Effect of intraoperative inspired gas mixtures on postoperative nocturnal oxygen saturation

Continuous postoperative nocturnal pulse oximetry was performed in 20 patients undergoing elective cholecystectomy to examine if the composition of anaesthetic gas mixtures affects postoperative gas exchange. The patients were allocated randomly to receive either nitrogen or nitrous oxide during anaesthesia, and oximetry was performed on the night before operation and the first and third nights after operation. Considerable oxygen desaturation was seen in both groups. During the first night after operation the proportion of the night during which oxygen saturation was less than 85% was greater in the nitrogen group than in the nitrous oxide group, but there was no significant difference between the mean overnight saturation values of the two groups.