Pulmonary Edema

In pulmonary edema, fluid accumulates in the extravascular spaces of the lung. In cardiogenic pulmonary edema, fluid accumulation results from elevations in pulmonary venous and capillary hydrostatic pressures. A common complication of cardiac disorders, pulmonary edema can occur as a chronic condition or develop quickly and rapidly become fatal.

In most cases, heart problems are the cause of pulmonary edema. But fluid can accumulate in your lungs for other reasons, including lung problems such as pneumonia, exposure to certain toxins and medications, and exercising or living at high elevations.

Acute pulmonary edema is a medical emergency and requires immediate care. Although pulmonary edema can sometimes prove fatal, the outlook is often good when you receive prompt treatment for pulmonary edema along with therapy for the underlying problem.

Causes

Pulmonary edema usually results from left ventricular failure due to arteriosclerotic, hypertensive, cardiomyopathic, or valvular cardiac disease. In such disorders, the compromised left ventricle requires increased filling pressures to maintain adequate output; these pressures are transmitted to the left atrium, pulmonary veins, and pulmonary capillary bed.

This increased pulmonary capillary hydrostatic force promotes transudation of intravascular fluids into the pulmonary interstitium, decreasing lung compliance and interfering with gas exohange. Other factors that may predispose a person to pulmonary edema include:

• infusion of excessive volumes of I.V. fluids
• decreased serum colloid osmotic pressure as a result of nephrosis, extensive burns, hepatic disease, or nutritional deficiency
• impaired lung lymphatic drainage from Hodgkin's disease or obliterative lymphangitis after radiation
• mitral stenosis and left atrial myxoma, which impair left atrial emptying
• pulmonary veno-occlusive disease.

Signs and symptoms

The main symptom of pulmonary edema is extreme shortness of breath. At first this occurs only during exertion. Then, the patient begins to have difficulty breathing even when at rest. Lying down can make the patient feel as if he or she is drowning, causing gasping and wheezing.

Additional symptoms that may be associated with this disease:

• Nasal flaring
• Coughing up blood
• Inability to speak from air hunger
• Decrease in level of awareness

Diagnosis

A doctor can usually diagnose pulmonary edema based on the patient's symptoms and a physical exam. Patients with pulmonary edema will have a rapid pulse, rapid breathing, abnormal breath and heart sounds, and enlarged neck veins. A chest x ray is often used to confirm the diagnosis. Arterial blood gas testing may be done. Sometimes pulmonary artery catheterization is performed to confirm that the patient has pulmonary edema and not a disease with similar symptoms (called adult respiratory distress syndrome or "noncardiogenic pulmonary edema").

Treatment

In pulmonary edema, treatment is designed to reduce extravascular fluid, to improve gas exchange and myocardial function and, if possible, to correct the underlying disorder.

Administration of high concentrations of oxygen by a cannula, a face mask and, if the patient fails to maintain an acceptable partial pressure of arterial oxygen, assisted ventilation improves oxygen delivery to the tissues and usually improves acid-base disturbances.

Diuretics-furosemide and bumetanide, for example-promote diuresis, which in turn helps to mobilize extravascular fluid.

Treatment of myocardial dysfunction includes a digitalis glycoside or pressor agents to increase cardiac contractility, antiarrhytlunics (particularly when arrhythmias are associated with decreased cardiac output) and, occasionally, arterial vasodilators, such as nitroprusside, which decrease peripheral vascular resistance, preload, and after­load.

Other treatment includes morphine to reduce anxiety and dyspnea and to dilate the systemic venous bed, promoting blood flow from the pulmonary circulation to the periphery

Prevention

Cardiogenic pulmonary edema can sometimes be prevented by treating the underlying heart disease. These treatments, can including maintaining a healthy diet, taking appropriate medications correctly, and avoiding excess alcohol and salt.