Makindo Medical Notes

Air Embolism occurs when air bubbles enter the bloodstream, obstructing blood flow. Air can be introduced during surgeries, medical procedures, trauma, or diving accidents, causing blockages in arteries or veins. The severity of the condition depends on the volume of air and the site of obstruction, potentially leading to life-threatening complications. Positioning the patient: Place the patient head down and left side down (left lateral decubitus position) to help trap air in the apex of the right ventricle, where it can be more slowly reabsorbed.

About Air Embolism

• Mechanism: Air is introduced into the venous or arterial circulation, potentially traveling to the heart or lungs, causing blockages and leading to impaired circulation.
• Venous Air Embolism (VAE): Air enters the venous system, reaches the right side of the heart, and may block pulmonary arteries, leading to respiratory distress and decreased oxygenation.
• Divers and Decompression: In divers, rapid ascent without proper decompression can cause nitrogen gas bubbles in the bloodstream, resulting in decompression sickness or "the bends," which can present similarly to air embolism.
• Severity: The severity of an air embolism depends on the volume of air and its location. Even small amounts of air can cause serious complications if trapped in critical areas such as the coronary or cerebral arteries.

Pathophysiology

• Air can enter the venous circulation through a pressure gradient, where a low-pressure area in the veins allows air to be sucked in, such as during surgery or trauma.
• Venous air embolism is more common when the air entry site is elevated above the level of the right atrium, creating a negative pressure gradient.
• In arterial air embolism, air can travel from the lungs or directly enter the arterial system, posing a risk of blockage in critical organs like the brain or heart.

Causes

• Surgical Procedures: Air may enter the bloodstream during surgeries involving the chest, brain, or during the insertion and removal of central venous catheters.
• Trauma: Chest trauma, penetrating injuries, or fractures can create an entry point for air into the veins, particularly when major veins are involved.
• Intravascular Catheters: Improper insertion, handling, or removal of central lines or catheters can introduce air into the venous system.
• Diving Accidents: Rapid ascent during scuba diving can cause nitrogen gas to form bubbles in the bloodstream (decompression sickness), but severe cases can also result in an air embolism.
• Positive Pressure Ventilation: In mechanically ventilated patients, air can enter the bloodstream if there is an abnormal communication between the airways and blood vessels.

Types of Air Embolism

• Venous Air Embolism (VAE): Air enters the veins, reaching the right side of the heart, where it can obstruct blood flow to the lungs and cause pulmonary complications, including acute respiratory distress.
• Arterial Air Embolism (AAE): Air enters the arterial system directly, potentially traveling to the brain, heart, or other vital organs, leading to strokes, myocardial infarctions, or other critical events.

Clinical Signs

• Difficulty breathing (dyspnea), hypoxia, or cyanosis
• Sudden onset of chest pain
• Neurological symptoms such as dizziness, confusion, or focal deficits
• Low blood pressure (hypotension) or shock
• Seizures or altered level of consciousness
• Cardiac arrest in severe cases

Investigations

• Arterial Blood Gas (ABG): May show hypoxia, hypercarbia, or metabolic acidosis.
• ECG: Can show signs of right heart strain, tachycardia, or ischemic changes like ST segment deviations.
• Chest X-ray (CXR): May show signs of air in the pulmonary arteries (pulmonary oligaemia) or help rule out other causes.
• Transesophageal Echocardiography (TEE): Can visualize air bubbles in the heart or major vessels in severe cases.

Differential Diagnosis

• Pulmonary embolism (PE)
• Stroke or transient ischemic attack (TIA)
• Myocardial infarction (MI)
• Tension pneumothorax
• Traumatic cardiac tamponade

Complications

• Cardiac Arrest: Air emboli can cause obstructive shock by blocking blood flow through the heart, leading to cardiac arrest.
• Myocardial Infarction: Air can obstruct coronary arteries, causing ischaemia and infarction of cardiac tissue.
• Anoxic Brain Injury: Prolonged cerebral hypoperfusion due to air in the cerebral circulation can cause severe brain injury or death.
• Respiratory Failure: Due to pulmonary artery obstruction, leading to decreased oxygenation and potential ARDS.

Prevention

• During Medical Procedures: Careful handling of IV lines, catheters, and surgical instruments is essential to avoid introducing air into the bloodstream.
• For Divers: Proper training, gradual ascent, and adherence to decompression protocols are crucial to prevent nitrogen bubble formation and air embolism.
• In Hospital Settings: Use of air filters during IV infusions, appropriate patient positioning, and careful removal of central lines can reduce the risk of air embolism.

Management

• Initial Management: Follow the ABC protocol, ensure airway, breathing, and circulation, and administer 100% high-flow oxygen (O₂) via a non-rebreather mask.
• Patient Positioning: Place the patient in the left lateral decubitus (left side down) and Trendelenburg (head down) positions to trap air in the right ventricular apex, reducing the risk of it entering systemic circulation.
• Intubation and Ventilation: Intubate if there is severe respiratory distress or hypoxia. Mechanical ventilation may be necessary in cases of respiratory failure.
• Fluid Resuscitation: Administer IV fluids to support blood pressure and maintain circulation. Use inotropes if needed to support cardiac output.

Advanced Management

• Aspiration: If a central venous catheter is in place in the right atrium or right ventricle, attempt to aspirate the air from the catheter to remove air bubbles.
• Hyperbaric Oxygen Therapy (HBOT): Indicated for severe cases, especially with neurological symptoms. HBOT increases the partial pressure of oxygen, reduces the size of air bubbles, and helps improve tissue oxygenation.
• Open Chest Management: If the chest is open (e.g., during cardiac surgery), direct aspiration of air from the right ventricle or pulmonary arteries using a needle can be performed, followed by cardiac massage to improve circulation.

Prognosis

• The prognosis of air embolism depends on the volume of air introduced, the site of entry, and the speed of diagnosis and intervention.
• Early recognition and immediate management, including high-flow oxygen and positioning, can significantly improve outcomes.
• Delayed treatment or continued air entry can result in irreversible neurological damage or death.

References

• Air Embolism: A Comprehensive Review
• Management of Air Embolism in Clinical Practice
• Medscape: Air Embolism Overview