Relative adrenal insufficiency as a predictor of disease severity and mortality in severe septic shock

OBJECTIVE: To evaluate if cortisol responses to 250 µg of intravenously administered adrenocorticotropic hormone are related to disease severity and, hence, mortality. METHODS: This is a retrospective study in a medical-surgical intensive care unit of a university hospital. We studied 69 consecutive patients with septic shock over a 1-yr period; these patients underwent a short 250-µg adrenocorticotropic hormone test because they exhibited >6 hours of progressive hemodynamic instability requiring repeated fluid challenges and vasopressor treatment to maintain blood pressure. The test was performed by intravenously injecting 250 µg of synthetic adrenocorticotropic hormone and measuring cortisol immediately before injection, 30 minutes post-injection and 60 minutes post-injection. RESULTS: The mean APACHE II score was 22±7. The intensive care unit mortality rate at day 28 was 55%. Median baseline cortisol levels (19 [11-27] µg/dL versus 24 [18-34] µg/dL, p=0.047) and median baseline cortisol/albumin ratios (7.6 [4.6-12.3] versus 13.9 [8.8-18.5]; p=0.01) were lower in survivors than in non-survivors. Responders and non-responders had similar baseline clinical data and outcomes. The variables that were significantly correlated with outcome based on the area under the ROC curves (AUC) were APACHE II (AUC=0.67 [0.535 to 0.781]), baseline cortisol (µg/dl) (AUC=0.662 [0.536 to 0.773], peak cortisol (µg/dl) (AUC=0.642 [0.515 to 0.755]) and baseline cortisol/albumin (AUC=0.75 [0.621 to 0.849]). CONCLUSIONS: Increased basal cortisol is associated with mortality and disease severity. Cortisol responses upon adrenocorticotropic hormone stimulation were not related to outcome. The cortisol/albumin ratio does not predict unfavorable outcomes better than total cortisol levels or help to improve the accuracy of the adrenocorticotropic hormone test.