Heater-cooler devices are necessary for use in certain surgeries to regulate a patient’s body temperature (to keep them from becoming too warm or too cold). These devices are especially important for use in surgeries involving the heart and lungs (cardiothoracic surgeries), such as cardiopulmonary bypass procedures, which involve the intentional and temporary stopping of a patient’s heart and/or lung functioning.
Heater-cooler devices are categorized as Class II devices by the U.S. Food and Drug Administration (FDA). They have been approved for use in medical practice for a little more than a decade. As defined by the FDA, Class II devices “are higher risk than Class I and require greater regulatory controls” to ensure the device’s safety and effectiveness.
The surgical-assistive devices fall under one of two cardiovascular (relating to the heart and blood vessels) classification regulations: cardiopulmonary bypass (CPB) temperature controller or thermal regulating system. Although they fall under cardiovascular classification regulations, heater-cooler devices can be used in a variety of other medical procedures as well.
In 2015, the FDA issued a safety communication advising the public and health care practitioners of a certain serious, potentially fatal, bacteria associated with heater-cooler devices. The bacteria known as nontuberculous mycobacterium (NTM) is commonly found in the environment in our natural resources, such as water and soil.
While the bacteria are generally not harmful, exposure can lead to infections in some patients, especially those who have undergone open-chest surgery. Treatment can persist for months and even years; and if left untreated, patients infected by NTM can be at risk of death.
How Does a Heater-Cooler Device Work?
The heater-cooler device includes a water tank separating warm water from cold water as well as a heater-cooler unit with an air inflow and outflow. It provides temperature-controlled water to an external heat exchanger, such as a heart-lung machine, or to warming/cooling blankets through closed water circuits (no contact with open air). This mechanical process helps maintain homeostasis (internal balance versus external changes) in a patient’s body.
The water in the heater-cooler device is isolated from the patient, the cardioplegia (intentional and temporary stopping of the heart) solution and blood circuits.
Heater-coolers falling under the classification of a cardiopulmonary bypass (CPB) temperature controller are typically associated with heat exchangers and devices such as blood oxygenators, used to keep blood circulating and maintaining organs at a specific temperature. Those falling under the thermal regulating system classification are generally used with warming/cooling blankets.
Cardiothoracic surgeries involve any surgical procedure having to do with the heart, lungs, esophagus and other organs in the chest. There are two types of Cardiothoracic surgeries: Thoracic surgery and Cardiac surgery.
Thoracic (having to do with the part of the body between the neck and the abdomen, primarily the chest) surgeries are usually performed to treat the lungs, esophagus and chest wall.
Thoracic surgeries can treat the following conditions:
- Lung cancer
- Benign diseases and tumors of the lung
- Chest reconstruction
- Esophageal (esophagus) cancer
- Esophageal reconstruction
- Benign tumors in the esophagus
- Gastroesophageal reflux
- Pleural (lung membranes) diseases
- Chest wall tumors
- Excessive sweating
- Lung transplant
- Insertion of stent for narrowing airways
Cardiac procedures or surgeries
Cardiac (relating to the heart) surgeries are performed to treat the heart, heart valves and arteries in the heart and chest.
Some cardiac procedures or surgeries include:
Angioplasty – Surgical repair or unblocking of a blood vessel
Artificial heart valve surgery – To replace a damaged heart valve with a functioning one
Atherectomy – To remove atherosclerosis – build-up of fats, cholesterol and other substances – from blood vessels)
Bypass surgery – Taking arteries or veins from other parts of the body –grafts – and using them to reroute blood around a blocked artery)
Cardiomyoplasty – Healthy muscle from another part of the body is wrapped around the heart
Heart transplant – Replacing an old heart with a new one.
Insertion of stents – To open arteries, improve blood flow or relieve chest pain (angina)
What is a Cardiopulmonary Bypass?
For a cardiothoracic surgeon to work in the vicinity of the heart and lungs, they need to stop a patient’s blood flow, which means they need to stop the heart and lungs from functioning. A cardiopulmonary bypass (CPB) requires the intentional and temporary stopping of these vital organs.
A cardiopulmonary bypass (CPB) temporarily stops the flow of blood to the heart and lungs in order to perform cardiothoracic surgery.
In order to keep blood flowing to all of the other organs throughout the body, delivering oxygen and other essential nutrients to sustain life, physicians utilize the process of CPB.
During this process, blood is rerouted from the body through special tubing into a mechanical pump that is regulated for the patient’s specific cardiac output. From there, the blood runs into an oxygenator (artificial lung) where carbon dioxide is removed and oxygen is restored. The blood is then transported back to the body through another tube placed in the aorta, the main artery in the body.
