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

Abstract

SummaryIn 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.

Bacterial and viral contamination of breathing circuits after extended use – an aspect of patient safety?

“…Particularly during low-flow anaesthesia, when increased temperature and humidity within the circle system occurs, the risk of endoluminal bacterial growth during prolonged use of ABC has to be considered, as the CO2-absorber might provide a very hostile environment for microorganisms. Of the three studies mentioned above, 18,19,30 only one provided data on contamination rates of the outer surface of ABC; 19 these were 12% and 21% after 1 and 7 days of use respectively, and thus lie in the same range as our findings (7% vs. 17%). Our microbiological results were obtained in ABC applied for low-flow anaesthesia; samples obtained from the y-piece and the water trap indicated no difference in the rate of endoluminal contamination of ABC after 1 day compared to 7 days of use.…”

“…The fact that none of the examined 233 ABC revealed contamination with viruses strongly suggests that BSF meeting the quality criteria prescribed in Germany 28 provide effective protection against virus transmission into the ABC. 18 Interestingly, the bacterial species found in our study in the ABC on day 1 and day 7 differed markedly. This problem was addressed by investigating the ABC used on patients with known viral infection of the respiratory tract.…”

“…18 For the first time, it has been shown in practice that BSF indeed prevent viral contamination of ABC. 18 For the first time, it has been shown in practice that BSF indeed prevent viral contamination of ABC.…”

“…To our knowledge, this study is the largest investigation of microbiological contamination of anaesthetic breathing circuits to consider the inner as well as the outer surface of the equipment; it is also the first study testing ABC for respiratory viruses in a clinical setting systematically. 18 For the first time, it has been shown in practice that BSF indeed prevent viral contamination of ABC. To date, the protective effect of BSF against virus cross-transmission via ABC has been derived solely from in vitro data of the filtering properties of BSF.…”

“…Microbiological investigations of breathing circuits after 7-day use are scarce, 18,19 and, to our knowledge, a systematic clinical investigation of viral contamination is completely lacking. 18,20 Thus, there is still a dearth of data regarding a potential anaesthesiological safety issue. To address these questions, this study evaluated the contamination of ABC not only with bacteria but also with respiratory viruses after 1 and 7 days of routine use.…”