Background and Objective : Today, laparoscopic surgeries, because of reducing postoperative complications, are increasingly developing. Intraperitoneal insufflations of CO2_�and systemic absorption of it during laparoscopy results in hypercarbia. Using N₂O during maintenance of anesthesia in these patients can enhance hypercarbia. This is because N₂O increases the volume of pneumoperitoneum. This study was performed to determine the effect of N₂O in enhancing hypercarbia during laparoscopy.

  Methods : Sixty Patients, with physical status I or II, undergoing outpatient diagnostic gynecologic laparoscopy according to ASA (American Society of Anesthesiology) scaling took part in this clinical and single blind trial, and were randomly divided in to two groups, each with 30 patients. In all patients, general anesthesia with end tracheal intubation was administered. The technique of anesthesia and ventilation were the same in all patients. Only, during the maintenance of anesthesia, N₂O was not administered to group I (control) of patients, but in group II (case), patients received N₂O, in 50% concentration in oxygen. The variables under study were evaluated and recorded at certain times and finally the data were analyzed using chi-square test, student t-test and EPI-5_�software.

  Results : There was no significant difference between two groups in terms of demographic data, homodynamic variables (heart rate, mean arterial pressure, and electrocardiogram changes), oxygen saturation, and the use of any additional analgesic drug (instead of N₂O in group I). Comparing the End tidal CO₂ (Etco₂) in two groups indicated that Etco₂ increases in those patients who used N₂O during maintenance of anesthesia (p=0.02).

  Conclusions : With regard to significant difference between two groups in the enhancement of intraoperative hypercarbia (although it was not associated with homodynamic changes in this study), it is better not to use N₂O in general anesthesia for laparoscopic procedures.