Subarachnoid block is the preferred method of anaesthesia for caesarean section, but is
associated with hypotension and bradycardia, which may be deleterious to both parturient and
baby. Animal studies suggest that in the presence of decreased blood volume, 5-HT may be an
important factor inducing the Bezold Jarisch reflex via 5-HT3 receptors located in
intracardiac vagal nerve endings. In this study, the investigators evaluated the effect of
ondansetron, as a 5-HT3 receptor antagonist, on the haemodynamic response following
subarachnoid block in parturients undergoing elective caesarean section.