Atelectasis and oxygenation in major surgery with either propofol with or without nitrous oxide or isoflurane anaesthesia.

Forty-two patients undergoing major colonic surgery were assigned at random to receive isoflurane-fentanyl anaesthesia with nitrous oxide in oxygen, propofol-fentanyl anaesthesia with air in oxygen or propofol-fentanyl anaesthesia with nitrous oxide in oxygen. The groups were comparable in demographic data. Atelectases were identified, and the area measured by computerised tomography of the chest 203 +/- 69 min after extubation, and oxygenation was determined by arterial blood gas samples taken during operation at 30, 60, 90 and 120 min after extubation and on postoperative days 1, 2 and 3. Atelectases were seen in all three groups with no differences in the mean area between groups. After operation, the effect of 4 l.min-1 of oxygen by nasal catheter on PaO2 was similar in all groups. A significant decrease in PaO2 was found during the first 3 days after surgery, and was also the same in all groups. There was no correlation between area of atelectasis and postoperative PaO2. We conclude there is no difference in the incidence of postoperative atelectasis or oxygenation when using propofol, with or without nitrous oxide or isoflurane.