Laboratory analysis to prevent infection after open heart surgery

Spectrum Medical case study: Pseudomonas aeruginosa and mycobacteria testing within heater-cooler units  

Spectrum Medical is a medical equipment manufacturer, supplying world leading technologies to hospitals and healthcare settings. These technologies lead to greater patient safety, improved patient outcomes and significantly improved health economics. 
One of the devices that they manufacture is a heater-cooler unit which is used in open heart surgery and other surgical procedures. It is needed to warm or cool a patient during surgery. Cooling the heart allows surgeons to operate for 2-4 hours without damaging the heart tissue and improves patient outcomes.
There is, however, a risk that the fluid in the heater-cooler unit can be contaminated by bacteria including mycobacteria and Pseudomonas aeruginosa. Managing this risk is therefore really important for the wellbeing of patients.
Spectrum Medical designed a new heater-cooler unit to eliminate the risk of these bacteria but they needed to know:

  • How quickly the new units killed off bacteria
  • How long this was effective for


They wanted to demonstrate and prove that this was the case so they could be confident in the results for using the device in a healthcare setting.

The solution

SUEZ, through our Latis Scientific laboratory, conducted a trial to demonstrate that the Heat Transfer Fluid (HTF) in Spectrum Medical’s heater-cooler units had bactericidal and bacteriostatic properties that would reduce the risk of any potential contamination.

  • Bactericidal - substance that kills bacteria
  • Bacteriostatic - the agent that prevents the growth of bacteria


To support the trial, we selected clinically relevant bacteria including Pseudomonas aeruginosa and environmental mycobacteria. We took samples and added them to the HTF from the heater-cooler unit. We then assessed the reduction in bacteria from 4 hours to 28 days. This was to prove if the fluid was bactericidal.
Next, we analysed the HTF after storage to see how long the HTF maintained its ability to eliminate bacteria. This analysis was done every 3 months for up to 2 and a half years.

The results

The final report from our UKAS accredited laboratory outlined:

  • The different bacteria that were analysed and the methods of testing
  • The stages of the trial, including feasibility assessments of methods, efficacy testing of HTF and efficacy testing of HTF subjected to working environment
  • Recovery levels for each clinically significant pathogen
  • The shelf life of the fluid

We reported a 99.9% reduction in bacteria between 1 hour and 28 days depending on the bacteria. We were therefore able to prove that the HTF does act as an effective biocide against the bacteria tested.

The results also showed that the storage of the fluid had little impact on its bactericidal properties. The test indicated that the HTF is significantly more effective in terms of reducing bacterial load within heater-cooler units than the water previously used in these machines.

These results gave Spectrum Medical the assurance needed to start manufacturing and distributing their new heater-cooler units. The new units are now being widely used in Europe and as a result of the trial, the FDA has provided approval for use in the USA.