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04-11-2010 | Anaesthesiology | Article

Hypoxemia still a problem during surgery


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MedWire News: Hypoxemia remains "surprisingly" common, despite advances in monitoring technology, researchers reveal.

"Anesthesia providers strive to avoid hypoxemia because of the risk of irreversible damage to the myocardium, brain, and other end organs," say Jesse Ehrenfeld (Massachusetts General Hospital, Boston, USA) and co-workers.

"Despite these efforts, hypoxemia continues to occur in the operating room at a surprisingly high rate."

The researchers analyzed 95,407 electronic anesthesia records from two hospitals, finding that 6.8% of patients suffered hypoxemia, defined as blood oxygenation (SpO2) levels below 90%, lasting 2 minutes or longer during surgery.

Severe hypoxemia (SpO2 <85%) occurred in 3.5% of patients, they report in the Canadian Journal of Anesthesia. Hypoxemia or severe hypoxemia occurred for at least 5 minutes in 1.6% and 0.8% of patients, respectively.

The proportion of patients suffering hypoxemia was similar for the three phases of intra-operative care, namely, induction, surgery, and emergence. However, induction and emergence each lasted an average of 12 minutes, whereas surgery lasted 93 minutes, meaning that the risk for hypoxia was highest during induction and emergence.

Overall, the results suggest that anesthesiologists can expect to encounter hypoxemia lasting at least 2 minutes roughly once every 29 hours of intra-operative time, say Ehrenfeld and team, with severe hypoxemia occurring once every 56 hours.

They note that the frequency is probably far higher in resource-poor settings, in which anesthesiologists may not have access to pulse oximetry.

Although hypoxemia was infrequent, Gregory Hare (St Michael's Hospital, Toronto, Ontario, Canada) and Brian Kavanagh (The Hospital for Sick Children, Toronto) said that it was "perhaps too common for an entity that anesthesiologists always try to avoid."

They added: "Practices that reduce the risk of hypoxemia in this setting, including pre-oxygenation, increased intra-operative F1O2 concentration, and preserving adequate ventilation, are essential to prevent intra-operative hypoxemia."

"Finally, novel approaches must be sought to minimize the frequency of anesthesia-related hypoxemia, even as basic and clinical science research is being pursued to elucidate further the perhaps more subtle contributing mechanisms."

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Eleanor McDermid