The low-dose corticotropin stimulation test in acute traumatic and non-traumatic brain injury: incidence of hypo-responsiveness and relationship to outcome

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Abstract
Objective To investigate adrenal responses to the low-dose corticotropin (ACTH) stimulation test in acute traumatic or non-traumatic brain injury (BI) and to assess its value in predicting outcome. Design Prospective study. Setting Intensive care unit (ICU) in a university hospital. Patients and participants Seventy-five patients with acute BI, with a median age of 45 years were investigated. BI was due to trauma (n=51), ischemic stroke (n=17), subarachnoid hemorrhage (n=4) or intracerebral hemorrhage (n=3). Interventions Blood was taken on day 16 (median) after admission to the ICU to determine baseline cortisol and ACTH. Thereafter, a low-dose stimulation test (LDST) was performed: 1 µg of tetracosactrin was injected and 30 min later a second blood specimen was obtained to measure stimulated cortisol. Patients having a stimulated cortisol below 500 nmol/l were defined as non-responders to the LDST. Measurements and results Median baseline and stimulated cortisol were 491 nmol/l and 690 nmol/l, respectively. The median increment in cortisol was 154 nmol/l (range 5–579 nmol/l). Mean ACTH was 46±21 pg/ml. Ten (13%) patients were non-responders to the LDST; these had a higher mortality rate compared to patients with adequate cortisol production (70 vs 32%, p=0.034). Logistic regression analysis revealed that APACHE II (pp=0.04) and age (p=0.02) were independent outcome predictors. In contrast, the increment in cortisol (p=0.26) did not add to outcome prediction. Conclusions Adrenal hypo-responsiveness in the setting of acute traumatic or non-traumatic BI is not an independent outcome predictor in the presence of high APACHE II, low GCS and older age.