Heater-cooler devices regulate a patient's body temperature during cardiopulmonary bypass surgeries like lung transplants or open-heart surgery. But the FDA and studies link these devices to dangerous nontuberculous mycobacteria (NMT) infections that can cause serious illness and death.
Heater-Cooler devices are machines that regulate a patient’s body temperature during cardiopulmonary bypass procedures such as organ transplants or open-heart surgery. When a doctor needs to temporarily stop the heart, a procedure called cardioplegia, heater-cooler devices help regulate blood flow and temperature. Water tanks on the machines provide temperature-controlled water to external heat exchangers or warming/cooling blankets through closed circuits.
Some cardiopulmonary bypass surgeries that may use a heater-cooler include:
- Heart valve replacement
- Heart transplant
- Lung transplant
- Coronary artery bypass graft (CABG)
- Extracorporeal membrane oxygenation (ECMO)
- Left ventricular assist device (LVAD) implant
- Aortic anomaly surgery
- Pulmonary artery banding
- Lung resection
While these devices serve an important role in cardiothoracic surgeries, the U.S. Food and Drug Administration recently warned that these devices can spread bacteria into a patient’s chest cavity during surgery. The bacteria, called nontuberculous mycobacteria (NTM), may cause serious, life-threatening infections. Patients undergoing heart or lung surgery are especially vulnerable because of their compromised health.
Officials at several Pennsylvania hospitals recently linked heater-cooler devices used in cardiac surgery to outbreaks of NTM. So far, NTM infected about 20 people in the state, and possibly hundreds more. Patients infected by NTM filed lawsuits against heater-cooler device manufacturers, saying the device is defective.
In October 2016, the CDC and FDA issued a stronger warning for patients and hospitals regarding the Sorin Stockert 3T, the most popular brand of heater-cooler. Sixty percent of about 250,000 heart bypass procedures in the U.S. use the Sorin Stockert 3T. According to the CDC, the risk of contracting an NTM infection from the device is “between about 1 in 100 and 1 in 1,000.”
Heater-Cooler Device Brands
The Sorin Stockert 3T — one of the first heater-cooler devices approved by the FDA in 2006 — is the most popular heater-cooler device. There are other FDA-approved heater cooler devices, however.
Heater-Cooler device models include:
- Sorin/Liva Nova Stockert 3T
- Maquet HCU20, HCU30, HCU40
- Cincinnati Sub-Zero 333W and Hemotherm
- Terumo HX2
Infections Associated with Heater-Coolers
Nontuberculous mycobacterium (NTM) are a specific type of bacteria linked to heater-cooler devices. These organisms are common and exist in the environment in water and soil. Typically, these bacteria do not pose a threat to healthy people. But people who are ill, have compromised immune systems or chronic diseases are susceptible to infection.
Heater-coolers have water tanks that provide temperate-controlled water. There is a potential for this water to become contaminated and grow bacteria. The patient is not directly exposed to the water, but the bacteria can pass through the device’s exhaust vent and spread into the air by the fan. Once airborne, the bacteria may enter a patient’s chest cavity or contaminate an implant during surgery, according to a 2015 Swedish study published by Hugo Sax and colleagues in Clinical Infectious Diseases.
According to the Society for Healthcare Epidemiology of America (SHEA), the most commonly reported infection from hospitals within the organization’s network is Mycobacterium chimaera. M. chimaera is not commonly found in humans and studies link its transmission to heater-cooler devices.
There are several types of NTM infections that heater-coolers may spread, these include:
- avium intracellulare
So far, M. chimaera cases linked to water-heaters make up the majority of reports. According to studies, NTM bacteria is slow growing and may not produce symptoms for months or even years after the infection. This makes it difficult to diagnose. In Dr. Hugo Sax’s 2015 study, it took between 1.5 and 3.6 years before patients presented with symptoms.
