The incidence of hypoxemia during surgery: evidence from two institutions

Abstract

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.

Fig. 1

Distribution of All SpO₂ Readings. The distribution of SpO₂ readings from the 95,407 anesthesia cases. Of the 15,985,965 SpO₂ readings, 99.63% were within the normal range (≥ 90%) and 0.37% of all readings represented values < 90%

Fig. 2

Duration of Hypoxemic Episodes at Hospitals A & B. The incidence and maximum duration of intraoperative hypoxemic episodes. Episodes are grouped by maximum duration per patient for both hypoxemic (SpO₂ < 90) and severely hypoxemic episodes (SpO₂ ≤ 85). The percentage of patients experiencing two consecutive minutes or longer of hypoxemia and severe hypoxemia was 6.8% and 3.5%, respectively