Venous Gas Embolism
4/2/09
FANZCA Notes
= ingress of gas into the venous circulation -> embolism into pulmonary circulation -> right heart
failure and cardiovascular compromise
PATHOPHYSIOLOGY
- gas introduced -> travels through right heart -> trapped in pulmonary arteries -> right
ventricular HT -> failure
- if happens quickly -> failure
- if happens gradually -> platelets, fat and neutrophils build up around bubble -> inflammatory
reaction -> APO
- gas can travel to arterial circulation via PFO and intra-pulmonary shunts (thebesian veins,
bronchial vessels)
AETIOLOGY
Requires
1. source of gas
2. communication between gas and venous system
3. pressure gradient allowing ingress of gas
CLINICAL FEATURES
- high risk patient: head up with central access, multiple infusion, rapid fluid transfusions under
pressure
- high risk surgery -> any surgery where the operative field is above the heart and veins are
large and held open by connective tissue (gas insufflation procedures, sitting craniotomy,
posterior fossa craniotomy, spinal surgery, large bore venous lines, Caesarian section)
-
lightheadness, dizziness, SOB, chest pain, anxiety, tacypnoea, tachycardia, decreased LOC
arrhythmias
hypotension
apnoea -> hypoxia -> cardiovascular collapse
‘mill wheel’ murmur
APO
INVESTIGATIONS
- sudden increase in ET nitrogen
- increased dead space -> sudden fall in ETCO2
- ECG abnormalities; tachyarrhythmias, AV block, right heart strain, T wave changes, ST changes
Jeremy Fernando (2011)
-
increase in CVP
increase in PCWP
bubbles seen on TOE
bubbles heard on praecordial Doppler
fall in SpO2 (late sign)
CXR; normal -> non-cardiogenic pulmonary oedema
PREVENTION
- screening for PFO -> transcranial Doppler for IV bubble administration or ECHO
- avoid sitting position
- reduce the height from operative site to RA
- keep CVP full
- pressure over jugular veins @ high risk times
- PEEP (not in sitting position -> increased likelihood of paradoxical embolism in patients with
PFO)
- military antishock trousers
- meticulous surgical technique
- @ insertion or removal of CVL keep RA above site
- check lines for bubbles/air
DETECTION
-
capnography
praecordial Doppler
TOE (most sensitive and specific)
ETN2
PA catheter
transcranial Doppler
praecordial or oesophageal stethoscope
CVP
clinical signs
MANAGEMENT
Goals
1.
2.
3.
4.
Maintain oxygenation
Minimise further air entrainment
Reduce size of embolism
Overcome mechanical obstruction caused by embolism
A – ETT
B – FiO2 1.0
C – CPR if required
Prevent further Air entrainment
- flood field with saline and compress wound edges
Jeremy Fernando (2011)
- position operative site below RA then supine to for cerebral protection.
- load with IVF
- increase intrathoracic pressure -> Valsava (decrease VR)
Reduce size of embolism
- 100% O2 (prevents nitrogenation and therefore expansion of bubble)
- aspirated blood with CVL (won’t be effective unless tip in RA)
- hyperbaric O2
Overcome mechanical obstruction
- if air in RA – left lateral position will hopefully mean bubble travel superiorly allowing RV to
empty
- inotropes
- bypass -> air can be aspirated from PA
-
admit to ICU/HDU
discuss with family and patient
document
debrief
case review and preventative strategies implemented
Jeremy Fernando (2011)