Abstract: In order to determine and estimate blood/gas partition coefficient of volatile a nesthetics during open heart surgery, blood samples were obtained from six adult patients undergoing valvular replacement with hypothermic cardiopulmonary bypas s 6 times: before induction, skin incision, aortic cannulation, before rewarming during bypass, weaning of bypass and skin suture. Blood/gas partition coefficient of desflurane, isoflurane and halothane were measured simultaneousl y at rectal temperature when blood was sampled. Significant differences were fou nd in blood/gas partition coefficient of the three anesthetics between differen t times during operation (P<0.05). Blood/gas partition coefficient at weanin g of bypass was the lowest, about 75% of that before anesthesia induction. The r esults of this study indicate that blood/gas partition coefficients of volatile anesthetics vary dynamically during open heart surgery and they are influenced b y the combination of hypothermia and hemodilution.

Key words: volatile anesthetics, blood/gas partit ion coefficient, cardiopulmonary bypass