Vasopressin stimulation testing in hospitalized foals.

BACKGROUND

Hypothalamic-pituitary-adrenal gland axis (HPAA) dysfunction impairs survival and can be diagnosed with an arginine vasopressin (AVP) stimulation test.

HYPOTHESIS/

OBJECTIVES

Adrenocorticotropic hormone (ACTH) and cortisol response to an AVP stimulation test will be attenuated in hospitalized foals compared to healthy foals and associated with severity of disease.

ANIMALS: Fifteen healthy and 45 hospitalized foals: 19 septic, 26 sick non-septic (SNS).

METHODS

A prospective, observational case-control design was utilized to assess HPAA function and compare corticotropin-releasing hormone, ACTH, and cortisol concentrations at 0, 15, 30, 60, and 90 min after administration of AVP (5 IU). Adrenocorticotropic hormone and cortisol fold increase were calculated at 15 and 30 min compared to baseline.

RESULTS

Adrenocorticotropic hormone and cortisol concentrations increased at 15 and 30 min after AVP administration in all groups (P < .05). Adrenocorticotropic hormone concentration was lower in septic (112; 95% CI, 86.3-181.8 pg/mL) and SNS (102; 95% CI, 82.8-150 pg/mL) compared to healthy foals (179; 95% CI, 135.6-275.8 pg/mL) 15 min after AVP administration (P < .05). Fold increase in ACTH was lower in septic (3.3; 95% CI, 2.3-5.6) compared to SNS (3.7; 95% CI, 3.5-6.1) and healthy foals (7; 95% CI, 5.7-9.5; P < .01). Fold increase in cortisol was lower in septic (2; 95% CI, 1.8-8.3) compared to healthy foals (4.3; 95% CI, 2.8-9.4; P < .05).

CONCLUSIONS AND CLINICAL

IMPORTANCE

Hypothalamic-pituitary-adrenal gland axis dysfunction, evidenced by ACTH and cortisol responses to an AVP stimulation test, appears linked to disease severity and is a complication of illness. An AVP stimulation test might help guide therapy in ill foals.