An embolism is an obstruction in a blood vessel due to a blood clot or other foreign 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 are caused 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) that 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 who die 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.
Causes and symptoms
Arterial emboli are usually a complication of heart disease where blood clots form in the heart's chambers. Gas emboli are caused by rapid changes in environmental pressure that could happen when flying or scuba diving. A pulmonary embolism 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 pulmonary embolism are a complication of deep vein thrombosis, which typically occurs in patients who have had orthopedic surgery
and patients with cancer
or 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
Symptoms of an arterial embolism include:
- severe pain in the area of the embolism
- pale, bluish cool skin
- muscular weakness or paralysis
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
- swollen neck veins
An embolism can be diagnosed through the patient's history, a physical exam, and diagnostic tests. The use of various tests may change, as physicians and clinical guidelines evaluate the most effective test in terms of accuracy and cost. 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.
Diagnosing an arterial embolism
Ultrasound uses sound waves to create an image of the heart, organs, or arteries. The technologist applies gel to a hand-held transducer, then presses it against the patient's body. The sound waves are converted into an image that can be displayed on a monitor. Performed in an outpatient diagnostic laboratory, the test takes 30-60 minutes.
An arteriogram is an x ray in which a contrast medium is injected to make the arteries visible. It can be performed in a radiology unit, outpatient clinic, or diagnostic center of a hospital.
Diagnosing a pulmonary embolism
A chest x ray can show fluid build-up and detect other respiratory diseases. The perfusion lung scan shows poor flow of blood in areas beyond blocked arteries. The patient inhales a small amount of radiopharmaceutical and pictures of airflow into the lungs are taken with a gamma camera. Then a different radiopharmaceutical is injected into an arm vein and lung blood flow is scanned. A normal result essentially rules out a pulmonary embolism. A lung scan can be performed in a hospital or an outpatient facility and takes about 45 minutes.
Pulmonary angiography is one of the most reliable tests for diagnosing a pulmonary embolism. Pulmonary angiography is a radiographic test that involves injection of a radio contrast agent to show the pulmonary arteries. A cinematic camera records the blood flow through the patient, who lies on a table. Pulmonary angiography is usually performed in a hospital's radiology department and takes 30-60 minutes.
An electrocardiograph shows the heart's electrical activity and helps distinguish a pulmonary embolism from a heart attack. Electrodes covered with conducting jelly are placed on the patient's chest, arms, and legs. Impulses of the heart's activity are traced on paper. The test takes about 10 minutes.
Arterial blood gas measurements are sometimes helpful but, alone, they are not diagnostic for pulmonary embolism. Blood is taken from an artery instead of a vein, usually in the wrist.
Venography is used to look for the most likely source of a pulmonary embolism, deep vein thrombosis. It is very accurate, but it is not used often, because it is painful, expensive, exposes the patient to a fairly high dose of radiation, and can cause complications. Venography identifies the location, extent, and degree of attachment of the blood clots and enables the condition of the deep leg veins to be assessed. A contrast solution is injected into a foot vein through a catheter. The physician observes the movement of the solution through the vein with a fluoroscope while a series of x rays are taken. Venography takes between 30-45 minutes and can be done in a physician's office, a laboratory, or a hospital. Radionuclide venography, in which a radioactive isotope is injected, is occasionally used, especially if a patient has had reactions to contrast solutions. Venous ultrasound is the preferred evaluation of leg veins.
As noninvasive methods such as high-speed computed tomography (CT) scanning improve, they may be used to diagnose emboli. For instance, spiral (also called helical) CT scans may be the preferred tool for diagnosing pulmonary embolism in pregnant women.
Patients with emboli require immediate hospitalization. They are generally treated with clot-dissolving and/or clot-preventing drugs. Thrombolytic therapy
to dissolve blood clots is the definitive treatment for a severe pulmonary embolism. Streptokinase, urokinase, and recombinant tissue plasminogen activator (TPA) are used. Heparin has been the anticoagulant drug of choice for preventing formation of blood clots. A new drug has been approved for treatment of acute pulmonary emboli. Called fondaparinux (Arixtra), it usually is administered with Warfarin, an oral anticoagulant. Warfarin is sometimes used with other drugs to treat acute embolism events and is usually continued after the hospitalization to help prevent future emboli. Arixtra also has been used on an ongoing basis to prevent pulmonary emboli.
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 properly diagnosed 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 drugs such 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 antiembolism stockings, decrease the risk 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 Heart Association 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 that inflates and deflates, mimicking the heart's normal pumping action and reducing the pooling of blood. Intermittent pneumatic compression can be used during 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.
Doyle, Nora M., et al. "Diagnosis of Pulmonary Embolism: A Cost-effective Analysis." American Journal of Obstetrics and Gynecology September 2004: 1019-1024.
