Heater-cooler units: contamination of crucial devices in cardiothoracic surgery

Background: Several cases of Mycobacterium chimaera infection have recently been reported in cardiosurgical patients. So-called heater-cooler units (HCUs) used in cardiosurgical procedures are suspected to be the reservoir for pathogen growth and dissemination.

Aim: To assess the contamination status of HCUs at our facility.

Methods: Air sampling for mycobacteria was conducted at different distances from the machines and in the area around the operating table. Air sampling was also conducted for non-fermenters as a surrogate parameter for water-associated pathogens.

Findings: Mycobacterium chimaera was detected in the water tanks of the HCUs. When the devices were operating, M. chimaera was also found in their exhaust air, as well as in the area around the operating table. Non-fermenters were identified at different distances from the running HCU and the area around the operating table. Cultures remained negative when the devices were switched off.

Conclusions: Exhaust air from HCUs may be a pathway of pathogen transmission to patients undergoing open chest heart surgery. Although, for technical reasons, relocation of HCUs is difficult to achieve, only strict separation of the HCU from the operating room appears to enhance patient safety. Using non-fermenters as a surrogate parameter may be considered a viable option for a timely risk assessment. The design of HCUs should be modified to keep susceptibility to contamination at a minimum.