Gaseous microemboli: sources, causes, and clinical considerations

Patients undergoing open-heart surgery are exposed to gaseous microemboli (GME) from several sources, including bubble oxygenators, which are used in a majority of cases for cardiopulmonary bypass. If present in large quantities, GME can reduce blood flow and delivery of oxygen to tissues and may be responsible, in part, for some of the complications that commonly follow cardiopulmonary bypass. Gaseous microemboli are defined, and the causes of this phenomenon are examined. The literature from the last 30 years on this topic is also reviewed, and measures for reducing GME during cardiopulmonary bypass are recommended. Current considerations for users of cardiopulmonary bypass systems are discussed, and five unanswered questions are raised in the conclusion.