TIME-COURSE OF POSTOPERATIVE HYPOXEMIA

Objective: To study the time course of nocturnal episodic and constant hypoxaemia during the first five nights after a major abdominal opera tion in patients not given supplementary oxygen. Design: Open study. S ubjects: 17 patients undergoing major elective operations and with no recognised risk factors. Main outcome measures: Arterial oxygen satura tion measured by pulse oximetry. Results: The level of constant hypoxa emia 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 n ights. Episodic hypoxaemia was most common during night 3 (p < 0.05). It was not possible to predict the postoperative occurrence of hypoxae mia from the preoperative spirometric measurements. Preoperative awake arterial oxygen saturation correlated significantly with mean constan t hypoxaemia on postoperative nights 1, 3, 4, and 5, but not with epis odes of sudden desaturation after operation. Preoperative overnight ox imetry correlated significantly with constant hypoxaemia on all five p ostoperative nights and with episodic hypoxaemia on nights 3 and 4. Co nclusion: 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 ox ygen in the late postoperative period are warranted.