title: Effect of age on the solubility of volatile anesthetics in human tissues.
abstract: To determine the effect of age on the solubility of volatile anesthetics in human tissues, the authors measured the solubilities of isoflurane, enflurane, halothane, and methoxyflurane in vitro at 37 degrees C in 35 postmortem human tissue specimens. Specimens were taken from neonates, and young (20-50 yr), middle-aged (50-70 yr), and elderly adults (greater than 70 yr). Brain/gas, heart/gas, and liver/gas partition coefficients for all four anesthetics increased significantly (P less than 0.05) between birth and adulthood, although brain/gas partition coefficients in young adults tended to be higher than those in middle-aged and elderly adults. Heart/gas and liver/gas partition coefficients tended to increase with aging. Muscle/gas partition coefficients for the four anesthetics increased linearly with age. Fat/gas partition coefficients did not change significantly with age. Tissue/blood solubilities for the four anesthetics were of the same order of magnitude for a given tissue and age group. Tissue/blood solubilities for enflurane were 30% lower than those for isoflurane in the same tissue and age group. In summary: the solubility of volatile anesthetics in human tissues increases with age; the lower solubility of anesthetics in neonates partially explains the more rapid increase of alveolar and tissue anesthetic partial pressures in neonates; despite the higher blood solubility of enflurane, its lower tissue solubility may explain a rate of recovery comparable with that of isoflurane.
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D000368:Aged; D000375:Aging; D000769:Anesthesia, Inhalation; D001921:Brain / Q000378:metabolism; D004737:Enflurane; D006221:Halothane; D006801:Humans; D007231:Infant, Newborn; D007530:Isoflurane; D008099:Liver / Q000378:metabolism; D008733:Methoxyflurane; D008875:Middle Aged; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D012995:Solubility
chemical_list: D008733:Methoxyflurane; D004737:Enflurane; D007530:Isoflurane; D006221:Halothane