Laboratory testing to prevent infections following open-heart surgery

Spectrum Medical Case Study: Pseudomonas aeruginosa and Mycobacteria Testing in Heating and Cooling Units

Topic

Spectrum Medical is a medical device manufacturer that provides cutting-edge technologies to hospitals and healthcare facilities. These technologies ensure greater patient safety, better treatment outcomes, and significantly improved healthcare economics.    One of the devices they produce is a heating and cooling unit used during open-heart surgery and other surgical procedures. This device is necessary to heat or cool a patient during surgery. By cooling the heart, surgeons can operate for 2 to 4 hours without damaging heart tissue, which improves treatment outcomes.   However, there is a risk that the fluid in the heating and cooling unit could become contaminated with bacteria, including mycobacteria and Pseudomonas aeruginosa. Managing this risk is therefore critical to patient well-being. Spectrum Medical designed a new heating and cooling unit to eliminate the risk posed by these bacteria, but they needed to know the following:

• How quickly the new units killed bacteria
• How long this effect lasted

They wanted to demonstrate and prove that this was indeed the case, so they could have confidence in the results when using the device in a healthcare setting.

The Solution

Normec Latis Scientific conducted a test to demonstrate that the heat transfer fluid (HTF) in Spectrum Medical’s heating and cooling units had bactericidal and bacteriostatic properties that would reduce the risk of potential contamination.

• Bactericidal – a substance that kills bacteria
• Bacteriostatic – an agent that inhibits bacterial growth

To support the test, we selected clinically relevant bacteria, including Pseudomonas aeruginosa and mycobacteria from the environment. We collected samples and added them to the HTF from the heating and cooling units. We then assessed the reduction in bacterial counts over a period ranging from 4 hours to 28 days. The purpose of this was to demonstrate whether the fluid was bactericidal.   We then analyzed the HTF after storage to determine how long it retained its ability to eliminate bacteria. This analysis was performed every 3 months for up to 2.5 years.

The Results

The final report from our UKAS-accredited laboratory provided an overview of:

• The various bacteria analyzed and the test methods
• The phases of the study, including feasibility assessments of methods, efficacy tests of HTF, and efficacy tests of HTF in a work environment
• The recovery rates for each clinically relevant pathogen
• The shelf life of the solution

We reported a 99.9% reduction in bacterial counts between 1 hour and 28 days, depending on the bacterial species. We were thus able to demonstrate that the HTF does indeed function as an effective biocide against the tested bacteria. The results also showed that storage of the liquid had little effect on its bactericidal properties. The test demonstrated that HTF is significantly more effective at reducing the bacterial load in heating and cooling units than the water previously used in these devices.

These results gave Spectrum Medical the confidence needed to begin production and distribution of their new heating and cooling units. The new units are now widely used in Europe, and following the trial, the FDA has granted approval for their use in the U.S.