Methods: In this double-blind study, 75 patients were randomized into 3 groups. Group O and Group M were given ondansetron 8 mg and meperidine 0.4 mg/kg intravenously immediately before spinal anesthesia, respectively. Group C received saline at identical times. The core temperatures and the incidence of shivering were recorded. Association between maximum block height and mean rectal temperatures of the patients were also evaluated.

Results: The core temperature was preserved in both ondansetron and meperidine groups with respect to the control group. Shivering was observed in 8% of patients in groups O and M and 36% in group C. The correlation between maximum block height and mean rectal temperatures was lost in the ondansetron and meperidine groups.

Conclusion: Ondansetron and meperidine have similar antishivering effects. In addition, both ondansetron and meperidine altered the correlation between the core temperature and block level during spinal anesthesia.