Adrenal Axis Dysfunction in Equine Sepsis

Presentation Description / Summary: Sepsis is a leading cause of morbidity and mortality in both human and equine neonates and is a complex process of the innate immune system as a response to both infectious and noninfectious stimuli. Sepsis can ultimately lead to septic shock and multiple organ dysfunction (MODS), which the body responds to by releasing a series of neurotransmitters and neuropeptides via several negative feedback loop mechanisms to maintain the function of vital organs. The hypothalamic-pituitary-adrenal axis (HPAA) is one of these vital negative feedback mechanisms that attempt to maintain homeostasis in times of health and illness. A well-described syndrome, relative adrenal insufficiency (RAI) or critical illness-related corticosteroid insufficiency (CIRCI), occurs in both human and equine patients and refers to the impairment of the HPAA during times of critical illness resulting in abnormal cortisol production, cellular activity, and metabolism. Diagnosis of CIRCI is traditionally performed using baseline cortisol levels and/or dynamic evaluation of the HPAA through ACTH stimulation testing. However, this diagnostic test has remained controversial and produces variable results in both equine and human patients. Recently, arginine vasopressin (AVP) and corticotropin-releasing hormone (CRH) stimulation tests have been reported in healthy and critically ill foals to assess the HPAA function. This lecture will provide an in-depth review of the HPAA dysfunction in equine critical illness. Current diagnostic and treatment options will also be discussed. The audience will be invited to participate by online voting and contributing their own experiences.

Learner Outcomes: 1. Understand strategies for monitoring endogenous ACTH and cortisol responses to ACTH, AVP, and CRH stimulation tests in critically ill foals and horses 2. Interpret various HPAA axis assessment test results, including resting endogenous cortisol and ACTH concentrations and ACTH, AVP, and CRH stimulation tests 3. Understand current diagnostic and therapeutic approaches for HPAA dysfunction in critically ill foals and adult horses.