The microbiological and sustainability effects of washing anaesthesia breathing circuits less frequently

In the presence of single-use airway filters, we quantified anaesthetic circuit aerobic microbial contamination rates when changed every 24 h, 48 h and 7 days. Microbiological samples were taken from the interior of 305 anaesthetic breathing circuits over a 15-month period (3197 operations). There was no significant difference in the proportion of contaminated circuits when changed every 24 h (57/105 (54 , 95 CI 45?64 )) compared with 48 h (43/100 (43 , 95 CI 33?53 , p = 0.12)) and up to 7 days (46/100 (46 , 95 CI 36?56 , p = 0.26)). Median bacterial counts were not increased at 48 h or 7 days provided circuits were routinely emptied of condensate. Annual savings for one hospital (six operating theatres) were AU 5219 ( 3079, ?3654, US 4846) and a 57 decrease in anaesthesia circuit steriliser loads associated with a yearly saving of 2760 kWh of electricity and 48 000 l of water. Our findings suggest that extended circuit use from 24 h up to 7 days does not significantly increase bacterial contamination, and is associated with labour, energy, water and financial savings.