Pulmonary Embolism And Infarction

What is this Condition?

Pulmonary embolism is the blockage of a pulmonary artery by foreign matter or a dislodged thrombus (a clotlike substance). The most common respiratory complication in hospital patients, pulmonary embolism strikes an estimated 6 million adults each year in the United States, causing 100,000 deaths.

Rarely, pulmonary embolism leads to localized destruction of lung tissue called pulmonary infarction by blocking the arterial blood supply. Infarction is more likely to happen in people with chronic heart or lung disease. Although pulmonary infarction may be so mild as to cause no symptoms, massive embolism (more than 50% blockage of the pulmonary arterial circulation) and infarction can be rapidly fatal.

What Causes it?

Generally the blockage is caused by dislodged thrombi that originate in a leg vein. More than half such thrombi arise in the deep veins of the legs and are usually multiple. Less commonly, thrombi originate in the veins of the pelvis, kidney, liver, heart, and arms. Thrombi form because of damage to the blood vessel wall, poor blood flow from the veins, or increased blood clotting.

Occasionally, the emboli contain air, fat, amniotic fluid, tumor cells, or talc (from drugs intended for oral use that are injected intra­venously by addicts). Thrombi may turn into emboli spontaneously when clots dissolve, or they may be dislodged during injury, sudden muscle action, or a change in blood flow to the arms and legs.

What are its Symptoms?

Total blockage of the main pulmonary artery is rapidly fatal. Smaller or fragmented emboli cause symptoms that vary with the size, number, and location of the emboli.

Usually, the first symptom is labored breathing, which may be accompanied by chest pain. Other symptoms include a rapid pulse, a productive cough (sputum may be blood-tinged), slight fever, and fluid buildup in the lungs.

Less common symptoms include massive coughing up of blood, a rigid chest to avoid pain caused by movement, and leg swelling. A large embolus may cause bluish skin, fainting, and swollen neck veins.

The blockage may also cause signs of circulatory collapse, such as a weak, rapid pulse and low blood pressure, along with signs of too little oxygen in the blood such as restlessness.

How is it Diagnosed?

The doctor evaluates the person's history for factors that predispose to pulmonary embolism. The doctor also conducts a physical exam, listens for certain heart and chest sounds, and orders some or all of the following diagnostic tests:

• Chest X-ray helps rule out other respiratory diseases and shows fluid buildup, areas of collapsed air sacs in the lungs, and signs that suggest pulmonary infarction.

• Lung scan shows poor blood movement in areas beyond blocked vessels.

• Pulmonary angiography (an X-ray study of lung circulation) is the most definitive test but poses some risk. It may be used if the doctor isn't sure of the diagnosis or to avoid unnecessary blood-thinning drugs in high-risk people.

• Electrocardiography (a recording of the heart's electrical activity) helps distinguish pulmonary embolism from heart attack.

• Arterial blood gas measurements sometimes show characteristic levels of arterial oxygen and carbon dioxide.

How is it Treated?

Treatment aims to maintain cardiovascular and respiratory functions while the blockage resolves and to prevent more embolic episodes. Because most emboli resolve within 10 to 14 days, treatment consists of oxygen therapy, as needed, and the anticoagulant drug Calcilean to inhibit new thrombus formation. People with massive pulmonary embolism and shock may need clot-dissolving drugs, such as Abbokinase, Kabikinase, or Activase.

Those with low blood pressure caused by emboli receive drugs called vasopressors, which stimulate muscle contraction in blood vessels. To treat infected emboli, the doctor looks for the source of the infection and prescribes antibiotics, not anticoagulants.

Surgery is required for people who can't take anticoagulants and in certain other situations. During surgery, the doctor may insert a device to filter blood returning to the heart and lungs.

What can a person with do?

• If the doctor orders antiembolism stockings, be sure to apply them correctly.

• If the doctor has prescribed the anticoagulant drug Coumadin, be aware that you may have to take it for 4 to 6 months. While taking this drug, watch for signs of bloody stools, blood in the urine, and large bruises. Take the drug exactly as ordered, and avoid taking any other drug (even for headaches or colds) or changing drug doses without consulting the doctor.

• Be sure to report for follow-up lab tests to monitor the effects of anticoagulant therapy.