The mechanical pump and other devices are often collectively called the heart-lung machine. When the patient is support by the heart-lung machine, they are said to be “on bypass.”
Heater-Cooler Device Brands Used In Surgeries
Various manufacturers are responsible for the manufacturer and marketing of several different brands of heater-cooler devices used in surgeries. One of the primary manufacturers is LivaNova, PLC, previously known as Sorin Group Deutschland GmbH.
LivaNova is the maker of the Stockert 3T heater-cooler, which has been used in about 60 percent of the 250,000 surgeries performed in the United States requiring a heater-cooler device. The German-made model has also been the front-runner in controversy surrounding the safety of the devices and patients’ potential exposure to possibly life-threatening bacteria through the use of them.
Other manufacturers and heater-cooler device brands include:
- Maquet – Heater-Cooler Unit HCU 40 (as well as older models)
- Medtronic, Inc. – Biotherm Heat Exchanger and ECMOtherm II Heat Exchanger
- Alsius Corporation – Thermoguard XP
- Jostra AB – Jostra HCU 30
- Cincinnati Sub-Zero Products, Inc. – Cicinnati Sub-Zero Hemotherm 400CE Dual Reservoir Cooler/Heater and CSZ Hemotherm 400MR
- Terumo (Sarns) Cardiovascular Group – Terumo HX@ Heater Cooler; Terumo Sarns 11160 Heater Cooler and Terumo Sarns TCM II Heater Cooler
Heater-Cooler Device Complications
Between January 2010 and August 2015, the FDA received 32 Medical Device Reports (MDRs) of patient infections resulting from contaminated heater-cooler devices used during various open-heart or open-chest (bypass) surgical procedures. In 2015 alone, the FDA received a total of 25 of those 32 reports.
The particular bacteria causing the infections were found to be nontuberculous mycobacteria (NTM).
In some cases, patients became aware of the infections months or even years following their surgeries. The FDA noted that for this reason, it is possible that not all cases have been reported. In 2016, the Washington Post reported that “more than a half-million patients could have been exposed to the bacteria.”
The FDA issued its first safety communication regarding the problem in 2015, advising the public of a link between the use of heater-cooler devices and contracted NTM infections. The agency pointed out that the majority of patients acquiring the infection had undergone cardiothoracic surgical procedures.
The FDA said that the bacteria, which is also found naturally occurring in sources such as water (including tap water) and soil, is typically not harmful. However, the agency added that in some cases it “may cause infections in very ill patients and/or in individuals with compromised immune systems,” which would include the majority of patients undergoing cardiothoracic surgical procedures.
Contamination from Heater-Cooler Devices
The bacterial contamination of heater-cooler devices originates in the devices’ water tanks. The water tanks hold temperature-controlled water that is provided to external heat exchangers or warming/cooling blankets through closed circuits (sealed from outside elements). The FDA reported that “there is the potential for NTM bacteria to grow in a water tank in the heater-cooler units.”
Although the water in the circuits never comes into direct contact with the patient, there is the potential for the contaminated water source to enter other parts of the device or to transmit the bacteria through the air. The possibility of airborne bacteria exposure is due to the device’s exhaust vent producing an inflow and outflow of air, which can filter into the environment and the patient during a surgical procedure. This is called aerosolization, which is the process of converting a physical substance into the form of particles able to be carried in the air (aerosol).
Factors that may increase the potential for aerosolization of NTM bacteria
- Water agitation or bubbling inside the tank via pumps (heart-lung machines)
- Mixing components
- Return circuit water
Additional environmental and device-specific factors
- Laminar (constant streamline) flow disruption the location and the positioning of the device’s exhaust fan may come into play here
- Air filters – some heater-cooler devices have them and some do not; but most are likely unable to capture NTM bacteria
- Water filters – not all devices have these either; but these should be able to remove most NTM from tap water used in the device
- Fans – these are on most devices and may facilitate the movement of aerosolized NTM from the device into the operating room
In 2016, the Centers for Disease Control and Prevention (CDC) alerted hospitals and patients of the potential for exposure to NTM for patients who underwent open-heart or open-chest surgeries involving the Stockert 3T heater-cooler device going back to January 1, 2012.
The CDC said in its health alert that “new information” indicated that the devices manufactured by LivaNova were contaminated with the bacteria during manufacturing.
Signs and Symptoms of Nontuberculous Mycobacteria (NTM) Infection
Nontuberculous mycobacteria infections are rare, affecting only one in 100,000 people in the U.S. each year. However, the CDC advised that in hospitals where at least one infection has been identified following surgeries utilizing the 3T heater-cooler device, the risk of NTM infection is closer to one in 100 or one in 1,000 patients.
