A systematic review of 20 included studies comparing a bolus dose of etomidate for rapid sequence induction with other induction agents resulted in the following conclusion:

“The available evidence suggests that etomidate suppresses adrenal function transiently without demonstrating a significant effect on mortality. However, no studies to date have been powered to detect a difference in hospital, ventilator, or ICU length of stay or in mortality”

The Effect of a Bolus Dose of Etomidate on Cortisol Levels, Mortality, and Health Services Utilization: A Systematic Review
Ann Emerg Med. 2010 Aug;56(2):105-13