While the FDA warned the public about NTM, heater-cooler devices at the University of Washington Medical Center tested positive for another bacteria, Legionella. Legionella causes Legionnaries’ disease, a serious type of pneumonia. Two of the infected patients died, the Seattle Times reported in September 2016.
Diagnosing Heater-Cooler NTM
Doctors use blood tests to diagnose these infections, but often do not test patients without symptoms. In the wake of the recent outbreaks, the Centers for Disease Control and Prevention released a guide for identifying patients who may have NTM infections from surgeries that require cardiopulmonary bypass. The CDC suggested doctors evaluate three criteria to identify patients at risk for possible NTM infection: laboratory assessment, clinical assessment and exposure assessment.
This involves culturing NTM bacteria from blood, pus, tissue or an implant. Each hospital or institution may take different amounts of time to do a lab review. Most hospitals test after four years because it can take that long for patients to show symptoms, the CDC said.
Doctors cross-reference NTM-positive cultures with medical records to identify patients who suffered from certain infection-related conditions, including:
- Wound infection
- Blood infection
- Infection in lungs, bones, or organs
- Inflammation in the chest
If patients meet criteria from lab or clinical assessment, doctors will check for a history of cardiopulmonary bypass. The CDC urges doctors to report their findings to the FDA and local and state authorities.
A person infected with NTM may not be aware of the symptoms immediately. Patients who had a transplant or other type of open-chest surgery should be aware of several symptoms of infection. Also, it is important to remember that someone infected with NTM might have symptoms of infection several years after the original surgery where they were infected.
These symptoms include:
- Night sweats
- Difficulty breathing
- Persistent cough
- Joint or muscle pain
- Weight loss
In studies, people who did not have a compromised immune system most commonly reported symptoms of fever, fatigue and muscle and joint pain.
Treatment of NTM
Doctors typically treat NTM infections with a number of antibiotics, but they can be difficult to treat. There is a 50 percent chance that patients may die as a result.
But, if doctors implanted a device into a patient’s chest, this implant may also be infected. In this case, the patient will have to undergo more surgery to remove the infected implant and replace it.
There have been a few recent studies on the problem of NTM bacteria transmitted by heater-coolers. Rami Sommerstein and colleagues published one of the most recent studies in Emerging Infectious Diseases in June 2016. Using smoke-disbursal techniques and video observation, researchers found bacteria particles could travel from the ventilator unit of the heater-cooler and reach the surgical area where they could infect the patient. Hospitals in the U.S. and in Europe reported contaminated units.
In Sax and colleagues’ 2015 study, researchers found six male patients between 49 and 64 years old with prosthetic valve endocarditis or vascular graft infection from M. chimaera. Using biopsies, blood cultures or heart tissue samples, doctors were able to diagnose the infection. They also found the bacteria in heater-cooler units used during the surgeries.
The FDA released its first safety communication about heater-cooler devices and NTM infections in October 2015. The agency reported it received 32 Medical Device Reports (MDRs) or infections linked to hearer-cooler devices or reports of contaminated devices. The majority of these reports came in 2015. Eight of these reports came from the U.S. But, the agency said it is possible there are more unreported cases.
Since then, there have already been more incidents of NTM infections from heater-coolers. For example, the recent outbreak in Pennsylvania where officials identified at least 20 cases statewide. There may be hundreds more that are infected without symptoms.
In June 2016, the FDA narrowed its focus to one specific heater-cooler, the Sorin Group Deutschland GmgH Stockert 3T, also called the Sorin Stockert 3T. The FDA warned that the manufacturer shipped devices contaminated with M. chimaera worldwide.
So far, only one manufacturer issued a Class II recall, Sorin/Liva Nova. In July 2015, the company recalled the Sorin Stockert 3T, 120V/60 Hz because of M. chimaera contamination “if proper disinfection maintenance is not performed per instructions for use.”
Sorin Group issued letters to all affected customers in June 2015. The company told customers to maintain-heater coolers according to the instructions. The manufacturer also required a signed confirmation form. The recall involved 1,755 units.