Reducing by 50% the incidence of maternal hypotension during elective caesarean delivery under spinal anesthesia: Effect of prophylactic ondansetron and/or continuous infusion of phenylephrine - a double-blind, randomized, placebo controlled trial

Abstract

Background:Prophylactic administrations of ondansetron or phenylephrine have been reported to provide a protective effect against hypotension in women undergoing cesarean delivery under spinal anesthesia (SA). The main hypothesis is that ondansetron improves the hemodynamic response, especially combined with phenylephrine infusion.Methods:This prospective, double-blind, randomized, placebo-controlled study included 265 healthy pregnant women scheduled for elective cesarean delivery under SA. Women were randomly allocated into four groups to receive either placebo (control), ondansetron (O) 8 mg intravenously before induction of SA, phenylephrine infusion (50 mcg/min) (P) or ondansetron plus phenylephrine (OP). Demographic, obstetric, intraoperative timing, and anesthetic variables were assessed at 16 time points. Anesthetic variables assessed included blood pressure, heart rate, oxygen saturation, nausea, vomiting, electrocardiographic changes, skin flushing, discomfort or pruritus, and vasopressor requirements.Results:There were differences (P = 0.0001) in the number of patients with hypotension (50.8% control, 44.6% O, 20.9% P, 25.0% OP), the percentage of time points (P = 0.0001) with systolic hypotension per patient (17.4% control, 8.7% O, 2.1% P, 6.7% OP) and the number of patients requiring supplementary boluses of ephedrine (P = 0.003), phenylephrine (P = 0.017) or atropine (P = 0.0001).Conclusions:A 50 μg/min phenylephrine infusion reduces by 50%, the incidence of maternal hypotension compared with placebo, but infusions of phenylephrine are still not routine in our environment. Prophylactic ondansetron 8 mg might be considered in this situation, because it does not reduce the incidence of maternal hypotension but diminishes its severity, reducing the number of hypotensive events per patient by 50%.

Prevention of hypotension after spinal anaesthesia for caesarean section: a systematic review and network meta‐analysis of randomised controlled trials

“…We included 109 out of 1021 retrieved trials, which included 8561 women (Fig. and see also Supporting Information, Table S1) . Twelve interventions (eleven active treatments and one inactive control) to prevent intra‐operative hypotension were studied, with 30 direct comparisons (see also Supporting Information, Table S2).…”

Effect of ondansetron on spinal induced hypotension in caesarean deliveries

“…Overall the deceased dose of intrathecal bupivacaine along with longer period of fasting could have resulted in the lack of effect of ondansetron on the blood pressure following the administration of spinal anesthesia. The same groups of investigators recently performed a similar study with larger sample size of 67 patients in ondansetron group and concluded that although ondansetron does not decrease the incidence of maternal hypotension it does reduce the severity of hypotension reducing the number of hypotensive episodes per patient by 50% 20 .…”

Comparison of prophylactic phenylephrine infusion versus intravenous ondansetron on hypotension during spinal anesthesia for cesarean section

“…handled the same perspective and reported no difference between the study groups regarding patient demographics. [ 2 ]…”

“…In severe cases, fetal acidosis and bradycardia along with cardiovascular collapse could be encountered. [ 2 ]…”