Addison's disease (ie, hypoadrenocorticism) is typically diagnosed in young female dogs. All breeds can be affected, although some (eg, bearded collie, border terrier, English pointer, standard poodle, Portuguese water dog) appear to be overrepresented.3 Dogs in an Addisonian crisis exhibit signs of cardiovascular collapse, including lethargy, weakness, hypotension, poor peripheral pulses, cool extremities, and prolonged capillary refill time. These are often accompanied by GI signs (eg, vomiting, diarrhea, inappetence, melena, weight loss) and occur because of a deficiency of glucocorticoids normally secreted by the adrenal glands. Concurrent electrolyte abnormalities (eg, hyponatremia, hyperkalemia, sodium:potassium ratio <27:1) can occur when mineralocorticoid deficiency is also present.4
Emergency management of a dog in Addisonian crisis should include rapid IV fluid therapy with isotonic crystalloids (eg, Plasmalyte-A, lactated Ringers solution, 0.9% NaCl) as 20 mL/kg boluses over 15 minutes until hemodynamic stability is achieved (up to 90 mL/kg total). GI protectants and antiemetics can also be provided as supportive care.4 Postadrenocorticotropic-hormone (ACTH) stimulation cortisol results less than 2 µg/dL is standard for diagnosing hypoadrenocorticism, whereas a baseline cortisol greater than 2 µg/dL rules out hypoadrenocorticism.5 If the test cannot be performed in an emergency situation, an anti-inflammatory dose of dexamethasone can be given before performing the ACTH test without affecting results.
Once hypoadrenocorticism is diagnosed, anti-inflammatory (ie, stress) doses of corticosteroids should be administered daily for one week. The dose can then be decreased to physiologic amounts, which require lifelong administration, and used with mineralocorticoid replacement (eg, fludrocortisone, desoxycorticosterone) in dogs with electrolyte abnormalities.