Rationale: Adrenal insufficiency occurs with varying frequency in critically ill patients. It is usually associated with a high mortality and poor clinical outcome.

Objective: To determine the incidence of adrenal failure in patients with severe sepsis and septic shock admitted to our intensive care unit.

Design: Prospective observational study, over a two year period (June 2003 – June 2005). Setting: University hospital multi-disciplinary intensive care unit in South Africa.

Patients: One hundred and fifty-two patients with severe sepsis and septic shock. Patients with a history of adrenal insufficiency, those on steroid therapy and all those who received etomidate within a week prior to enrollment were excluded.

Interventions: None.

Measurements and main results: A random plasma cortisol level was measured in consecutive patients with severe sepsis and septic shock. Adrenal insufficiency was defined as a cortisol level below 20μg/dL. The incidence of adrenal insufficiency was 26, 97% (CI: 19, 97% - 34, 03%). Patients with adrenal insufficiency had lower APACHE II scores and better short-term survival rates. The occurrence of adrenal dysfunction in patients with septic shock was low with an incidence of 15.6%. The type of infecting organism, site of infection and the origin of the sepsis were not associated with differences in the incidence of adrenal deficiency.

Conclusion: Absolute adrenal insufficiency is not uncommon among our critically septic patients. The presence of adrenal failure was inversely correlated with illness severity and mortality.