Con: Etomidate—The Ideal Induction Agent for a Cardiac Anesthetic?

Abstract

N IDEAL INDUCTION AGENT would be one that has rapid on- and offset, is easy to administer, and is devoid of clinically significant side effects. Such an agent does not exist currently. Drawbacks to currently available induction agents include the high incidence of hypotension and pain on injection with propofol; dysphoria, tachycardia, hallucinations, and increased secretions with ketamine; hypotension, and an increased incidence of laryngospasm with barbiturates. Etomidate often is the favored induction agent for patients who are hemodynamically compromised because of its relative cardiovascular stability. However, there is ongoing debate about its usage in critically ill patients because of its inhibition of adrenal steroidogenesis.1-8 Unlike propofol, barbiturates, and ketamine, etomidate has a very high therapeutic index. Unique among the general anesthetic induction drugs, the chemical structure of etomidate includes an imidazole ring that is critical for its anesthetic actions, which are mediated by specific -aminobutyric acid type-A receptors in the central nervous system. 9 Regarding its hemodynamic stability, there are minimal effects on blood pressure and heart rate when a single bolus injection is given, even in patients who are in shock or who exhibit depressed left ventricular function. 10 Because of this stability, it often is the agent of choice in the emergency room and the intensive care unit for rapid-sequence inductions and the induction of general anesthesia in the cardiac surgical operating room. However, as early as 1983, reports of adrenal suppression from etomidate injection began to surface. 11,12 The mechanism of adrenal insufficiency is by the inhibition of 11--hydroxylase, the enzyme responsible for the conversion of 11-deoxycortisol to cortisol and 11-deoxycorticosterone to corticosterone.