Relative adrenal failure in intensive care: an identifiable problem requiring treatment?

Adequate adrenocortical function is essential to survive critical illness. Most critically ill patients display an elevated plasma cortisol level, reflecting activation of the pituitary-adrenal axis, which is considered to be a homeostatic adaptation. In the setting of critical illness, the failure of an appropriate neuroendocrine response can lead to the picture of vasopressor-dependent refractory hypotension. This state of relative or functional adrenal insufficiency is characterized by an inadequate production of cortisol in relation to an increased demand during periods of severe stress, particularly prolonged critical illness such as multi-organ failure. This clinical entity, however, lacks clear-cut diagnostic criteria. What are the appropriate cortisol concentrations in the critically ill? Should base-line and adrenocorticotropic hormone-stimulated cortisol concentrations be assessed? The classical adrenocorticotropic hormone stimulation test is often used, but there are problems with interpreting its results. Other diagnostic tools, such as the low-dose adrenocorticotropic hormone test and relative eosinophilia, are promising but also lack proper criteria. A prompt response to hydrocortisone treatment is a major clue to the diagnosis. Recent studies with stress doses of hydrocortisone in sepsis and septic shock have shown a marked haemodynamic improvement, but whether patients with relative adrenal dysfunction benefit most from this treatment and whether there is definitely an effect on outcome is still undecided.