Truelove, Christiane. "First for Pulmonary Embolism." Med Ad News August 2004: 82.
American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.
— Drugs that suppress, delay, or prevent blood clots. Anticoagulants are used to treat embolisms.
— A blood vessel that carries blood from the heart to other body tissues. Embolisms obstruct arteries.
Deep vein thrombosis
— A blood clot in the calf's deep vein. This frequently leads to pulmonary embolism if untreated.
— Clots or other substances that travel through the blood stream and get stuck in an artery, blocking circulation.
— Drugs that dissolve blood clots. Thrombolytics are used to treat embolisms.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
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.
. 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.
embolism of a cerebral artery, one of the three main causes of stroke syndrome
(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.
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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
embolism (em'bo-lizm) [ embolus + -ism]
Sudden obstruction of a blood vessel by debris. Blood clots, cholesterol-containing plaques, masses of bacteria, cancer cells, amniotic fluid, fat from the marrow of broken bones, and injected substances (e.g., air bubbles or particulate matter) all may lodge in blood vessels and obstruct the circulation.
Obstruction of a blood vessel caused by an air bubble.
Air may enter a vessel postoperatively, during intravenous injections, after failure to purge intravenous lines, or as a result of rupture of a central line balloon. NOTE: A very small amount of air in a vessel or intravenous tubing is not hazardous.
Symptoms include sudden onset of dyspnea, unequal breath sounds, hypotension, weak pulse, elevated central venous pressure, cyanosis, sharp chest pains, hemoptysis, a churning murmur over the precordium, and decreasing level of consciousness.
When an air or gas embolism is suspected in the systemic venous circulation, echocardiography should be used to confirm its presence. The suspected site of gas entry should be secured and flooded with normal saline to prevent entry of more gas into the circulation. One hundred percent oxygen should be administered to the patient by nonrebreather mask. The patient should be immediately repositioned with the right atrium above the gas entry site, so that air will be trapped there and not move into the pulmonary circulation or the right heart. A central venous catheter should be placed into the central venous circulation and any gas bubbles and air aspirated from the catheter. Intravenous fluids and inotropic medications may be needed to support blood pressure and pulse.
Prevention: All air should be purged from the tubing of all IV administration sets before hookup and when solution bags or bottles are changed; air elimination filters should be used close to the patient; infusion devices with air detection capability should be used, as well as locking tubing, locking connection devices, or taped connections. For central lines, to increase peripheral resistance and prevent air from entering the superior vena cava, the patient should be instructed to perform a Valsalva maneuver as the stylet is removed from the catheter, during attachment of the IV tubing, and when adapters or caps are changed on ports.
amniotic fluid embolism
The entry of amniotic fluid through a tear in the placental membranes into the maternal circulation. This rare event may occur at any gestational age, but most commonly during labor, delivery or in the immediate postpartum period. The contents of the fluid (e.g., shed fetal cells, meconium, lanugo, vernix) may produce pulmonary or cerebral emboli. Cardiac arrest and disseminated intravascular coagulation (DIC) commonly occur. Maternal death is a frequent complication
Chest pain, dyspnea, cyanosis, tachycardia, hemorrhage, hypotension, or shock are potential symptoms. Amniotic fluid embolism is frequently fatal.
Embolism due to injected drugs, debris, or talc, often resulting in pulmonary infarction.
fat embolism Abbreviation: FE
Embolism caused by globules of fat obstructing small blood vessels in the brain, lungs, and skin. It frequently occurs after fracture of long and pelvic bones or after orthopedic surgery and has been linked to episodes of acute pancreatitis, sickle-cell crisis, diabetes mellitus, osteomyelitis, and liposuction. Effects may be mild and undetected but can be severe, leading to acute respiratory distress syndrome, multiple organ dysfunction syndrome, or disseminated intravascular coagulation. Those most at risk for FE are males age 20 to 40 injured in serious motor vehicle accidents and elderly adults after hip fracture.
Findings often include agitation, restlessness, delirium, convulsions, coma, tachycardia, tachypnea, dyspnea, wheezing, blood-tinged sputum, and fever, esp. during the first 12 to 72 hr after injury or insult, when fat emboli are most likely to occur. Petechiae may appear on the buccal membranes, conjunctival sacs, and the chest and axillae in a vestlike distribution. Retinal hemorrhages may be seen on fundoscopic examination. If fat globules lodge in the kidneys, renal failure may occur. Laboratory values are nonspecific but may show hypoxemia, suddenly decreased hemoglobin and hematocrit levels, leukocytosis, thrombocytopenia, increased serum lipase, and fat globules in urine and/or sputum.
