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.

The researchers investigated whether the floor-to-ceiling temperatures around a draped manikin in a laminar-flow theatre differed when using forced-air warming or conductive warming.  Mean (SD) temperatures were significantly elevated over the surgical site with forced-air warming vs those measured with the conductive blanket (+2.73 (0.7) °C; p < 0.001).

Forced-air warming technologies release significantly higher levels of excess heat than conductive warming technologies, the researchers found.

“This finding is of concern because temperature elevations are the direct result of hot air-pockets moving upwards and against the downward laminar airflow currents…any temperature elevations are the result of convection current activity. The clinical concern is that these currents may disrupt ventilation airflows intended to clear airborne contaminants from the surgical site.”

What is the safest way to warm patients undergoing surgery with implanted foreign materials?  Air-free warming methods are best say the researchers.  “Conductive warming technologies have little or no impact on ventilation airflows.”

“There is now overwhelming published support showing that forced-air patient warming disrupts the sterile field.  The Dasari study validates the findings of McGovern’s research that showed a 74% reduction in implant infection rates after discontinuing the use of forced-air warming,” said Dr. Scott Augustine, the leading expert on thermoregulation and temperature management in surgical patients, “This is about patient safety and improving surgical outcomes.”

Dr. Augustine has contributed to improved outcomes in hundreds of millions of patients with his invention of Bair Hugger® forced-air warming 25 years ago.  Today he is CEO of Augustine Temperature Management, maker of HotDog® air-free conductive fabric patient warming.

Research Citation:
Dasari, K.B.; Albrecht, M; Harper, M. Effect of forced-air warming on the performance of theatre laminar flow ventilation.Anaesthesia. Vol. 67; 2012: 244-249.

This study was conducted by Anesthesiologists at Royal Sussex County Hospital, UK.  Mark Albrecht, a former employee of Augustine Biomedical + Design (ABD), was a graduate student in statistics at the University of Minnesota at the time of the study and contributed to the statistical analysis and manuscript preparation.  ABD also provided the temperature mapping equipment.  No other financial support was provided.