August 2013
Research in the August edition of Anesthesia & Analgesia, a publication of the International Anesthesia Research Society, and appearing under the name of the Anesthesia Patient Safety Foundation stated:

“[F]orced air warming was found to establish convection currents that mobilized resident air from nonsterile areas (under the anesthesia drape) upward and into the surgical site.”

The clinical concern, according to the article, is that the convection currents created by Bair Hugger will mobilize contaminants and/or impede the ventilation systems’ ability to clear contaminants from the surgical site.  The concerns, they stated, “are most relevant for smaller airborne particles…such as free-floating bacteria and skin cell fragments.”

The study compared the impact of Bair Hugger warming with air-free HotDog conductive fabric warming.  No convective currents were detected when HotDog warming was applied.  In explanation, the scientists stated:

 “Because conductive blankets (like HotDog) are localized in their application, they tend to have higher thermal efficiencies and contribute less excess heat to the environment than forced air.”

In contrast, Bair Hugger “was found to have a significant disruptive impact on clean airflow patterns over the surgical site….”

The research has been available online for a year, but was just recently published in print along with an Editorial and a press release.
This research follows several other recent publications raising questions about the safety of Bair Hugger forced-air warming, particularly in orthopedic surgery.