The incidence of perioperative myocardial infarction was increased in men, which was an unexpected finding. (Image source: Thinkstock)

The incidence of perioperative myocardial infarction was increased in men, which was an unexpected finding. (Image source: Thinkstock)

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How many patients die as a result of cardiac arrest under the care of an anesthesiologist? The number is sufficiently low that we need large databases to answer the question. Many perioperative databases are composed of patients who underwent an operative procedure. Anesthesiologists provide anesthesia care for patients both inside and outside the operating room. To capture outcome data across the breadth of anesthesia practice, the American Society of Anesthesiologists established the Anesthesia Quality Institute in October of 2008. By 2013 the National Anesthesia Clinical Outcomes Registry (NACOR) had a collection of over 20 million cases from more than 200 practices, almost 2,000 facilities, and 8,000 providers.  Dr. Mark Nunnally, Department of Anesthesia & Critical Care, The University of Chicago, Chicago, Illinois, and colleagues used data from the database for the period from January 1, 2010, through September 1, 2013, to determine factors associated with cardiac arrest. Their analysis is published in this month’s issue of Anesthesia & Analgesia and summarized in the article “The Incidence and Risk Factors for Perioperative Cardiac Arrest Observed in the National Anesthesia Clinical Outcomes Registry.”

For this study, cardiac arrest was defined as any unexpected episode of cardiopulmonary resuscitation (open or closed chest) in the OR or PACU. 951 cardiac arrests were reported during OR and PACU care. Slightly more than 40% of patients survived. Cardiac arrest was highest in patients less than 1 year (0.35%) of age. The incidence decreased until the age group 66 to 79 years. Mortality was twice as high in males compared to females. Most arrests occurred in patients ASA 3 or 4 (62.5%). As expected, the mortality rate was highest in patients whose ASA class was 5. Most arrests were seen in patients who underwent general anesthesia (89.1%). Intracranial procedures (0.35%) had the highest arrest incidence per procedure, while intraabdominal procedures (15.75% of total arrests) had the most overall arrests.

This represents an early effort at number crunching using the NACOR/AQI registry. The study design is purely observational and thus lacks any comparison group, any intervention, adequate outcomes data, or independent verification of the data input. The study found that risk increased with age and ASA status, which we already knew. The only unexpected finding was that incidence of cardiac arrest and perioperative mortality was increased in men. Since this was an exploratory study, this needs to be considered “hypothesis generation” requiring subsequent confirmation in an hypothesis testing study.