The incidence of hypoxemia during surgery: evidence from two institutions

Purpose The incidence of hypoxemia in patients undergoing surgery, is largely unknown and may have a clinical impact. The objective of this study was to determine the incidence of intraoperative hypoxemia in a large surgical population. Methods We performed a retrospective study of electronically recorded pulse oximetry data obtained from two large academic medical centres. All adults (age >= 16 yr) undergoing non-cardiac surgery during a three-year period at the two hospitals were included in the analysis. Our main outcome measure was the percentage of patients with episodes of hypoxemia (SpO(2) < 90) or severe hypoxemia (SpO(2) <= 85) for two minutes or longer during the intraoperative period (induction of anesthesia, surgery, and emergence). Results We evaluated 95,407 electronic anesthesia records at the two hospitals. During the intraoperative period, 6.8% of patients had a hypoxemic event, and 3.5% of patients had a severely hypoxemic event of two consecutive minutes or longer. Seventy percent of the hypoxemic episodes occurred during either induction or emergence time periods that represent 21% of the total intraoperative time. From induction to emergence, one episode of hypoxemia occurred every 28.9 hr, and one episode of severe hypoxemia occurred every 55.7 hr of intraoperative time. Conclusion Despite advances in monitoring technology, hypoxemia continues to occur commonly in the operating room and may be a serious safety concern because of its potential impact on end organ function and long-term outcomes. Further studies are needed to improve our understanding of the clinical impact of intraoperative hypoxemia and the strategies that will be most useful in minimizing its occurrence.