EMBOLISM

obstruction of the flow of blood by an embolus, a particle or aggregate of substance that is abnormally present in the bloodstream. The substance may be a blood clot that has broken loose from its point of formation (while it is still adherent to the vessel at the point where it was formed, the clot is called a thrombus); it may be a drop of oil from a crushing injury of fatty tissue, a clump of cancer cells, of bacteria, or of detached tissue cells; it may be a foreign body such as a bullet, which has penetrated a vessel wall; or it may be even an air bubble (called an air embolism) or a bubble of some other gase.g., nitrogen in decompression sickness. So long as the embolus travels unimpeded through the bloodstream, it is not likely to cause symptoms or damage. Trouble develops when the substance becomes wedged in a channel, usually an arterial branch, and blocks the flow of blood. Obstruction of a vessel that supplies blood to the brain may cause a stroke, with effects that include a period of unconsciousness, temporary or lasting paralysis of all or part of one side of the body, inability to use words (aphasia), impaired memory, and in severe cases, death. When there is a pulmonary embolisman obstruction of blood flow to the lungs by an embolus in the pulmonary artery or in one of its branchesthe affected person has difficulty breathing and experiences an unpleasant sensation beneath the breastbone, a feeling like that experienced in angina pectoris. When the blockage causes a section of lung tissue to die (this is called a pulmonary infarction), the affected person becomes feverish, and his heart beats rapidly. The physician attending him notes abnormal chest sounds, an increased number of white cells in the blood, and abnormalities in the chemical composition of the blood (a rise in bilirubin and in certain enzymes). Treatment includes administration of drugs to relieve pain, an anticoagulant to help prevent recurrence due to blood clot formation, and oxygen to aid breathing; fluid intake is reduced, and antibiotics are used to combat or prevent infection. Embolism in a coronary artery, which supplies blood to the heart muscle, can cause a number of serious effects, including death of a section of the heart muscle (myocardial infarction). See also thrombosis.