Infection Risk from Forced-air Warming Considered; Study on Bacterial Contamination Recommended

International Orthopedic Consensus 

“We recognize the theoretical risk posed by forced air warming blankets,” concluded the Consensus Statement recently released by the International Consensus on Periprosthetic Joint Infection.  While not urging a change in practice, the Consensus Statement recommended that further studies be undertaken regarding the safety of forced-air warming (“FAW”) in orthopedic implant surgery.
Delegates from more than 50 countries and 80 different societies met in August 2013 to evaluate scientific literature and identify areas for further research.  Among the other conclusions relating to periprosthetic joint infections and the risk of airborne contamination:
 
1. Airborne particulate bacteria are a major source of contamination in the operating room.  The number of airborne bacteria around the wound is correlated to the incidence of periprosthetic joint infections.  Bacteria “circulate through the operating room via air currents.”

“Legg et al,” the Consensus Statement noted, “found increased particles above the surgical site when using FAW compared to radiant warming.” To be precise, the Legg study, published in Bone & Joint Journal, found 2,000 times more contaminant particles in the air over the wound with Bair Hugger forced-air 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%.

2.  The probability of infection reflects the quantity of bacteria that reaches the wound.  “Accordingly,” the Consensus Statement concluded, “we support strategies to lower particulate and bacterial counts at surgical wounds.”

The Consensus Statement cited to research by Albrecht et al that the inefficiency of FAW intake filters results in bacterial colonization of the air-flow paths of FAW devices, “mostly Staphylococci species.”  The study, published in the American Journal of Infection Control, revealed that 58% of FAW blowers “were internally generating and emitting airborne contaminants.”

The report also cited to a study by U.K. orthopedic surgeon P.K. McGovern published in the Journal of Bone & Joint Surgery that showed a 74% reduction in joint-implant infections after forced-air warming was discontinued.  The research included 1,437 patients undergoing hip or knee replacement.

As evidence that FAW does not disrupt laminar flow OR ventilation, the report cited to a computer simulation and a study by 3M advisor and lecturer Daniel Sessler.  3M manufactures Bair Hugger forced-air warming.

“This Consensus Statement is extraordinary,” said Dr. Scott Augustine, the inventor of Bair Hugger warming who has cautioned against using FAW in orthopedic implant surgery, “especially considering that 3M was a Platinum Sponsor of the meeting.  The co-chair of the meeting, Dr. Javad Parvizi, was paid by 3M to write a marketing ‘white paper’ that 3M distributed to doctors all over the world.
“Nevertheless, the Consensus acknowledged that forced-air warming could pose a risk.”

Taken together, Dr. Augustine observed, the Consensus and the published research make the risks of FAW clear:

        1. Airborne bacteria leads to increased periprosthetic infections.

        2.  More bacteria in the wound means more infections.

        3.  FAW mobilizes floor-level contaminates and lifts them to the wound—the Legg study showed a 217,300% increase.

“In my opinion,” Dr. Augustine concluded, “the Consensus acted appropriately.  As more research is published, I expect that it will issue even more aggressive warnings."