Hypothalamo-pituitary-adrenal axis activity after intracranial catastrophies: what is enough?

This commentary on a paper by Bendel and colleagues in the previous issue of Critical Care describes the difficulty in assessing the sufficiency of adrenal responses to endogenous, stress-induced adrenocorticotropic hormone (ACTH) release by the pituitary or to exogenous ACTH administration in the critically ill patient in general, and after subarachnoid hemorrhage in particular. It is argued that comparisons with responses under circumstances of equal stress as well as assessments of severity of disease are necessary to judge the sufficiency of cortisol responses to endogenous and exogenous ACTH before treatment is considered. There are no universally applicable cutoff values for cortisol levels--and increases in cortisol levels with increasing levels of ACTH--for the diagnosis of relative adrenal insufficiency (or as it is now commonly termed, critical illnes-related corticosteroid insufficiency) following, for example, subarachnoid hemorrhage or other intracranial catastrophes. The paper by Bendel and colleagues is critically discussed in view of these concepts.