Microbial Contamination of Anaesthesia Apparatus

Abstract

One of the most important tasks in preventing post-operative infection is in maintaining a proper contamination control in the operating rooms. However, we often overlook anaesthesia apparatus because of their having no direct relation with operative fields.Our purposes of this investigation are to know the microbial contamination of anaesthesia apparatus and the possibility of cross-infection due to contaminated equipments. Anaesthesia apparatus used for microbiological examination were corrugated breathing tubes (inhalation side and exhalation side), rebreathing bags, rubber tubes for suction, Nelaton's catheter, suction water and endotracheal tubes. In 40 operations which had been done from June 1976 to March 1978 at our surgical center we examined microbial contamination, relationship between microbial flora of contaminated equipments and the patient's pharynx, and contamination sources of anaesthesia apparatus.Microbial species isolated from endotracheal tubes, Nelaton's catheter, suction water and rubber tubes for suction were nearly coincident with those from patient's pharynx. Microorganisms detected from corrugated breathing tubes and rebreathing bags were different from that of patient's pharynx. They were unidentified gram-negative rods and Fungi in most cases. Especially, gram-negative rods and Fungi from corrugated breathing tubes and rebreathing bags used at operating room (OR-A) presented higher detection rate. That is, anaesthesia machine in OR-A was contaminated by these microorganisms certainly.The quantitative comparison of microorganisms detected from inhalation side and exhalation side of corrugted breathing tubes and rebreathing bags were performed. The greatest number of microbial colonies was found in rebreathing bags, followed by inhalation side of corrugated breathing tubes and exhalation side of those. It was estimated that the contaminants had moved from inhalation side's tubes to exhalation side through patients. On this account, we suggest the risk of cross-infection by the anaesthetic machine's contaminants of these anaesthesia apparatus.