Pheochromocytoma - Management of Patients With Adrenal Disorders

PHEOCHROMOCYTOMA

Pheochromocytoma is a tumor that is usually benign and origi-nates from the chromaffin cells of the adrenal medulla. In 80% to 90% of patients (O’Connell, 1999), the tumor arises in the medulla; in the remaining patients, it occurs in the extra-adrenal chromaffin tissue located in or near the aorta, ovaries, spleen, or other organs. Pheochromocytoma may occur at any age, but its peak incidence is between ages 40 and 50 years (Rakel & Bope, 2001). It affects men and women equally. Because of the high incidence of pheochromocytoma in family members, the pa-tient’s family members should be alerted and screened for this tumor. Ten percent of the tumors are bilateral, and 10% are malignant.

Pheochromocytoma is the cause of high blood pressure in 0.2% of patients with new onset of hypertension (O’Connell, 1999). Although it is uncommon, it is one form of hypertension that is usually cured by surgery; without detection and treat-ment, it is usually fatal. Pheochromocytoma may occur in the familial form as part of multiple endocrine neoplasia type 2; therefore, it should be considered a possibility in patients with medullary thyroid carcinoma and parathyroid hyperplasia or tumor.

Clinical Manifestations

The nature and severity of symptoms of functioning tumors of the adrenal medulla depend on the relative proportions of epi-nephrine and norepinephrine secretion. The typical triad of symptoms comprises headache, diaphoresis, and palpitations (Matthews et al., 1999). Hypertension and other cardiovascular disturbances are common. The hypertension may be intermittent or persistent. Only half of patients with pheochromocytoma, however, have sustained or persistent hypertension. If the hyper-tension is sustained, it may be difficult to distinguish from other causes of hypertension. Other symptoms may include tremor, headache, flushing, and anxiety. Hyperglycemia may result from conversion of liver and muscle glycogen to glucose by epineph-rine secretion; insulin may be required to maintain normal blood glucose levels.

The clinical picture in the paroxysmal form of pheochromo-cytoma is usually characterized by acute, unpredictable attacks lasting seconds or several hours. During these attacks, the patient is extremely anxious, tremulous, and weak. The patient may experience headache, vertigo, blurring of vision, tinnitus, air hunger, and dyspnea. Other symptoms include polyuria, nausea, vomiting, diarrhea, abdominal pain, and a feeling of impending doom. Palpitations and tachycardia are common. Blood pressures exceeding 250/150 mm Hg have been recorded. Such blood pres-sure elevations are life-threatening and may cause severe compli-cations, such as cardiac dysrhythmias, dissecting aneurysm, stroke, and acute renal failure. Postural hypotension occurs in 70% of patients with untreated pheochromocytoma

Assessment and Diagnostic Findings

Pheochromocytoma is suspected if signs of sympathetic nervous system overactivity occur in association with marked elevation of blood pressure. These signs can be associated with the “five Hs”: hypertension, headache, hyperhidrosis (excessive sweating), hypermetabolism, and hyperglycemia. The presence of these signs has a 93.8% specificity and a 90.9% sensitivity for pheochro-mocytoma. Absence of hypertension excludes pheochromocytoma with a 99% certainty. Paroxysmal symptoms of pheochromo-cytoma commonly develop in the fifth decade of life.

Measurements of urine and plasma levels of catecholamines are the most direct and conclusive tests for overactivity of the adrenal medulla. Measurements of urinary catecholamine metabolites (metanephrines [MN] and vanillylmandelic acid [VMA]) or free catecholamines are the standard diagnostic tests used in the diagnosis of pheochromocytoma. Levels can be as high as three times normal limits (O’Connell, 1999). A 24-hour specimen of urine is collected for determining free cate-cholamines, MN, and VMA; the use of combined tests increases the diagnostic accuracy of testing. A number of medications and foods (eg, coffee, tea, bananas, chocolate, vanilla, aspirin) may alter the results of these tests; therefore, careful instructions to avoid restricted items must be given to the patient. Urine col-lected over a 2- or 3-hour period after an attack of hypertension can be assayed for catecholamine content.

