Air Embolism

Air embolism is a rare but potentially life-threatening medical condition that occurs when air bubbles enter the bloodstream, which can block the flow of blood to vital organs.^1,2 When an air bubble enters a vein, it is referred to as a venous air embolism, while an air bubble entering an artery is an arterial air embolism.¹

Epidemiology and Etiology of Air Embolism

Air embolism is a rare condition, estimated to occur in less than 1% of patients who undergo medical procedures associated with the development of air embolism.³ An analysis of 25 years of electronic medical records at a tertiary medical center identified 67 cases of air embolism over 25 years. The age of affected patients ranged from 3 years to 89 years, with a mean age of 59.¹ Almost all cases of air embolism (94%) occurred in a hospital, with 77.8% occurring during surgery or other invasive procedures, most often vascular access-related procedures (33%).

Air embolism is a result of a pressure gradient that allows air to enter the blood stream.^1,2 Although air embolism most commonly occurs with ambient air, it also can occur with gases such as nitrogen, helium, and carbon dioxide.³

Air embolism can occur in various settings, including during surgery, central line placement, hemodialysis, and diagnostic tests. Surgical procedures are a common source of air embolism, especially those involving the head, neck, chest, or abdomen.³ When central venous catheters are inserted into large veins (such as subclavian or jugular veins), there is a risk of introducing air into the vascular system. This can happen if the catheter is not properly primed or there are breaks or disconnections in the tubing.³

Patients undergoing hemodialysis can be at risk of air embolism due to issues with the dialysis machine or tubing, or due to improper handling of the access site. An air embolism can occur during intravenous (IV) therapy if air bubbles are inadvertently injected into the bloodstream through IV lines.

Other causes of air embolism are less common. Penetrating traumatic injuries, such as gunshot wounds, stab wounds, or accidents that puncture blood vessels, can introduce air into the bloodstream. ³ Rapid ascent while scuba diving can lead to decompression sickness, which includes the formation of nitrogen gas bubbles in the bloodstream.^1,3 Air embolism can occur during certain obstetric and gynecological procedures, such as cesarean delivery or hysteroscopy, if there is a breach in the uterine or vaginal wall.

Risk Factors for Air Embolism

Patients undergoing invasive procedures, such as catheterization, surgery, or dialysis, are at risk of developing an air embolism.⁴ Certain surgical positions, such as sitting or semi-sitting (Fowler position), can increase the risk of air embolism. Rapid changes in pressure, such as those encountered during scuba diving, can increase the risk of gas bubbles forming in the bloodstream. Individuals who use illicit drugs intravenously can introduce air into their veins.⁵ The presence of central venous catheters or other venous access devices increases the risk of air embolism, especially if they are not properly maintained.⁶

Prognosis

The prognosis for a patient with air embolism varies based on the size, quantity, and location of the emboli, and how quickly the condition is diagnosed and treated.

Smaller emboli may be less likely to cause severe symptoms or complications compared with larger ones.³ The end location of the air emboli in the vascular system affects the prognosis. If small air bubbles block small vessels, the prognosis is generally better than when large emboli block major blood vessels or critical organs such as the heart or brain.³

Early detection and rapid initiation of treatment are crucial in improving the prognosis for a patient with air embolism.¹ Prompt treatment often leads to a favorable outcome, but the prognosis is worse for a patient who develops a complication, such as cardiac arrest, stroke, or organ damage, as a result of the air embolism. Patients with underlying heart or lung disease may be at higher risk for severe complications. Untreated or severe cases of air embolism can be life-threatening.

Presentation of Air Embolism

The onset of symptoms of air embolism often is sudden and may occur during or shortly after medical procedures or activities that can introduce air into the circulation.³ Common early signs include dyspnea, chest pain, and coughing. These symptoms can resemble those of a pulmonary embolism or myocardial infarction.³ In some cases, air embolism can lead to cardiac-related symptoms such as right heart failure, decreased cardiac output, right ventricular ischemia, arrhythmia, or cardiac arrest if a large embolus obstructs blood flow to the heart.³

Depending on the end location of the emboli, a patient may develop neurological symptoms such as confusion, altered mental status, dizziness, weakness, seizures, or loss of consciousness. These symptoms can be similar to those seen in strokes or other neurological emergencies.³

Patients may also experience nonspecific symptoms such as nausea, vomiting, and anxiety.⁷

Diagnostic Workup of Air Embolism

The clinical evaluation begins with a thorough assessment of the patient’s symptoms, medical history, and the circumstances surrounding their presentation. Suspicion for air embolism should be high if symptoms developed during or after invasive medical procedures.⁸ Air embolism should be suspected when a patient experiences sudden onset respiratory distress (venous air embolism) and/or a neurological event (arterial embolism) in the setting of a known risk factor, such as catheter placement or removal.⁹

Physical examination of a patient with air embolism may reveal the following:

• Abnormal heart sounds, such as a mill wheel murmur or arrhythmias;
• Decreased blood pressure;
• Neurological deficits, such as weakness or paralysis;
• Signs of respiratory distress; and
• Altered mental status.