NTM does not cause tuberculosis and it is not contagious. However, it can cause severe lung disease especially in individuals with impaired immune systems. The FDA concluded that NTM infections were appearing more frequently in patients having open-chest surgery and receiving an implanted device, such as a heart valve or vascular (relating to blood vessels) graft.
NTM infections may take months or even years to develop following exposure to the bacteria.
Some signs and symptoms of NTM infection include:
- Loss of energy
- Difficulty breathing
- Muscle pain
- Joint pain
- Night sweats
- Weight loss
- Lack of appetite
- Abdominal pain
- Persistent cough or cough with blood
- Redness, heat or pus at the surgical site
Diagnosis and Treatment of NTM Infection
Early diagnosis of NTM infection can be difficult because some patients do not experience any signs or symptoms of the disease until months or even years after introduction of the bacteria has occurred. Infection or disease that occurs after NTM exposure can result in a slow progressing yet very destructive condition.
The bacteria can infect the airways and lung tissue in more susceptible individuals causing inflammation in the respiratory system. Without treatment, many patients will develop a progressive lung infection that can take months and more likely years to treat. Over half of the individuals acquiring a lung infection will experience lifelong recurring symptoms and/or complications even after treatment.
- Detailed medical history, including knowledge of a recent open-heart/open-chest surgical procedure
- Physical examination
- Computed tomography (CT) scan
- Sputum (or mucous) culture
A CT scan can show small nodules (an abnormal lump or swelling of cells, sometimes called “tree-in-bud” because it appears “branch-like”) or, in some more advanced or destructive forms of the infection, cavities or holes in the lungs. But a definitive diagnosis is made through the evaluation of a culture of a specimen obtained from the respiratory system, such as a sample of the patient’s mucous.
Treatment is most effective when started early. Some patients may require prolonged treatment for months or even years. Some heart valve patients who develop the infection following a cardiac surgery may require additional surgeries. In any case, most treatment options of NTM infection are long and often accompanied by several side effects from antibiotics. However, if left untreated, NTM infections can become fatal.
Since the bacteria is often resistant to antibiotics and/or can become resistant over time, treatment often requires the use of two or more antibiotics to effectively combat the illness. Treatment typically continues until a patient’s respiratory cultures produce negative results for at least 12 months.
Regular blood testing and/or vision and hearing tests may be necessary to make sure patients are handling the drugs well.
Sorin Group Recalls its Heater-Cooler
In June 2015, Sorin Group, now known as LivaNova, recalled its Stockert 3T Heater-Cooler devices due to “potential colonization of organisms, including mycobacteria.” The recall noted that the potential is greater if devices are not properly disinfected and maintenance is not performed per the Instructions for Use.
The FDA determined cause at the time was an “error in labeling.”
In a Field Safety Notice sent to all potentially affected customers, the manufacturer instructed them to “review their inventory and identify any affected devices.” They were further advised to “strictly adhere” to the new Instructions for Use.
Potentially affected devices were distributed worldwide and nationwide in the U.S., reaching nearly 100 various consumer markets around the globe.
FDA Warning Letter and Ongoing Investigations
The FDA issued a Warning Letter to LivaNova in December 2015 after inspecting its facilities at two different locations, one in Germany and one in the U.S. The letter stated that during the FDA’s inspection of LivaNova’s Germany facility investigators determined the “firm’s devices are adulterated” in methods used for manufacturing, packing, storing or installation.
The FDA found that such practices were "Not in conformity with the current good manufacturing practice requirements of the Quality System regulation.”
The FDA noted that as a part of its recall, the company issued a Design Change Order to update its cleaning and disinfection Instructions for Use following complaints of patient deaths due to infections caused by the Stockert 3T. But the FDA concluded that the acceptance criteria for the test did not demonstrate that the updated procedures produced a reduction in bacteria.
In an updated FDA safety communication in 2016, the FDA confirmed that NTM infections reported after certain surgeries, particularly bypass or open-heart surgeries, were directly linked to the LivaNova’s 3T heater-cooler device. The specific type of NTM associated with the device was classified as Mycobacterium chimaera (M. chimaera).
The FDA advised patients that in the U.S. most cardiopulmonary bypasses include the use of a heater-cooler device. It was further found that the affected devices may have been in distribution up until 2014, with the first incident of infection being reported as early as 2012.
The FDA said that the manufacturer initiated an ongoing corrective action in July 2015 and is subject to future updates to be evaluated by the FDA “for their ability to further reduce infection risk.”
The FDA said that it would remain “actively engaged” in the process.