Total plasma catecholamine (epinephrine and norepineph-rine) concentration is measured with the patient supine and at rest for 30 minutes. To prevent elevation of catecholamine levels by the stress of venipuncture, a butterfly needle, scalp vein needle, or venous catheter may be inserted 30 minutes before the blood specimen is obtained.

Factors that may elevate catecholamine levels must be con-trolled to obtain valid results; these factors include consumption of coffee or tea, use of tobacco, emotional and physical stress, and use of many prescription and over-the-counter medications (eg, amphetamines, nose drops or sprays, decongestant agents, and bronchodilators).

Normal plasma values of epinephrine are 100 pg/mL (590 pmol/L); normal values of norepinephrine are generally less than 100 to 550 pg/mL (590 to 3,240 pmol/L). Values of epi-nephrine greater than 400 pg/mL (2,180 pmol/L) or norepi-nephrine values greater than 2,000 pg/mL (11,800 pmol/L) are considered diagnostic of pheochromocytoma. Values that fall be-tween normal values and those diagnostic of pheochromocytoma indicate the need for further testing.

A clonidine suppression test may be performed if the results of plasma and urine tests of catecholamines are inconclusive. Cloni-dine (Catapres) is a centrally acting, antiadrenergic medication that suppresses the release of neurogenically mediated cate-cholamines. The suppression test is based on the principle that cat-echolamine levels are normally increased through the activity of the sympathetic nervous system. In pheochromocytoma, in-creased catecholamine levels result from the diffusion of excess cat-echolamines into the circulation, bypassing normal storage and release mechanisms. Therefore, in patients with pheochromocy-toma, clonidine does not suppress the release of catecholamines.

The results of the test are considered normal if 2 to 3 hours after a single oral dose of clonidine, the total plasma cate-cholamine value decreases at least 40% from baseline. Patients with pheochromocytoma exhibit no change in catecholamine lev-els. False-positive results, however, may occur in patients with primary hypertension.

Imaging studies, such as CT scans, MRI, and ultrasound, may also be carried out to localize the pheochromocytoma and to de-termine whether more than one tumor is present. Use of ¹³¹I-metaiodobenzylguanidine (MIBG) scintigraphy may be re-quired to determine the location of the pheochromocytoma and to detect metastatic sites outside the adrenal gland. MIBG is a specific isotope for catecholamine-producing tissue. It has been helpful in identifying tumors not detected by other tests or pro-cedures. MIBG scintigraphy is a noninvasive, safe procedure that has increased the accuracy of diagnosis of adrenal tumors.

Other diagnostic studies may focus on evaluating the function of other endocrine glands because of the association of pheochro-mocytoma in some patients with other endocrine tumors.

Medical Management

During an episode or attack of hypertension, tachycardia, anxi-ety, and the other symptoms of pheochromocytoma, the patient is placed on bed rest with the head of the bed elevated to promote an orthostatic decrease in blood pressure.

PHARMACOLOGIC THERAPY

The patient may be moved to the intensive care unit for close monitoring of ECG changes and careful administration of alpha-adrenergic blocking agents (eg, phentolamine [Regitine]) or smooth muscle relaxants (eg, sodium nitroprusside [Nipride]) to lower the blood pressure quickly.

Phenoxybenzamine (Dibenzyline), a long-acting alpha-blocker, may be used when the blood pressure is stable to prepare the patient for surgery. Beta-adrenergic blocking agents, such as pro-pranolol (Inderal), may be used in patients with cardiac dys-rhythmias or those not responsive to alpha-blockers. Alpha-adrenergic and beta-adrenergic blocking agents must be used with caution because patients with pheochromocytoma may have increased sensitivity to them. Still other medications that may be used preoperatively are catecholamine synthesis inhibitors, such as alpha-methyl-p-tyrosine (metyrosine). These are occasionally used when adrenergic blocking agents do not reduce the effects of catecholamines.

