A Study of Phenylephrine Administration for the Prevention and Treatment of Hypotension in Cesarean Section during Spinal Anaesthesia: A Randomised Clinical trial

Background: Hypotension remains the most common complication following spinal anesthesia in cesarean sections. Despite using various preventive measures, hypotension occurs in most cases; vasopressors are often required. The current study evaluated the safety and efficacy of prophylactic phenylephrine infusion in preventing spinal anesthesia-induced hypotension in the Cesarean Section.Materials and Methods: A total of ۵۰ parturients aged ۲۰-۳۵ years with American Society of Anesthesiologists (ASA) grade II, scheduled for elective cesarean sections were randomly allocated into one of the two groups. Group A (n=۲۵) received intravenous prophylactic phenylephrine infusion at ۱۰۰μg/min for ۳min after spinal anesthesia using a syringe pump. Each minute, systolic arterial pressure (SAP) was measured, and infusion stopped if SAP > baseline and continued if less than or equal to baseline systolic arterial pressure. Intravenous phenylephrine bolus ۱۰۰μg was given when SAP decreased to <۸۰% of baseline. Group B (n=۲۵) received only intravenous phenylephrine bolus ۱۰۰μg when SAP decreased to <۸۰% of baseline. After ۱ minute of spinal anesthesia, Heart Rate (HR), SAP, and diastolic blood pressure (DBP) were recorded every minute until the baby's extraction. After the delivery of the baby, APGAR scores at ۱ minute and ۵ minutes were noted. Umbilical artery blood was sent for analysis of the pH. The total volumes of study solutions given up to the time of delivery of the baby were recorded.Results: Phenylephrine infusion decreased the incidence and frequency of hypotension compared with control and the phenylephrine dose was much higher in the infusion group than in the control group (p=۰.۰۰۰۱). None of the patients had any incidence of nausea or vomiting. There was no significant difference in umbilical artery blood pH and no reduction in the APGAR scores. HR was significantly slower in the infusion group compared with the control group.Conclusion: A prophylactic infusion of phenylephrine۱۰۰ μg/min in patients receiving spinal anesthesia for elective cesarean delivery decreased the incidence of hypotension and without any deleterious neonatal outcome.

Keywords:

Phenylephrine , Hypotension , Bradycardia , Spinal Anaesthesia , Cesarean section , APGR , Umbilical artery blood pH