Disinfection of hemodialysis machines

Three Centry 2 dialysis control units were intrinsically contaminated with a water-adapted Pseudomonas aeruginosa which grows well in distilled, deionized and reverse osmosis water. Three disinfectants (3.7% formaldehyde, 1:34 dilution of cidex HD and 1:34 dilution of Sporicidin) were introduced into the dialysis machines via the water supply lines, remained in the machines for variable time periods, then were rinsed out of the machines for 45 minutes. None of the disinfectants eradicated the test organism from the machines when the disinfectant contact time was 5, 10 or 15 minutes. However, 3.7% formaldehyde and 1:34 dilution of Cidex HD were effective when the disinfectant contact time was 24 or 72 hours. After 10 minutes of rinsing, the concentrations of all disinfectants were less than 1 μg/ml. Following overnight machine disinfection with either 3.7% formaldehyde or 1:34 dilution of Cidex HD, a 10-minute rinse immediately prior to use should minimize patient risk of exposure to these disinfectants.