The Heater Cooler Conundrum: Has the Sky Fallen?

“If anyone has a chart or list/table that compares all of the current Heater Coolers, that would go a long way to helping institutions make informed choices as to selecting systems that have the smallest potential footprint regarding impact on laminar flow in the OR, as well as the least amount of potential pt. exposure to these pathogens.”

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FA 2016

Editor’s Note:

I’m sure all  of us are equally concerned regarding the surge of FDA reports and studies discussing the dissemination of mycobacterium chimaera, a slow-growing mycobacteria, that is aerosolized by Heater-Coolers during the conduct of open heart surgery and cardiopulmonary bypass.

While one or two manufacturers have been identified regarding their particular Heater Coolers, the jury is still not out as to the across-the-board implications for the other models out there.

Some institutional adjustments have gone as far as to extend the water lines and placing the HC outside of the OR suite, with another clinician operating the device controls.  The theoretical 5 meter barrier limit (length of water lines)?  Is it an issue?  And how are institutions or perfusionists bypassing (no pun) it?

If anyone has a chart or list/table that compares all of the current Heater Coolers, that would go a long way to helping institutions make informed choices as to selecting systems that have the smallest potential footprint regarding impact on laminar flow in the OR, as well as the least amount of potential pt. exposure to these pathogens.


Plz feel free to render advice on how you are dealing with these issues, and share your ideas or suggestions on how to mitigate the impact.

Thanks 🙂


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What exactly is going on here?

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Click image above to view source article

  • 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 the device’s heat exchanger(s) or to 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 (0.2 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. Air filters located on some units are not efficient enough to capture NTM bacteria. An air filter that has the capability to capture NTM bacteria may alter device safety or performance and would therefore need to be evaluated by each 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.


  • Laminar flow disruption:
    Laminar air flow refers to an engineering control within the operating room environment that intends to provide protection by reducing the risk of airborne exposure to bacteria or other contamination 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 that NTM that is airborne may then be carried into the surgical field.

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Getting to the True Scope of the Issue


Kudos to the Authors as well as Specialty Care– for writing and sponsoring this excellent article!  The full article is in PDF format, can be viewed and downloaded by clicking HERE.


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Reality Check

Impact and Notes:  (Not to diminish the seriousness of the situation, but rather to put it into a rational perspective.)

  • Nosocomial infections are a recognized risk in any operating room theater.
  • These organisms in a lot of places in the operating room as well your home environment- HVAC systems  (Heating and Cooling)
  • Absolutely countless patients as well as clinicians are and have been exposed to these organisms since inception of not only open heart bypass, but the myriad of other operations that require similar devices etc-
  • Excessive device cleaning, does not necessarily eliminate the microorganism.
  • Class action law suits and litigation are far more opportunistic and beginning to pop up.

Background: Non-Tuberculous Mycobacteria (NTM)

  • Common water-borne environmental contaminant
  • FDA has recognized that “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 very ill
    patients and/or in individuals with compromised immune systems.”
  • NTM presence can result in post-surgical infection only if directly
    transmitted to the patient
  • Rare transmission by aerosolization only recently appreciated
  • NTM post-surgical infection appears to be exceedingly uncommon.
    • For example, in an October 2015 publication, Public Health England stated:
      “This new risk is extremely small. Approximately 1 in 10,000 patients having this type of surgery might be affected. This level of risk is so small that surgery
      should not be delayed, as the risks of delaying surgery are greater than proceeding.”
    • “This risk identified above is extremely small compared to the background risk of infection recognized following this type of surgery.”

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FDA Recommendations:

Recommendations for Health Care Facilities and Staff
In addition to following standard precautions, the FDA recommends that facilities and staff using heater-cooler devices consider implementing the following measures to reduce risk to patients:

  • Strictly adhere to the cleaning and disinfection instructions provided in the manufacturer’s device labeling. Ensure you have the most current version of the manufacturers’ instructions for use readily available to promote adherence.
  • Do not use tap water to rinse, fill, refill or top-off water tanks since this may introduce NTM organisms. Use only sterile water or water that has been passed through a filter of less than or equal to 0.22 microns. When making ice needed for patient cooling during surgical procedures use only sterile water or water that has been passed through a filter of less than or equal to 0.22 microns. Deionized water and sterile water created through reverse osmosis is not recommended because it may promote corrosion of the metal components of the system.
  • Direct the heater-cooler’s vent exhaust away from the surgical field to mitigate the risk of aerosolizing heater-cooler tank water into the sterile field and exposing the patient.
  • Establish regular cleaning, disinfection and maintenance schedules for heater-cooler devices according to the manufacturers’ instructions to minimize the risk of bacterial growth and subsequent patient infection.
  • Develop and follow a comprehensive quality control program for maintenance, cleaning, and disinfection of heater-cooler devices. Your program may include written procedures for monitoring adherence to the program and documenting set up, cleaning, and disinfection processes before and after use.
  • Immediately remove from service heater-cooler devices that show discoloration or cloudiness in the fluid lines/circuits, which may indicate bacterial growth. Consult your hospital infection control officials to perform the appropriate follow up measures and report events of device contamination to the manufacturer.
  • Consider performing environmental, air, and water sampling and monitoring if heater-cooler contamination is suspected. Environmental monitoring requires specialized expertise and equipment to collect and process samples, which may not be feasible in all facilities.
  • Health care facilities should follow their internal procedures for notifying and culturing patients if they suspect infection associated with heater-cooler devices.
  • Submit a report to the manufacturer and to the FDA via MedWatch if you suspect heater-cooler devices have led to patient infections.

