Study: Contamination Increased 2000x With Bair Hugger Warming

Minneapolis, MN: March 14, 2013— The use of Bair Hugger forced-air warmers during surgery creates convection currents that capture particles below the surgical table, lifting them into the sterile surgical field, according to research recently published by orthopedic surgeons. The waste heat radiating through the surgical drape induced the formation of tornado-like vortexes of rapidly spinning air near the surgical site. The vortexes sucked contaminated air from the operating room floor and deposited it over the surgical wound. 

2,000 times more contaminant particles were found in the air over the wound with Bair Hugger warming than with air-free HotDog conductive warming. With HotDog patient warming, only 1,000 particles per cubic meter of air were present. With Bair Hugger warming, the particle count was 2,174,000 per cubic meter, an increase of 217,300% 

Concerned by convection currents produced by hot-air warming devices, orthopedic surgeons A.J. Legg and A.J. Hamer from Northern General Hospital in Sheffield, United Kingdom, compared the torso-style disposable blankets of 3M’s Bair Hugger system with the reusable, air-free HotDog conductive warming system. The surgeons released particles below the surgical table and then measured how many were transported to the surgical site. Neither surgeon has any financial relationship with either of the products studied. 

The study was published in the February issue of The Bone and Joint Journal and entitled “Forced-air patient warming blankets disrupt unidirectional airflow.” 

Dr. Scott Augustine, inventor of both products studied, stated, “Such a massive increase in airborne contamination is obviously a safety issue in contamination-sensitive surgeries. In joint replacement surgery, for example, a single airborne bacterium can cause a deep joint infection.” 

Periprosethetic joint infections are often catastrophic: immense pain and suffering, permanent disability and an enormous cost to the hospital. 

“Every joint infection is a disaster—both for the patient and the system,” said Dr. Augustine. “The process is horrific: ex-plant the joint, prolonged hospitalization, 6-8 weeks of IV antibiotics and then—assuming no amputation—re-implant the joint. The average cost is around $100,000.” More than 12,000 of these infections occur each year in the US, a rate that some see as a significant public health problem.

The Paradox of Forced-Air Patient Warming

Studies show that forced-air warming (FAW) reduces soft-tissue surgical infections. How can FAW be linked to increased deep-joint infections?

The paradox is easy to explain: BIOFILM.  A bacterium that lands on a prosthetic implant can secrete a coating of biofilm that protects it from both antibodies and antibiotics. Bacteria in soft-tissue cannot form effective biofilm coatings.

Secretion of biofilm allows a single airborne germ to cause a deep infection of a joint implant (Lidwell, 1983).  When the germ lands on the new implant, it protects itself in a biofilm coating and then sprouts weeks-to-months later as a catastrophic deep joint infection.  The increased airborne contamination from FAW vastly increases the chances of an airborne bacterium landing on the new implant.

In contrast, without biofilm protection, the germs in soft-tissue are susceptible to antibiotics and to an immune system activated by heat.  As a result, the creation of soft-tissue surgical infections require large inoculums of more than 100,000 germs (Elek & Cohen, 1957).

This also explains why soft-tissue surgical infections may not be increased by contaminated FAW air, while blowing even one germ into the surgical site during implant surgery can have significant negative concequences.

Watch this terrific video about bacterial biofilms 

produced by the Arthroplasty Patient Foundation:

Here is another interesting video about bacterial biofilms 

and orthopedic implants produced by the Arthroplasty Patient Foundation:

Evidence of the risks of forced-air warming just keeps growing.

A study published online ahead of print in Anesthesia & Analgesia concludes that forced-air patient warming produces waste heat that disrupts operating room ventilation airflows over the surgical site, transporting non-sterile air to the area and hindering the ventilation system’s ability to clear potential airborne contaminants.

“There are some in our industry that would like you to believe that hot air doesn’t rise,” says Dr. Scott Augustine, “this study proves, once again, that that argument is insulting to science and common sense.”

Belani, et al, focused on contamination-sensitive surgery at the University of Minnesota, using a mannequin draped for total knee replacement.  Introducing neutral buoyancy bubbles near the mannequin’s head, researchers found a significant increase in bubble-count over the surgical site when forced air warming was used, as opposed to conductive fabric or the control.  The study states:

3M accuses Augustine of "instilling fear through misleading claims." Really? Let's look at the facts...

Four independent peer reviewed studies have been published showing that forced-air patient warming devices generate convection currents that disrupt the sterile field.  One such study (McGovern, JBJS-br, 2011) even showed a 74% decrease in deep-joint infection rates after discontinuing the use of forced-air patient warming. They switched to air-free HotDog patient warming (1250 patients, 2.5 years).

Despite this strong evidence, 3M, the manufacturer of Bair Hugger® forced-air warming, has continued to obfuscate and assure the world that its forced-air warming products are universally safe.  In a recent letter to healthcare professionals, Bob Buehler, VP of 3M Patient Warming, even accuses us of “promoting a campaign designed to instill fear through misleading claims.”

