cerebral embolism


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Related to cerebral embolism: cerebral thrombosis, air embolism

embolism

 [em´bo-lizm]
the sudden blocking of an artery by a clot of foreign material (embolus) that has been brought to its site of lodgment by the blood current. The obstructing material is most often a blood clot, but it may be a fat globule, air bubble, piece of tissue, or clump of bacteria.
Symptoms. The symptoms of an embolism usually do not appear until the embolus lodges within a blood vessel and suddenly obstructs the blood flow; this usually occurs at divisions of an artery, where the vessel narrows. The signs of obstruction appear almost immediately with severe pain at the site. If the embolus lodges in a limb, the area becomes pale, numb, and cold to the touch, and normal arterial pulse below the site is absent. Fainting, nausea, vomiting, and eventually severe shock may occur if a large vessel is occluded. Unless the obstruction is relieved, gangrene of the adjacent tissues served by the affected vessel develops.
Prevention. Venous thrombosis is the most common predisposing cause of embolism, particularly when a thrombus lodges in a limb. In order to prevent the development of emboli it is necessary to avoid venous stasis in patients confined to bed because of surgery, illness, or injury. In addition to physical inactivity, heart failure and pressure on the veins of the legs and pelvis can inhibit blood flow and thus set the stage for inflammation, clot formation, and the possibility of embolism. Although frequent changing of position, exercise, and early ambulation are necessary to the prevention of thrombosis and embolism, sudden and extreme movements should be avoided. Under no circumstances should the legs be massaged to relieve “muscle cramps,” especially when the pain is located in the calf and the patient has not been up and about; pain in the calf may be symptomatic of a thrombosis. The occurrence of an air embolism can be avoided by careful handling of equipment used for intravenous therapy, correct technique in administering intramuscular injections, and intra-arterial monitoring.
cerebral embolism embolism of a cerebral artery, one of the three main causes of stroke syndrome.
pulmonary embolism (PE) obstruction of the pulmonary artery or one of its branches by an embolus. The embolus usually is a blood clot swept into circulation from a large peripheral vein, particularly a vein in the leg or pelvis. Factors that predispose a patient to this condition include: (1) stasis of blood flow, as in a patient who is on prolonged bed rest, is immobilized for some reason, or is aged, obese, or suffering from a burn; (2) venous injury, as from surgical procedures or trauma and fractures of the legs or pelvis; (3) predisposition to clot formation because of malignancy or use of oral contraceptives; (4) cardiovascular disease; (5) chronic lung disease; and (6) diabetes mellitus.

The effects of pulmonary embolism will depend on the size of the embolus and the amount of lung tissue involved. When an embolus becomes lodged in a pulmonary blood vessel, it prevents adequate blood supply to the lung, interferes with the exchange of oxygen and carbon dioxide, and results in arterial hypoxemia. As pressure within the obstructed pulmonary artery increases there is strain on the right ventricle and it may eventually fail. Two other complications are pulmonary infarct and pulmonary hemorrhage.

Signs and symptoms of pulmonary embolism vary greatly, depending on the extent to which the lung is involved, the size of the clot, and the general condition of the patient. Simple, uncomplicated embolism produces such cardiopulmonary symptoms as dyspnea, tachypnea, persistent cough, pleuritic pain, and hemoptysis. Apprehension is a common symptom. On rare occasions the cardiopulmonary symptoms may be acute, occurring suddenly and quickly producing cyanosis and shock.

