title: Defining normal adrenal function testing in the intensive care unit setting: a canine study.
abstract: OBJECTIVE
  To determine whether intensive care medicine therapies and testing influence hypothalamic-pituitary-adrenal test results. It is routine in intensive care medicine to measure hypothalamic-pituitary-adrenal function, commonly utilizing the adrenocorticotropic hormone stimulation test to diagnose absolute or relative adrenal insufficiency.
  
  
  METHODS
  Prospective, 96-hr animal study.
  
  
  METHODS
  Research laboratory.
  
  
  METHODS
  Twenty-four healthy canines.
  
  
  METHODS
  Animals were randomized into two groups--awake and unrestrained or treated with intensive care medicine therapies, including sedation, intubation, and mechanical ventilation. Animals were further randomized to receive dexamethasone (or placebo) or undergo either a total of four or seven adrenocorticotropic hormone stimulation tests over 96 hrs.
  
  
  RESULTS
  Sedation, intubation, and mechanical ventilation transiently increased both basal and postadrenocorticotropic hormone total and free cortisol concentrations >2-fold as compared with baseline for the first 24 hrs (p < or = .05 for both). Performance of seven stimulation tests increased both basal and postadrenocorticotropic hormone total and free cortisol concentrations from baseline by >1.5-fold for the duration of the 96-hr study (p < or = .05). Neither sedation, intubation, and mechanical ventilation nor the performance of more stimulation tests affected delta cortisol measurements (total or free cortisol, p = NS). In contrast, dexamethasone suppressed basal total cortisol concentrations by >2-fold (p < or = .005) at all time points and transiently increased delta total cortisol by approximately 35% during the first 24 hrs of the study (p < or = .05).
  
  
  CONCLUSIONS
  Total and free cortisol measurements--whether pre- or post- adrenocorticotropic hormone or as a calculated delta--were altered by intensive care therapies or frequent adrenocorticotropic hormone stimulation testing with one exception. Delta free cortisol was the only hypothalamic-pituitary-adrenal measurement unaffected by sedation, intubation, and mechanical ventilation, completion of more adrenocorticotropic hormone stimulation tests, or dexamethasone therapy. These findings support the need to determine normal ranges for hypothalamic-pituitary-adrenal testing in subjects receiving intensive care medicine before establishing laboratory criteria for the diagnosis of relative adrenal insufficiency.
authors.affiliation: Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD, USA. sweeneyda@cc.nih.gov
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Sweeney
authors.forename: Charles
authors.initials: C
authors.lastname: Natanson
authors.forename: Steven M
authors.initials: SM
authors.lastname: Banks
authors.forename: Steven B
authors.initials: SB
authors.lastname: Solomon
authors.forename: Ellen N
authors.initials: EN
authors.lastname: Behrend
mesh_terms: D000311:Adrenal Glands / Q000187:drug effects / Q000502:physiology; D000309:Adrenal Insufficiency / Q000175:diagnosis* / Q000209:etiology; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000450:Aldosterone / Q000097:blood; D000818:Animals; D016292:Procedural Sedation / Q000009:adverse effects; D003907:Dexamethasone / Q000494:pharmacology; D004285:Dogs; D006854:Hydrocortisone / Q000097:blood; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D007362:Intensive Care Units; D007442:Intubation, Intratracheal / Q000009:adverse effects; D008297:Male; D019095:Point-of-Care Systems; D015742:Propofol / Q000494:pharmacology; D012121:Respiration, Artificial / Q000009:adverse effects
chemical_list: D006993:Hypnotics and Sedatives; D000450:Aldosterone; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone; D015742:Propofol