Air embolus
Air entry into the venous circulation
Pathophysiology
[edit | edit source]- Can occur during central venous cannulation when a pressure gradient favouring movement of air into venous circulation develops, via negative intra-thoracic pressure from spontaneous breathing, and gravitational gradient towards the right atrium
- 100mL/sec of air can be drawn through a 14 gauge cannula with just a 5mmHg gradient
- 200-300mL over a few seconds is generally required for fatal embolus
- Causes right heart failure from an air lock in the right ventricle, which can progress to cardiogenic shock, leaky-capillary APO, and acute embolic stroke from air bubbles that pass through a PFO
Prevention
[edit | edit source]- PPMV
- Trendelenburg position for subclavian/IJV catheters
Clinical presentation
[edit | edit source]- Sudden onset dyspnoea +/- distressing cough
- If severe, there is rapid progression to hypotension, oliguria, and reduced GCS
- Can sometimes hear a drum-like, mill wheel murmur in RV just prior to CV collapse
Investigation
[edit | edit source]- TOE is the most sensitive method of detecting air in right heart
Management
[edit | edit source]- Fix underlying entry point
- Some say position in left lateral decubitus to relieve the air lock, but the value of this is questionable
- Some say chest compressions to force air out of heart, but again this is unproven
- Pure oxygen breathing - promotes movement of nitrogen out of air bubbles in the blood - unproven
- General CV support