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8 thoughts on “The Heater Cooler Conundrum: Has the Sky Fallen?

  1. Split comments due to word count: Firstly, in answer to the practical question of the extended water lines above. The length of the pipe is limited, as when the operator ‘pulls back’ the circulating water into the tank by closing the circuits, there is only 500ml spare space in the water tanks. Longer lines would need bigger tanks.
    I have worked on the original studies of these pieces of equipment, in operational use. This study led to the development of sterilisation procedures as an ongoing, possibly permanent process in our facility. We worked with only one manufacturers device, so I cannot comment on any other pieces of equipment. Initially, the recommended biocide used, on the last generation of devices, de-plated the interior surfaces of the water tank. This led to the emission of gases, believed to be nickel oxide, in the OR. This was presumed to be at relatively low levels. These machines were quickly swapped out and the current generation of heater/coolers commissioned. (cont.)

  2. In my opinion, these machines were not field-ready. Specifically, they have issues with the pumping mechanism, design of the filler which is open to the air, and level measurement technology. This required the devices to be filled at a very slow rate in order for the correct fill level to be reported by the machine (less than 2l/min), otherwise it would generate a fill level error. Anyone who knows how biofilms are formed in terms of planktonic mycobacteria laying down exopolysaccharides as an adhesive foundation before building a matrix, would know that the risk here is lack of shear force operating on the interface of the interior of the water supply pipework to dislodge this layer. My thoughts were that this may raise the risk of Legionella. (cont.)

  3. Legionella pneumophilla was duly found in water samples at 60cfu. It also became apparent that these units were acting as a ‘canary in the coalmine’ in clinical settings. There were two principal reasons for this as far as I am able to see. Firstly, the presence of other water-containing, air-blown devices in the OR. These include, but are not limited to, patient warmers, head coolers, ecmo heater/cooler units. It was clear to me that there was both an infection interaction between these different pieces of equipment via aerosol. Secondly, that the patient on the table could be a source of transmission of pathogens to the open-to-air units. (cont.)

  4. In our case, we dealt with CF procedures in mixed patient OR’s, and found Pseudomonas Aeruginosa, commonly found in the lungs of CF patients. Along with other fungal and mycobacterial cultures common in the general environment, including Gordonae, Chellonae etc. We did not find Chimaera. The other issue to note is that part of the sterilisation procedure requires that dilute H2O2 is added to the water tank as an bacterial inhibitor. My reading suggests that this may actually be a possible cause of mutagenicity for organisms within the water tank. The larger concern are the ecmo units, which can be sterilised, but are sent back with inevitable traces of water in the pipework. They are then stored ‘dry’ until use. To date, there is no reliable method of ensuring that these components are colony-free when used, as far as I am aware.

  5. I personally believe this problem has been with us since we started using heater/coolers. I recall in the mid-’90s following the protocols for monthly cleaning/maintenance and daily chlorine verification of Sarns TCMs. We never gave it any thought despite the exposed water tanks of these machines. When it became an issue was at the onset of the OPCAB era when a Chief suggested and allowed the nurses and techs to wet their bandanas to wear in a hot 80 degree OR over an open chest. I strongly objected to this practice given I had to clean and maintain these machines. It was obvious my chief had never considered contamination due to the “maintained chlorine levels.” To convince him I cultured the water and shared the results with him. The list of bacteria spanned 3 pages and had Infectious Diseases inquiring about the source. That practice stopped immediately. We grew over 28 different bacteria from that chlorinated water sample(reverse osmosis was the source of the replacement/cleaning water) I’m surprised this is only now becoming an issue. With the 3Ts we utilized Chlorox then moved to Minntech solution but we never went as far as culturing the water…

  6. I should add that I was more concerned about patient infection rates rather than the cleaning process, which though laborious, was a minor consideration. Patient infection rates depend on the entire treatment process. It’s up to each specialty to eliminate all variables that contribute to infections. That being said, Perfusionists are not Biomeds and I question our participation and accountability in this process.

  7. On the 3T’s, we were initially getting TVC’s of between 8-14,000 cfu after the field notice came out. We then switched to a daily water change with dilute h2o2 and a weekly disinfection. We were using Purasteril, which de-plated the tanks after 11 disinfections, releasing nickel and copper particles into the oxygenator. After that, we swapped to flextherms, but they have been so much trouble. The flextherms were not fully field tested, in my opinion. Even with this protocol and every possible precaution, and elaborate filtration, we are still sometimes getting high TVC’s of >100 cfu. after periods of 0-5. We have evolved a completely separate Dept. It’s one of those things that wasn’t ever considered a high risk, along with the other aerosol-producing units in theatre.There are so many variables as to mains quality, filter saturation, environment. I would be interested in your bacteria list if you can be bothered, Ted. Just to see how much of an overlap there is.

  8. That situation occurred in 1998 and I have since moved on. I would tell you that it encompassed almost every known bacterium to me and then some( Staphs A/E, Salmonella, EColi, Pneumococcus’, all the more common types and on and on…). You might have just as well been culturing “gray water.”

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