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Pulmonary Embolism

What is Embolism?

Embolism occurs when an object (the embolus, pulmonary emboli) migrates from one part of the body through circulation and causes a blockage of a blood vessel in another part of the body.


Ø Most embolisms happen to people who have risk factors for blood clot formation, like smoking, high blood pressure, high cholesterol, and heart disease.
Ø The primary cause of most pulmonary embolisms is deep vein thrombosis (DVT). This is a condition in which the veins of the legs develop clots. Natural agents in the blood often dissolve small clots. Some clots are too big to dissolve and are big enough to block major blood vessels in the lungs or in the brain.
Ø Factors that slow blood flow in the legs may promote clotting. People can develop a DVT or pulmonary emboli after sitting still on long flights or after immobilization of the leg in a cast, or after prolonged bedrest without moving the legs. Other factors associated with DVT or pulmonary embolism include cancer, previous surgery, a broken leg or hip, and genetic conditions affecting the blood cells that increase the chance of blood clot formation.


Ø The treatment for thromboembolism (blood clot embolism) involves anticoagulant or thrombolytic medications. Anticoagulants prevent further clotting and thrombolytic help the body to dissolve the original clot.
Ø The anticoagulants called heparin or warfarin are the main medications given for pulmonary embolism. They can also be given to people with DVT to prevent the condition.

What is Pulmonary Embolism?

An embolism is a blood clot that breaks off from the wall of a vein and travels with the blood to other organs in the body. Pulmonary embolism is a blood clot that lodges in the lungs and blocks the lung arteries so the flow of blood to the lungs and heart is reduced.


More than 90 percent of the blood clots that cause pulmonary embolism usually form in the deep veins of the legs, a condition called deep vein thrombosis. Although it is uncommon, an embolism can also form from fat that escapes from the bone marrow when a bone is fractured or from amniotic fluid during childbirth.


Treatment depends on the size and severity of the embolus. Current treatments include anticoagulant (‘blood thinner’) and oxygen therapy, thrombolysis, or a vena cava filter. If surgery is required, procedures include traditional pulmonary embolectomy or catheter-directed pulmonary embolectomy.

Ø Oxygen therapy: If the pulmonary embolism results in a low blood oxygen level, oxygen will be administered either by nasal cannulae (small prongs that fit in the nostrils) or by face mask. In cases of severe pulmonary embolism, mechanical ventilation, (artificial respiration) may be necessary.
Ø Anticoagulant therapy: Patients with stable acute pulmonary embolism are hospitalized immediately so that an anticoalgulant (blood thinning agent) can be given and oxygen can be administered (if needed). Anticoagulants permit quicker absorption of the clot, reducing the threat of another embolus.
The most widely used intravenous anticoagulant is heparin as it acts quickly and can stop blood-clot formation almost immediately. Treatment with heparin often requires frequent blood testing to ensure that the level of anticoagulation is neither too low nor too high. Other intravenous anticoagulant medications are available for those who have allergies to heparin.
Several related medications known as “low molecular weight heparins” are available as subcutaneous (under the skin) injections, such as enoxaparin (Lovenox®), dalteparin (Fragmin®), or tinzaparin (Innohep®). When a person is receiving one of these medicines, blood testing does not need to be done so frequently. In some cases, a patient with a blood clot in the legs or a pulmonary embolism may be treated as an outpatient with a low molecular weight heparin.
After a day or two of heparin or low molecular weight heparin, patients are often given warfarin (Coumadin® or Jantoven®), which is available as a pill. This medication acts more slowly and in a different way from heparin. Warfarin takes about three to five days to take effect so an injected drug is given until warfarin takes full effect.
Ø Thrombolysis: Thrombolysis, or reperfusion therapy, involves injecting a clot-dissolving medication into the circulation to dissolve the blood clot and restore blood flow. Unlike heparin, thrombolytic agents can dissolve an existing clot in both the deep venous system and the pulmonary circulation.
Ø Vena Cava Filter: If the patient cannot tolerate the anticoagulant therapy or has other conditions that might lead to excessive bleeding, a filter device may be placed in the inferior vena cava (main vein leading to the heart). The filter is introduced with a catheter and positioned within the vena cava to trap large clots before they reach the pulmonary arteries.
Ø Pulmonary embolectomy (surgical removal of the emboli): An embolectomy may be useful for unstable patients with pulmonary embolism when other treatments fail. In surgical embolectomy, an operation is performed to cut open the heart or arteries where the clot is lodged. Catheter-directed pulmonary embolectomy involves inserting a catheter into the femoral or internal jugular vein and using fluoroscopic (x-ray) guidance to navigate into the pulmonary artery. Emboli are then extracted from the pulmonary bed using suction.

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