A Comparative Study of the Effect of Two Different Doses of Ondansetron on the Reduction of Maternal Hemodynamic Changes in Cesarean Section under Spinal Anesthesia

Hypotension and bradycardia are among the common side effects of spinal anesthesia. The effect of ondansetron on the reduction of hypotension and bradycardia caused by spinal anesthesia has been studied considering its antagonistic effect on the Bezold–Jarisch reflex. The present study was conducted to determine the effectiveness of two different doses of intravenous ondansetron on the reduction of the incidence of hypotension and bradycardia among candidates for elective caesarean section under spinal anesthesia.

This double-blind clinical trial was conducted in Shahid Beheshti Hospital in Isfahan in 2020 and included 90 patients aged 18 to 45 years in full-term pregnancy who were candidates for elective caesarean section in three groups of 30. 5 minutes before spinal anesthesia, 6 and 8 mg of ondansetron were injected in the first and second groups, respectively, and normal saline was injected in the third group. Vital signs were examined every 15 minutes during surgery and during recovery, and the incidence of hemodynamic disorders, nausea and vomiting was compared between the three groups.

There was no significant difference between the three groups in terms of demographic and baseline variables, blood pressure (systolic, diastolic and mean arterial pressure), heart rate, ephedrine intake and incidence of hemodynamic disorders. The frequency of nausea during recovery was significantly different between the three groups (p=0.035); 12 people in the ondansetron 6 mg group, 12 people in the ondansetron 8 mg group and 21 people in the control group had nausea during recovery (40%, 40%, and 70%, respectively). The frequency of vomiting in recovery was significantly different between the three groups (p=0.002); 5 people in the ondansetron 6 mg group, 1 person in the ondansetron 8 mg group, and 12 people in the control group experienced vomiting during recovery (16.7%, 3.3%, and 40%, respectively).

The results of this study showed that administration of ondansetron at 6 and 8 mg doses in caesarean section under spinal anesthesia has no significant effect in reducing the incidence of hypotension, bradycardia, and administration of ephedrine and atropine. However, it is associated with a reduction in the incidence of nausea and vomiting in the recovery room (ondansetron 8 mg is more effective than 6 mg).