air embolism

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Related to gas embolus: nitrogen embolism

air em·bo·lism

an embolism caused by air bubbles in the vascular system; venous air embolism can result from the introduction of air through intravenous lines, especially central lines, and generally must be substantial to block pulmonary blood flow and cause symptoms; arterial air embolism is also usually iatrogenic, caused by cardiopulmonary bypass or other intravascular interventions, occurs rarely after penetrating lung injury; small amounts of arterial air can cause death by blockage of coronary and/or cerebral arteries; small bubbles introduced into the venous system may similarly cause symptoms if they reach the arterial side. Compare: paradoxical embolism.
Synonym(s): gas embolism
Farlex Partner Medical Dictionary © Farlex 2012

air embolism

The presence of gas in blood vessels, which is most significant in the coronary and cerebral arteries. An estimated 100 cc of gas (air) may suffice to cause death, as it blocks blood flow, not unlike a vapour lock in a hydraulic system. To document AE at autopsy, the organ must be opened underwater to detect bubbling.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

transfusion reaction

Blood transfusion reaction, incompatibility reaction Transfusion medicine Any untoward response to the transfusion of non-self blood products, in particular RBCs, which evokes febrile reactions that are either minor–occurring in 1:40 transfusions and attributed to nonspecific leukocyte-derived pyrogens, or major–occurring in 1:3000 transfusions and caused by a true immune reaction, which is graded according to the presence of urticaria, itching, chills, fever and, if the reaction is intense, collapse, cyanosis, chest and/or back pain and diffuse hemorrhage Note: If any of above signs appear in a transfusion reaction, or if the temperature rises 1ºC, the transfusion must be stopped; most Pts survive if < 200 ml has been transfused in cases of red cell incompatibility-induced transfusion reaction; over 50% die when 500 ml or more has been transfused; TF mortality is ± 1.13/105 transfusions Clinical Flank pain, fever, chills, bloody urine, rash, hypotension, vertigo, fainting
Transfusion reactions
Immune, non-infectious transfusion reactions  
• Allergic Urticaria with immediate hypersensitivity
• Anaphylaxis Spontaneous anti-IgA antibody formation, occurs in ± 1:30 of Pts with immunoglobulin A deficiency, which affects 1:600 of the general population–total frequency: 1/30 X 1/600 = 1/18,000
• Antibodies to red cell antigens, eg antibodies to ABH, Ii, MNSs, P1, HLA
• Serum sickness Antibodies to donor's immunoglobulins and proteins
Non-immune, non-infectious transfusion reactions  
• Air embolism A problem of historic interest that occurred when air vents were included in transfusion sets
• Anticoagulant Citrate anticoagulant may cause tremors and EKG changes
• Coagulation defects Depletion of factors VIII and V; this 'dilutional' effect requires massive transfusion of 10 + units before becoming significant
• Cold blood In ultra-emergent situations, blood stored at 4º C may be tranfused prior to reaching body temperature at 37º C; warming a unit of blood from 4 to 37º C requires 30 kcal/L of energy, consumed as glucose; cold blood slows metabolism, exacerbates lactic acidosis, ↓ available calcium, ↑ hemoglobin's affinity for O2 and causes K+ leakage, a major concern in cold hemoglobinuria
• Hemolysis A phenomenon due to blood collection trauma, a clinically insignificant problem
• Hyperammonemia and lactic acid Both molecules accumulate during packed red cell storage and when transfused, require hepatorenal clearance, of concern in Pts with hepatic or renal dysfunction, who should receive the freshest units possible
• Hyperkalemia Hemolysis causes an ↑ of 1 mmol/L/day of potassium in a unit of stored blood, of concern in Pts with poor renal function, potentially causing arrhythmia
• Iron overload Each unit of packed RBCs has 250 mg iron, potentially causing hemosiderosis in multi-transfused Pts
Microaggregates Sludged debris in the pulmonary vasculature causing ARDS may be removed with micropore filters
Pseudoreaction Transfusion reaction mimics, eg anxiety, anaphylaxis related to a drug being administered at the same time as the transfusion
Infections transmitted by blood transfusion
• Viruses B19, CMV, EBV, HAV, HBV, HCV, HDV, HEV, Creutzfeldt-Jakob disease, Colorado tick fever, tropical viruses–eg Rift Valley fever, Ebola, Lassa, dengue, HHV 6, HIV-1, HIV-2, HTLV-I, HTLV-II
• Bacteria Transmission of bacterial infections from an infected donor is uncommon and includes brucellosis and syphilis in older reports; more recent reports include Lyme disease and Yersinia enterocolitica  Note: Although virtually any bacteria could in theory be transmitted in blood, the usual cause is contamination during processing rather than transmission from an infected donor
• Parasites Babesiosis, Leishmania donovani, L tropica, malaria, microfilariasis–Brugia malayi, Loa loa, Mansonella perstans, Mansonella ozzardi, Toxoplasma gondii, Trypanosoma cruzi
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

