Pheochromocytoma: Surgery

Adrenal tumors represent a challenge for the anesthetist, the surgeon, and the criticalist during the post-operative period. Adrenal tumors can be adenoma, carcinoma, or pheochromocytoma. Rare cases of aldosteronoma have bee described in dogs and cats. Adenoma and carcinoma are secreting tumors that induces a Cushing’s syndrome with its effect on metabolism, electrolytes and coagulation. Pheochromocytoma are tumors secreting vasoactive mediators that have a profound effects on the cardiac and hemodynamic functions of the patients. Pheochromocytomas are tumors that have a tendency to invade the caudal vena cava that makes the surgery more complicated.

Treatment of dogs with phenoxybenzamine has been strongly recommended for two weeks before surgery. This treatment helps lowering the arterial blood pressure and helps stabilize the patient during surgery while manipulating the adrenal tumor. Beta-blockers can also be added to the medical treatment after the phenoxybenzamine has been lowering the blood pressure. Usually this is necessary since ultra short acting beta blockers (esmolol) can be used intra-operatively to control the heart rate. Prazosine can also be used as an alpha antagonist to control the blood pressure before surgery.

If the tumor is a pheochromocytoma, heparin is not required during the surgery unless the tumor is invading the vena cava. It is recommended to heparinize the dogs if vascular surgery is performed to minimize the risk of thrombus formation on the suture line. If there is some doubt on the nature of the tumor then heparin is recommended to minimize the risk of pulmonary thromboembolism associated with Cushing’s disease. When heparin is used PTT is measured to document the efficacy of the treatment. The goal is to increase the baseline PTT time by 50%. Supplementation with steroids during the surgery and the post operative period is not necessary for pheochromocytoma however it will be recommended if their is any doubt on the nature of the tumor.  [...]