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 immediate management of venous air embolism (VAE) during posterior fossa craniotomy in sitting position requires positioning the patient in left lateral decubitus head-down position, aspirating air if possible, and providing hemodynamic support with vasopressors and inotropes as needed. 1

Detection and Risk Assessment

• VAE is a well-documented complication of posterior fossa surgery in the sitting position, with significantly higher incidence compared to horizontal positioning (41.3% vs 11.0%) 2
• Continuous monitoring with precordial Doppler or transesophageal echocardiography (TEE) enables early detection of small venous air emboli, allowing for prompt intervention 3
• The severity of VAE is directly related to the volume and rate of air entrainment, with clinical manifestations ranging from subtle neurological, respiratory, or cardiovascular signs to shock and cardiac arrest 4

Immediate Management Protocol

Initial Steps

• Position the patient in left lateral decubitus head-down position to prevent air migration to the pulmonary artery and trap air in the apex of the right ventricle 1
• If a central venous catheter is in place, attempt to aspirate air from the right heart 1
• Flood the surgical field with saline and identify the site of air entry 5
• Apply bone wax or other appropriate materials to seal the site of air entry 5
• Consider performing a Valsalva maneuver to help localize the site of air entry 5

Hemodynamic Support

• Initiate inotropic support with dobutamine to improve right ventricular contractility if right ventricular failure is present 1
• Consider milrinone as an alternative inotrope with additional pulmonary vasodilatory effects 1
• Use vasopressors such as norepinephrine or vasopressin to maintain coronary perfusion pressure if hypotension is present 1
• Avoid excessive fluid administration as this may worsen right ventricular distention 1

Respiratory Management

• Administer 100% oxygen to reduce the size of air bubbles and improve oxygenation 4
• Avoid hyperventilation as it can compromise cerebral blood flow during sitting position 3
• Consider discontinuing nitrous oxide if being used, as it can expand air bubbles 4

Monitoring and Additional Considerations

• Continuously monitor heart rate, blood pressure, and oxygen saturation 1
• Use 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
• Be alert for potential complications including Takotsubo cardiomyopathy, which has been reported following VAE during sitting position craniotomy 6

Prevention Strategies

• Consider using a modified semi-sitting (lounging) position with lower head and higher legs positioned above the top of the head to create positive pressure in the transverse and sigmoid sinuses, which decreases the incidence and severity of VAE 3
• Maintain positive end-expiratory pressure (PEEP) to increase central venous pressure and reduce the risk of air entrainment 4
• Use meticulous surgical technique during exposure of venous sinuses 4
• Implement a strict team protocol between neurosurgeons and neuroanesthesiologists, including all necessary monitoring 3

Special Considerations

• Patients with known patent foramen ovale can be operated on in a sitting position under strict protocol, though they have increased risk of paradoxical air embolism 3
• Be aware that VAE can also occur in prone position, though it is less common than in sitting position 7
• Central nervous system and cardiovascular complications are significantly higher in sitting position compared to horizontal position (71% vs 34% and 17% vs 6%, respectively) 2