Effects of anaesthesia and surgery on the solubility of volatile anaesthetics in blood

Empirical relations predicting human and rat tissue:air partition coefficients of volatile organic compounds

Based on the hypothesis that tissue partitioning of volatile organic compounds (VOCs) is due to lipophilic and hydrophilic interactions with tissue components, empirical relations are established between olive oil (P(oil:air)), saline (P(saline:air)), and tissue partition coefficients (P(tissue:air)) for human and rat tissues. Reported values of partition coefficients of a wide range of VOCs with distinct chemical structures (n = 137) have been compiled from the literature. Bilinear regression analysis shows that partition coefficients of VOCs in human blood, brain, fat, liver, kidney, and muscle tissues are well described by a linear combination of P(oil:air) and P(saline:air) with tissue-specific regression coefficients. The regression coefficient associated with the hydrophilic component of VOC partitioning in rat tissues is systematically higher than that of human tissues. For the human model, tissue concentrations calculated from predicted partition coefficients are generally within a factor 4 of tissue concentrations calculated from experimentally observed partition coefficients. These results demonstrate that, without prior knowledge of tissue composition, it is possible to obtain estimates of human tissue partition coefficients of VOCs with an accuracy that is in the same range as that commonly used in risk assessment.

Quantitative determination of isoflurane enantiomers in blood samples during and after surgery via headspace gas chromatography-mass spectrometry

The quantitative analysis of the chiral volatile anesthetic isoflurane (1) for biomedical applications by means of enantioselective gas chromatography (mass sensitive detector, selected ion monitoring) was studied. Two methods for the quantification of the enantiomers in blood samples drawn during and after narcosis were compared. Either the isomeric enflurane (2) was selected as an internal standard or a single enantiomer of 1 was used for the standard addition method, an approach referred to as 'enantiomer labeling'. Concentrations up to 0.3 micromol/l of the single enantiomers could be differentiated two days after anesthesia. The presented data imply that the body clearance for (+)-(S)-1 and (-)-(R)-1 proceeds to a measurable degree of enantioselectivity.