Surgical treatment of pheochromocytomas - Home Study Program article, includes examination, answer sheet and learners evaluation

AORN Journal, June, 1997 by Mary Gavaghan

Side effects of phenoxybenzamine hydrochloride include postural hypotension, miosis (ie, pupil constriction), nasal congestion, inhibition of ejaculation, diarrhea, and fatigue. Cautious dosage begins with 10 mg of oral phenoxybenzamine hydrochloride twice a day with an increase of 10 to 20 mg every two days until patients can tolerate daily dosages of 40 to 100 mg of oral phenoxybenzamine hydrochloride. Patients also must demonstrate normotension or only moderate postural hypotension and have no paroxysmal symptoms. Surgeons may withhold phenoxybenzamine hydrochloride from patients 48 to 72 hours before surgery to prevent postoperative hypotension, or they may continue the medication until the day before surgery to prevent possible intraoperative hypertensive episodes.

Other medications. Alternative preoperative medications include [alpha].[sub.1]]-adrenergic blocking agents (eg, prazosin hydrochloride, terazosin hydrochloride). These medications have fewer side effects than phenoxybenzamine hydrochloride and are preferred for long-term therapy in patients with malignant pheochromocytomas and metastases. Patients who have tachycardia greater than 120 beats per minute, arrhythmias, or tumors that primarily secrete epinephrine also require [Beta]-adrenergic blocking agents. Beta-adrenergic blocking agents must not be administered before [alpha]-adrenergic blocking agents are given to patients because they will inhibit [Beta]-receptor-induced vasodilation and cause severe vasoconstriction that may result in hypertensive crises.(48)

Propranolol hydrochloride is a [Beta]-adrenergic blocking agent that is used if patients do not have a history of bronchospasms. Patients who have bronchospastic disease can be given metoprolol tartrate, which primarily acts on the heart's [Beta].[sub.1]]-adrenergic receptors and spares the bronchial [Beta].[sub.2]]-adrenergic receptors.(49) Metyrosine, which inhibits tyrosine conversion to catecholamines, also may be given preoperatively. It frequently is used in patients with unresectable tumors and catecholamine-induced cardiomyopathy. Calcium channel blockers (eg, nifedipine, verapamil) that inhibit calcium-mediated catecholamine secretion from tumors, also may be administered to preoperative patients. Calcium channel blockers are believed to prevent myocarditis and coronary artery spasms.(50) Depending on institutional procedures, patients may be placed in a special care unit for close observation and continuous monitoring by nurses a few days before surgery.

Preoperative nursing care measures. Liberal salt diets often are prescribed for patients to offset their contracted blood volumes -- a result of prolonged vasoconstriction. Nurses administer 1 to 2 L of IV fluids to patients daily to ensure adequate hydration before surgery. They also draw blood samples for blood-type and cross-match screens because the vascularity of pheochromocytomas may cause intraoperative hemorrhage. Preoperative nurses monitor patients for hypertension or postural hypotension, by measuring patients' BPs consistently in the same arm and with patients in both lying and standing positions. They also record patients' daily weights at the same time of day to detect possible dehydration or edema.