Episodic arterial oxygen desaturation and heart rate variations following major abdominal surgery.

In 20 patients undergoing elective major abdominal surgery, heart rate and arterial oxygen saturation were monitored continuously during the night 2 days before operation and during the first and second nights after operation (23:00 to 07:30). Mean heart rate increased by 16 beat min-1 (P less than 0.0006) and mean oxygen saturation decreased by 3.2% (P less than 0.0002) after operation. Four patients had 21, 27, 120 and 372 episodes of sudden desaturation to a value less than 80% on the second night after operation. The patient with 372 episodes of sudden desaturation had severe cardiac arrhythmias on the morning of the third day after operation. In another patient the episodes of desaturation correlated with increases in heart rate. There was no correlation between administration of opioids and heart rate and saturation disturbances. The mechanism and clinical relevance of episodic desaturation in the late postoperative period remain unknown, but may be important in the pathogenesis of post-operative cardiac, cerebral and wound dysfunction.