Heater-cooler devices are used during cardiothoracic surgeries, as well as other medical and surgical procedures to warm or cool a patient to optimize medical care and improve patient outcomes. Heater-cooler devices include water tanks that provide temperature-controlled water to external heat exchangers or warming/cooling blankets through closed circuits. Although the water in the circuits does not come into direct contact with the patient, there is the potential for contaminated water to enter other parts of the device or transmit bacteria through the air (aerosolize) through the device’s exhaust vent into the environment and to the patient.
Through the FDA’s analysis of adverse event reports, the medical literature, and information from national and international public health agencies, we are aware that the use of heater-cooler devices has been associated with Nontuberculous Mycobacteria (NTM) infections, primarily in patients undergoing cardiothoracic surgical procedures. NTM organisms are widespread in nature and can be found in soil and water, including tap water sources. They are typically not harmful, but in rare cases may cause infections in some patients.
The FDA is collaborating with professional societies, public health partners, heater-cooler manufacturers, and experts to evaluate additional strategies for mitigating infections associated with heater-cooler devices. This includes working with:
- Health care facilities and professional medical societies to understand their experiences using heater-cooler units, and to become more informed about challenges in diverse hospital environments, as well as their capabilities for implementing potential risk mitigation measures.
- Infectious disease specialists, health care providers, members of academia, aerosolization science and public health experts to better understand the causes and risk factors for transmission of microbial agents associated with heater-cooler devices and to develop strategies to minimize patient exposure.
- The Centers for Disease Control and Prevention and state public health departments to evaluate documented events of heater-cooler contamination and subsequent patient infection.
- International public heath regulatory agencies to heighten awareness of infections associated with heater-cooler units and to discuss activities to reduce the risks of infection.
Our current analyses have identified potential root causes of contamination from heater-cooler devices, which include:
- NTM bacteria transmitted through the air (aerosolization):
There is the potential for NTM bacteria to grow in a water tank in the heater-cooler units. Although the water in the heater-cooler unit does not come into direct contact with the patient, there is the potential for contaminated water to enter other parts of the device or disperse the NTM through the device’s vent(s) or other small openings between the inside and outside of the water tanks into the operating room environment and the patient’s open surgical cavity. Water agitation (bubbling) inside the water tanks via pumps, mixing components, return circuit water, etc., may increase the potential for aerosolization of NTM bacteria.
For example, mycobacteria are found in much higher concentrations in water droplets emitted into the air from air bubbles rising and bursting in the tank, as compared to the concentration of mycobacteria found in the water in the tank. The water tanks are not air tight, so these aerosolized NTM in the water droplets can escape from the inside of the heater-cooler unit possibly facilitated by the unit’s fans and out the vent(s) and into the surgical suite. In addition, these water droplets containing NTM bacteria may remain suspended in the air, which may increase the chances of entering the patient’s open surgical cavity or contaminating a sterile implant such as a heart valve.
- Laminar flow disruption:
Laminar air flow is an engineering control, which in this case, describes the operating room environment that is intended to add a level of protection by reducing airborne contaminants during surgery. One study2, utilizing a single heater-cooler unit, suggests that the device’s exhaust fan, depending on the distance and direction of the exhaust, may disrupt the protective nature of the laminar air flow above the patient. The authors of this study hypothesized NTM that is airborne may then be carried into the surgical field.
- Heater-cooler design:
The designs of most heater-cooler devices are similar since they contain between one and three large tanks filled with water that are either heated or cooled for delivery to heat exchanger(s) or blankets. While the heater-cooler device is running, the water in these tanks is agitated during normal circulation through the circuits.
Some heater-cooler devices contain air filters and water filters; others do not. Water filters (0.22 micron) should be able to remove most NTM from tap water that is used in filling/refilling, topping off, rinsing, making ice and cleaning the heater cooler units. However, the air filters located on some units are not sufficient enough to capture NTM bacteria. An air filter that has the capability of capturing NTM bacteria may alter device safety or performance and would therefore need to be evaluated by the manufacturer as a possible mitigation technique before implementation.