air em·bo·lism

(ār em'bŏ-lizm)
Embolism that occurs when air enters a blood vessel, usually a vein, as a result of trauma, surgery, or deliberate injection; a large air embolism can cause lethal derangement of cardiac function.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

air embolism

Bubbles of air in the circulating blood, which cause blockage of small arteries, thereby cutting off supply to important areas, such as parts of the brain.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Air Embolism

DRG Category:175
Mean LOS:6.6 days
Description:MEDICAL: Pulmonary Embolism with Major CC

An air embolism is an obstruction in a vein or artery caused by a bubble of gas. Air enters the circulatory system when the pressure gradient favors movement of air or gas from the environment into the blood. A venous air embolism is the most common form of air embolism. It occurs when air enters the venous circulation, passes through the right side of the heart, and then proceeds to the lungs. In relatively small amounts, the lungs can filter the air; it is absorbed without complications. When large amounts of air (80 to 100 mL) are introduced into the body, however, the lungs no longer have the capacity to filter the air, and the patient has serious or even lethal complications. One of the most serious complications is when the large air bubble blocks the outflow of blood from the right ventricle into the lungs, preventing the blood from moving forward. The patient develops cardiogenic shock because of insufficient cardiac output. Experts have found that the risk from air embolism increases as both the volume and the speed of air injection increase.

An arterial embolism occurs when air gains entry into the pulmonary venous circulation and then passes through the heart and into the systemic arterial circulation. An arterial embolism can also form in the patient who has a venous embolism and a right-to-left shunt (often caused by a septal defect in the heart) so that the air bubble moves into the left ventricle without passing through the lungs. Pulmonary capillary shunts can produce the same effect. The arterial embolism may cause serious or even lethal complications in the brain and heart. Scientists have found that as little as 0.05 mL of air in the coronary arteries can cause death.


The two major causes of air embolism are iatrogenic and environmental. Iatrogenic complications are those that occur as a result of a diagnostic or therapeutic procedure. Situations in which iatrogenic injury is a possibility include insertion, maintenance, or removal of the central line. The risk is highest during catheter insertion because the large-bore needle, which is in the vein, is at the hub while the catheter is threaded into the vein. The frequency of clinically recognized venous air embolism following central line insertion is less than 2%, but in that setting, it has a mortality rate as high as 30%. In addition, air can be pulled into the circulation whenever the catheter is disconnected for a tubing change or the catheter tubing system is accidentally disconnected or broken. When the catheter is removed, air can also enter the fibrin tract that was caused by the catheter during the brief period between removal and sealing of the tract. Other procedures that can lead to air embolism are cardiac catheterization, coronary arteriography, transcutaneous angioplasty, embolectomy, and hemodialysis. Some surgical procedures also place the patient at particular risk, including orthopedic, urological, gynecological, open heart, and brain surgery, particularly when the procedure is performed with the patient in an upright position. Conditions such as multiple trauma, placenta previa, and pneumoperitoneum have also been associated with air embolism.

