The physical and antimicrobial effects of microwave heating and alcohol immersion on catheters that are reused for clean intermittent catheterisation.

INTRODUCTION: Due to worldwide different health insurance policies, patients are often forced to reuse the catheters when performing Clean Intermittent Catheterisation (CIC). We have compared the physical qualities and the antimicrobial effects of two methods of reusing catheters: microwave heating and storage of the catheters in a 70% alcohol solution. The studies were performed during different lengths of time.
MATERIALS AND METHODS: Three types of catheters (a standard polyvinylchloride catheter, a special polyvinylchloride catheter with flexible Ergothan tip and a prelubrified catheter), normally intended for single use, were submitted to the effect of a microwave oven (Multitech 215 High Grade and Whirlpool M220 750 W and 1000 W with rotating plate) or preservation in a 70% alcohol solution. To study the effects of microwave heating, a recipient of water was placed in the oven to spread the microwaves and to absorb the heat. The catheters were placed in a resealable plastic bag (Ziploc. To study the effects of preservation in a 70% alcohol solution, the catheters were immerged in the solution for different lengths of time. Thereafter were the physical qualities of the catheters evaluated by using the technique of Differential Scanning Calorimetry (DSC). The antimicrobial effect of the method was evaluated after grafting the catheters with pathogenic E. coli, P. aeruginosa or S. aureus strains.
RESULTS: Microwave heating up to 12 minutes at 750 W caused only minimal changes in the physical qualities of all the catheters. However, there was only an antimicrobial effect of the microwave heating on E. coli and not on P. aeruginosa or S. aureus. If the catheter remained longer than 45 minutes in a 70% alcohol solution, the physical qualities of the catheter changed either minimal in the special polyvinylchloride catheter with flexible Ergothan top but changed significantly in the prelubrified catheter). However, already after 5 minutes of immersion in the 70% alcohol solution there was a complete antimicrobial effect on E. coli, P. aeruginosa and S. aureus in all catheters.
CONCLUSIONS: It should be recommended to patients on CIC to use a sterile packed and not previously used catheter. In this study we have shown that immersing the catheters in a 70% alcohol solution during 5 minutes can effectively disinfect the catheter without jeopardising the physical qualities. Thereafter, the catheters could be placed in a resealable (e.g. Ziploc bag without being rinsed under water, in order that the few drops of alcohol cause alcohol vapours within the closed plastic bag and maintain the antimicrobial effect.