- Factors that increase the risk for VAE
- An operative site above the level of the heart
- Presence of non-collapsible veins.
- Both are usually present during posterior fossa surgery, especially in the sitting position.
- Incidence of VAE in posterior fossa surgery has been reported to be
Position | Incidence of VAE | Haemodynamically significant VAE |
Sitting | 30-75% | 8-15% |
Prone or park bench | 10-15% | 3-5% |
- If air entrainment is stopped immediately after detection, the effects can be short-lived and insignificant with low morbidity.
- Pathophysiology
- An elevation in pulmonary vascular pressure leading to impaired gas exchange, hypoxemia, and CO₂ retention (decrease in end-tidal CO₂ tension on capnography).
- Bronchoconstriction may occur, and further air entrainment will lead to progressive decreases in cardiac output, hypotension, arrhythmias, and myocardial ischemia or failure.
- The sudden entry of a large bolus of air into the right heart can have a dramatic effect by causing an airlock that blocks the right ventricular outflow tract and leads to cardiac arrest or cardiovascular collapse.
- Patent foramen ovale (PFO)
- PFO + VAE → paradoxical air embolism → myocardial and cerebral ischemia.
- Prevalence 25% of the adult population.
- It is recommended that any patient scheduled for surgery in the sitting position undergo bubble echocardiography to rule out PFO.
- Intraoperatively monitoring
- Gold standard
- Capnography
- Precordial Doppler ultrasonography can detect as little as 0.25 ml of air.
- Less usable
- Transesophageal echocardiography (TOE) is the most sensitive of all monitors and can detect paradoxical embolism but use in the presence of neck flexion is not well established.
- Pulmonary artery pressure monitoring is as sensitive as capnography.
- Prevention
- Decrease the gradient between the heart and the site of surgery
- Maintain normovolemia to hypervolemia
- Apply bone wax during surgery
- Avoid PEEP
- It could promote paradoxical air embolism in patients with an asymptomatic patent foramen ovale (PFO).
- PEEP without PFO is protective vs VAE
- Treatment
- Flood the surgical site
- Lower the operative site
- Left sided down lateral position
- To prevent air from entering pulmonary system
- Stop N₂O administration
- If N₂O saturates the alveoli and enters the air embolus in the lung capillary it can expand the air embolus volume since it is more soluble in Blood than nitrogen.
- Give 100% O₂
- Perform aspiration of air through a central venous line
- Consider compression of the jugular veins
- Provide cardiopulmonary support (fluids, pressors, inotropes)
Made with Bullet