Arterial and mixed venous xenon blood concentrations in pigs during wash-in of inhalational anaesthesia

There are no data available on the kinetics of blood concentrations of xeno n during the washin phase of an inhalation anaesthesia aiming at I MAC end- expiratory concentration. Therefore, we anaesthetized eight pigs with conti nuous propofol and fentanyl and measured arterial, mixed venous and end-exp iratory xenon concentrations by gas chromatography-mass spectrometry 1, 2, 3, 4, 5, 7, 10, 15, 20, 30, 60 and 120 min after starting the anaesthetic g as mixture [67% xenon/33% oxygen; 3 litre min(-1) during the first 10 min, thereafter minimal flow with 0.48 (SD 0.03) litre min(-1)]. End-expiratory xenon concentrations plateaued (defined as <5% change from the preceding va lue) at 64 (6) vol% after 7 min, and arterial and mixed venous xenon concen trations after 5 and IS min respectively. The highest arterio-venous concen tration difference occurred after 3 min. Using the Fick principle, we calcu lated a mean xenon uptake of 3708 (829) and 9977 (3607) ml after 30 and 120 min respectively.