: Forced air warming is effective in maintaining patient temperature, but it may affect airflow patterns and drive particles from behind the anesthesia drape into the surgical field. (Image source: Thinkstock)
Forced air warming is effective in maintaining patient temperature, but it may affect airflow patterns and drive particles from behind the anesthesia drape into the surgical field. (Image source: Thinkstock)

The evidence to show the importance of keeping a patient warm during surgery is strong.  For example, the risk of surgical site infection increases when patients are cold. In  patients undergoing bowel surgery, infection risk is increased as much as three times when temperature drops 2°C.

Forced air warming is the most common method used today to help maintain normothermia during surgery.  Though more effective than conductive warming blankets placed underneath patients, forced air may disrupt airflow within an operating room.  Dr. Kumar G. Belani, Department of Anesthesiology, University of Minnesota, Minneapolis, Minnesota, and colleagues used neutrally buoyant detergent bubbles to measure air flow patterns. Their study compared forced air warming with conductive fabric warming in an operating room used for total knee replacement surgery.  The operating room was set up for orthopedic surgery, although mannequins were used in place of surgeons and nurses. Their findings appear in the August issue of Anesthesia and Analgesia in the article titled “Patient Warming Excess Heat: The Effects on Orthopedic Operating Room Ventilation Performance.”

Forced air warming disrupted the airflow patterns over the surgical site, mobilizing  air from behind the anesthesia drape into the surgical field.  Of course, these findings depend on exactly how the operating room was set up, including placement of lights, draping, and personnel.  Instrument trays were not included in study setup, nor were devices present that might disrupt airflow, such as high-speed cutters, lasers, or electrocautery instruments.

Where do we go from here?  Does this mean that forced air warming should not be used in operating rooms where knees or hips are implanted?  No.  The accompanying editorial “It’s Not Just Another Room…” by Drs. Charles Weissman (Department of Anesthesiology, Hadassah-University Hospital, Kiryat Hadassah, Jerusalem) and W. Bosseau Murray (Clinical Simulation Center, Pennsylvania State University College of Medicine, Hummelstowm, Pennsylvania) notes that “given the controversies over the best method for warming patients and the possibility of increased airborne contaminants with forced air warming, the prudent course for clinicians might be to continue with the presently proven successful warming therapies, but keep an open mind about the possible future need to change practice.”

To see a discussion on temperature, go to OpenAnesthesia.org.