Prediction of volatile anaesthetic solubility in blood and priming fluids for extracorporeal circulation

Volatile anaesthetics are often used during cardiopulmonary bypass (CPB). T o understand the kinetics of inhaled anaesthetics during CPB, anaesthetists should understand changes in blood solubility caused by fluid use. We set out to predict the solubility of three volatile anaesthetics, desflurane, i soflurane and halothane, during CPB by determining: (i) their solubility in fresh whole blood and eight CPB priming fluids at 37 degreesC; (ii) the ef fect of temperature on the solubility of these anaesthetics in lactated Rin ger's, gelofusin, banked blood and plasma; (iii) their solubility in differ ent mixtures of these four priming fluids at different temperatures; and (i v) their estimated and actual solubility in blood during hypothermic CPB. W e calculated solubility using a concept of volume fraction partition coeffi cient and compared estimated and measured solubilities. For the three anaes thetics tested, solubilities are in the order: fresh whole blood approximat e to plasma > banked blood > normal saline approximate to lactated Ringer's approximate to gelofusin approximate to Haemaccel approximate to hydroxyet hyl starch > mannitol. The solubilities of the anaesthetics in all priming fluids increased logarithmically at lower temperatures (P<0.05). The volume -fraction estimates of the partition coefficients were within approximately +/-20% of the measured values for all values of solubility. The correspond ing estimates of solubility for CPB blood samples were between -36% and +24 % of the measured values. During normothermic CPB, blood solubility of vola tile anaesthetics would be unchanged when using plasma, slightly reduced wh en using banked blood and markedly reduced when using crystalloids and coll oids.