Environmental causes occur when a person is exposed to atmospheric pressures that are markedly different from atmospheric pressure at sea level. Two such examples are deep-sea diving (scuba diving) and high-altitude flying. Excessive pressures force nitrogen, which is not absorbable, into body tissues and the circulation. Nitrogen accumulates in the extracellular spaces, forms bubbles, and enters into the bloodstream as emboli.

Genetic considerations

No clear genetic contributions to susceptibility have been defined.

Gender, ethnic/racial, and life span considerations

An air embolism can occur with either gender and at any age if the individual is placed at risk for either an iatrogenic or an environmental cause. Ethnicity and race have no known effects on the risk for air embolism.

Global health considerations

No data are available.



The patient may have been scuba diving or flying at the onset of symptoms. Usually patients who develop an iatrogenic air embolism are under the care of the healthcare team, who assesses the signs and symptoms of air embolism as a complication of treatment. Some patients have a gasp or cough when the initial infusion of air moves into the pulmonary circulation. Suspect an air embolism immediately when a patient becomes symptomatic following insertion, maintenance, or removal of a central access catheter. Patients suddenly become dyspneic, dizzy, nauseated, confused, and anxious, and they may complain of substernal chest pain. Some patients describe the feeling of “impending doom.”

Physical examination

On inspection, the patient may appear in acute distress with cyanosis, jugular neck vein distension, or even seizures and unresponsiveness. Some reports explain that more than 40% of patients with an air embolism have central nervous system effects, such as altered mental status or coma. When auscultating the patient’s heart, listen for a “mill-wheel murmur” produced by air bubbles in the right ventricle and heard throughout the cardiac cycle. The murmur may be loud enough to be heard without a stethoscope but is only temporarily audible and is usually a late sign. More common than the mill-wheel murmur is a harsh systolic murmur or normal heart sounds. Most patients have a rapid apical pulse and low blood pressure. You may also hear wheezing from acute bronchospasm. The patient may have increased central venous pressure, pulmonary artery pressures, increased systemic vascular resistance, and decreased cardiac output.


Most patients respond with fear, confusion, and anxiety. The family or significant others are understandably upset as well. Evaluate the patient’s and family’s ability to cope with the crisis and provide the appropriate support.

Diagnostic highlights

TestNormal ResultAbnormality With ConditionExplanation
Arterial blood gasesPao2 80–100 mm Hg; Paco2 35–45 mm Hg; SaO2 > 95%Pao2 < 80 mm Hg; Paco2 varies; SaO2 < 95%Poor gas exchange leads to hypoxemia and hypercapnea from dead-space ventilation

Other Tests: Supporting tests include electrocardiogram, chest x-ray, transthoracic or transesophageal echocardiography, and precordial Doppler.

Primary nursing diagnosis


Decreased cardiac output related to blocked left ventricular filling


Cardiac pump effectiveness; Circulation status; Tissue perfusion: Cerebral, Peripheral, Cardiac


Cardiac care; Circulatory care; Shock management; Hemodynamic regulation

Planning and implementation


Several strategies can help prevent development of air embolism. First, maintain the patient’s level of hydration because dehydration predisposes the patient to decreased venous pressures. Second, some clinicians recommend that you position the patient in Trendelenburg’s position during central line insertion because the position increases central venous pressure. Third, instruct the patient to perform Valsalva’s maneuver on exhalation during central line insertion or removal to increase intrathoracic pressure and thereby increase central venous pressure.

Prime all tubings with intravenous fluid prior to connecting the system to the catheter. Immediately apply an occlusive pressure dressing after catheter removal and maintain the site with an occlusive dressing for at least 24 hours. To prevent air embolism during surgical procedures, the surgeon floods the surgical field with liquid in some situations so that liquid rather than air enters the circulation.

