Air Embolism
Synonyms
Venous Air Embolism, Arterial Air Embolism
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Related Condition
Vascular Air Embolism
1. Description of the problem
Definition
Air embolism is the insertion of air in either the venous or arterial circulation. It can be a complication of venous or arterial catheterization, a complication of surgery or secondary to trauma.
Clinical features
Hypoxia
Tachycardia
Hypotension
Mental status change
Cardiac arrest
Prevention: Trendelenburg position, adequate volume status (avoid dehydration)
2. Emergency Management
Provide 100% supplemental oxygen.
Consider positioning the patient in left lateral decubitus and slightly Trendelenburg, to try to move the air towards the right ventricular apex and allow it to dissipate over time.
If neurologic symptoms are present, then consider, in consultation with a hyperbaric specialist, transferring the patient to a facility with hyperbaric oxygen capabilities.
If a central catheter is already in place, you can consider attempting to aspirate air from the right atrium.
3. Diagnosis
The right clinical scenario: Surgery (especially upright neurosurgery), vascular catheter placement/removal or diving (especially in setting of lung disease and air travel).
Clinical symptoms, including shortness of breath, cough, hypotension, cardiovascular collapse, mental status change, seizure or focal neurologic deficit, develop rapidly or immediately following a surgical or vascular procedure.
Transthoracic echocardiogram: may see air; detect right heart strain, diagnose a patent foramen ovale (which places patients at increased risk for cerebral air embolism)
In OR: precordial Doppler ultrasound
Non-contrast chest CT may detect PTX or subcutaneous emphysema.
Infrequently, air in central vasculature can be seen on chest x-ray if the volume of air is large enough and centrally located.
EKG (nonspecific): ST elevation, tachyarrhythmias
Head CT: If neurologic deficits
The presence of acute hypoxia, tachycardia and/or hypotension in a relevant clinical scenario is concerning for air embolism. This may occur with insertion or removal of a central venous catheter, particularly when the patient inspires. Other surgical procedures in which multiple vessels are exposed to air may place a patient at risk. It can also be seen during neurosurgery (especially if the patient is positioned in an upright position) and the surgery is being done far enough above the heart such that the central venous pressure is not high enough to prevent air entry into the vasculature. Cesarean sections tend to also be higher-risk procedures. Finally, laparoscopic procedures that involve the insertion of air into a body cavity also run the risk of causing an air embolism.
4. Specific Treatment
Deliver 100% supplemental oxygen.
Position the patient to prevent right ventricular tract obstruction (left lateral decubitus and Trendelenburg).
If patient is stable for transfer and neurologic manifestations are present, consider hyperbaric oxygen treatment.
Support hemodynamics. If patient is in shock related to air embolism it is likely due to right heart failure. Pressors should be chosen accordingly (dobutamine, etc.). If cardiac arrest occurs CPR may facilitate movement of the obstructive air bubble.
For arterial air embolism during a cardiac catheterization, the main concern is that the air bubble will travel down a coronary artery and get stuck and cause distal ischemia. The treatment of choice in these cases is to continuously flush the coronary artery with saline and try to flush the air bubble out. Cardiac ischemia and ventricular fibrillation can be rare complications if not treated emergently.
5. Disease monitoring, follow-up and disposition
In the great majority of cases, venous air embolisms spontaneously resolve. Temporary supportive measures such as supplemental oxygen and patient positioning allow the air to dissipate and not cause any permanent damage.
Arterial air embolism can cause myocardial ischemia, stroke or distal limb and/or organ ischemia depending on which vessel is affected. In these rare cases, long-term follow-up should be determined by the side affected.
Air embolism that is of hemodynamic significance is a rare occurrence. If the symptoms of tachycardia, hypotension, and hypoxia do not resolve in a few minutes to an hour or if there is no definite evidence of air on either echo or radiologic imaging, further workup to look for other causes of hemodynamic instability should be done.
Patients should be monitored closely, but there is no consensus on how long a patient should be watched after an event once the symptoms have dissipated. Hyperbaric treatments may be repeated several times and only terminated after no additional clinical improvement is observed.
Pathophysiology
An air embolism can cause obstruction in small or large vessels and the extent of injury is related to the quantity of air and how quickly the air enters the vessel. This can be life-threatening when the air bubble is large enough to obstruct blood flow on the right side of the heart. Often, however, this may be a subclinical event, with no significant detriment as the lungs are able to filter out the air bubble. If a patent foramen ovale is present, this may lead to a venous embolism entering the arterial circulation with the potential to interrupt cerebral blood flow, which may result in CVA-like symptoms.
In addition to vessel obstruction, an air embolism can cause damage to the endothelial cells that make up the blood vessel walls. This injury may result in the release of cytokines that enhance capillary leakiness both systemically and in the lungs. The former may result in SIRS and the latter in pulmonary edema.
Epidemiology
Occurs particularly in patients undergoing medical or surgical procedures, particularly those in a sitting position (neurosurgical) or where vasculature is exposed to air or manipulated or requiring air insufflation (laparoscopic procedures). An increased incidence is also reported in cesarean deliveries and neck and hip surgeries. It is reported much less commonly in procedures such as percutaneous biopsy of the chest, ERCP, cardiac surgery or in lumbar punctures.
Prognosis
The prognosis in air embolism is largely dependent on the rate and volume of air entrained into the circulation and the patient’s underlying comorbidities. Overall mortality ranges from 50%-80%.
Special considerations for nursing and allied health professionals.
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What's the evidence?
Mirski, M.A.. “Diagnosis and treatment of vascular air embolism”. Anesthesiology. vol. 106. 2007. pp. 164-77.
Vann, R.D.. “Decompression sickness”. Lancet. vol. 377. 2010. pp. 153-64.
Kapoor, T.. “Air embolism as a cause of systemic inflammatory response syndrome: A case report”. Critical Care. vol. 7. 2003. pp. R98-100.
Wu, C.C.. “Complications of CT-guided percutaneous needle biopsy of the chest: Prevention and management”. AJR. vol. 196. 2011. pp. W678-82.
Gibson, A.J., Davis, F.M.. “Hyperbaric oxygen in the treatment of post cardiac surgical strokes — a case series and review of the literature”. Anesth Intensive Care. vol. 38. 2010. pp. 175-84.
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