University of Colorado Global Anesthesiology Fellowship

A pheochromocytoma is a neuroendocrine tumor that secretes norepinephrine and epinephrine, resulting in hypertension, palpitations, severe headaches, shortness of breath, and in some cases, anxiety. The “classic triad” of symptoms in patients with a pheochromocytoma consists of episodic headache, sweating, and tachycardia. When a patient presents with these symptoms, measurement of plasma fractionated metanephrines may rule out a pheochromocytoma; however, the most reliable method for diagnosis is measuring fractionated metanephrines and catecholamines in a 24-hour urine collection, which has a reported sensitivity and specificity of greater than 98%.

The increase in arterial blood pressure and vascular resistance is a result of continued stimulation of alpha-1 adrenergic receptors. Indeed, the hallmark of preoperative treatment of a pheochromocytoma is the use of alpha-blockers, such as phenoxybenzamine, for at least 10 - 14 days prior to the resection of the tumor. This helps to control the effects of norepinephrine and epinephrine hypersecretion prior to resection. The goals of this pre-operative treatment are to restore normal blood volume and control blood pressure, heart rate, and arrhythmias. After resection of the tumor, the continued presence of the alpha-1 receptor antagonists can lead to hypotension. As phenylephrine is a selective alpha-1 adrenergic receptor agonist, the presence of the alpha-blockers given prior to surgery may prevent phenylephrine from increasing blood pressure.