Risk factors of postoperative nausea and vomiting following the use of N2O in general anesthesia

not yet clear that when, why, in whom and under which circumstances dose N2O induce nausea and vomiting. Objective: To determine the incidence rate of PONV after the administration of N2O according to age, sex, anatomical site of the operation, duration of anesthesia and history of motion sickness in order to define the main risk factors. Methods: 100 patients who were scheduled for surgery in four of the teaching hospitals of Rasht city were sequentially and non-randomly studied. Except N2O, all other PONV inducing factors, as described in the literature, were defined as exclusion criteria. All patients received general balanced anesthesia with the same regimen including N2O in 50% to 70% concentrations. No antiemetics were administered. The occurrence of PONV was recorded for six hours after the termination of anesthesia. Findings: PONV (Nausea/Vomiting/both) occurred in 55% of the patients. In the 15-35 years age group 50.8%, in the 36-55 years age group 62.1%, among females 63.2% and in males 44.2% experienced PONV. 80% of the patients with a history of motion sickness and 46.7% of those without it suffered PONV. Considering the anatomical site of the operation the highest incidence (63.9%) of PONV was seen in the case of lower abdomen and pelvic operations. Incidence of PONV in-groups with different length of anesthesia was almost the same. Conclusion: Women, patients with a history of motion sickness and those undergoing a lower abdomen or pelvic operations are more prone to PONV following the use of N2O. Therefore they require more scrutinizing postoperative care till a proper alternative is found for N2O.