Pulmonary hypertension
Pulmonary hypertension: Excerpt from Handbook of Diseases
Pulmonary hypertension occurs when pulmonary artery pressure (PAP) rises above normal and isn’t attributable to the effects of aging or altitude. There isn’t a definitive set of values used to diagnose pulmonary hypertension; however, the National Institutes of Health requires that the resting mean PAP measures 25 mm Hg or more.
Primary, or idiopathic, pulmonary hypertension is rare, occurring most commonly in women between ages 20 and 40; pregnant women have the highest mortality. Secondary pulmonary hypertension results from existing cardiac or pulmonary disease. The prognosis depends on the severity of the underlying disorder.
Causes
Primary 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. Because this form of pulmonary hypertension occurs in association with collagen diseases, it’s thought to result from altered immune mechanisms.
Usually, pulmonary hypertension is secondary to hypoxemia from an underlying disease process, including:
❑ alveolar hypoventilation from chronic obstructive pulmonary disease (most common cause in the United States), sarcoidosis, diffuse interstitial pneumonia, pulmonary metastasis, and certain diseases such as sclero-derma.
These diseases may cause pulmo-nary hypertension through alveolar destruction and increased pulmonary vascular resistance. 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 obstructions 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 disease, such as rheumatic valvular disease and mitral stenosis, increases pulmonary venous pressure by restricting blood flow returning to the heart.
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 hepato-megaly. Other clinical features vary according to the underlying disorder.
Diagnosis
Characteristic diagnostic findings in patients with pulmonary hypertension include the following:
❑ auscultation: abnormalities associated with the underlying disorder
❑ arterial blood gas (ABG) analysis: hypoxemia (decreased partial pressure of oxygen)
❑ electrocardiography: in right ventricular hypertrophy, shows right-axis deviation and tall or peaked P waves in inferior leads
❑ cardiac catheterization: increased PAP — pulmonary systolic pressure above 30 mm Hg; pulmonary artery wedge pressure (PAWP) increased if the underlying cause is left-sided myxoma, mitral stenosis, or left-side failure — otherwise normal
❑ pulmonary angiography: detects filling defects in pulmonary vasculature, such as those that develop in patients with pulmonary emboli
❑ pulmonary function tests: in underlying obstructive disease, may show decreased flow rates and increased residual volume; in underlying restrictive disease, total lung capacity may decrease.
Treatment
Appropriate treatment usually includes oxygen therapy to decrease hypoxemia and resulting pulmonary vascular resistance. 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. An important goal of treatment is correction of the underlying cause.
CLINICAL TIP: Patients with primary pulmonary hypertension usually respond to epoprostenol (PGI2) as a continuous home infusion.
Special considerations
❑ Pulmonary hypertension requires keen observation and careful monitoring as well as skilled supportive care.
❑ Administer oxygen therapy as required, and observe the response. Be alert for signs of increasing dyspnea so that treatment can be adjusted accordingly.
❑ Monitor ABG levels for acidosis and hypoxemia. Watch for changes in level of consciousness.
❑ When caring for a patient with right-sided heart failure, especially one receiving diuretics, record weight daily, carefully measure intake and output, and explain all medications and diet restrictions.
❑ Check for increasing jugular vein distention, which may indicate fluid overload.
❑ Monitor vital signs, especially blood pressure and heart rate. Watch for hypotension and tachycardia. If the patient has a pulmonary artery catheter, check PAP and PAWP as required and watch for any changes.
❑ Advise against overexertion and suggest frequent rest periods between activities.
❑ Refer the patient to the social services department if special equipment (such as oxygen equipment) is needed for home use.
❑ Make sure that the patient understands the prescribed diet and medications.
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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