PubMed · 10184402
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A W Grogono. 1995. Closed circuit anesthesia: the man-machine interface.. https://pubmed.ncbi.nlm.nih.gov/10184402/
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BACKGROUND: The minimum alveolar concentration (MAC) is a traditional index of the hypnotic potency of an inhalational anaesthetic. To investigate the anaesthetic as well as the unwanted effects of xenon (Xe) in a swine model, it is useful to know MAC(Xe). METHODS: The study was performed using ten swine (weight 27.8-35.4 kg) anaesthetized with halothane and Xe 0, 15, 30, 40, 50 and 65% in oxygen. With each Xe concentration, various concentrations of halothane were administered in a step-by-step design. For each combination, a supramaximal pain stimulus (claw clamp) was applied and the appearance of a withdrawal reaction was recorded. The MAC(Xe) with halothane was calculated using a logistic regression model. RESULTS: During stable ventilation, haemodynamics and temperature, MAC(Xe) value was determined as 119 vol. % (95% confidence limits 103-135). CONCLUSION: MAC(Xe) in swine was calculated by extrapolation of a logistic regression model. Its theoretical value is 119 vol. %.
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AIM: The large number of anaesthetics administered means that the total cost to a hospital of inhalational anaesthetic agent such as isoflurane or sevoflurane can be considerable. The total anaesthetic gas flow is a major determinant of the use of these agents. Modern anaesthetic machines and monitoring facilitate reduced gas flows, which can significantly reduce wastage of these anaesthetic agents. The purpose of this study was to audit gas flow rates and volatile anaesthetic use. METHODS: We audited gas flows and choice of anaesthetic agent over two one-month periods in one theatre at Christchurch Hospital. Data were collected directly from the anaesthetic machine using a computer. The second study period was clearly advised and followed widespread discussion of results from the first study period. RESULTS: Average fresh-gas flow was approximately 2 l/min (Month 1 = 2.0 l/min, Month 2 = 2.1 l/min). Use of the more expensive agent, sevoflurane, increased but gas flows with this agent decreased. CONCLUSIONS: Given the low flows used, the small difference between study periods was not surprising. The gas flows recorded represent responsible use of anaesthetic agents and are at least as good as flows achieved in previous studies that employed various methods to encourage their reduction.