The relative adrenal insufficiency syndrome in the intensive care unit: incidence and relationship to outcome

The aim of the current study was to investigate the incidence of relative adrenal insufficiency in a large cohort of critically ill patients. Furthermore, we wished to assess the relationship of adrenal function tests to outcome of patients admitted to an adult medical and surgical ICU.

To this end, 151 (119 men) critically ill patients having various principal diagnoses were studied. The median age was 52 years (range 17–84 years). The median APACHE II score was 11. Blood was sampled within 48 hours of admission for measurement of serum concentrations of baseline cortisol and corticotropin (ACTH). Immediately after, a low-dose (1 μg) ACTH stimulation test was performed. Patients having stimulated cortisol levels below 18 μg/dl were defined as non-responders to the test.

Median values for baseline cortisol and ACTH were 16.0 μg/dl (range 0.3–61.3 μg/dl) and 16.8 pg/ml (range 0.9–166.4 pg/ml) respectively. The median stimulated cortisol value was 22.4 μg/dl (range 4.7–70.0 μg/dl) and the median increment in cortisol was 7.1 μg/dl (range 0.2–25.6 μg/dl). There was a positive correlation between ACTH and baseline cortisol (r = 0.42, P < 0.001). Thirty-nine (26%) patients were non-responders to the low-dose ACTH stimulation test. Overall mortality was 26%. Non-survivors were older (64 vs 24 years, P = 0.002), and had a higher APACHE II score (13 vs 11, P = 0.007) compared with survivors. There were no differences between the two groups with regard to baseline or stimulated cortisol levels. Similarly, ACTH and the increment in cortisol was comparable in the two groups.

In conclusion, this study involving a large number of severely ill patients showed that the relative adrenal insufficiency syndrome is quite common in the ICU; however, baseline or stimulated cortisol concentrations do not differ between survivors and non-survivors on admission to the ICU.