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Anesthesia Risk Factors Not Proven by Case–Control Study

Schmidt, Kenneth A. M.D.

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To the Editor:—

I applaud Arbous et al.1 for attempting a large multicenter study to identify anesthesia care factors that may cause mortality. However, the design of the study could allow for misleading conclusions. Failure to have controls of similar case type resulted in the conclusions that two anesthesia personnel at emergence, reversal of neuromuscular agents, postoperative pain medication, and no anesthesiologist relief were associated with less mortality.
My previous experience at a trauma center is that patients who die often have long surgery at night when anesthesiologists change shift. After surgery, the patient is kept intubated and transported to the recovery room without need of additional anesthesia personnel. The neuromuscular agents are not reversed, and the patient is often too unstable to receive opiate pain therapy. Proper selection of control cases would show that this method of anesthesia care did not cause the death of the patient.
There is an old joke that oxygen is the most dangerous anesthetic, because all trauma patients who receive only oxygen for major surgery die. It is no joke when the lack of proper controls in a study leads to conclusions that will be quoted to change proper anesthesia care. The editorial by Dr. Warner2 was correct to state that case–control methodology does not prove that these are risk factors. This should have been stressed by Arbous et al.
Kenneth A. Schmidt, M.D.
Valley Hospital, Ridgewood, New Jersey.
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1. Arbous MS, Meursing AEE, van Kleef JW, de Lange JJ, Spoormans HHAJM, Touw P, Werner FM, Grobbee DE: Impact of anesthesia management characteristics on severe morbidity and mortality. Anesthesiology 2005; 102:257–68

2. Warner MA: Perioperative mortality: Intraoperative anesthetic management matters. Anesthesiology 2005; 102:251–2

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