New ECRI Guidance Expresses “Concern” About Forced-Air Warming in Implant Surgery

In the latest issue of Health Devices, ECRI Institute analyzed the safety of forced-air patient warming, concluding that thermal currents are “particularly worrisome” in implant surgery. Dr. Scott Augustine, inventor of both Bair Hugger and (air-free) HotDog patient warming and CEO of Augustine Temperature Management, comments.

Minneapolis, MN (PRWeb), April 17, 2013 -  After reviewing multiple published, peer-review articles addressing the consequences of the convection currents created by the waste heat produced by forced-air devices, ECRI stated:

• “The disruption of air-flow patterns is particularly worrisome in laminar-flow and ultraclean ORs, in which a wide variety of implant surgeries are performed.”
• “This is especially concerning during orthopedic surgeries because contamination of the surgical site may present a greater risk of developing a PJI, which is harder to treat and resolve than would be the case with SSIs in general.”

Video Evidence of the Vortex Caused by the Radiant Waste Heat from FAW Blankets

The video clip below is an excerpt from a nurse education course.  It shows the vortex-effect caused by the radiant waste heat from forced-air patient warming (FAW) blankets, similar to what was recently studied and published by orthopedic surgeons A.J. Legg and A.J.Hamer.

The Legg and Hamer study, published in the Bone & Joint Journal in March 2013, is different than the four previous studies examining the unintended consequence of FAW.  Studies by Belani, Dasari, McGovern and a previous study by Legg all showed the mass effect of waste heat forming thermals under the drapes and rising from the floor to the surgical field.  The latest study is unique because it shows that the radiant heat travels through the drapes, interacts with the downward flow of air from the ceiling ventilation, and forms vortices that suck contaminated air from the floor.  Legg and Hamer discovered 2,000x more contaminant particles at the surgical site when FAW was used than when air-free HotDog patient warming was used.

This is especially concerning in orthopedic surgery, where airborne contaminants can cause devastating deep-joint infections.

As you’re watching the short video clip, notice the tight-spinning vortex captured by orthopedic surgeons in Northumbria, UK, towards the end.

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 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.

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.

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.