Effect of Three Different Prophylactic Bolus Doses of Phenylephrine on Hypotension Following Caesarean Section Under Combined Spinal-Epidural Anaesthesia

Background: Maternal hypotension is a frequent and potentially serious complication of spinal anaesthesia during Caesarean section. Phenylephrine is a commonly used vasopressor for prevention, but optimal dosing remains uncertain. Objective: To evaluate the effectiveness of three prophylactic bolus doses of phenylephrine in preventing spinal-induced maternal hypotension during elective Caesarean section under combined spinal–epidural anaesthesia. Methodology: A prospective comparative study at the University of Port Harcourt Teaching Hospital included 136 parturients scheduled for elective Caesarean section. All received an admixture of intrathecal 10 mg of 0.5% hyperbaric bupivacaine and 25 µg fentanyl. Participants were randomly assigned to four groups: a control group receiving normal saline and three intervention groups receiving 50 µg, 60 µg, or 80 µg of phenylephrine. Haemodynamic parameters were monitored every five minutes. Total phenylephrine used and neonatal Apgar scores were recorded. Results: Demographic characteristics were comparable across groups. The incidence of hypotension was highest in the saline group (85.5%) and lowest in the 80µg group (10.0%). Differences in hypotension rates were statistically significant between the 80 µg and saline group (p < 0.0001), and between other dose comparisons. Bradycardia was more frequent in the 80µg group (20.6%) (p = 0.030). Apgar scores were similar across groups, though umbilical cord venous pH was significantly lower in the saline group (p < 0.0001). Conclusion: Prophylactic bolus doses of phenylephrine, particularly 80 µg, are effective in preventing spinal-induced maternal hypotension but with a relatively higher incidence of bradycardia during Caesarean section without adverse neonatal outcomes.