Air contamination during hemodialysis should be minimized.

During preparation of the hemodialysis (HD) extracorporeal circuit (ECC) a priming solution is used to remove air from the tubes and dialyzer. Ultra sound techniques have verified micro embolic signals (MES) in the ECC that may derive from clots or gas embolies. In vitro studies could clarify that embolies of air develop within the ECC and also pass the safety systems such as air traps and enter the venous line that goes into the patient. Clinical studies have confirmed the presence of MES within the ECC that pass into the return-venous-line during conventional HD without inducing an alarm. In addition, studies confirmed that such MES were present within the AV fistula and subclavian vein, but also detected within the carotid artery. Autopsy studies revealed the presence of gas embolies surrounded by clots within the lung but also brain and myocardial tissue. This review will focus on how the MES develop and measures of how the exposure can be limited.