Effect of co-administration of different doses of phenylephrine with oxytocin on the prevention of oxytocin-induced hypotension in caesarean section under spinal anaesthesia: A randomised comparative study

Abstract

Introduction:Co-administration of phenylephrine prevents oxytocin-induced hypotension during caesarean section under spinal anaesthesia (SA), but higher doses cause reflex bradycardia. This study compares the effects of co-administration of two different doses of phenylephrine on oxytocin-induced hypotension during caesarean section under SA.Methods:In this prospective, double-blind study, 90 parturients belonging to the American Society of Anesthesiologists' physical status 1 or 2, undergoing caesarean section under SA were randomised into Group A: oxytocin 3U and phenylephrine 50 μg, Group B: oxytocin 3U and phenylephrine 75 μg, Group C: oxytocin 3U and normal saline, administered intravenously over 5 min after baby extraction. The incidence of hypotension (the primary outcome), rescue vasopressor requirement and side effects were recorded. Statistical analyses were with analysis of variance, Kruskal-Wallis, chi-square and Fisher's exact tests.Results:Demographic parameters such as age, height, weight, level of sensory block at 20 min and duration of surgery were comparable in all the groups. The incidence of hypotension (Group A – 90%, Group B – 10%, Group C – 98%, P = 0.001), magnitude of fall in mean arterial pressure (Group A-15.03 ± 6.12 mm of Hg, Group B – 6.63 ± 4.49 mm of Hg and Group C-13.03 ± 3.39 mm of Hg, P < 0.001) and rescue vasopressor requirement (Group A-45 ± 15.25 mg, Group B-5 ± 15.25, Group C-91.66 ± 26.53, P < 0.001) were significantly lower in Group B compared to A and C.Conclusion:Co-administration of phenylephrine 75 μg with oxytocin 3U reduces the incidence of oxytocin-induced hypotension compared to phenylephrine 50 μg with oxytocin 3U during caesarean section under spinal anaesthesia.

A randomised double-blind trial of minimal bolus doses of oxytocin for elective caesarean section under spinal anaesthesia: Optimal or not?

“…The uterine tone was rated as either adequately retracted or inadequately retracted. [ 8 ] Then 10 units of oxytocin infusion in 500 mL normal saline was commenced at 125 mL/h. A five-point Likert scale can be used to assess the uterine tone by palpation.…”

“…If inadequate, then intramuscular methergine 0.2 mg was administered as alternative uterotonic therapy. [ 8 ] The other uterotonics kept ready for back-up were carboprost (0.25 mg) or misoprostol (800–1000 μg).…”