If an air embolus occurs, the first efforts are focused on preventing more air from entering the circulation. Any central line procedure that is in progress should be immediately terminated with the line clamped. The catheter should not be removed unless it cannot be clamped. Place the patient on 100% oxygen immediately to facilitate the washout of nitrogen from the bubble of atmospheric gas. Place the patient in the left lateral decubitus position. This position allows the obstructing air bubble in the pulmonary outflow tract to float toward the apex of the right ventricle, which relieves the obstruction. Use Trendelenburg’s position to relieve the obstruction caused by air bubbles. Other suggested strategies are to aspirate the air from the right atrium, to use closed-chest cardiac compressions, and to administer fluids to maintain vascular volume. Hyperbaric oxygen therapy may improve the patient’s condition as well: This therapy increases nitrogen washout in the air bubble, thereby reducing the bubble’s size and the absorption of air. Note that if the patient has to be transferred to a hyperbaric facility, the decrease in atmospheric pressure that occurs at high altitudes during fixed-wing or helicopter transport may worsen the patient’s condition because of bubble enlargement or “bubble explosion.” Ground transport or transport in a low-flying helicopter is recommended, along with administering 100% oxygen and adequate hydration during transport.

Pharmacologic highlights


If the patient suddenly develops the symptoms of an air embolism, place the patient on the left side with the head of the bed down to allow the air to float out of the outflow track. Notify the physician immediately and position the resuscitation cart in close proximity. Initiate 100% oxygen via a nonrebreather mask immediately before the physician arrives according to unit policy. Be prepared for a sudden deterioration in cardiopulmonary status and potential for cardiac arrest.

The patient and family need a great deal of support. Remain in the patient’s room at all times, and if the patient finds touch reassuring, hold the patient’s hand. Provide an ongoing summary of the patient’s condition to the family. Expect the patient to be extremely frightened and the family to be anxious or even angry. Ask the chaplain, clinical nurse specialist, nursing supervisor, or social worker to remain with the family during the period of crisis.

Evidence-Based Practice and Health Policy

Austin, L.S., VanBeek, C., & Williams, G.R. (2013). Venous air embolism: An under-recognized and potentially catastrophic complication in orthopaedic surgery. Journal of Shoulder and Elbow Surgery, 22(10), 1449–1454.

  • Identification of air embolism requires hypervigilance since the clinical presentation can vary widely relative to a number of factors, such as the volume of air that is introduced, the rate at which the air enters the heart, and whether the patient is conscious and breathing independently.
  • The possibility for air embolism is increased during surgical procedures. For example, factors that increase the risk for air embolism during orthopedic surgery include exposure of venous sinusoids to gas as a result of gas arthroscopy, negative pressure gradients between the surgical site and the right atrium due to patient positioning, hypovolemia, or hypotensive anesthesia.
  • Recommendations to prevent air embolism in orthopedic surgical patients include increasing the right atrial pressure by elevating the lower extremities, maintaining adequate hydration and blood pressure during surgery, and eliminating the introduction of air into closed pump systems and arthroscopic tubing.
  • Recommendations if an air embolism is suspected include flooding the surgical site with saline, placing moist sponges over all exposed venous sinusoids and cancellous bone, and discontinuing nitrous oxide immediately to reduce enlargement of any air bubbles.

Documentation guidelines

  • Physical findings: Changes in vital signs, cardiopulmonary assessment, skin color, capillary blanch, level of activity, changes in level of consciousness
  • Pain: Location, duration, precipitating factors, response to interventions
  • Responses to interventions: Positioning, oxygen, hyperbaric oxygen, evacuation of air, cardiopulmonary resuscitation
  • Development of complications: Seizures, cardiac arrest, severe anxiety, ineffective patient or family coping

Discharge and home healthcare guidelines

Instruct the patient to report any signs of complications. Make sure that the patient and family are aware of the next follow-up visit with the healthcare provider. If the patient is being discharged with central intravenous access, make sure that the caregiver understands the risk of air embolism and can describe all preventive strategies to limit the risk of air embolism.

Diseases and Disorders, © 2011 Farlex and Partners

air em·bo·lism

(ār em'bŏ-lizm)
Obstruction that occurs when air enters a blood vessel, usually a vein, as a result of trauma, surgery, or deliberate injection; a large air embolism can cause lethal derangement of cardiac function.
Medical Dictionary for the Dental Professions © Farlex 2012