Waste Heat Causes Contamination
Forced-air Warming Discontinued: Joint Infections Reduced 74%
In contrast, the waste heat from forced-air warming (FAW) is proven to be a vector for contaminating the surgical site. The diagram below shows the three different ways that FAW waste heat contributes to surgical site contamination.
Waste heat from forced-air warming brings contaminant particles to the surgical site as seen here in total knee arthroplasty:
*Waste heat takes the path of least resistance. Waste heat rising under the drapes is far more prevalent with lower body and underbody blankets.
ERAS: forced-air warming not recommended in H&K replacement surgery
The Enhanced Recovery After Surgery (ERAS)-compliant normothermia protocol for hip or knee replacement surgery urges maintenance of normal body temperature, but also includes the following statement:
“However, the use of forced air-warming is not recommended as there is evidence that this is associated with an increased risk of infection (McGovern et al. 2011, Koc et al. 2017).” >Read More
Implement an ERAS-compliant protocol with effective air-free HotDog patient warming.
In February 2020, citing to a pilot study and “the results of forth coming trials,” ERAS added an addendum stating that the 2019 wording was “too strong.” The altered statement simply encouraged active warming.
- The pilot study showed significantly increased risk of infection with forced-air warming.
- There is no new research regarding the safety (or danger) of forced-air warming.
- By definition, forthcoming trials have not yet occurred…so their results cannot be evaluated.
- Although non-public, unpublished, “new” information could not logically be the basis for a protocol change that will be utilized by clinicians around the world, ERAS must have had some reason to make the change.
- Absent legitimate clinical evidence, one must wonder whether the change in the protocol resulted from industry influence.
1. Waste heat rises from under drapes
“The risks of developing deep joint infections were significantly greater for patients… treated with forced-air warming (FAW) versus conductive fabric warming [3.1% vs 0.8%]”
“Excess heat from (FAW) resulted in [hot air convection currents] that transported floor-level air upwards and into the surgical site. In contrast, conductive fabric warming did not release sufficient excess heat to establish these convection currents.”
“Air-free warming, therefore, is recommended over (FAW) for orthopedic procedures.”
Moretti, B. ; et al. J Hosp Infect 2009
Scherrer, M.; et al. Min Invasive Thermal Allied Tech, Nov 2003
Elghobashi, S.; et al. Int J Numer Method Biomed Eng. May 2018
2. Exhaust air travels over anesthesia drape
“The direct mass-flow exhaust from forced-air warming generated hot-air convection currents that mobilized [non-sterile] air over the anesthesia drape and into the surgical site.”
3. Excess radiant heat creates vortex
The waste heat from forced-air warming (FAW) blankets radiated through the surgical drape to form tornado-like vortices of rapidly spinning air near the surgical site. The vortices 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 FAW than with air-free HotDog conductive warming. With HotDog, only 1,000 particles per m³ of air were present. With FAW, the particle count was 2,174,000 per m³.
The Chain of Infection