Preoperative ondansetron does not reduce the incidence of maternal hypotension during elective caesarean delivery under spinal anaesthesia, but mitigate its severity: a double blind, randomized, placebo controlled trial

Background. The prophylactic administration of ondansetron has been reported to provide a protective effect against hypotension in spinal anaesthesia (SA). Material and methods. This prospective double-blind, randomised, placebo-controlled study included 130 healthy pregnant women scheduled for elective caesarean delivery under SA randomly allocated to receive placebo (n = 65) or ondansetron 8 mg (n = 65) intravenously before SA. Demographic, obstetric, intraoperative timing and anaesthetic variables were assessed at 16 different time points, including blood pressure, heart rate, oxygen saturation, nausea, vomiting, electrocardiographic changes, skin flushing, discomfort or pruritus and vasopressor requirements. Results. There were no differences in the number of patients with hypotension: 33 (placebo) vs. 29 (ondansetron). However, as a single patient could had more than one hypotensive episode, we analysed the number of hypotensive events per patient (placebo 2.9 ± 4.0 vs. ondansetron 1.4 ± 2.2) (P = 0.011) and the percentage of time points with systolic hypotension (placebo 17.4% vs. ondansetron 8.7%) (P = 0.012). We also found differences at min 9 in diastolic blood pressure (DBP) (P = 0.014), mean arterial pressure (MAP) (P = 0.049), the variations from baseline of systolic blood pressure at min 5 to 13 and 20 (Figure 3), DBP at min 7 to 11, and MAP at 7 to 13 min between groups (P < 0.05) and the number of patients requiring ephedrine (P = 0.042). There were no differences in the number of patients with adverse effects excepting pruritus (P = 0.042). Conclusions. prophylactic administration of ondansetron 8 mg has a certain protective effect in the prevention of maternal hypotension in healthy women scheduled for elective caesarean delivery under spinal anaesthesia. Anestezjologia i Ratownictwo 2016; 10: 19-27.