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CPB oxygenator: Gas embolism

One of the most deleterious complications of cardiopulmonary bypass is an embolism. Gas embolism is specifically a concern as it relates to the oxygenator.

One key point is that prevention of gaseous microemboli is dependent on the temperature gradient between water and blood. This should not exceed 10°C. Currently, membrane oxygenators are widely used and greatly decrease the incidence of gas embolism as compared to bubble oxygenators, which were used more common 20+ years ago. Detection of gas emboli includes direct visualization, radiography, CT, screen sampling, fluorescein angiography, ultrasound and other techniques. Ultrasound in the most commonly used method, especially through the use of transesophageal echo and transcranial Doppler.

The most feared complication of gas embolism is diffuse cerebral dysfunction which is typically detected post operatively. Visual disturbance or loss can occur as well and would be detected post operatively. Intraoperatively one can occasionally see transient changes in the electroencephalogram and changes in cerebral oximetry.

Treatment is complex and mostly supportive. Prevention is the key. In cases of gross air embolism hyperbaric oxygen can be employed.


  1. Clark RE. Microemboli: an overview. Med Instrum 1985;19:53–54. PubMed Link