Pulmonary Hypertension

Pulmonary Hypertension

Pulmonary hypertension is a condition that is not clinically evi-dent until late in its progression. Pulmonary hypertension exists when the systolic pulmonary artery pressure exceeds 30 mm Hg or the mean pulmonary artery pressure exceeds 25 mm Hg. These pressures cannot be measured indirectly as can systemic blood pressure; instead, they must be measured during right-sided heart catheterization. In the absence of these measurements, clinical recognition becomes the only indicator for the presence of pul-monary hypertension.

There are two forms of pulmonary hypertension: primary (or idiopathic) and secondary. Primary pulmonary hypertension is an uncommon disease in which the diagnosis is made by exclud-ing all other possible causes. The exact cause is unknown, but there are several possible causes (Chart 23-7). The clinical pre-sentation of primary pulmonary hypertension exists with no evi-dence of pulmonary and cardiac disease or pulmonary embolism. It occurs most often in women 20 to 40 years of age and is usu-ally fatal within 5 years of diagnosis.

Secondary pulmonary hypertension is more common and re-sults from existing cardiac or pulmonary disease. The prognosis depends on the severity of the underlying disorder and the changes in the pulmonary vascular bed. A common cause of secondary pul-monary hypertension is pulmonary artery constriction due to hy-poxemia from COPD.

Pathophysiology

The underlying process of pulmonary hypertension varies, and multiple factors are often responsible. Normally, the pulmonary vascular bed can handle the blood volume delivered by the right ventricle. It has a low resistance to blood flow and compensates for increased blood volume by dilation of the vessels in the pulmonary circulation. However, if the pulmonary vascular bed is destroyed or obstructed, as in pulmonary hypertension, the ability to handle whatever flow or volume of blood it receives is impaired, and the increased blood flow then increases the pulmonary artery pressure. As the pulmonary arterial pressure increases, the pulmonary vas-cular resistance also increases. Both pulmonary artery constriction (as in hypoxemia or hypercapnia) and a reduction of the pul-monary vascular bed (which occurs with pulmonary emboli) re-sult in an increase in pulmonary vascular resistance and pressure. This increased workload affects right ventricular function. The myocardium ultimately cannot meet the increasing demands im-posed on it, leading to right ventricular hypertrophy (enlargement and dilation) and failure.

Clinical Manifestations

Dyspnea is the main symptom of pulmonary hypertension, oc-curring at first with exertion and eventually at rest. Substernal chest pain also is common, affecting 25% to 50% of patients. Other signs and symptoms include weakness, fatigue, syncope, occasional hemoptysis, and signs of right-sided heart failure (pe-ripheral edema, ascites, distended neck veins, liver engorgement, crackles, heart murmur).

Assessment and Diagnostic Findings

A complete diagnostic evaluation includes a history, physical ex-amination, chest x-ray, pulmonary function studies, electrocar-diogram (ECG), echocardiogram, ventilation–perfusion scan, and cardiac catheterization. In some cases, a lung biopsy, performed by thoracotomy or thoracoscopy, may be needed to make a defi-nite diagnosis. Cardiac catheterization of the right side of the heart reveals elevated pulmonary arterial pressure. An echocardiogram can assess the progression of the disease and rule out other condi-tions with similar signs and symptoms. The ECG reveals right ventricular hypertrophy, right axis deviation, and tall peaked P waves in inferior leads, tall anterior R waves, and ST-segment depression and/or T-wave inversion anteriorly. The PaO₂ also is decreased (hypoxemia). A ventilation–perfusion scan or pul-monary angiography detects defects in pulmonary vasculature, such as pulmonary emboli. Pulmonary function studies may be normal or show a slight decrease in vital capacity (VC) and lung compliance, with a mild decrease in the diffusing capacity.

Medical Management

The goal of treatment is to manage the underlying cardiac or pul-monary condition. Most patients with primary pulmonary hyper-tension do not have hypoxemia at rest but require supplemental oxygen with exercise. However, patients with severe right ventric-ular failure, decreased cardiac output, and progressive disease may have resting hypoxemia and require continuous oxygen supple-mentation. Appropriate oxygen therapy reverses the vasoconstriction and reduces the pulmonary hypertension in a rel-atively short time.

In the presence of cor pulmonale, which is discussed in the section that follows, treatment should include fluid restriction, diuretics to decrease fluid accumulation, cardiac glycosides (eg, digitalis) in an attempt to improve cardiac function, calcium channel blockers for vasodilation, and rest. In primary pulmonary hypertension, vasodilators have been administered with variable success (eg, calcium channel blockers, intravenous prostacyclin). Prostacyclin (PGX [Flolan]) is one of the prostaglandins pro-duced by the pulmonary endothelium. Intravenous prostacyclin (epoprostenol) helps to decrease pulmonary hypertension by re-ducing pulmonary vascular resistance and pressures and increas-ing cardiac output. Anticoagulants such as warfarin (Coumadin) have been given to patients because of chronic pulmonary em-boli. Heart– lung transplantation has been successful in select pa-tients with primary hypertension who have not been responsive to other therapies.

Nursing Management

The major nursing goal is to identify patients at high risk for pul-monary hypertension, such as those with COPD, pulmonary emboli, congenital heart disease, and mitral valve disease. The nurse also must be alert for signs and symptoms, administer oxy-gen therapy appropriately, and instruct patients and their fami-lies about the use of home oxygen supplementation.