To be clear: we are educating the healthcare community about a practice that puts orthopedic patients at risk for infection.  Every claim we make is backed by science and published research.  Our mission is to protect patients and to provide a safe, effective, and affordable solution. 

Evidence Growing Against Safety of Forced-air Patient Warming

Yet another peer-reviewed study—the third in the past five months—has been published showing that forced-air patient warming generates convection current activity in the vicinity of the surgical site, which could lead to contamination of the sterile field.

The study, published by Dr. Kiran Dasari in the March issue of Anaesthesia, is more evidence that a significant patient safety issue exists.  Surgeries with implanted foreign materials, like hip and knee replacements, could be greatly compromised depending on the type of warming technology used.

Another Study Shows the Risks of Using Forced-air Patient Warming

Researchers in the UK published a study in the February, 2012, issue of the Journal of Bone and Joint Surgery-Br examining the effects of forced-air warming on operating room airflow and surgical site sterility.

Summary:

“Forced-air warming resulted in a significant mean increase in the temperature (1.1°C vs 0.4°C, p<0.0001) and number of particles (1038.2 vs 224.8, p=0.0087) over the surgical site when compared with [HotDog®] warming, which raises concern as bacteria are known to require particles for transport.”
 

Study Links Forced-air Warming to Infections: 3.8x Increase In Orthopedic Implant Cases

Previously, research studying the effects of forced-air warming on laminar flow operating theaters was limited to contamination…until now.

The use of forced-air warming during orthopedic implant surgery was associated with a 3.8 times increase in deep joint infections as compared to warming patients without forced-air, according to a newly published study.

FAW's Impact on SSIs

“How can forced-air warming be unsafe when research shows that it reduces infections?”

This is a common question, and the best explanation was given by Yale scientist Dr. Marc Abreu in the October 2010 Anesthesiology News Review. In the article, titled New Concepts in Perioperative Temperature Management: Monitoring and Management, Dr. Abreu wrote that, “…any potential airborne contamination caused by FAW waste heat must have a negligible effect on soft tissue SSIs. However, patients undergoing surgery involving implanted foreign materials, especially for orthopedics, may be at higher risk for infection from airborne contamination.” (emphasis added)

The risk of infection with FAW, at least as established so far, is specific to ultra-clean surgeries involving implanted foreign materials: orthopedics, neuro, and cardiac. There is a fundamental difference in causation between soft-tissue infections and surgical infections involving implanted foreign materials—and that is the point commonly missed.

Latest Evidence of Forced-Air Contamination -- Must See

Here is the latest evidence of forced-air warming units contaminating the operating room by overcoming protective laminar flow ventilation. The room temperature tracer particles and bubbles are neutrally buoyant, which is to say they follow the air currents of the room. When forced-air warming units dump 900 watts of waste heat into the operating room, it is no surprise that we can visualize the effects: heat rises. Notice the laminar flow working properly with conductive fabric warming, or with forced-air "Heat OFF" as control. Then with "Heat ON" watch the stunning evidence of forced-air waste heat mobilizing air from the dirty floor and sending it right up into the surgical site, contaminating it. The evidence speaks for itself: as hot air rises, so does risk.

The Northumbria orthopedic team has set up their own blog to show their findings. With patient safety in mind, they have compiled excellent research and the visual evidence is stunning. To access their blog, click on the following link: www.northumbriaorthopaedics.blogspot.com

Laminar vs. Conventional Ventilation

Common Question: “My OR doesn’t use laminar flow. Does waste hot air still matter?”

Answer: Absolutely. Consider the following:

What is laminar ventilation and what is conventional ventilation?

Operating room air is typically introduced from the ceiling, moves towards the floor, and exits through the side vents. US standards for hospital construction require that operating room ventilation be filtered, at a minimum, to an efficiency of >90% for the removal of germ sized particles. Many ventilation systems do much better than that, by employing High Efficiency Particulate Air filtration commonly known as HEPA, which by definition removes >99.97% of germ sized particles from the airflow.

Posting in "Controversies in Hospital Infection Prevention" Blog

An infectious diseases expert from Richmond, Virginia posted information on his blog about the contamination risk of forced-air warming devices. The blog, titled, "Controversies in Hospital Infection Prevention" had this to say:

Bair Hugger vs HotDog
This morning's New York Times business section has an article about Dr. Scott Augustine, the inventor of the Bair Hugger, a device used in the operating room that uses forced air to keep patients warm so as to reduce postoperative infections. Perioperative warming is one of the Surgical Care Improvement Project (SCIP) metrics. The Bair Hugger is now made by Arizant and Dr. Augustine no longer has any connection to the product. He has invented a new warming product that uses conductive fabric, called the HotDog warmer, and now claims that the Bair Hugger causes infections. The New York Times article points out that there may be some theoretical concerns for infection caused by the Bair Hugger, but no definitive evidence.

