Patient warming systems may affect ventilation in OR, study suggests

July 24, 2013

Forced-air systems used to keep patients warm during surgery may affect the performance of operating room (OR) ventilation systems—potentially increasing exposure to airborne contaminants, reports a study in the August issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

By comparison, conductive systems don't disrupt airflows over the surgical site, according to the report by Dr Kumar G. Belani of University of Minnesota and colleagues. But an accompanying editorial notes that there's not yet enough evidence to change current practice with regard to patient warming in the OR.

Patient Warming Affects OR Ventilation Airflow The researchers compared the effects of two different types of patient warming systems on airflow in the OR. Modern ORs use "sophisticated ventilation systems to create localized zones of highly filtered air over the surgical site," according to Dr Belani and coauthors.

For the experimental study, the researchers set up an OR as for knee replacement surgery, using a mannequin. They then assessed the performance of the OR ventilation system using "neutrally buoyant detergent bubbles," which made it possible to visualize airflow patterns under different conditions.

Airflow was compared using a forced-air warming system, which distributes heated air under the surgical drapes and over the patient; and a conductive warming system (such as heated water blankets), which applies direct heat to the patient's skin.

Forced-air warming "generated hot air convection currents that mobilized bubbles over the anesthesia site and into the surgical site," Dr Belani and colleagues write. The average "bubble count" in the simulated surgical field was more than 100 with the forced-air warmer, compared to about 0.50 with a conductive warming system.

The convection currents created by the forced-air system drew air from under the surgical drapes and into the surgical site. The concern is that this could mobilize bacteria or other contaminants from nonsterile areas, or interfere with the ventilation system's ability to clear contaminants from the .

Too Early to Assume Increased Infection Risk? The use of " downward displacement" OR ventilation systems had previously been shown to reduce exposure to microbes and infection rates during certain types of surgery. But more recent studies have found no reduction in infection rates. The new study was designed to test whether forced-air warming systems—a relatively recent introduction to ORs—could be affecting ventilation performance.

The results suggest that forced-air patient warming systems may indeed affect airflows in the OR, potentially increasing exposure to bacteria and other contaminants during surgery. Dr Belani and coauthors conclude, "These findings warrant future research into the effects of forced air warming excess heat on clinical outcomes during contamination-sensitive surgery."

In the editorial, Drs Charles Weissman and W. Bosseau Murray note that the findings provide only indirect evidence of potential infection risk, in a simulated setting. That's in contrast to the known benefits of preventing drops in body temperature during surgery. Pending further research, Drs Weissman and Murray write, "The prudent course…might be to continue with the presently proven successful warming therapies, but keep an open mind about the possible future need to change practice."

Explore further: Preoperative warming does not appear to be beneficial

More information: www.anesthesia-analgesia.org/c … ntent/117/2/406.full

Related Stories

Preoperative warming does not appear to be beneficial

April 1, 2013
(HealthDay)—Prewarming devices do not seem to affect patients' postoperative temperatures, nor do they reduce the proportion of patients who experience postoperative hypothermia, according to two studies published in the ...

Energy efficiency could increase infection risks in hospital wards

April 16, 2013
The chance of infection in some hospital wards varies dramatically according to whether the nurses leave the windows open.

Operating room wait time increases infection risk

July 11, 2013
(HealthDay)—The risk of surgical site infections (SSIs) is significantly elevated with lengthier waits in the operating room prior to surgical incision, according to a study published in the July 1 issue of Spine.

Natural ventilation effective in 'nightingale' wards

April 25, 2013
(HealthDay)—For large environments with multiple openings, natural ventilation is effective, and can be supplemented with extract fans in cold weather, according to a study published in the July issue of Building and Environment.

Air shield keeps bacteria out of open wounds

October 10, 2011
This spring, Nimbic Systems, based near Houston, Texas, received Food and Drug Administration (FDA) clearance for the company's Air Barrier System, a unique medical device for reducing surgical-incision site contamination ...

Recommended for you

Exploring the potential of human echolocation

June 25, 2017
People who are visually impaired will often use a cane to feel out their surroundings. With training and practice, people can learn to use the pitch, loudness and timbre of echoes from the cane or other sounds to navigate ...

Team eradicates hepatitis C in 10 patients following lifesaving transplants from infected donors

April 30, 2017
Ten patients at Penn Medicine have been cured of the Hepatitis C virus (HCV) following lifesaving kidney transplants from deceased donors who were infected with the disease. The findings point to new strategies for increasing ...

'bench to bedside to bench': Scientists call for closer basic-clinical collaborations

March 24, 2017
In the era of genome sequencing, it's time to update the old "bench-to-bedside" shorthand for how basic research discoveries inform clinical practice, researchers from The Jackson Laboratory (JAX), National Human Genome Research ...

The ethics of tracking athletes' biometric data

January 18, 2017
(Medical Xpress)—Whether it is a FitBit or a heart rate monitor, biometric technologies have become household devices. Professional sports leagues use some of the most technologically advanced biodata tracking systems to ...

Financial ties between researchers and drug industry linked to positive trial results

January 18, 2017
Financial ties between researchers and companies that make the drugs they are studying are independently associated with positive trial results, suggesting bias in the evidence base, concludes a study published by The BMJ ...

Best of Last Year – The top Medical Xpress articles of 2016

December 23, 2016
(Medical Xpress)—It was a big year for research involving overall health issues, starting with a team led by researchers at the UNC School of Medicine and the National Institutes of Health who unearthed more evidence that ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.