Fibrinolytic therapy should be initiated as soon as possible for patients with massive or unstable pulmonary embolism. heparin will not dissolve existing clots but is a drug often used in treatment of the condition; it prolongs clotting time and allows the body time to resolve the existing clot. The drug most often used in the treatment of PE is heparin, which prolongs clotting time and allows the body time to resolve the existing clot.
Patient Care. Major goals in the care of patients at risk for pulmonary embolism are prevention and early detection. Those who are at risk and require diligent preventive measures and periodic monitoring are patients who have had surgery or cardiovascular disease associated with clot formation (such as after myocardial infarction or stroke), patients with multiple trauma, and those who are therapeutically immobilized.ƒ

Preventive measures include passive or active dorsiflexion of each foot at least ten times each hour; turning, coughing, and deep breathing after surgery; early ambulation whenever possible; and avoidance of pressure, such as propping pillows under the knees or bending the bed at the knees, that could produce venous stasis. Since patients receiving continuous intravenous therapy also are at risk for formation of clots and emboli, intravenous sites should be changed at frequent intervals.

Detection of pulmonary embolism in its earlier and more treatable stages demands constant vigilance for signs that a clot is forming or an embolus is in the blood stream. The more common signs of simple, uncomplicated embolism are listed above. Additionally, the patient is watched for increased jugular pressure, elevated pulse and heart rate, and friction rub. Eliciting Homans' sign (discomfort behind the knee on forced dorsiflexion of the foot), noting skin and temperature changes in the area of the calf, and assessing edema of the extremities are important monitoring activities in the care of patients at risk for pulmonary embolism.

cerebral embolism

n.
An obstruction in a cerebral artery by an embolus, usually resulting in transient or permanent impairment of cognitive, motor, or sensory function.

cerebral embolism

Etymology: L, cerebrum + embolos, plug
a condition in which an embolus blocks blood flow through the vessels of the cerebrum, resulting in tissue ischemia distal to the occlusion. See also cerebrovascular accident.

Cerebral embolism

A blockage of blood flow through a vessel in the brain by a blood clot that formed elsewhere in the body and traveled to the brain.
Mentioned in: Stroke

embolism

the sudden blocking of an artery by a clot of foreign material (embolus) that has been brought to its site of lodgment by the blood current. The obstructing material is most often a blood clot, but may be a fat globule, air bubble, piece of tissue, e.g. degenerated intervertebral disk, or clump of bacteria. It may therefore be the site of origin of a shower of microabscesses or a neoplastic metastasis. See also saddle thrombus, iliac artery thrombosis.

air embolism
air injected accidentally into veins which may cause temporary paralysis or dyspnea, or may be fatal if the embolism occurs in the heart or brain. It has been used as a method of performing euthanasia but is too uncertain and inhumane to be recommended.
cerebral embolism
embolism of a cerebral artery; one of the causes of cerebral vascular accident.
renal embolism
embolism in the kidney causes no observable clinical effect unless it involves a very large area, when toxemia may result and be followed by uremia.
References in periodicals archive ?
In a study of recurrent cerebral embolism in nonvalvular atrial fibrillation, Hart el al (14) reported a 20% recurrence rate of cerebral embolism within 11 days of the initial embolus in patients who had not undergone anticoagulant therapy.
Mitral annulus calcification has been cited as a possible source of cerebral embolism on the basis of anecdotal reports.
39) According to the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Data Bank, (40,41) features supportive of a cardiogenic source of cerebral embolism include history or presence of systemic embolism, abrupt onset, diminished level of consciousness at onset, visual field abnormalities, neglect, and aphasia.
Cerebral arteriography is often normal in patients with cerebral embolism.
Despite the intuitive appeal of PFO closure as a means to eliminate the risk of a paradoxical cerebral embolism, the apparent benefit of a surgical procedure will be reduced by surgical complications, incomplete efficacy of surgical closure, and the presence of false-positive diagnoses of paradoxical embolism.
Diffusion weighted MRI of the brain performed 3 hours after the procedure excluded cerebral embolism.
Neurosonix, based in Israel, is engaged in the development and commercialization of medical devices for the prevention of acute cerebral embolism during open-heart cardiac surgery as well as other invasive and minimally-invasive procedures.
Patients fitted with a Nonpulsatile LVAS are at a higher risk of cardiogenic cerebral embolisms and require anticoagulation therapy.