The present study of the effect of two common anaesthetic
gases on blood
acid-base parameters shows that the micro-Astrup measurement of
carbon dioxide tension is not invalidated by the presence of
nitrous oxide. This result was anticipated from the theoretical aspect of this technique. The mean error involved in estimating plasma
carbon dioxide content in the presence of
nitrous oxide using the volumetric Van Slyke apparatus without absorption of
carbon dioxide by
sodium hydroxide can be of the order of 25%. No such effect was measurable in estimating
carbon dioxide contents in the presence of
halothane. The degree of
respiratory alkalosis during anaesthesia reported in earlier papers (Walker, Morgan, Breckenridge, Watt, Ogilvie, and Douglas, 1963; Morgan, Ogilvie, and Walker, 1963) was greater than had been originally appreciated.A ;false' increase in
carbon dioxide content will also falsely increase
buffer base or ;base excess' as calculated from standard nomograms (Singer and Hastings, 1948; Davenport, 1958; Siggaard-Andersen, 1963).