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Pheochromocytoma: Rx of HTN

Preoperative Hypertension Treatment: Adrenergic blockade is THE most helpful in treating hypertension preoperatively.These drugs probably reduce the complications of hypertensive crisis, the wide BP fluctuations during manipulation of the tumor (especially until venous drainage is obliterated), and the myocardial dysfunction that occurs perioperatively. A reduction in mortality associated with resection of pheochromocytoma (from 40% to 60% to the current 0% to 6%) occurred when α-adrenergic receptor blockade was introduced as preoperative therapy for such patients. Perioperative α-adrenergic receptor blockade with prazosin or phenoxybenzamine (t 1/2 ~ 24 hours) will help by counteracting the excessive catecholamine stimulation that results in hypertension. This medication has been recommended to commence at least 10-14 days prior to surgery. β-Adrenergic receptor blockade with propranolol is suggested for patients who have persistent arrhythmias or tachycardia because these conditions can be precipitated or aggravated by α-adrenergic receptor blockade. β-Adrenergic receptor blockade should not be used without concomitant α-adrenergic receptor blockade lest the vasoconstrictive effects of the latter go unopposed and thereby increase the risk for dangerous hypertension.

Other drugs, including calcium channel blocking drugs, clonidine, dexmedetomidine, and magnesium, have also been used to achieve suitable degrees of α-adrenergic blockade before surgery.

Intraoperative Hemodynamic Treatment: because of ease of use, there is a preference to give phenylephrine hydrochloride or norepinephrine for hypotension and nitroprusside for hypertension. Phentolamine (t 1/2 19 mins) has too long an onset and duration of action.