SURGICAL MANAGEMENT

The definitive treatment of pheochromocytoma is surgical re-moval of the tumor, usually with adrenalectomy. Bilateral adrenalectomy may be necessary if tumors are present in both adrenal glands. Patient preparation includes control of blood pressure and blood volumes; usually this is carried out over 7 to 10 days. Phentolamine or phenoxybenzamine (Dibenzyline) may be used safely without causing undue hypotension. Other medications (metyrosine [Demser] and prazosin [Minipress]) have been used to treat pheochromocytoma. The patient needs to be well hydrated before, during, and after surgery to prevent hypotension.

Manipulation of the tumor during surgical excision may cause release of stored epinephrine and norepinephrine, with marked increases in blood pressure and changes in heart rate. Therefore, use of sodium nitroprusside (Nipride) and alpha-adrenergic blocking agents may be required during and after surgery. Ex-ploration of other possible tumor sites is frequently undertaken to ensure removal of all tumor tissue. As a result, the patient is subject to the stress and effects of a long surgical procedure, which may increase the risk of hypertension postoperatively.

Corticosteroid replacement is required if bilateral adrenalec-tomy has been necessary. Corticosteroids may also be necessary for the first few days or weeks after removal of a single adrenal gland. Intravenous administration of corticosteroids (methyl-prednisolone sodium succinate [Solu-Medrol]) may begin the evening before surgery and continue during the early postopera-tive period to prevent adrenal insufficiency. Oral preparations of corticosteroids (prednisone) will be prescribed after the acute stress of surgery diminishes.

Hypotension and hypoglycemia may occur in the postopera-tive period because of the sudden withdrawal of excessive amounts of catecholamines. Therefore, careful attention is di-rected toward monitoring and treating these changes. Blood pressure is expected to return to normal with treatment; how-ever, one third of patients continue to be hypertensive after surgery. This may result if not all pheochromocytoma tissue was removed, if pheochromocytoma recurs, or if the blood vessels were damaged by severe and prolonged hypertension. Several days after surgery, urine and plasma levels of catecholamines and their metabolites are measured to determine whether surgery was successful.

Nursing Management

The patient who has undergone surgery to treat pheochromocy-toma has experienced a stressful preoperative and postoperative course and may remain fearful of repeated attacks. Although it is usually expected that all pheochromocytoma tissue has been re-moved, there is a possibility that other sites were undetected and that attacks may recur. The patient is monitored for several days in the intensive care unit with special attention given to ECG changes, arterial pressures, fluid and electrolyte balance, and blood glucose levels. Several intravenous lines are inserted for administration of fluids and medications.

PROMOTING HOME AND COMMUNITY-BASED CARE

Teaching Patients Self-Care. 

During the preoperative and post-operative phases of care, the nurse informs the patient about the importance of follow-up monitoring to ensure that pheochro-mocytoma does not recur undetected. After adrenalectomy, use of corticosteroids may be needed. Therefore, the nurse instructs the patient about their purpose, the medication schedule, and the risks of skipping doses or stopping their administration abruptly.

It is important to teach the patient and family how to measure the patient’s blood pressure and when to notify the physician about changes in blood pressure. Additionally, the nurse provides verbal and written instructions about the procedure for collecting 24-hour urine specimens to monitor urine catecholamine levels.

Continuing Care.

A follow-up visit from a home care nurse maybe indicated to assess the patient’s postoperative recovery, surgi-cal incision, and compliance with the medication schedule. This may help to reinforce previous teaching about management and monitoring. The home care nurse also obtains blood pres-sure measurements and assists the patient in preventing or deal-ing with problems that may result from long-term use of corticosteroids.

Because of the risk of recurrence of hypertension, periodic checkups are required, especially in young patients and in pa-tients whose families have a history of pheochromocytoma. The patient is scheduled for periodic follow-up appointments to ob-serve for return of normal blood pressure and plasma and urine levels of catecholamines.