Fans are found on most units and are usually used to cool the unit and/or aid in the cooling efficiency of a compressor. These fans may facilitate the movement of aerosolized NTM from the inside of the unit into the operating room, and possibly into the sterile surgical field.
FDA activities to date include:
- On November 1, 2016, the FDA conducted a stakeholder call with health care providers and staff of health care facilities and health departments to discuss the Agency’s investigation of the LivaNova Stӧckert 3T Heater-Cooler System and to review the recommendations to help prevent the spread of infection related to the use of these devices.
- On October 13, 2016, the Centers for Disease Control and Prevention published a Morbidity and Mortality Weekly Report (MMWR) titled "Mycobacterium chimaera Contamination of Heater-Cooler Devices Used in Cardiac Surgery - United States." This report was written by CDC and FDA staff.
- On October 13, 2016, the FDA updated its June 1, 2016 Safety Communication to provide new information about Mycobacterium chimaera (M. chimaera) infections associated with the use of the LivaNova PLC (formerly Sorin Group Deutschland GmBH) Stӧckert 3T Heater-Cooler System (3T) in U.S. patients who have undergone cardiothoracic surgeries. This communication also contains updated recommendations to help prevent the spread of infection related to the use of these devices.
- On June 2-3, 2016, the FDA convened the Circulatory System Devices Panel of the Medical Devices Advisory Committee and received expert clinical opinion and recommendations for patient notification and patient follow-up procedures.Recommendations for sampling and monitoring of the 3T and other heater-cooler devices were also discussed and included regular visual monitoring of contamination within the water circuit, replacement of accessories (e.g. tubing) on a regular basis, and testing for water quality to assure adequate disinfection procedures are being performed.
- On June 1, 2016, the FDA issued Mycobacterium chimaera Infections Associated with Sorin Group Deutschland GmbH Stӧckert 3T Heater-Cooler System- Safety Communication to provide new information and recommendations about Mycobacterium chimaera infections associated with the use of the Stӧckert 3T Heater-Cooler System in patients who have undergone cardiothoracic surgeries.
- On May 16, 2016 the FDA held a webinar for our state, local, tribal and territorial regulatory and public health partners to discuss Nontuberculous Mycobacterium (NTM) infections associated with heater-cooler devices and to review recommendations to minimize patient exposures to infections.
- On December 29, 2015, the FDA issued a warning letter to LivaNova (formerly Sorin Group S.p.A.) on for its Heater Cooler 3T thermal regulator device after inspections conducted at facilities in Munchen, Germany and Arvada, Colorado revealed violations to the Quality Systems Regulation, a part of the Federal Food, Drug and Cosmetic Act. Since the LivaNova 3T heater-cooler device model is manufactured in Germany, it is under restricted import until the violations are corrected.
- On October 15, 2015, the FDA issued Nontuberculous Mycobacterium Infections Associated with Heater-Cooler Devices – Safety Communication to provide recommendations to minimize patient exposure.
- Continuing to evaluate information about documented and potential infections from multiple sources, including medical device reports (MDRs) submitted to the FDA, published studies and updates from U.S and international public health agencies, state and local governments.
- Working with manufacturers to review their existing cleaning and disinfection protocols and determining appropriate interim mitigations.
- Analyzing design characteristics of currently marketed heater-cooler devices to determine whether certain design features contribute to aerosolization, and paying particular attention to such features on any new devices that may come to market.
Reporting Problems to the FDA
If you suspect patient infection(s) possibly associated with heater-cooler devices and/or bacterial contamination of a heater-cooler device, we encourage you to file a voluntary report through MedWatch, the FDA Safety Information and Adverse Event Reporting program.
Device manufacturers and user facilities must comply with the applicable Medical Device Reporting (MDR) regulations.
If you have questions about this communication, please contact the Division of Industry and Consumer Education (DICE) at DICE@FDA.HHS.GOV, 800-638-2041 or 301-796-7100.
2 Sommerstein R, Rűegg. Kohler P, Bloemberg G, Kuster SP, Sax H. Transmission of Mycobacterium chimaera from Heater-Cooler Units during Cardiac Surgery despite an Ultraclean Air Ventilation System. Emerg Infect Dis. 2016 June;22(6):1008-13.).