Residual protein contamination of ProSeal laryngeal mask airways after two washing protocols.

The risk of prion protein cross-infection has focussed attention on the potential hazards of protein contamination of re-usable medical devices. This study determined the frequency of protein contamination of ProSeal laryngeal mask airways (PLMA) after two cleaning procedures and tested the hypothesis that the combination of hand- and machine-washing removes protein contamination more effectively than hand-washing alone. After clinical use fifty-four PLMAs were randomly allocated to be washed by hand or by hand then machine. All PLMAs were then autoclaved at 134 degrees C for 4 minutes. After processing, each PLMA was immersed in a 1.2% solution of erythrosin B and examined for uptake of stain. The site (outer surface, bowl and edges of the cuff airway and drain tube, finger strap) and severity (nil/mild/moderate/severe) of staining was scored by a blinded observer. There were no differences in the site or severity of staining between the two cleaning procedures. Staining was detected on 89% of PLMAs that were hand-washed and 78% of PLMAs that were hand-, then machine-washed (P=0.27). When staining occurred, it was mild in 98%, moderate in 2% and was never severe. Staining was more frequent on the edge than at any other location (all comparisons: P < or = 0.01). The strap never had any staining. We conclude that residual contamination of PLMAs with protein deposits is common even when machine-washing is used to augment hand-washing before autoclaving. The infection risk associated with these deposits remains to be determined.