The effect of temperature on solubility of volatile anesthetics in human tissues

Hypothermia often occurs during surgery, a factor influencing anesthetic ph armacokinetics through its influence on solubility. Information on the tiss ue solubility of volatile anesthetics under hypothermia is limited. The pre sent study supplies this information for the solubility of volatile anesthe tics in human tissues. Tissue specimens of brain, heart, liver, muscle, and fat were obtained from 10 postmortem males (27 +/- 8 yr). Tissue/gas parti tion coefficients of desflurane, sevoflurane, enflurane, isoflurane and hal othane were measured at 37 degreesC, 33 degreesC, 29 degreesC, 25 degreesC, 21 degreesC, and 17 degreesC. For each given tissue, the order of tissue/g as partition coefficient was halothane > enflurane > isoflurane > sevoflura ne > desflurane. Tissue/gas partition coefficients at 37 degreesC differed significantly (P < 0.05) across drugs, except that liver/gas partition coef ficients for isoflurane and enflurane did not differ. The logarithm of all tissue/gas partition coefficients increased linearly with decreasing temper ature (P < 0.05). In conclusion, hypothermia increases tissue/gas partition coefficients of volatile anesthetics. The increases are proportional to th ose for blood/ gas partition coefficients, and therefore tissue/blood parti tion coefficients will not change during hypothermic conditions.