Aetiology
- risk of air embolism whenever a surgical wound disrupts veins creating a
blood-air interface that lies above the level of RA eg craniotomy
- air may be left in circulation after arterial surgery
- injection during medical procedures
- open heart surgery
- haemodialysis
- vaginal insufflation during oral sex
- crush injury of chest*
- overpressure injury to lung during scuba diving due to ascent with a closed
glottis*
* = may lead to injection of air into pulmonary veins and hence embolization
into brain with prior pulmonary air emboli
Pathophysiology
- introduction of a small volume of air into venous circulation usually well
tolerated
- primary pathophysiological event is intense vasoconstriction of pulmonary
circulation (air lock effect interferes with RV outflow). Results in VQ
mismatch, hypoxia, interstitial pulmonary oedema, systemic hypotension
- rise in RA pressure may create right to left shunt across patent foramen ovale
(patent in 20-30%) with risk of paradoxical emboli
Clinical features
- sudden occurrence of unexplained cardiopulmonary dysfunction with
neurological findings during or soon after a surgical procedure should suggest
possibility of venous air embolism leading to paradoxical emboli
- churning murmur over L sternal border
- hypotension
- hypoxia
- crackles
- neurological abnormalities include coma, hemiplegia, visual disturbances,
disorientation, apnoea
Management
- place in left lateral head down position to decrease air leaving through RV
outflow tract
- insert CVP line and aspirate air
- supportive treatment
- avoid PEEP: impairs haemodynamic performance, does not protect patient against
air embolism and probably further increases risk of paradoxical emboli
- uncontrolled data suggest that hyperbaric oxygen with recompression to the
equivalent of 60 feet is beneficial in cerebral air embolism even if treatment
is delayed for 4-6h
Further reading
Bove AA. Air embolism and decompression sickness. In Rippe, 3rd ed, 1996
© Charles Gomersall July 1999
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