Pheochromocytoma
Pheochromocytoma: Excerpt from Professional Guide to Diseases (Eighth Edition)
A pheochromocytoma is a chromaffin-cell tumor of the adrenal medulla that secretes an excess of the catecholamines epinephrine and norepinephrine, resulting in severe hypertension, increased metabolism, and hyperglycemia. This disorder is potentially fatal but the prognosis is generally good with treatment. However, pheochromocytoma-induced kidney damage is irreversible.
Causes and incidence
A pheochromocytoma may result from an inherited autosomal dominant trait. According to some estimates, about 0.5% of newly diagnosed patients with hypertension have pheochromocytoma. While this tumor is usually benign, it may be malignant in as many as 10% of these patients. It affects all races and both sexes, occurring primarily between ages 30 and 40.
Signs and symptoms
The cardinal sign of pheochromocytoma is persistent or paroxysmal hypertension. Common clinical effects include palpitations, tachycardia, headache, diaphoresis, pallor, warmth or flushing, paresthesia, tremor, excitation, fright, nervousness, feelings of impending doom, abdominal pain, tachypnea, nausea, and vomiting. Orthostatic hypotension and paradoxical response to antihypertensive drugs are common, as are associated glycosuria, hyperglycemia, and hypermetabolism. Patients with hypermetabolism may show marked weight loss but some patients with pheochromocytomas are obese. Symptomatic episodes may recur as seldom as once every 2 months or as often as 25 times a day. They may occur spontaneously or may follow certain precipitating events, such as postural change, exercise, laughing, smoking, induction of anesthesia, urination, or a change in environmental or body temperature.
Pheochromocytoma is commonly diagnosed during pregnancy, when uterine pressure on the tumor induces more frequent attacks; such attacks can prove fatal for both mother and fetus as a result of a stroke, acute pulmonary edema, cardiac arrhythmias, or hypoxia. In such patients, the risk of spontaneous abortion is high but most fetal deaths occur during labor or immediately after birth.
Diagnosis
The most common presentation for pheochromocytoma is continuous hypertension with or without orthostatic hypotension. A history of acute episodes of hypertension, headache, sweating, and tachycardia — particularly in a patient with hyperglycemia, glycosuria, and hypermetabolism — strongly suggests pheochromocytoma. A patient who has intermittent attacks may have no symptoms during a latent phase. The tumor is rarely palpable; when it is, palpation of the surrounding area may induce an acute attack and help confirm the diagnosis. Generally, diagnosis depends on laboratory findings.
Confirming diagnosis Increased urinary excretion of total free catecholamines and their metabolites, vanillylmandelic acid (VMA) and metanephrine, as measured by analysis of a 24-hour urine specimen, confirms pheochromocytoma.
Labile blood pressure necessitates urine collection during a hypertensive episode and comparison of this specimen with a baseline specimen. Direct assay of total plasma catecholamines shows levels 10 to 50 times higher than normal.
Provocative tests with glucagon and phentolamine suggest the diagnosis; however, because they may precipitate a hypertensive crisis or induce a false-positive or false-negative result, they’re seldom used. The clonidine suppression test will cause decreased plasma catecholamine levels in normal patients but no change in those with pheochromocytoma. After demonstrating biochemical evidence of pheochromocytoma, computed tomography scan or magnetic resonance imaging of the abdomen (where 95% of pheochromocytomas are located) is warranted. If a tumor isn’t located — or if there is more than one — a radioactive iodine metaiodobenzylguanidine scintiscan or nuclear scan usually confirms the diagnosis in unclear cases. Angiography and excretory urography are no longer used; adrenal venography is used, but rarely.
Treatment
Surgical removal of the tumor is the treatment of choice. To decrease blood pressure, an alpha-adrenergic blocker or metyrosine is given from 1 to 2 weeks before surgery. A beta-adrenergic blocker (propranolol) may also be used after achieving alpha blockade. Postoperatively, I.V. fluids, plasma volume expanders, vasopressors and, possibly, transfusions may be required for hypotension. Persistent hypertension in the immediate postoperative period can occur. If surgery isn’t feasible, alpha-adrenergic blockers and beta-adrenergic blockers — such as phenoxybenzamine and propranolol, respectively — are beneficial in controlling catecholamine effects and preventing attacks. Management of an acute attack or hypertensive crisis requires I.V. phentolamine (push or drip) or nitroprusside to normalize blood pressure.
Special considerations
To ensure the reliability of urine catecholamine measurements, make sure the patient avoids foods high in vanillin (such as coffee, nuts, chocolate, and bananas) for 2 days before urine collection of VMA. Also, be aware of possible drug therapy that may interfere with the accurate determination of VMA (such as guaifenesin and salicylates). Collect the urine in a special container, with hydrochloric acid, that has been prepared by the laboratory.
❑ Obtain blood pressure readings often because transient hypertensive attacks are possible. Tell the patient to report headaches, palpitations, nervousness, or other symptoms of an acute attack. If hypertensive crisis develops, monitor blood pressure and heart rate every 2 to 5 minutes until blood pressure stabilizes at an acceptable level.
❑ Check blood for glucose, and watch for weight loss from hypermetabolism.
❑ After surgery, blood pressure may rise or fall sharply. Keep the patient quiet; provide a private room, if possible, because excitement may trigger a hypertensive episode. Postoperative hypertension is common because the stress of surgery and manipulation of the adrenal gland stimulate secretion of catecholamines. Because this excess secretion causes profuse sweating, keep the room cool, and change the patient’s clothing and bedding often. If the patient receives phentolamine, monitor blood pressure closely. Observe and record adverse effects: dizziness, hypotension, and tachycardia. The first 24 to 48 hours immediately after surgery are the most critical because blood pressure can drop drastically.
❑ If the patient is receiving vasopressors I.V., check blood pressure as per facility protocol or every 15 minutes while titrating, and regulate the drip to maintain a safe pressure. Arterial pressure lines facilitate constant monitoring.
❑ Watch for abdominal distention and return of bowel sounds.
Alert Check dressings and vital signs for indications of hemorrhage (increased pulse rate, decreased blood pressure, cold and clammy skin, pallor, and unresponsiveness).
❑ Give analgesics for pain, as ordered, but monitor blood pressure carefully because many analgesics, especially meperidine, can cause hypotension.
❑ If autosomal dominant transmission of pheochromocytoma is suspected, the patient’s family should also be evaluated for this condition.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Pregnancy-induced hypertension (Professional Guide to Diseases (Eighth Edition))
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