There is evidence that FE can be prevented when long bone fractures are immobilized immediately. Limited movement and gentle handling of any fractures before fixation may help prevent fat globule release. Patients at risk, i.e., those with fractures of long bones, severe soft tissue bruising, or fatty liver injury, are assessed for symptoms of fat embolism. Chest radiograph reports are reviewed for evidence of mottled lung fields and right ventricular dilation, and the patient's electrocardiogram is checked for large S waves in lead I, large Q waves in lead III, and right axis deviation.
The patient's respiratory and neurological status are monitored frequently for signs of hypoxemia. The treatment for the syndrome is nonspecific: good general supportive care of fluid balance, vital signs, oxygenation, electrolytes, and hemodynamics. The patient is placed in the high Fowler's, orthopneic, or other comfortable position to improve ventilation; high-concentration oxygen is administered, and endotracheal intubation and mechanical ventilation are initiated if the patient cannot maintain a PaO2 of 60 mm Hg on 40% oxygen by face mask. Positive and end-expiratory pressure may be used to keep functional alveoli inflated to improve functional reserve capacity. IV fluid administration helps prevent shock. Deep breathing exercises and incentive spirometry to open and stabilize atelectatic lung areas may improve lung capacity and ventilation. Prescribed pharmacological agents are administered; these may include steroids, heparin, and anxiolytic agents such as diazepam.
Embolism arising from the venous circulation that enters the arterial circulation by crossing from the right side of the heart to the left side through a patent foramen ovale or septal defect. It may occasionally cause stroke in a patient with a deep venous thrombosis.
PULMONARY EMBOLISM: Septic pulmonary emboli seen in plain chest x-ray
pulmonary embolism Abbreviation: PE
Embolism of the pulmonary artery or one of its branches, usually caused by an embolus from a blood clot in a lower extremity. Roughly 10% to 15% of patients with the disease will die. Risks for it include genetic predisposition, recent limb or pelvic fracture, burns, surgery (esp. hip or knee replacement), long-term immobility, enforced immobilization (long car or plane trips or hospitalization), pregnancy, use of estrogen-containing hormonal contraceptives, postmenopausal hormones, atrial fibrillation, vascular injury, IV drug abuse, polycythemia vera, heart failure, autoimmune hemolytic anemia, sickle cell anemia, thrombocytosis, dehydration, , advanced age, cancer, and obesity. Diagnosis is challenging because symptoms are nonspecific and often misinterpreted and may mimic other diseases of the limbs, abdomen, or chest. It is often assumed that a sudden, unexpected death occurring after a hospitalization was caused by an unsuspected PE, which is the third most common cause of death in the U.S. When a pulmonary embolism is suspected, evaluation includes oximetry, chest x-ray, blood tests for D-dimer, and, depending on local hospital practices, duplex venous ultrasonography of the legs, ventilation/perfusion scanning, or multidetector CT angiography of the chest. Pulmonary angiography was formerly the standard test but is now rarely performed because it is invasive, poses risk to the patient, and requires angiographic skill and excellent radiographic equipment. Treatment includes the administration of anticoagulants (low molecular weight heparins or unfractionated heparins, followed by oral warfarin). Oxygen is administered as prescribed by nasal cannula or mask. In critically ill patients, intubation and mechanical ventilation may be required. Thrombolytic drugs may be needed for massive emboli, i.e., those that cause shock or that impair the filling of the right atrium and ventricle with blood. Thrombolectomy may be attempted in critically ill patients when a competent surgical team is available. See: illustration
; thrombosis, deep venous
In the hospitalized patient, early mobilization, administration of prophylactic anticoagulants, and compression stockings (elastic or pneumatic) may prevent deep venous thrombosis (DVT). Vital signs, oxygen saturation, respiratory effort, breath sounds, cardiac rhythm, and urinary output are monitored closely in affected patients. Signs of deterioration are promptly reported. The nurse assists with diagnostic studies and medical treatment and provides explanations of procedures and treatments, analgesics for pain, prescribed medications, supplemental oxygen, patient education, and emotional support. Once the pain is stable, the patient is encouraged to resume normal activities. After a pulmonary embolism most patients remain on anticoagulant therapy for at least 6 months. The patient is taught about taking the medication dosage precisely as prescribed, bleeding signs to be reported, avoidance of over-the-counter and prescription drugs that may influence anticoagulation, regulation of foods high in vitamins, and the need for frequent blood tests to ensure appropriate levels of anticoagulation. See: International Normalized Ratio.
In patients who cannot use anticoagulants, a filtering device may be inserted transvenously into the vena cava to try to prevent blood clots from embolizing from the legs to the heart and lungs.
pyemic embolismSeptic embolism.
An embolism made up of purulent matter that arises from the site of an infection caused by a pyogenic (pus-forming) organism. It can result in the spread of infection to a distant site. Synonym: pyemic embolism
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