title: Hypothalamic-pituitary-adrenal axis dysfunction in critically ill patients with traumatic brain injury: incidence, pathophysiology, and relationship to vasopressor dependence and peripheral interleukin-6 levels.
abstract: OBJECTIVE
  To investigate hypothalamic-pituitary-adrenal axis function in patients requiring mechanical ventilation for traumatic brain injury and to assess the relation of hypothalamic-pituitary-adrenal axis abnormalities with vasopressor dependence and peripheral cytokine levels.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  General intensive care unit in a university teaching hospital.
  
  
  METHODS
  Forty patients (33 men and 7 women) with moderate to severe traumatic brain injury (mean age, 37 +/- 16 yrs) were studied the day after termination of mechanical ventilation (7-60 days after trauma).
  
  
  METHODS
  First, a morning blood sample was obtained to measure baseline cortisol, corticotropin, interleukin-6, and tumor necrosis factor alpha. Subsequently, 1 microg of synthetic corticotropin was injected intravenously, and 30 mins later, a second blood sample was drawn to determine stimulated plasma cortisol. Based on data derived from healthy volunteers, patients having stimulated cortisol levels <18 microg/dL were defined as nonresponders to the low-dose stimulation test. Thirty-one patients underwent also a human corticotropin releasing hormone test.
  
  
  RESULTS
  In traumatic brain injury patients, mean baseline and low-dose stimulation test-stimulated cortisol levels were 17.2 +/- 5.4 microg/dL and 24.0 +/- 6.6 microg/dL, respectively. The median increment in cortisol was 5.9 microg/dL. Basal corticotropin levels ranged from 3.9 to 118.5 pg/mL. Six of the 40 patients (15%) failed the low-dose stimulation test. The human corticotropin releasing hormone test (performed in 26 responders and five nonresponders) revealed diminished cortisol release only in the low-dose stimulation test nonresponder patients. Corticotropin responses to corticotropin releasing hormone were consistent with both primary (three patients) and/or secondary (two patients) adrenal dysfunction. In retrospect, nonresponders to the low-dose stimulation test more frequently required vasopressors (6/6 [100%] vs. 16/34 [47%]; p =.02) and for a longer time interval (median, 0 vs. 293 hrs; p =.006) compared with responders. Furthermore, nonresponders had higher interleukin-6 levels compared with responders (56.03 vs. 28.04 pg/mL; p =.01), whereas tumor necrosis factor alpha concentrations were similar in the two groups (2.42 vs. 1.55 pg/mL; p =.53).
  
  
  CONCLUSIONS
  Adrenal cortisol secretion after dynamic stimulation is deficient in a subset of critically ill patients with moderate to severe head injury. This disorder is associated with prior vasopressor dependency and higher interleukin-6 levels.
authors.affiliation: Department of Clinical Care Medicine, Evangelismos Hospital, Athens, Greece.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Dimopoulou
authors.forename: Stylianos
authors.initials: S
authors.lastname: Tsagarakis
authors.forename: Andreas T
authors.initials: AT
authors.lastname: Kouyialis
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Roussou
authors.forename: Georgios
authors.initials: G
authors.lastname: Assithianakis
authors.forename: Marietta
authors.initials: M
authors.lastname: Christoforaki
authors.forename: Ioannis
authors.initials: I
authors.lastname: Ilias
authors.forename: Damianos E
authors.initials: DE
authors.lastname: Sakas
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Thalassinos
authors.forename: Charis
authors.initials: C
authors.lastname: Roussos
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000328:Adult; D001930:Brain Injuries / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology*; D003346:Corticotropin-Releasing Hormone; D016638:Critical Illness; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000494:pharmacology; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology*; D015994:Incidence; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D011446:Prospective Studies; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D015850:Interleukin-6; D014662:Vasoconstrictor Agents; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D006854:Hydrocortisone