Uptake and elimination of sevoflurane in rabbit tissues-An in vivo 19F magnetic resonance study

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Background : An in vivo pharmacokinetic study of fluorinated inhalational anesthetics is possible using ^<19>F magnetic resonance spectroscopy. Previous pharmacokinetic studies were performed mainly in brain as it is considered as a site of anesthetic action. Investigation of other tissues will give us more precise informations of the pharmacokinetics of inhalatlonal anesthetics in a whole body. In this study we investigated the pharmacokinetics of uptake and elimination of sevoflurane in brain, liver, muscle, venous blood and arterial blood of rabbits using in vivo 19F MRS in order to compare differences of pharmacokinetics among tissues and also differences between uptake and elimination in each tissue. Methods : In twenty two rabbits 19F magnetic resonance spectroscopy was conducted at 4.7 Tesla using a 1 cm diameter surface coil for brain (n-4), liver (n-5) and muscle (n-5), and a 1.3 cm diameter surface coil for arterial (n-4) and venous (n=4) blood.Results : Sevoflurane was administered for 120 min, followed by a 120-min period of elimination. Both uptake and elimination kinetics were best fit to a biexponential curve which was divided into the fast and slow components. During an uptake experiment times to reach half of the maximum spectroscopic intensity in each tissue were 1.5 min in arterial blood, 4.5 min in liver, 12.7 min in brain, 13.1 min in venous blood and 27.3 min in muscle. During an elimination experiment times to reach half of the maximum intensity in each tissue were 2.4 min in arterial blood, 5.5 min in liver, 12.5 min in venous blood, 20.4 min in brain and 26.7 min In muscle.Conclusions : Sevoflurane uptake or elimination in each tissue was able to be expressed by biexponential kinetics. Sevoflurane uptake and elimination kinetics in arterial blood were rapid and almost similar to end-tidal sevoflurane kinetics. Those in liver were next fastest followed by brain, venous blood and muscle.