What is the management of venous air embolism during posterior fossa craniotomy in the sitting position?

Management of Venous Air Embolism During Posterior Fossa Craniotomy in Sitting Position

The management of venous air embolism (VAE) during posterior fossa craniotomy in the sitting position requires immediate intervention with patient positioning in left lateral decubitus head-down position, hemodynamic support, and air aspiration if possible. 1

Risk and Incidence

• The sitting position for posterior fossa craniotomies significantly increases the risk of VAE, with reported incidence of severe VAE (defined as VAE with >20% decrease in systolic blood pressure) of 41.3% compared to 11% in horizontal position. 2
• VAE occurs due to entrainment of air into exposed venous sinuses during posterior fossa surgery, creating potentially life-threatening systemic effects. 3
• Modified semi-sitting (lounging) positions with lower head and higher legs positioned above the head can decrease the incidence and severity of VAE by creating positive pressure in the transverse and sigmoid sinuses. 4

Prevention and Monitoring

• Preoperative detection of patent foramen ovale is important, though patients with known PFO can still undergo surgery in sitting position under strict protocols. 4
• Essential monitoring includes:
  • Precordial Doppler ultrasound or transesophageal echocardiography (TEE) for early detection of small VAEs 4
  • Continuous end-tidal CO2 monitoring (sudden decrease indicates VAE) 2
  • Invasive arterial blood pressure monitoring 1
  • Central venous pressure monitoring 1
  • Pulse oximetry 1

Immediate Management When VAE Occurs

1. Position the patient in left lateral decubitus head-down position to trap air in the apex of the right ventricle and prevent migration to the pulmonary artery. 1

2. Notify the surgeon immediately to:

   • Flood the surgical field with saline
   • Apply bone wax to exposed bone edges
   • Apply pressure on suspected venous sinus entry points
   • Perform Valsalva maneuver (inspiratory hold after lung inflation) to help localize the site of air entry 5

3. Aspirate air if a central venous catheter is in place, attempting to remove air from the right heart. 1

4. Provide hemodynamic support:

   • Administer inotropes (dobutamine or milrinone) to improve right ventricular contractility 1
   • Use vasopressors (norepinephrine or vasopressin) to maintain coronary perfusion pressure if hypotension occurs 1
   • Avoid excessive fluid administration which may worsen right ventricular distention 1

5. Administer 100% oxygen to reduce the size of air bubbles and improve oxygenation. 3

6. Consider discontinuing nitrous oxide if being used, as it can increase the size of air bubbles. 3

Monitoring and Additional Interventions

• Perform bedside echocardiography to assess right ventricular function and confirm resolution of the air embolus. 1
• For patients with significant right ventricular dysfunction, consider pulmonary vasodilators such as inhaled nitric oxide. 1
• Avoid hyperventilation as it can compromise cerebral blood flow during sitting position. 4
• Be vigilant for complications beyond hemodynamic instability, including:
  • Stress-induced cardiomyopathy (Takotsubo cardiomyopathy) 6
  • Neurological deficits from paradoxical embolism 3
  • Cardiac arrest in severe cases 3

Post-Event Management

• Continue close hemodynamic monitoring after the acute event. 3
• Consider ICU admission for patients with significant hemodynamic compromise. 2
• Perform neurological assessments to identify any deficits from cerebral air embolism. 3
• Be aware that although postoperative ventilator time may be shorter in sitting position cases, ICU and hospital stay duration are similar to horizontal position cases. 2

Special Considerations

• In patients with severe VAE unresponsive to initial management, consider changing patient position from sitting to supine or prone if feasible. 7
• For persistent hemodynamic instability despite maximal medical therapy, cardiopulmonary bypass may be considered in extreme cases. 1