Comparison of the effect of different doses of ondansetron on spinal anesthesia induced hypotension in lower segment caesarean section: A double blinded randomized controlled study.

Subarachnoid block (spinal anesthesia) is the preferred anesthetic technique for elective lower segment cesarean section (LSCS) due to its rapid onset, reliability, and safety profile. However, it is frequently associated with significant hemodynamic disturbances, primarily hypotension and bradycardia, resulting from sympathetic blockade and decreased venous return.  These changes can adversely affect both maternal and fetal outcomes by reducing uteroplacental perfusion. Ondansetron, a selective 5-HT3 receptor antagonist commonly used as an antiemetic, has been shown to modulate the Bezold–Jarisch reflex-a vagally mediated cardiovascular reflex implicated in spinal anesthesia-induced hypotension and bradycardia . Some  studies suggest that intravenous ondansetron administered prior to spinal anesthesia at different time interval has shown a variable hemodynamic changes, reducing the incidence and severity of hypotension and bradycardia in patients undergoing cesarean section. The onset of sympathectomy after spinal anaesthesia and onset of intravenous ondansetron are almost similar that is 1-5 minutes and its peak effect around 10-15 minutes. Therefore, we will be conducting study to assess haemodynamic changes with simultaneous administration of intraveneous ondansetron during subarachnoid block.