We shared a new video with Dr. Edmond that is a snippet from a new CEU presentation that will soon be available about airflow disruptions in the operating room.

Addendum 12/30/10:
Dr. Scott Augustine emailed me about this posting and included a video which allows you to visualize the air currents when a forced air warming device is used. It's worth viewing and I think demonstrates plausibility for increased infection risk.

Latest Laminar Disruption Evidence -- Stunning

Here is yet more clear evidence from the Northumbria orthopedic team, of forced-air warming units disrupting protective laminar flow ventilation. The tracer bubbles are neutrally buoyant, which is to say they follow the air currents of the room. Notice the laminar flow working properly with conductive fabric warming. Then watch the stunning evidence of forced-air waste heat mobilizing air from the dirty floor and sending it right up into the surgical site, contaminating it. The evidence speaks for itself: as hot air rises, so does risk.

The Northumbria orthopedic team has set up their own blog to show their findings. With patient safety in mind, they have compiled excellent research and the visual evidence is stunning. To access their blog, click on the following link: www.northumbriaorthopaedics.blogspot.com

More Evidence of Forced-Air Disrupting Protective Laminar Flow

Here is more clear evidence from the Northumbria orthopedic team, of forced-air warming units disrupting protective laminar flow ventilation. As you can see in the video, the addition of normal operating room factors like operating lights, and even an anesthetist, can increase the negative impact of forced-air blowers on proper laminar flow.

This evidence begs the question: should normal operating room procedures be held captive by the fickle whims of the waste heat air currents from forced-air warming units? Now there is an alternative. Free your operating room, replace the forced-air warming units: with non-disruptive, air-free conductive fabric warming.

The Northumbria orthopedic team has set up their own blog to show their findings. With patient safety in mind, they have compiled excellent research and the visual evidence is stunning. To access their blog, click on the following link: www.northumbriaorthopaedics.blogspot.com

Laminar Disruption: Forced-Air Compared to Conductive Fabric Warming

The orthopedic team at Northumbria Healthcare NHS Trust in the UK has shown a great interest in the effects of air movement in laminar flow operating environments. In orthopedics, airborne contamination is a primary concern, given the susceptibility of implantables to sepsis. The Northumbria orthopedic team spends vast sums of money on protective laminar flow ventilation systems and personal isolation "space suits" for this very reason. With the primary goals of providing better care to patients and improving patient safety, the Northumbria orthopedic team set out to investigate and eliminate potential sources of infection.

After testing different forms of positioning and draping, they investigated the equipment in their operating room. Forced-air warming equipment, with its disruptive air flow and vast wattage output, was a natural object of concern. Their findings were quite shocking.

This video, produced by the Northumbria orthopedic team, shows the disruptive effect of forced-air equipment on protective laminar flow, using neutral-buoyancy helium bubbles to show air currents. As a control, the team tested conductive fabric warming blankets as well. The video evidence is quite clear: forced-air, in a normal operating room setting, disrupts laminar flow. Conductive fabric warming does not. Prudence, and good sense, dictates that these findings be taken into consideration when choosing between forced-air and conductive fabric warming systems.

The Northumbria orthopedic team has set up their own blog to show their findings. With patient safety in mind, they have compiled excellent research and the visual evidence is stunning. To access their blog, click on the following link: www.northumbriaorthopaedics.blogspot.com

Hot Air Disrupts the Protection of Laminar Flow

Watch the Video about Laminar Flow Disruption by Forced-air Warming



Please watch the video. It is honest, unaltered footage taken in a simulated OR of laminar flow ventilation being disrupted by forced-air warming. What you will see is physics at work.

The physics is simple: heat rises! After passing over the patient’s skin and dropping near the dirty floor, the waste hot air rises--overpowering the ultra- clean downward air current of laminar flow-- and then, having cooled, falls into the surgical site.

Reducing surgical site infections (SSIs) is of the highest priority for hospitals, insurance companies, and national health initiatives. Not to mention patients and their families.

Providing an ultra clean surgical environment with laminar flow has become the standard of care because it helps reduce hospital acquired infections. A study cited by the Centers for Disease Control revealed a reduction in SSIs from 3.4% to 1.6% merely as a result of laminar flow.

Warming surgical patients, of course, is also the standard of care. Normothermic patients are far less likely to acquire a post-operative wound infection—64% less likely by one study (Mahoney, AANA J, 1999)—than those who aren’t warmed. The device used to warm patients, however, should not increase the risk of bacterial contamination.

Fortunately, there is an [air-free] alternative. HotDog® conductive fabric warms as effectively as forced air, but is safe, eco-friendly, and much less expensive.

We encourage you to conduct the simple test detailed at the end of the video to prove that the forced-air exhaust heat rises in your operating room. Of course, it will. Hot air always rises.

We want to hear your comments about hot air and its effects on laminar flow. Your thoughts and knowledge are important to us.