Time course of postoperative hypoxaemia.

OBJECTIVE: To study the time course of nocturnal episodic and constant hypoxaemia during the first five nights after a major abdominal operation in patients not given supplementary oxygen. DESIGN: Open study. SUBJECTS: 17 patients undergoing major elective operations and with no recognised risk factors. MAIN OUTCOME MEASURES: Arterial oxygen saturation measured by pulse oximetry. RESULTS: The level of constant hypoxaemia was lowest during night 2 (p < 0.01) as was the time spent below 90% saturation (p < 0.01) compared with the other four postoperative nights. Episodic hypoxaemia was most common during night 3 (p < 0.05). It was not possible to predict the postoperative occurrence of hypoxaemia from the preoperative spirometric measurements. Preoperative awake arterial oxygen saturation correlated significantly with mean constant hypoxaemia on postoperative nights 1, 3, 4, and 5, but not with episodes of sudden desaturation after operation. Preoperative overnight oximetry correlated significantly with constant hypoxaemia on all five postoperative nights and with episodic hypoxaemia on nights 3 and 4. CONCLUSION: In the light of these results which show the natural history of postoperative hypoxaemia without supplementary oxygen, and because postoperative hypoxaemia may be associated with dysfunction of organ systems after major operations, controlled studies of supplementary oxygen in the late postoperative period are warranted.