Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 10 3 2023 11 13 221 226 Mohammadreza Safavi Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Azim Honarmand Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Behzad Nazemroaya Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Negar Maleky Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. 2023 05 27 2023 06 28 Background: Nausea and vomiting after operation has high prevalence and cause adverse effect. The aim of this study was to compare the effect of dexmedetomidine with ondansetron in prevention of post-operative nausea and vomiting (PONV) after middle ear surgery under general anesthesia.and saliva gas in traumatic patients under mechanical ventilation. Methods: This in this double-blinded clinical trial study, one hundred and sixty-two patients undergoing middle ear surgery under general anesthesia were randomly divided into three groups of 55 each: ondansetron (O), dexmedetomidine (D) and control (C). Group O received 0.1 mg/kg of ondansetron, Group D received 1 μg/kg/min of dexmedetomidine and Group C received 10 cc of normal saline 15 to 20 minutes before surgical incision. After that, the patients were examined in post-anesthesia care unit (PACU) and up to 24 hours after the operation in terms of PONV and other study variables. Results: The severity of nausea after operation based on VAS (visual analog scale) was significantly different between Group O (2.2±0.7) and Group D (3.9± 0.7) and Group C (5.15±1.3) (P= 0.04). The incidence of vomiting in the first 24h postoperatively was 14.8% in Group O, 46.3% in Group D and 88.8% in Group C (P= 0.003). Conclusion: Our study showed that ondansetron was better than dexmedetomidine for prevention of PONV after middle ear surgery. https://aacc.tums.ac.ir/index.php/aacc/article/view/778