Hypoadrenocorticism, also known as Addison’s disease, stems from a deficiency of glucocorticoid and/or mineralocorticoid secretion. The signs of this disease can be vague at first and can mimic many other more common diseases. It occurs most commonly in young to middle-aged dogs and rarely in cats (Bassett 2007). While taking a history, owners may describe waxing and waning that has occurred over weeks or months (Bassett 2007). Other symptoms include weakness, depression, dehydration, abdominal discomfort, and melena. Dogs presenting in an acute crisis are common. Life-threatening clinical signs may include weak pulses, hypothermia, hypotension, hyperkalemia, and hyperkalemia-induced bradycardia. Anesthesia should be avoided in unmanaged patients because cardiovascular collapse is possible.
Preoperative workup should include serum chemistries, blood gases, ECG, and blood pressure. Be sure to correct hypovolemia and electrolyte imbalances prior to anesthesia. Steroid replacement should be started prior to induction of anesthesia and may be repeated every 2–4 hours perioperatively (Kerr 2007). For the patient that is stable on mineralocorticoid and glucocorticoid therapy, the anesthetic protocol depends on the surgical procedure to be performed. The fluid of choice for Addisonian patients is 0.9% NaCl. During anesthesia it is very important to use an ECG to monitor for arrhythmias as well as a blood pressure monitor to watch for hypotension.