Background
The unopposed vagal activity with sympathetic block and maternal bradycardia that is likely to occur with phenylephrine infusion might be some causes of intraoperative nausea and vomiting (IONV) during spinal anaesthesia. We aimed at comparing hyoscine butyl-bromide (HBB) and ondansetron in reduction of intraoperative bradycardia and thus IONV in women undergoing caesarean delivery (CD).
Methods
In a randomized, double-blind, placebo-controlled trial, women undergoing elective CD were randomly assigned to administer either IV HBB 20 mg, ondansetron 8 mg, or the same volume of 0.9% saline right before spinal anaesthesia. The primary endpoint was the incidence of IONV. Secondary endpoints included intraoperative maternal bradycardia and hypotension and postoperative nausea and vomiting (PONV).
Results
55 subjects in each group received the assigned intervention. During the intraoperative period, HBB decreased only the incidence of emesis when compared to the control group ( = 0.046) while ondansetron statistically decreased the incidence of IONV when compared to the control group ( = 0.034). HBB statistically decreased the incidence of intraoperative maternal bradycardia when compared to the controls (1.8% vs 14.5%; OR = 0.1, 95% CI = [0.01, 0.90];  < 0.039). Compared to the control group, ondansetron was superior to HBB in reducing PONV ( = 0.001 & 0.57), respectively.
Conclusions
In women scheduled for CD with spinal anaesthesia, prophylactic HBB was as effective as ondansetron in reducing intraoperative emesis, with the added benefit of the less incidence of intraoperative bradycardia than ondansetron. Meanwhile, Ondansetron reduced the incidence of PONV significantly.