THERE HAS BEEN little investigation of the effect on bacterial growth of volatile anaesthetics in concentrations used in clinical anaesthesia. Waterhouse, 1 a Surgeon from Charing Cross Hospital, was the first person to mention the clinical results obtained by the use of di-ethyl ether in cases of various pyogenic infections. Topley 2 a Bacteriologist from the same hospital, showed that ether vapour exerts a definite bactericidal action on certain micro-organisms. John Bray 8 described a method of suppressing proteus and coliform bacteria on routine blood agar plates and came to the conclusion that ether vapour had a weak antiseptic ef [ect. Hunter et al. 4 used chloroform vapour as a preservative for culture media. Barry, Paiement and Dubeau 5 were the first to claim that halothane and methoxyflurane vapour in clinical concentrations had no antibacterial activity against Staphylococcus aureus and E. coll. More recently Wardley-Smith and Nunn 6 confirmed the findings of Barry et al. and showed that for certain species of non-pathogenic bacteria in broth, the effect on bacterial growth rate was negligible at clinical concentrations of halothane. On the other hand, Horton, Sussman and Mushin 7 exposed E. coli spread on cellulose acetate membranes to the vapours of volatile anaesthetic agents and showed that halothane, chloroform, trichloroethylene and methoxyflurane reduce the number of surviving organisms and that the reduction in survival was proportional to the concentration of the agent used.There are three main reasons why this knowledge of the effect of anaesthetics in clinical concentration on bacteria is useful. Firstly, it has clinical relevance to anaesthesia in patients with severe infection; secondly, it appeared likely that it might add to our scanty knowledge of the effect of anaesthetics at the molecular and cellular level and might reveal the possible mechanism of narcosis (WardleySmith et al. 19716 and White et al. 19708); and thirdly, it might throw light on the antibacterial action of anaesthetic vapours on organisms present on the surface of anaesthetic equipment, a factor which might be responsible for an incidence of post-operative pulmonary infection which is much lower than might be expected (Horton et al. ~ 1970). This paper describes studies of the effect of clinical concentrations of halothane, methoxyflurane and trichloroethylene on the growth of two species of bacteria grown on blood agar plates and cellulose acetate membranes.
There has been little work on the action of vapours of volatile anaesthetics on respiratory pathogens. Topleyl and Bray2 observed definite bactericidal action of ether vapours on certain micro-organisms including respiratory pathogens. Both these workers used very high concentrations of ether vapour. Most of the subsequent work appears to have been carried out on Esclzericliia coli, Staphylococcus aureus and a number of non-pathogenic b a~t e r i a .~-~ Thus little is known of the effect of volatile anaesthetics on respiratory pathogens at the concentrations used in anacsthesia. This is important for three reasons. Firstly, it ha5 clinical relevance to anaesthesia in patients with severe infection,6 secondly, it might throw light on the antibacterial action of anaesthetic vapours on organisms present on the surface of anaesthetic equipment, a factor which might be responsible for an incidence of postoperatibe pulmonary infection which is much lower than might be expected4 and thirdly, it provides an opportunity to study the effect of anaesthetics at a cellular level by use of a simple biological system in which anaesthetic agents produce measurable functional changes.This paper describes studies of the effect of clinical concentrations of halothane, methoxyflurane and trichloroethylene on the growth of two species of common respiratory pathogens. Material9 and methodsIn the present investigation, two species of respiratory pathogens were selected, namely Streptococcus pneumoniae and Haemophilus injluenzae. The same strains of S . pneumoiziae and H. injlirenzue were used throughout the experiments. These strains were obtained from routine diagnostic work. Preparation of bacterial suspensionColonies from overnight growth of S. yneumoniue and H .
A passive method for the disposal of waste anaesthetic gases is described. The resistance characteristics of the collector valve, the balancing device and the disposal system were studied. It was found that the resistances offered by the conduction channels and the terminal exhaust valve were extremely low. The collector valves were found to be responsible for most of the expiratory resistance. Swabs taken from various components of the system showed that these were contaminated mainly with commensals and non-pathogenic organisms.
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