An embolism is an obstruction in a blood vessel due to a blood clot or otherforeign matter that gets stuck while traveling through the bloodstream. The plural of embolism is emboli.

Emboli have moved from the place where they were formed through the bloodstream to another part of the body, where they obstruct an artery and block the flow of blood. The emboli are usually formed from blood clots but are occasionally comprised of air, fat, or tumor tissue. Embolic events can be multiple and small, or single and massive. They can be life-threatening and require immediate emergency medical care. There are three general categories of emboli:arterial, gas, and pulmonary. Pulmonary emboli are the most common.

In arterial emboli, blood flow is blocked at the junction of major arteries,most often at the groin, knee, or thigh. Arterial emboli are generally a complication of heart disease. An arterial embolism in the brain (cerebral embolism) causes stroke, which can be fatal. An estimated 5-14% of all strokes arecaused by cerebral emboli. Arterial emboli to the extremities can lead to tissue death, and amputation of the affected limb if not treated effectively within hours. Intestines and kidneys can also suffer damage from emboli.

Gas emboli result from the compression of respiratory gases into the blood and other tissues due to rapid changes in environmental pressure, for example,while flying or scuba diving. As external pressure decreases, gases (like nitrogen) which are dissolved in the blood and other tissues become small bubbles that can block blood flow and cause organ damage.

In a pulmonary embolism, a common illness, blood flow is blocked at a pulmonary artery. When emboli block the main pulmonary artery, and in cases where there are no initial symptoms, a pulmonary embolism can quickly become fatal. According to the American Heart Association, an estimated 600,000 Americans develop pulmonary emboli annually and 60,000 die from it.

A pulmonary embolism is difficult to diagnose. Less than 10% of patients whodie from a pulmonary embolism were diagnosed with the condition. More than 90% of cases of pulmonary emboli are complications of deep vein thrombosis, blood clots in the deep vein of the leg or pelvis.

Arterial emboli are usually a complication of heart disease where blood clotsform in the heart's chambers. Gas emboli are caused by rapid changes in environmental pressure that could happen when flying or scuba diving. A pulmonaryembolism is caused by blood clots that travel through the blood stream to the lungs and block a pulmonary artery. More than 90% of the cases of pulmonaryembolism are a complication of deep vein thrombosis, which typically occursin patients who have had orthopedic surgery, in patients with cancer and other chronic illnesses like congestive heart failure.

Risk factors for arterial and pulmonary emboli include: prolonged bed rest, surgery, childbirth, heart attack, stroke, congestive heart failure, cancer, obesity, a broken hip or leg, oral contraceptives, sickle cell anemia, chest trauma, certain congenital heart defects, and old age. Risk factors for gas emboli include: scuba diving, amateur plane flight, exercise, injury, obesity,dehydration, excessive alcohol, colds, and medications such as narcotics andantihistamines.

Common symptoms of a pulmonary embolism include:

  • Labored breathing, sometimes accompanied by chest pain
  • A rapid pulse
  • A cough that may produce sputum
  • A low-grade fever
  • Fluid build-up in the lungs.

Less common symptoms include:

  • Coughing up blood
  • Pain caused by movement or breathing
  • Leg swelling
  • Bluish skin
  • Fainting
  • Swollen neckveins.

Symptoms of an arterial embolism include:

  • Severe pain in the area of the embolism
  • Pale, bluish cool skin
  • Numbness
  • Tingling
  • Muscular weakness or paralysis.

An embolism can be diagnosed through the patient's history, a physical exam,and diagnostic tests. For arterial emboli, cardiac ultrasound and/or arteriography are ordered. For a pulmonary embolism, a chest x ray, lung scan, pulmonary angiography, electrocardiography, arterial blood gas measurements, and venography or venous ultrasound could be ordered.

Patients with emboli require immediate hospitalization. They are generally treated with clot-dissolving and/or clot-preventing drugs. Thrombolytic therapyto dissolve blood clots is the definitive treatment for a very severe pulmonary embolism. Streptokinase, urokinase, and recombinant tissue plasminogen activator (TPA) are used. Heparin is the anticoagulant drug of choice for preventing formation of blood clots. Warfarin, an oral anticoagulant, is sometimes used concurrently and is usually continued after the hospitalization.

In the case of an arterial embolism, the affected limb is placed in a dependent position and kept warm. Embolectomy is the treatment of choice in the majority of early cases of arterial emboli in the extremities. In this procedure,a balloon-tipped catheter is inserted into the artery to remove thromboembolic matter.

With a pulmonary embolism, oxygen therapy is often used to maintain normal oxygen concentrations. For people who can't take anticoagulants and in some other cases, surgery may be needed to insert a device that filters blood returning to the heart and lungs.

Of patients hospitalized with an arterial embolism, 25-30% die, and 5-25% require amputation of a limb. About 10% of patients with a pulmonary embolism die suddenly within the first hour of onset of the condition. The outcome for all other patients is generally good; only 3% of patients die who are properlydiagnosed early and treated. In cases of an undiagnosed pulmonary embolism,about 30% of patients die.

Embolism can be prevented in high risk patients through antithrombotic drugssuch as heparin, venous interruption, gradient elastic stockings, and intermittent pneumatic compression of the legs. The combination of graduated compression stockings and low-dose heparin is significantly more effective than low-dose heparin alone.

Gradient elastic stockings, also called anti-embolism stockings, decrease therisk of blood clots by compressing superficial leg veins and forcing blood into the deep veins. They can be knee- thigh-, or waist-length. Many physicians order the use of stockings before surgery and until there is no longer an elevated risk of developing blood clots. The risk of deep vein thrombosis after surgery is reduced 50% with the use of these stockings. The American HeartAssociation recommends that the use of graduated compression stockings be considered for all high-risk surgical patients.

Intermittent pneumatic compression involves wrapping knee- or thigh-high cuffs around the legs to prevent blood clots. The cuffs are connected to a pump which inflates and deflates, mimicking the heart's normal pumping action and reducing the pooling of blood. Intermittent pneumatic compression can be usedduring surgery and recovery and continues until there is no longer an elevated risk of developing blood clots. The American Heart Association recommends the use of intermittent pneumatic compression for patients who cannot take anticoagulants, for example, spinal cord and brain trauma patients.

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