Aim: This prospective, randomized, double blinded studywas conducted to evaluate the effectof prophylactic intravenous 8 mgondansetron for attenuation ofhypotension and bradycardia incaesarean section under spinalanaesthesia. Materials & Methods:After obtaining the approval fromthe ethical committee of IGMCShimla 60 patients of ASA I and IIaged 20-40 years undergoing electivecaesarean section were included inthe study. Group 1 receivedpreloading with ringer lactate(500ml) thirty minutes beforesurgery and Ondansetron 8 mg in 5ml NS, 5 minutes before spinalanaesthesia.Group 2 receivedpreloading with ringer lactate (500ml) thirty minutes beforesurgery and 5 ml NS, 5 minutes before spinal anaesthesia. Results: Both the groups were comparable in demographic variables like age, ASAstatus and duration of surgery (p>0.05). The baselinehaemodynamic parameters were comparable in both the groups(p>0.05). The oxyhaemoglobin saturation was comparable andthere was no significant difference in both the study groups (p>0.05).The time for fixation of sensory and motor block was similar in both thegroups. The heart rate at all the time intervals was comparable in both the  groups with higher mean heart rate in Group 1 at 14 minutes and 16 minutes of time interval. The fall in MAP was significantly more (p=0.018) in Group 2 than in Group 1 and was seen at 2 minutes onwards whereas it was observed at 10 minutes to 25 minutes in Group 1. The mean phenylephrine consumption was more in Group 2 than in Group 1, 50µgms vs. 23±50µgms respectively, although the p value remained insignificant. (p=0.091). In our study we had significant fall in blood pressure at 2 minutes in Group 2 and the vasopressors were used more during the first 10 minutes after subarachnoid block in Group 2 as compared to Group 1. After 10 minutes, 3 patients required them to maintain BP in both the groups. In intra group comparison of blood pressure significant fall in BP from base line was observed at 10 min interval in group 1 (p=0.002). Whereas this fall was seen at 2 minutes of subarachnoid block in Group 2 (p=0.04). There were no statistically significant untoward effects observed in any of the study groups. Conclusion:- Ondansetron seems to prevent the initial fall in BP during first 10 minutes after  subarachnoid block. Though Ondansetron had attenuated hypotension in the first 10 minutes with lower vasopressor usage (13% in Group 1 vs. 40% in Group 2) after spinal anaesthesia in elective caesarean section in our study but since we did not get statistically significant results in vasopressors use after 10 minutes we recommend further studies with bigger sample size to prove the hypothesis that Ondansetron use obtunds the fall in blood pressure in spinal anaesthesia in cesarean section. 

Keywords: Ondansetron; Spinal Anaesthesia; Cesarean Section.