30-day mortality was higher for ASA III or IV patients who received etomidate compared to propofol. (Image source: Thinkstock)

30-day mortality was higher for ASA III or IV patients who received etomidate compared to propofol. (Image source: Thinkstock)

For the critically ill patient, some anesthesiologists might give “a little” propofol whilst others might give more anesthesia and use etomidate instead.  Those that prefer propofol note that etomidate suppresses adrenocortical function, which might affect outcome postoperatively.  Dr. Ryu Komatsu, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, and coauthors used their institution’s Perioperative Health Documentation System (PHDS) Registry to compare 30-day mortality, any major in-hospital cardiovascular morbidity, and any major in-hospital infectious morbidity in ASA physical status III and IV patients who underwent noncardiac surgery between 2005 and 2009. They matched over 7000 patients who received etomidate to those who received propofol.  Their study, titled “Anesthetic Induction with Etomidate, Rather than Propofol, Is Associated with Increased 30-Day Mortality and Cardiovascular Morbidity After Noncardiac Surgery,” is published in this month’s issue of Anesthesia & Analgesia.

Before propensity matching, patients who received etomidate tended to be older and sicker.  After propensity matching, patients who received etomidate had a higher incidence of 30-day mortality and a greater chance of having major cardiovascular morbidity.  Etomidate, however, was not associated with greater morbidity due to infection.  There was no dose-effect relationship of etomidate to 30-day mortality and cardiovascular morbidity.  Etomidate was also associated with a greater length of hospital stay.

This was a retrospective study and patients were not randomized.  When simply analyzing an anesthetic record, it might not be clear why one drug was used compared to another.    Nonetheless, the sample size was large.  In the accompanying editorial titled “Etomidate and General Anesthesia: The Butterfly Effect?,” Dr. Matthieu Legrand, Paris-Diderot University, Assistance Publique–Hôpitaux de Paris, Department of Anesthesiology and Critical Care and Burn Unit, and Dr. Benoît Plaud, Paris-Diderot University, Assistance Publique–Hôpitaux de Paris, Department of Anesthesiology and Critical Care, both Groupe Hospitalier Saint-Louis-Lariboisière, Paris, France, note that seeing how a drug used for induction can have a profound effect on outcome is similar to the butterfly effect described in chaos theory where a small condition can affect large complex systems.  (An example in chaos theory would be how a butterfly that flaps its wings in South American might affect weather patterns in a state in North America.)  Furthermore, they write, “only properly powered multicenter studies (ClinicalTrials.gov NCT01823328) will provide definitive answers and give us a sharper vision of the outcome associated with anesthetic drugs under the microscope of clinical research. Pending such trials, accumulation of data from observational studies should guide us in weighing the risk/ benefit ratio of the anesthetic drugs we use and finding out whether the butterfly effect applies to anesthesiology.”