[Dr. Sivilotti responds:]

Letters

CJEM 2007;9(1):3-4

I thank Dr. Green for weighing in on the etomidate commentary.1,2 His skepticism regarding the need for etomidate and his reluctance to use this drug are eloquent testimonials. I also congratulate his group on their valuable observations on the association between PIH and in-hospital outcomes.

I do wish to clarify one apparent misunderstanding however. The quotation attributed to me has been modified slightly, and the casual reader might be misled into believing that I recommend inducing hypotension in critically ill patients. This is simply not true. Instead, I believe that a fall in blood pressure shortly after endotracheal intubation represents not only an adverse event, but also an opportunity to recognize and correct circulatory instability that might otherwise be missed. This contrarian view was intended to illustrate how brief hypotension might not be entirely bad. Indeed, the argument that, since PIH is associated with and precedes negative events, any medication that reduces its incidence must improve outcomes is a typical example of the post hoc, ergo propter hoc ("after this, therefore because of this") fallacy. Green concedes that PIH "may only describe an epiphenomenon." Indeed, I think that the balance of probability favours this view, namely that it is an early marker of disease severity.

The causes of PIH are multifactorial, and include direct drug effects, decreases in sympathetic outflow, changes in oxygen supply/demand, and a rapid reversal of net intrathoracic pressures from negative to positive. Much like a single CVP measurement, or like a single mixed venous oxygen saturation (another indication for central access), a low mean arterial pressure 3 minutes after endotracheal intubation should be seen as an input datum into the complex decision making required during resuscitative care, rather than being seen as an outcome per se. Of course, physicians should aim to reduce the likelihood and degree of PIH, but not necessarily at all costs.

Marco L.A. Sivilotti, MD, MSc
Associate Professor
Departments of Emergency Medicine and of Pharmacology & Toxicology
Queen's University
Kingston, Ont.

References

1. Sivilotti MLA. You need tube, me give one amp of etomidate and SUX [editorial]. Can J Emerg Med 2006;8(5):351-3
2. Zed PJ, Mabasa VH, Slavik RS, et al. Etomidate for rapid sequence intubation in the emergency department: Is adrenal suppression a concern? [editorial]. Can J Emerg Med 2006;8(5):347-50.