- From sudden decompression, as a result of a diving accident
- From barotrauma during mechanical ventilation
- Blast injury, when close to an explosion
BEWARE THE ‘PERI-PROCEDURAL STROKE’!!
The pulmonary circulation generally filters bubbles in pulmonary arteries from the right ventricle and systemic veins. A right-to-left shunt in the heart can by-pass this filter, allowing bubbles to be pumped from left ventricle into aorta and its branches. Bubbles in the pulmonary veins can travel to the left side of the heart, and reach the aorta, and thus the brain (and rest of the body). The effect may appear like a cerebro-vascular accident (stroke) from any other cause. Bubbles may be seen in cerebral arteries or veins and may even be described as pneumocephalus.
Once in the cerebral vessels, the effects of these bubbles are:
- Mechanical obstruction to blood flow
- Direct damage to endothelium. The bubble surface acts as a foreign substance and activates the coagulation cascade
- Increased levels of C3a and C5a
- Prostaglandin, leukotriene synthesis
- Platelet and leukocyte activation, leading to ongoing impairment of microcirculation
- Fibrin release and adhesion to endothelium
- Vasospasm followed by vasodilatation
- Damage to the blood brain barrier
- Cerebral oedema and raised intracranial pressure
Once suspected, treatment for CGE must begin at once, the source identified and eliminated, life support be instituted as required and Hyperbaric Oxygen provided as quickly as possible.
Time is of the essence!