title: The incidence of hypoxemia during surgery: evidence from two institutions.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Anesthesia, Critical Care, & Pain Medicine, Massachusetts General Hospital, 55 Fruit St, Jackson 458, Boston, MA 02114, USA. jehrenfe@post.harvard.edu
authors.forename: Jesse M
authors.initials: JM
authors.lastname: Ehrenfeld
authors.forename: Luke M
authors.initials: LM
authors.lastname: Funk
authors.forename: Johan
authors.initials: J
authors.lastname: Van Schalkwyk
authors.forename: Alan F
authors.initials: AF
authors.lastname: Merry
authors.forename: Warren S
authors.initials: WS
authors.lastname: Sandberg
authors.forename: Atul
authors.initials: A
authors.lastname: Gawande
mesh_terms: D000046:Academic Medical Centers; D000758:Anesthesia / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000139:chemically induced / Q000453:epidemiology*; D007431:Intraoperative Complications / Q000139:chemically induced / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010092:Oximetry; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013514:Surgical Procedures, Operative / Q000379:methods