Shelf Exam

The most appropriate next step is to initiate phenoxybenzamine now and metoprolol 3 days prior to surgery. A pheochromocytoma is a neuroendocrine tumor originating from the chromaffin cells of the adrenal medulla. Pheochromocytomas are rare tumors that can arise sporadically from a de novo mutation or can be associated with a familial syndrome, such as von Hippel-Lindau syndrome or multiple endocrine neoplasia type 2. Pheochromocytomas produce at least one catecholamine (epinephrine, norepinephrine, or dopamine). Classic presentation involves intermittent tachycardia, sweats, headaches, and episodic or persistent hypertension. Radiologic evaluation with CT or MRI should be performed in patients whose biochemical testing with either plasma metanephrines or 24-hour urinary metanephrines is indicative of a pheochromocytoma. Patients with pheochromocytomas should undergo surgical resection, with laparoscopic adrenalectomy preferred for patients with single, small intra-adrenal tumors without malignant features. Preoperative medical therapy is necessary to manage tachycardia and hypertension (preventing a hypertensive crisis in surgery) and to expand volume prior to surgery. An alpha-adrenergic blocker, such as phenoxybenzamine, is recommended for 7–10 days prior to surgery. A beta-blocker, such as metoprolol, is started 2–3 days prior to surgery, but only after alpha-adrenergic blockade has been established to prevent unopposed alpha-adrenergic receptor stimulation.

Initiate both metoprolol and phenoxybenzamine now (A), initiate metoprolol now and phenoxybenzamine 3 days prior to surgery (B), and no medication therapy is necessary (D) are incorrect. This patient requires medical therapy prior to surgery. Preoperative beta-blockers should not be administered until alpha-adrenergic blockade has been achieved. Worsening hypertension can develop if vasodilatory peripheral beta-adrenergic receptors are blocked while there is unopposed alpha-adrenergic receptor stimulation.