Scientists in Sweden speak exclusively to gasworld about their theory, which is now being put to the test in clinical trials.

Professor Jan van der Linden, and Mikael Persson, both of the Karolinska Institute in Sweden, believe that carbon dioxide (CO2) is so effective when used to prevent infection in open surgery; it has the potential to be used alongside antibiotics in the future.

The scientists’ paper, which recently earned them the 2008 David Horrobin prize for medical theory, notes the serious complications which can arise after open surgery at present, resulting in increased hospital stay, costs and mortality.

It says, “Despite the progress in modern medicine, postoperative infections are still common.”

The authors note how an open surgical wound is subjected to airborne bacterial contamination, desiccation, and heat loss, all of which increase the bacterial load, cause superficial necrosis (dead cells), and impair tissue oxygenation and cellular immune functions, respectively.

They claim however, that when a wound is flooded with humidified CO2 during surgery, these risks can be avoided, and postoperative wound infection will therefore be prevented.

According to van der Linden and Persson, intraoperative insufflation with humidified CO2 inhibits airborne bacteria from reaching the wound, and acts as a bacteriostatic antibiotic on any germs present.

Their experimental studies also indicate that when using the humidified CO2, superficial tissue necrosis in the open wound will decrease, cellular immune functions will improve, and wound tissue oxygenation will increase, with the Bohr effect also occurring.

The paper reads, “It has been found that over 90% of the contaminating bacteria in clean surgical wounds come from the ambient air, and a substantial part of these bacteria contaminate the wound directly.”

“Moreover, it has been estimated that as few as 10 bacteria-carrying airborne particles are sufficient to cause deep surgical wound infection. This implies that preventing only a few airborne particles from reaching the surgical wound should have clinical significance.”

The scientists have developed a gas diffuser that can deliver CO2 at high flows but at very low velocity in an open surgical wound.

As a result, turbulence and admixture of ambient air is avoided and a 100% CO2 atmosphere within the surgical wound cavity is created.

Linde and AGA have been supplying CO2 for use in the scientists’ lab, and in their diffuser.

The gas diffuser, going by the name of CarbonAid™, is CE and FDA approved.

It is currently being used internationally for de-airing in open cardiac surgery, to avoid embolisation of air from the heart and great vessels when the patient is being weaned off the heart-lung machine.

Speaking to gasworld, Professor van der Linden compared the use of his device to the method used in food packaging, he said, “In food packaging, CO2 is used as a protective atmosphere within a closed cavity, thus inhibiting the growth of bacteria.”

“By continuously insufflating CO2 into an open wound with our device during surgery, we can create a protective atmosphere within an open surgical wound.”

Food related research focuses on the use of CO2 at low temperatures; therefore van der Linden and Persson have studied the use of the gas at body temperature.

In their paper, the authors add, “It was found that pure CO2 significantly decreased the growth rate of S. Aureus [Staphylococcus Aureus, a bacterium] at body temperature.”

“In comparison with growth in air, where the number of bacteria increased exponentially with time, the bacterial growth in CO2 appeared unchanged. After four hours the bacterial count in air was almost 100 times higher than that in CO2. The CO2 should have a similar effect on bacteria in an open surgical wound.”

The scientists are currently running a randomised clinical trial in patients undergoing open colon surgery.

The treatment group receives humidified warm CO2, insufflated via a gas diffuser in the open wound, and the control group receives standard treatment.

Professor van der Linden said, “After this initial trial that we hope to finish by the end of the summer, we are planning for a large randomised multicentre trial, provided that we get the necessary funding.”