Hypothalamic-pituitary-adrenal axis in lethal canine Staphylococcus aureus pneumonia

Area of Science:

• Endocrinology
• Critical Care Medicine
• Veterinary Pathology

Background:

• The existence and clinical relevance of critical illness-related corticosteroid insufficiency remain controversial.
• Severe Staphylococcus aureus pneumonia in canines serves as a model to investigate hypothalamic-pituitary-adrenal (HPA) axis function during critical illness.

Purpose of the Study:

• To characterize HPA axis function in severe canine pneumonia.
• To evaluate the impact of dexamethasone and desoxycorticosterone on outcomes.
• To identify HPA axis markers predictive of prognosis in septic shock.

Main Methods:

• Animals received antibiotics and supportive care.
• Serial measurements of cortisol, ACTH, and aldosterone were performed.
• ACTH stimulation tests were conducted.
• Dexamethasone treatment was administered and its effects analyzed.

Main Results:

• Dexamethasone, but not desoxycorticosterone, improved outcomes.
• Early HPA axis stress response (cortisol) was not predictive of outcome.
• Aldosterone levels were elevated longer and associated with survival.
• Dexamethasone suppressed cortisol/ACTH and restored responsiveness in survivors.
• Nonsurvivors exhibited hypercortisolemia, high ACTH, and hyporesponsiveness, unaffected by dexamethasone.

Conclusions:

• HPA axis unresponsiveness and elevated aldosterone identify a septic shock subpopulation with poor prognosis.
• Serial HPA axis measurements and provocative testing are crucial for assessing prognosis.
• This subpopulation may benefit from novel therapeutic strategies.