Effect of N2O in the Enhancement of Hypercarbia due to Co2 Absorption during Laparoscopy

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. 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. 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). 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.