Respiration during emergence from anaesthesia with desflurane/N2O vs. desflurane/air for gynaecological laparoscopy

The complications related to anaesthesia usually occur in the early postoperative period. Hypercapnia and hypoxaemia may result from any persistent depression of the respiratory drive relative to the metabolic demand. The purpose of this study was to compare the respiratory effects of desflurane anaesthesia with or without nitrous oxide during the period of emergence.

Twenty patients scheduled for a standardised surgical procedure, laparoscopic hysterectomy, were randomly allocated to anaesthesia with 1.3 MAC of desflurane/N2O (Group 1) or desflurane alone (Group 2), with 10 patients in each group. Times of resumption of spontaneous breathing and extubation were recorded and elimination rates of carbon dioxide, end-tidal concentrations of desflurane and N2O, and blood gases were measured.

Spontaneous breathing was resumed in both groups when pH had decreased by about 0.07 and PaCO2 increased by about 1.4 kPa compared with the values at the end of 1.3 MAC anaesthesia with controlled normoventilation. There were no significant differences between the groups with regards to extubation time, 6 vs. 13 min, or total MAC value at extubation, 0.20 vs. 0.19 in Group 1 and 2, respectively. Neither did the groups differ in minute ventilation, end-tidal carbon dioxide, oxygen concentrations, or blood gases. CO2 elimination decreased in both groups from about 220 ml 70 kg-1 min-1 at the end of anaesthesia to a lowest value of about 160 ml 70 kg-1 min-1.

The respiratory profiles during recovery from gynaecological laparoscopy with either desflurane/N2O or desflurane anaesthesia were similar with fast resumption of spontaneous breathing, short time to extubation, and no signs of CO2 retention.