Hipotalamo Adrenal En Potros

tJ Vet Intern Med 2009;23:901–912

H y p o t h a l a m i c - P i t u i t a r y - A d r e n a l A x i s D y s f u n c t i o n in H o s p i t a l i z e d Neonatal Foals
K.A. Hart, N.M. Slovis, and M.H. Barton
Background: Transient hypothalamic-pituitary-adrenal (HPA) axis dysfunction occurs frequently in critically ill humans and impacts survival. The prevalence and impact of HPA axisdysfunction in critically ill neonatal foals are not well characterized. Hypotheses: (1) HPA axis dysfunction occurs in hospitalized neonatal foals, and is characterized by inappropriately low basal serum cortisol concentration or inadequate cortisol response to exogenous adrenocorticotropic hormone (ACTH); (2) hospitalized foals with HPA axis dysfunction have more severe disease and are less likely tosurvive than hospitalized foals with normal HPA axis function. Animals: Seventy-two hospitalized foals and 23 healthy age-matched foals. Methods: Basal ACTH and cortisol concentrations were measured and a paired low-dose (10 mg)/high-dose (100 mg) cosyntropin stimulation test was performed at admission in hospitalized foals. HPA axis dysfunction was defined as (1) an inappropriately low basal cortisolconcentration or (2) an inadequate increase in cortisol concentration (delta cortisol) after administration of cosyntropin, with cut-off values for appropriate basal and delta cortisol concentrations determined from results obtained in healthy age-matched foals. Results: Forty-six percent of hospitalized foals had an inappropriately low basal cortisol concentration and 52% had an inadequate deltacortisol concentration after administration of the 100 mg dose of cosyntropin. An inadequate delta cortisol response to the high (100 mg) dose of cosyntropin was significantly correlated with shock and multiple organ dysfunction syndrome in hospitalized foals, and with decreased survival in a subgroup of septic foals. Conclusions and Clinical Importance: HPA axis dysfunction occurs frequently inhospitalized neonatal foals, and negatively impacts disease severity and survival. Key words: Corticosteroid; Cortisol; Horse; Relative adrenal insufficiency; Sepsis; Stress.

ntact hypothalamic-pituitary-adrenal (HPA) axis function is essential for regulating the physiologic, metabolic, and inflammatory responses to critical illness. Environmental, physiologic, and pathophysiologic stressorsactivate the HPA axis, resulting in release of adrenocorticotropic hormone (ACTH) by the anterior pituitary gland, which stimulates the subsequent synthesis and secretion of cortisol from the adrenal cortices. Cortisol exerts a variety of systemic effects that are vital for the response to severe illness, including maintenance of adequate blood pressure, provision of nutrients to tissues, and controlof an appropriate inflammatory response.1,2 Despite its vital role in the physiologic response to the stress of disease, transient dysfunction of the HPA axis is well documented in critically ill people, particularly in patients with sepsis and septic shock.3–7 This dysfunction

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From the Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA(Hart, Barton); and the Hagyard Equine Medical Institute, Lexington, KY (Slovis). This study was performed at the University of Georgia’s Veterinary Teaching Hospital, Athens, GA and Haygard Equine Medical Institute, Lexington, KY. Portions of this work were presented in abstract form at the 26th Annual Forum of the American College of Veterinary Internal Medicine, June 4, 2008, San Antonio, TX andthe 5th Dorothy Havemeyer Neonatal Septicemia Workshop, Salem, MA, November 19–22, 2008. Corresponding author: Dr Kelsey A. Hart, DVM, DACVIM, Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602; e-mail: khart4@uga.edu.

Submitted December 11, 2008; Revised March 31, 2009; Accepted March 31, 2009.
Copyright r 2009 by the American College...