infection control & hospital epidemiology july 2018, vol. 39, no. 7 original article
Different Types of Heater-Cooler Units and Their Risk of Transmission of Mycobacterium chimaera During Open-Heart Surgery: Clues From Device Design
Richard Kuehl;1,a Florian Banderet;1,a Adrian Egli;4,5 Peter M. Keller;2,3 Reno Frei;4 Thomas Döbele;6 Friedrich Eckstein;6 Andreas F. Widmer1
objective. Worldwide, Mycobacterium chimaera infections have been linked to contaminated aerosols from heater-cooler units (HCUs) during open-heart surgery. These infections have mainly been associated with the 3THCU(LivaNova, formerly Sorin). The reasons for this and the risk of transmission from other HCUs have not been systematically assessed.
design. Prospective observational study. setting. University Hospital Basel, Switzerland.
methods. Continuous microbiological surveillance of 3 types of HCUs in use (3T from LivaNova/Sorin and HCU30 and HCU40 from Maquet) was initiated in June 2014, coupled with an epidemiologic workup. Monthly water and air samples were taken. Construction design was analyzed, and exhausted airflow was measured.
results. Mycobacterium chimaera grew in 8 of 12 water samples (66%) and 22 of 24 air samples (91%) of initial 3T HCUs in use, and in 2 of 83 water samples (2%) and 0 of 41 (0%) air samples of new replacement 3T HCUs. Moreover, 7 of 12 water samples (58%) and 0 of 4 (0%) air samples from the HCU30 were positive, and 0 of 64 (0%) water samples and 0 of 50 (0%) air samples from the HCU40 were positive. We identified 4 relevant differences in HCUdesign compared to the 3T: air flow direction, location of cooling ventilators, continuous cooling of the water tank at 4°C, and an electronic alarm in the HCU40 reminding the user of the next disinfection cycle.
conclusions. All infected patients were associated with a 3T HCU. The individual HCU design may explain the different risk of dis- seminating M. chimaera into the air of the operating room. These observations can help the construction of improved devices to ensure patient safety during cardiac surgery.
Infect Control Hosp Epidemiol 2018;39:834–840
An international outbreak of devastating surgical site infec- tions (SSIs) with Mycobacterium chimaera has been linked to contaminated aerosols generated by heater-cooler units (HCUs) used during open-heart surgery.1 Since 2013, ~100 patients have been infected with this pathogen worldwide, with a mortality rate of up to 50%.2 There is no standardized, established treatment for M. chimaera systemic infections with high morbidity and mortality, and relapses occur even after routine replacement of the cardiac valve involved. Non- tuberculous mycobacteria have been cultured from most types of HCUs on the market.3,4 However, to the best of our knowledge, nearly all infections were associated with one type
of heater cooler, the 3T HCU (LivaNova, formerly produced by Stöckert, part of Sorin).5,6 It remains unclear why exposure to the 3T HCU led to infection. Exposure to other types of HCUs did not result in infections even though water tanks were also contaminated with M. chimaera. Thus far, 5 patients at our institution have been documented
with an M. chimaera infection. All patients had undergone cardiac surgery before June 2014 using a 3T HCU and had received a replacement or repair of a cardiac valvewith insertion of prosthetic foreign material (composite graft and ascending aortic replacement (n=4) or mitral ring annuloplasty (n=1)). All 4 composite grafts were replaced by homografts, and all
Affiliations: 1. Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, Switzerland; 2. Institute of Medical Microbiology,
University of Zurich, Switzerland; 3. Swiss National Center for Mycobacteria, University of Zurich, Switzerland; 4. Division of Clinical Microbiology, University Hospital Basel, Switzerland; 5. Applied Microbiology Research, Department of Biomedicine, University of Basel, Switzerland; 6. Division of Cardiac
Surgery, University Hospital Basel, Switzerland. aFirst authors with equal contribution. © 2018 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2018/3907-0010. DOI: 10.1017/ice.2018.102
Received January 9, 2018; accepted April 4, 2018; electronically published May 28, 2018
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