Granisetron versus Ondansetron: Comparison of 5HT3 antagonists in preventing spinal anaesthesia induced hemodynamic instability in obstetric patients.

Objectives: To evaluate and compare the Ondansetron and Granisetron in preventing spinal anaesthesia induced hemodynamic instability in obstetric patients. Methods: The comparative analytical study was conducted at Combined Military Hospital, Rawalpindi, from September to October, 2021. One hundred and twenty pregnant women undergoing cesarean section, were enrolled in the study via non probability convenience sampling, and divided into three groups containing 40 participants each based on the type of antiemetic premedication they received, if any: Group N were those not requiring antiemetic premedication, Group O consisted of those given ondansetron 4mg, and Group G had those receiving 3mg granisetron, 15 minutes prior to administration of spinal anaesthesia. Systolic blood pressures and heart rates were recorded before and at multiple intervals after spinal anaesthesia was administered. Episodes of hypotension and bradycardia were recorded. Requirement of phenylephrine and atropine as rescue drugs was recorded for each participant. Results: There was a statistically significant difference in incidence of hypotension among the three groups (p value <0.001), with both drugs being superior to the control group (p value <0.001 for both), and 3mg granisetron being superior to 4mg ondansetron (p value <0.001). As for incidence of bradycardia, ondansetron and granisetron were superior to control group (p value 0.03 and <0.001 respectively), but there was no significant difference between the two drug groups (p value 0.094). Conclusion: High dose granisetron (3mg) is superior to low dose ondansetron (4mg) in preventing hemodynamic fluctuations induced by spinal anaesthesia.