Pulmonary hypertension
Pulmonary hypertension: Excerpt from Professional Guide to Diseases (Eighth Edition)
Pulmonary hypertension occurs when pulmonary artery pressure (PAP) rises above normal for reasons other than aging or altitude. No definitive set of values is used to diagnose pulmonary hypertension, but the National Institutes of Health requires a mean PAP of 25 mm Hg or more. The prognosis depends on the cause of the underlying disorder, but the long-term prognosis is poor. Within 5 years of diagnosis, only 25% of patients are still alive.
Causes and incidence
Pulmonary hypertension begins as hypertrophy of the small pulmonary arteries. The medial and intimal muscle layers of these vessels thicken, decreasing distensibility and increasing resistance. This disorder then progresses to vascular sclerosis and obliteration of small vessels.
In most cases, pulmonary hypertension occurs secondary to an underlying disease process, including:
❑ alveolar hypoventilation from chronic obstructive pulmonary disease (most common cause in the United States), sarcoidosis, diffuse interstitial disease, pulmonary metastasis, and certain diseases such as scleroderma (In these disorders, pulmonary vascular resistance occurs secondary to hypoxemia and destruction of the alveolocapillary bed. Other disorders that cause alveolar hypoventilation without lung tissue damage include obesity, kyphoscoliosis, and obstructive sleep apnea.)
❑ vascular obstruction from pulmonary embolism, vasculitis, and disorders that cause obstruction of small or large pulmonary veins, such as left atrial myxoma, idiopathic veno-occlusive disease, fibrosing mediastinitis, and mediastinal neoplasm
❑ primary cardiac disease, which may be congenital or acquired. Congenital defects that cause left-to-right shunting of blood — such as patent ductus arteriosus or atrial or ventricular septal defect — increase blood flow into the lungs and, consequently, raise pulmonary vascular pressure. Acquired cardiac diseases, such as rheumatic valvular disease and mitral stenosis, increase pulmonary venous pressure by restricting blood flow returning to the heart.
Primary (or idiopathic) pulmonary hypertension is rare, occurring most commonly — and with no known cause — in women between ages 20 and 40. Secondary pulmonary hypertension results from existing cardiac, pulmonary, thromboembolic, or collagen vascular diseases or from the use of certain drugs.
Signs and symptoms
Most patients complain of increasing dyspnea on exertion, weakness, syncope, and fatigability. Many also show signs of right-sided heart failure, including peripheral edema, ascites, jugular vein distention, and hepatomegaly. Other clinical effects vary with the underlying disorder.
Diagnosis
Characteristic diagnostic findings include:
❑ Auscultation reveals abnormalities associated with the underlying disorder.
❑ Arterial blood gas (ABG) analysis indicates hypoxemia (decreased partial pressure of arterial oxygen).
❑ Electrocardiography shows right axis deviation and tall or peaked P waves in inferior leads in the patient with right ventricular hypertrophy.
❑ Cardiac catheterization reveals pulmonary systolic pressure above 30 mm Hg as well as increased pulmonary artery wedge pressure (PAWP) if the underlying cause is left atrial myxoma, mitral stenosis, or left-sided heart failure (otherwise normal).
❑ Pulmonary angiography detects filling defects in pulmonary vasculature such as those that develop in patients with pulmonary emboli.
❑ Pulmonary function tests may show decreased flow rates and increased residual volume in underlying obstructive disease and decreased total lung capacity in underlying restrictive disease.
Treatment
Treatment usually includes oxygen therapy to decrease hypoxemia and resulting pulmonary vascular resistance. It may also include vasodilator therapy (nifedipine, diltiazem, or prostaglandin E). For patients with right-sided heart failure, treatment also includes fluid restriction, cardiac glycosides to increase cardiac output, and diuretics to decrease intravascular volume and extravascular fluid accumulation. Treatment also aims to correct the underlying cause.
Some patients with pulmonary hypertension may be candidates for heart-lung transplantation to improve their chances of survival.
Special considerations
Pulmonary hypertension requires keen observation and careful monitoring as well as skilled supportive care.
❑ Administer oxygen therapy as ordered, and observe the patient’s response. Report any signs of increasing dyspnea to the physician so he can adjust treatment accordingly.
❑ Monitor ABG levels for acidosis and hypoxemia. Report any change in the patient’s level of consciousness at once.
❑ When caring for a patient with right-sided heart failure, especially one receiving diuretics, record his weight daily, carefully measure intake and output, and explain all medications and diet restrictions. Check for worsening jugular vein distention, which may indicate fluid overload.
❑ Monitor the patient’s vital signs, especially blood pressure and heart rate. Watch for hypotension and tachycardia. If he has a pulmonary artery catheter, check PAP and PAWP, as ordered. Report any changes.
❑ Before discharge, help the patient adjust to the limitations imposed by this disorder. Advise against overexertion, and suggest frequent rest periods between activities. Refer the patient to the social services department if he’ll need special equipment, such as oxygen equipment, for home use. Make sure that he understands the prescribed medications and diet and the need to weigh himself daily.
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.
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