarean section. It is usually administered in fixed rate infusion. However, its administration with  titrated infusion  according to the variation of  maternal hemodynamics may provide the same hemodynamic stability and may reduce the total dose used and  the incidence of bradycardia.

Comparison of two modes of phenylephrine administration for the management of spinal anesthesia-induced hypotension during cesarean section: randomized controlled trial