US researchers uncover high levels of contamination in heater-cooler devices used in open heart surgery

Over a third of heater-cooler devices used in open heart surgery might be contaminated with deadly bacteria, according to a recent study. Thirty-three of 89 (37 per cent) heater-cooler units (HCUs) that were assessed between July 2015 and December 2016 tested positive for Mycobacterium chimaera (M chimaera), a bacterium associated with fatal infections in open-heart surgery patients, as per research presented at the 44th Annual Conference of the Association for Professionals in Infection Control and Epidemiology (APIC).

HCUs controlled the temperature of a patient's blood and organs during heart bypass surgery. The US Food and Drug Administration (FDA) as also the Centres for Disease Control and Prevention (CDC) had earlier issued safety warnings that a widely used brand of HCUs might be contaminated during manufacturing, putting patients at risk for life-threatening infections. Around 60 per cent of heart bypass procedures performed in the US used the brand of device associated with these infections.

The research, presented by John Rihs, added to the knowledge about the extent of colonisation of M chimaera that might be present in these units. Rihs and colleagues assessed devices already in use for the presence of non-tuberculous mycobacteria (NTM) colonisation (primarily M chimaera) in HCUs before and after decontamination.

Around 60 per cent of surgery performed in the US used the brand of device associated with these infections. A total of 653 water samples from 89 units were tested and samples were received from 23 hospitals in 14 states, the District of Columbia, and Canada.

Researchers were surprised at the degree of  contamination of the units were, with 97 cultures deemed uninterpretable due to high levels of bacterial and fungal contamination. Mycobacteria of many other strains were also detected in many of the units.