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, and/or other unsealed openings, into the environment and to the patient.

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On this page:

• The FDA’s Analyses of Heater-Cooler Devices and Nontuberculous Mycobacteria (NTM) Infections
• Potential Root Causes of Contamination
• Testing Status for Cleaning and Disinfection Validation and Aerosolization
• Reporting Problems to the FDA

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The FDA’s Analyses of Heater-Cooler Devices and Nontuberculous Mycobacteria (NTM) Infections

Through the FDA's analysis of adverse event reports, the medical literature, and information from national and international public health agencies, the FDA is 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.

Potential Root Causes of Contamination

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 airtight, 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 study, 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.

Testing Status for Cleaning and Disinfection Validation and Aerosolization

In 2015, the FDA issued a final guidance, Reprocessing Medical Devices in Health Care Settings: Validation Methods and Labeling; Appendix E of the guidance was updated on June 9, 2017 to include heater-cooler devices. The guidance document reflects the scientific advances in knowledge and technology involved in reprocessing reusable medical devices and the FDA’s current thinking on submissions associated with reprocessed medical devices.

Because heater-cooler devices pose a risk of microbial transmission and patient infection through aerosolization if not adequately cleaned and disinfected, the guidance notes 510(k) submissions for these devices should include data to validate cleaning and disinfection instructions. Due to the knowledge gained since the FDA started its evaluation, the FDA is requesting methods to reduce aerosolization when applicable.

• Data to validate cleaning and disinfection instructions includes protocols and test reports demonstrating the procedures reliably and consistently achieve the specified endpoints and the instructions can be followed as intended.
• Data to reduce aerosolization includes protocols and test reports measuring the extent of aerosolization and demonstrating methods to reduce aerosolization (if occurring) are successful.

In the United States, there are currently three companies manufacturing and distributing heater-cooler devices. The table below lists the manufacturers, device models, and the status of the cleaning and disinfection validation and aerosolization testing. The FDA continues to work with heater-cooler manufacturers to ensure they provide testing results, and the FDA will update the table to notify the public when test results are complete and adequate.

Table: Testing status for cleaning and disinfection validation and aerosolization with water-based heater-cooler systems for use in operating rooms by manufacturer and model

Manufacturer	Model	Cleaning and Disinfection Validation	Aerosolization Testing
LivaNova	Heater-Cooler System 3T	Adequate	Adequate
CardioQuip	Modular Cooler- Heater 1000(i)	Pending	Pending
	Modular Cooler-Heater 1000(m)	Pending	Pending
Gentherm Medical LLC	Hemotherm CE Dual Reservoir Cooler/Heater, Model 400CE	Pending	Pending

Definition:

Adequate: The FDA completed its review of the manufacturer-provided data, determined that the data achieves acceptable cleaning and disinfection, or either no aerosolization or a reduction in aerosolization was demonstrated. 

Pending: The FDA is working with the manufacturer to ensure that the protocol for testing is adequate, and/or reviewing test reports.

Related Communications to date include:

Date	Communication	Description
10/13/2021	UPDATE: Potential Risk of Infection When Using Heater-Cooler Devices - Letter to Health Care Providers	To provide updated information to help mitigate potential infection risks when using heater-cooler devices by CardioQuip or Gentherm Medical LLC, and to amplify recall notices to discontinue use of heater-cooler devices by Maquet and Terumo
9/30/2020	Potential Risk of Infection during Cardiac Surgery When Using the CardioQuip Modular Cooler-Heater Device – Letter to Health Care Providers	To provide new information about Mycobacterium abscessus infections associated with the use of the CardioQuip Modular Cooler-Heater Device in patients who have undergone cardiothoracic surgeries and to remind users of recommendations to minimize patient exposure with any heater-cooler device.
2/25/2020	UPDATE: Reduce the Risk of Cardiac Surgery Infection While Using the LivaNova Heater-Cooler System 3T: FDA Safety Communication	To provide updated information to mitigate potential cardiac surgery infection risks associated with the LivaNova Heater-Cooler System 3T.
10/19/2018	Updated Information to Reduce Potential Cardiac Surgery Infection Risks Associated with the LivaNova 3T Heater-Cooler Systems: FDA Safety Communication	To provide updated information to mitigate potential cardiac surgery infection risks associated with the LivaNovaHeater-Cooler System 3T.
6/12/2018	Update: Availability of Deep-Cleaning Service of Certain LivaNova PLC (formerly Sorin Group Deutschland GmbH) Stӧckert 3T Heater-Cooler Systems in the U.S.: FDA Safety Communication	To amplify LivaNova's Medical Correction issued on April 20, 2018.
11/1/2016	FDA 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.
10/13/2016	CDC: Morbidity and Mortality Weekly Report (MMWR)	Notes from the Field "Mycobacterium chimaera Contamination of Heater-Cooler Devices Used in Cardiac Surgery — United States". This report was written by CDC and FDA staff.
10/13/2016	UPDATE: Mycobacterium chimaera Infections Associated with LivaNova PLC (formerly Sorin Group Deutschland GmbH) Stӧckert 3T Heater-Cooler System: FDA Safety Communication	Update to the 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.
6/2/2016 & 6/3/2016	FDA Meeting: Circulatory System Devices Panel	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.
6/1/2016	Mycobacterium chimaera Infections Associated with Sorin Group Deutschland GmbH Stӧckert 3T Heater-Cooler System: FDA 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.
5/16/2016	Non-Tuberculous Mycobacterium (NTM) Infections Associated with Heater Cooler Devices (HCD): FDA Webinar	State, local, tribal and territorial regulatory and public health partners discussed Nontuberculous Mycobacterium (NTM) infections associated with heater-cooler devices and to review recommendations to minimize patient exposures to infections.
12/29/2015	FDA Warning Letter to LivaNova (formerly Sorin Group S.p.A.)	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. Since the LivaNova 3T heater-cooler device model is manufactured in Germany, it is under restricted import until the violations are corrected.
10/15/2015	Nontuberculous Mycobacterium Infections Associated with Heater-Cooler Devices: FDA Safety Communication	To provide recommendations to minimize patient exposure.

Reporting Problems to the FDA

The FDA encourages health care providers and users to report any adverse events or suspected adverse events experienced with any heater-cooler devices, including patient infection, device contamination, or difficulty following manufacturer instructions for use.

Voluntary reports can be submitted 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.

Health care personnel employed by facilities that are subject to the FDA's user facility reporting requirements should follow the reporting procedures established by their facilities.

User facilities participating in the FDA's Medical Product Safety Network (MedSun) should report device related adverse events through the MedSun reporting site, not through MedWatch.

Prompt reporting of adverse events can help the FDA identify and better understand the risks associated with medical devices.

If you have questions about this communication, please contact the Division of Industry and Consumer Education (DICE) at [email protected], 800-638-2041 or 301-796-7100.