• most are subclinical

• https://pubs.asahq.org/anesthesiology/article/106/1/164/8884/Diagnosis-and-Treatment-of-Vascular-Air-Embolism
• Negative Pressure = Gravity
  • surgical field above heart = sitting position
    • sitting craniotomies (high)
    • posterior fossa surgery (high)
      • veins in occiput held open by bone matrix
  • large exposure tissue field
    • caesarean section (high)
    • mastectomy
    • total hip arthroplasty (high)
  • low CVP
  • patent veins = that don't collapse
    • diploic veins in skull = bone wax is applied
    • cerebral sinuses, eg. dural sinus laceration
      • sagittal sinus
• Positive Pressure = gas insufflation
  • laparoscopy (high)
  • hysteroscopy
  • IPPV
• high risk = incidence > 25%
  • sitting craniotomy, posterior fossa surgery, neck surgery
  • laparoscopy
  • total hip arthroplasty
  • CS
  • CVC insertion
• medium risk = 5-25%
• low risk < 5%

• air entrainment into veins

  • venous sinuses = patent veins

• gas enters heart via RV

• small amounts of air are broken up in capillary bed

• also causes ⬇ETCO2

  • interference with gas exchange
  • ⬆dead space (⬇perfusion) = V/Q mismatch
  • also ?dilutional from dissolved atmospheric air being expired (which is low in CO2)

• also causes ⬆ETN2

• large volume of air

  • creates air lock at RV outlet
  • 3-5 mL/kg = 200-350 mL

• small volume in critical vessels

  • LAD = 0.5 mL
  • cerebral arteries = 2-3 mL

• NB. paradoxical emboli

  • pulmonary > systemic shunt
  • pulmonary vascular bed / septal defects / PFO

• asystole = RV airlock arrest
• B = Respiratory
  • ⬇SpO2
  • ⬇ETCO2
• C = Cardiovascular
  • Backwards = ⬆CVP
  • ⬇forward = ⬇BP, reflex ⬆HR
  • Millwheel murmur = late sign

• Ultrasound of RA
  • air bubbles
  • TOE better than TOE
  • not possible in long operations / head flexion / etc
• Praecordial Doppler
  • Not available in Australia
  • sound heard if air present in cardiac chambers

• Anaesthetic emergency
  • inform surgical team
  • call for help
• Prevent further entrainment of air
  • Flood surgical field with saline
  • apply bone wax
  • ⬆venous pressure = head down = surgical site below RA
  • apply sustained PEEP until this is achieved
    • PEEP is of NO value and ⬆risk paradoxical air embolism??
  • surgical field BELOW level of HEART
• Manage existing embolism
  • SUPPORTIVE therapy
    • B = 100% O2, stop N2O
    • C = Cardiovascular
      • support BP
      • TOE to assess air and RV function
      • left lateral + head down (Trendelenberg) = may move air lock / bubble above RVOT
        • controversial = poor evidence and often impractical
  • Definitive
    • B = hyperbaric O2 therapy, esp if paradoxical air embolism
    • C = aspirate air from RA via CVC
    • C = CPR as required = mechanical disruption of air lock

• Pre-op
• Intra-op
• Post-op

https://www.sciencedirect.com/science/article/pii/B9780323321068000078

https://pubs.asahq.org/anesthesiology/article/106/1/164/8884/Diagnosis-and-Treatment-of-Vascular-Air-Embolism

https://emedicine.medscape.com/article/761367-workup#c6