Arterial oxygen saturation following premedication for cardiac surgery.

We studied patients scheduled for coronary artery bypass surgery following premedication with lorazepam, morphine and droperidol, using pulse oximetry and serial electrocardiographic (ECG) recordings. Arterial oxygen saturation (SaO2) values were compared with those obtained during two control periods when the patients were awake and asleep. All patients demonstrated progressive arterial oxygen desaturation during the premedication period, statistically significant from both controls (P less than 0.001). Twelve of the 15 patients developed hypoxaemia or severe hypoxaemia which was corrected immediately by administration of oxygen. New ECG changes developed during the premedication period in 33% of patients. It is concluded that additional oxygen should be administered to patients receiving this and similar premedication regimens.