What is an air embolism and what is the acute management?

Air Embolism: Definition and Acute Management

What is Air Embolism?

Air embolism is the entrainment of air or gas from the operative field or environment into the venous or arterial vasculature, causing potentially life-threatening obstruction of the right ventricular outflow tract or pulmonary arterioles by air bubbles and fibrin clots, resulting in cardiovascular dysfunction and failure. 1

Pathophysiology and Lethal Volumes

• The morbidity and mortality of air embolism are directly related to the volume of air entrainment and rate of accumulation 1
• The adult lethal volume is between 200-300 mL, or 3-5 mL/kg injected at a rate of 100 mL/s 1
• Air bubbles obstruct either the right ventricular pulmonary outflow tract or the pulmonary arterioles through a mixture of air and fibrin clots formed in the heart 1

Common Causes

• Central venous catheter procedures (insertion, manipulation, or removal) are the most common iatrogenic cause, accounting for 33% of cases 2, 3
• Neurosurgical procedures performed in the sitting position with exposure of venous sinuses 2
• Endovascular procedures and arterial catheterization 3, 4
• Disconnection of catheters is responsible for 93% of catheter-related air embolism cases 5

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Acute Management Algorithm

Step 1: Immediate Positioning and Oxygen (First Actions Within Seconds)

Place the patient immediately in the left lateral decubitus head-down (Trendelenburg) position and administer 100% oxygen. 1, 6, 7

• The left lateral decubitus position traps air in the apex of the right ventricle, preventing migration to the pulmonary artery 6, 7
• The head-down position increases central venous pressure and prevents further air entrainment 6
• 100% normobaric oxygen reduces air bubble size and improves tissue oxygenation 6

Step 2: Stop Further Air Entry

• Immediately stop the arthroscopic pump or any pressurized infusion system 6
• Secure all catheter connections to prevent disconnection 5
• Flood the surgical field with saline if the procedure is ongoing 8

Step 3: Attempt Air Aspiration (If Central Access Available)

If a central venous catheter or pulmonary artery catheter is in place, immediately attempt to aspirate air from the right atrium or right ventricle. 1, 6, 7

• Aspiration can provide immediate improvement by reducing the air burden 6, 5
• This intervention is occasionally performed intraoperatively to relieve large air bubbles 1

Step 4: Hemodynamic Support

Initiate aggressive hemodynamic support with fluid resuscitation and vasopressors to maintain coronary perfusion pressure. 6, 7

• Administer fluid resuscitation to increase central venous pressure 6
• Use norepinephrine or vasopressin if hypotension persists 6, 7
• Initiate inotropic support with dobutamine to improve right ventricular contractility 7
• Consider milrinone as an alternative inotrope with pulmonary vasodilatory effects 7
• Avoid excessive fluid administration as this may worsen right ventricular distention and compromise left ventricular filling 6, 7

Step 5: Continuous Monitoring

• Monitor heart rate, blood pressure, oxygen saturation, and end-tidal CO₂ continuously 6, 7
• Perform bedside echocardiography to assess right ventricular function and confirm air presence 6, 7
• Watch for gradual drops in end-tidal CO₂ as an early warning sign before cardiovascular collapse 6

Step 6: Advanced Interventions for Severe Cases

Consider hyperbaric oxygen therapy (HBOT) for severe cases, particularly with neurological symptoms or suspected paradoxical arterial embolism. 6, 3, 4

• HBOT is the definitive treatment that decreases air emboli size by facilitating gas reabsorption while improving tissue oxygenation and reducing ischemic reperfusion injury 4
• HBOT should be considered especially if paradoxical arterial air embolism is suspected (suggesting right-to-left shunt) 6
• 21% of patients in one series underwent HBOT with improved outcomes 3

Step 7: Pulmonary Vasodilators for Persistent RV Dysfunction

• For persistent right ventricular dysfunction, consider inhaled nitric oxide or sildenafil 6, 7
• These agents provide pulmonary vasodilation without worsening systemic hypotension 7

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Critical Pitfalls to Avoid

• Failing to recognize subtle early signs (gradual drop in end-tidal CO₂) before cardiovascular collapse occurs 6
• Delaying position change and oxygen administration while attempting other interventions 6
• Continuing to pump fluid/air after embolism is suspected 6
• Excessive fluid administration that worsens right ventricular distention 6, 7
• Failing to secure catheter connections, which is responsible for 93% of catheter-related cases 5

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Prognosis and Outcomes

• Overall mortality rate is 21%, with 69% of deaths occurring within 48 hours 3
• Patients with immediate cardiac arrest have a 53.8% mortality rate compared to 13.5% in those without cardiac arrest 3
• 63% of patients have no sequelae with appropriate management 3
• Treatment is mostly supportive, and outcomes depend on rapid recognition and intervention 1, 3