A chest X-ray, echocardiography, or computed tomography scan can be used to detect air emboli.⁸ A Doppler ultrasound can detect the presence of air in blood vessels and assess blood flow.⁸

Several medical conditions that may present with symptoms similar to those of air embolism should be included in the differential diagnosis:

• Acute coronary syndrome;
• Pulmonary embolism;
• Stroke;
• Transient ischemic attack;
• Myocardial infarction; and
• Hyperventilation.

Prevention and Management of Air Embolism

There are several steps clinicians can take to help minimize the likelihood of air embolism. During invasive line placement and removal, patients should be positioned to decrease the pressure gradient.⁴ When placing or removing a central venous catheter, the patient should be placed in the Trendelenburg position (lying down with the feet and legs raised above the heart) to raise the central venous pressure.² Avoid placing venous catheters during inspiration, when negative intrathoracic pressure is at its maximum.²

Patients should be instructed to perform the Valsalva maneuver during line removal.⁴ During invasive procedures, all tubing should be primed with saline and syringes checked to ensure no air is present.

If an air embolism is suspected, it should be considered a medical emergency requiring immediate intervention. The first priority is to identify and stop the source of the air entering the vascular system. The patient should be place in the Trendelenburg and left lateral decubitus position (Durant’s maneuver).^2,4 The goal of this positioning is to trap air in the right atrium and ventricle, in order to prevent or minimize entry of emboli into the right ventricular outflow tract and pulmonary artery.^3,4

Administering 100% high-flow oxygen is used to treat air embolism. This increases oxygen supply to tissues, helping to alleviate the effects of hypoxia caused by obstruction by the emboli, and reduces the size of the emboli by displacing nitrogen.⁷ To maximize end-organ oxygenation, high-flow oxygen is typically delivered through a non-rebreather mask.²

When available, hyperbaric oxygenation — administration of 100% oxygen in a chamber at a pressure 2 to 3 greater than sea level — should be provided because it is the definitive treatment for air embolism.^2,4,7 Hyperbaric oxygenation reduces the size of the emboli by minimizing and removing the nitrogen component of the emboli, improves tissue oxygenation, and reduces ischemic reperfusion injury.⁷ This treatment is most likely to be successful when administered immediately after air embolism is detected, but may be beneficial even after a significant delay.⁷

For certain patients, treatment of air embolism should include cardiopulmonary resuscitation, pharmacotherapy to address cardiovascular symptoms, and fluid resuscitation as required.²

Monitoring Patients Who Develop Air Embolism

Key monitoring parameters for patients who develop air embolism include the following:

• Blood pressure, heart rate, respiratory rate, and oxygen saturation;
• Electrocardiogram to detect cardiac arrhythmias or conduction abnormalities;
• Oxygen saturation to ensure adequate oxygen delivery to tissues; and
• Neurological assessments to detect changes in mental status, weakness, or paralysis.

Complications

Potential complications of air embolism can be categorized as follows^2,3,7:

• Neurological (seizures, facial droop, altered mental status, hemiparesis, hemiplegia);
• Pulmonary (pulmonary hypertension, pulmonary edema, lung damage); and
• Cardiovascular (arrhythmias, myocardial infarction, cardiovascular collapse).

References

1. McCarthy CJ, Behravesh S, Naidu S, Oklu R. Air embolism: Diagnosis, clinical management and outcomes. Diagnostics (Basel). 2017;7(1):5. doi:10.3390/diagnostics7010005

2. McCarthy CJ, Behravesh S, Naidu SG, Oklu R. Air embolism: Practical tips for prevention and treatment. J Clin Med. 2016;5(11):93. doi:10.3390/jcm5110093

3. Gordy S, Rowell S. Vascular air embolism. Int J Crit Illn Inj Sci. 2013;3(1):73. doi:10.4103/2229-5151.109428

4. Chuang DY, Sundararajan S, Sundararajan VA, Feldman DI, Xiong W. Accidental air embolism. Stroke. 2019;50(7):e183-e186. doi:10.1161/STROKEAHA.119.025340

5. Monroe EJ, Tailor TD, McNeeley MF, Lehnert BE. Needle embolism in intravenous drug abuse. Radiol Case Rep. 2015;7(3):714. doi:10.2484/rcr.v7i3.714

6. Wong SSM, Kwaan HC, Ing TS. Venous air embolism related to the use of central catheters revisited: With emphasis on dialysis catheters. Clin Kidney J. 2017;10(6):797-803. doi:10.1093/ckj/sfx064

7. Malik N, Claus P, Illman JE, et al. Air embolism: Diagnosis and management. Future Cardiol. 2017;13(4):365-378. doi:10.2217/fca-2017-0015

8. Mirski MA, Lele AV, Fitzsimmons L, Toung TJ. Diagnosis and treatment of vascular air embolism. Anesthesiology. 2007;106(1):164-177. doi:10.1097/00000542-200701000-000269.

9. Lanfranco J, Romero Legro I, Freire AX, Nearing K, Ratnakant S. Pulmonary air embolism: An infrequent complication in the radiology suite.Am J Case Rep. 2017;18:80-84. doi:10.12659/ajcr.901098