Pheochromocytoma

The Correct option Answer: c

This patient has a pheochromocytoma. The most efficient and sensitive means of screening for pheochromocytoma is measurement of the catecholamines, or metabolic products thereof, in the urine. The catecholamines, norepinephrine and epinephrine, are excreted in amounts under 100 µg/d in the normal person. Because of some overlap in values, specificity can be improved by using a normal range of up to 250 mg/d. The measurement of plasma 18-hydroxycorticosterone level is helpful in evaluating patients with hyperaldosteronism, as it is an intermediate product in its synthesis. The 18-hydroxycorticosterone levels are above 100 mg/dL in virtually all patients with aldosterone producing adenomas. The plasma value for this patient is normal. Perioperative treatment with either spironolactone and potassium replacement is appropriate for patients with hyperaldosteronism, but not pheochromocytoma.

Nonoperative treatment of pheochromocytoma is generally unsatisfactory and entails pharmacologic blockade of the effects of catecholamines. Phenoxybenzamine and prazosin are two preferred agents that block the a-adrenergic effects of the catecholamines preoperatively with pheochromocytoma. The use of b-adrenergic blockers, such as labetalol, may be required in those patients with obvious b-adrenergic effects, such as resting pulse rates above 100 beats/min.

Because of the potential for wide swings in blood pressure and other effects of chronic catecholamine secretion, careful preoperative preparation is required in patients with pheochromocytoma. It is customary to institute a-adrenergic blockade 2 to 3 weeks before anticipated surgery. This has beneficial effects of controlling blood pressure and allowing restoration of a decreased blood volume. It is the consensus that preoperative preparation in the manner makes the intraoperative management of the patient much more safe. In patients who require b-adrenergic blockade, it is essential to first establish good a-adrenergic blockade. These patients are prone to cardiac failure induced by b-adrenergic blockade because of the cardiomyopathy that may preexist. b-Adrenergic blockade in the cardiomyopathic patient with failure to first reduce the afterload by a-adrenergic blockade, can precipitate cardiac failure.

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