endocrine and metabolic disorders
Pheochromocytoma
Treatment of Pheochromocytoma
Hypertension control with combination of alpha-blockers and then beta-blockers Surgical removal of tumor with careful perioperative control of blood pressure and volume status Surgical removal is the treatment of choice. The operation is usually delayed until hypertension is controlled by a combination of alpha-blockers and beta-blockers (usuallyphenoxybenzamine20 to 40 mg orally 3 times a day andpropranolol20 to 40 mg orally 3 times a day). The blood pressure target is<130/80 mmHg; some suggest the target should also include achieving a certain postural drop in blood pressure, but this is not essential. Re-equilibration of the cardiovascular system requires about 10 to 14 days, after which blockade is presumed to be effective. Beta-blockers should not be used until adequate alpha-blockade has been achieved. Some alpha-blockers, such asdoxazosin, may be equally effective but better tolerated.Nitroprussidecan be infused for hypertensive crises preoperatively or intraoperatively. Give alpha-blockers first before beta-blockers. Unopposed beta-2-blockade can cause paradoxical increase in blood pressure by blocking beta-mediated vasodilation. When bilateral tumors are documented or suspected (as in a patient with multiple endocrine neoplasia [MEN]), sufficienthydrocortisone(100 mg IV twice a day) given before and during surgery avoids acute glucocorticoid insufficiency due to bilateral adrenalectomy. Most pheochromocytomas can be removed laparoscopically. Blood pressure must be continuously monitored via an Arterial Catheterization , and volume status is closely monitored. Anesthesia should be induced with a nonarrhythmogenic drug (eg, a thiobarbiturate) and continued with an inhaled drug (eg, enflurane, Preoperative blood transfusion (1 to 2 units) may be given before the tumor is removed in anticipation of blood loss. If blood pressure has been well controlled before surgery, a diet high in salt is recommended to increase blood volume. An infusion ofnorepinephrine4 to 12 mg/L in adextrose-containing solution beginning at 0.05 mcg/kg/minute and titrated to effect may be considered if hypotension develops. Some patients whose hypotension responds poorly tonorepinephrinemay benefit fromhydrocortisone100 mg IV, but adequate fluid replacement is usually all that is required. Malignant metastatic pheochromocytomashould be treated with alpha-blockers and beta-blockers. The tumor may be indolent and survival long-lasting. However, even with rapid tumor growth, blood pressure can be controlled. I-131 MIBG or more recently lutetium-177 dotatate can help relieve symptoms in patients with residual disease.Metyrosine, a tyrosine hydroxylase inhibitor, may be used to decrease catecholamine production in patients whose blood pressure is difficult to control. Radiation therapy may reduce bone pain due to metastases. Chemotherapy is rarely effective, but the most common regimen tried is the combination ofcyclophosphamide,vincristine, anddacarbazine. The chemotherapy agenttemozolomideand targeted therapy withsunitinibor possiblycabozantinibmay also be effective. 