TISSUE OXYGENATION WITH GRADED DISSOLVED-OXYGEN DELIVERY DURING CARDIOPULMONARY BYPASS

Background: Intravascular perfluorochemical emulsions together with a high oxygen tension may increase the delivery of dissolved oxygen to u seful levels, The hypothesis of this study is that increasing the diss olved oxygen content of blood with incremental doses of a perfluoroche mical emulsion improves tissue oxygenation during cardiopulmonary bypa ss in a dose-related fashion, Methods and Results: Oxygen utilization was studied in a profoundly anemic canine model of hypothermic cardiop ulmonary bypass, Forty-two dogs underwent normovolemic hemodilution to a hematocrit of 15.8% +/- 0.6% (mean +/- standard error of the mean), Cardiopulmonary bypass was begun and resulted in a hematocrit of 9.4% +/- 0.6%. A standard priming solution was used in the control group ( n = 12), and the test groups received 1.35 gm perfluorochemical . kg(- 1) (n = 10 dogs), 2.7 gm perfluorochemical . kg(-1) (n = 10 dogs), or 5.4 gm perfluorochemical . kg(-1) (n = 10 dogs) through the venous ret urn cannula, Each animal underwent a series of randomized pump flows ( 0.25, 0.5, 1.0, 1.5, 2.0, and 3.0 L . min(-1). m(-2)) at 32 degrees C, After the randomized flows were completed at 32 degrees C, the temper ature was raised to 38 degrees C and cardiopulmonary bypass was discon tinued, Mortality from cardiac failure on separation from cardiopulmon ary bypass was 42% in the control group and 20% in perfluorochemical-t reated groups. The mean perfluorochemical dose was higher in survivors than in nonsurvivors (2.9 +/- 0.4 versus 1.3 +/- 0.5 gm perfluorochem ical . kg(-1); p < 0.05), No differences in oxygen consumption or tran sbody lactate gradient were found between groups during cardiopulmonar y bypass, Analysis of mixed venous oxygen tension (a surrogate measure for tissue oxygenation) as a function of cardiopulmonary bypass flow normalized to body surface area showed that the control group had sign ificantly lower mixed venous oxygen tension (p < 0.05) than the perflu orochemical emulsion-treated groups, Furthermore, the differences were related to the perfluorochemical emulsion dose, These differences in mixed venous oxygen tension continued after termination of cardiopulmo nary bypass, The coronary sinus oxygen tension and cardiac arterial-ve nous oxygen content differences during and after cardiopulmonary bypas s were similar among the control and perfluorochemical emulsion-treate d animals, Dissolved oxygen consumption during and after cardiopulmona ry bypass was calculated, Dissolved oxygen consumption increased in th e perfluorochemical-treated animals in a perfluorochemical dose-relate d manner and was significantly higher in perfluoro-chemical-treated an imals than in the control animals (p < 0.05). Conclusions: Graded incr eases in mixed venous oxygen tension during cardiopulmonary bypass wer e observed in response to graded increases in the dissolved oxygen del ivery. These data suggest that enhancing oxygenation with perfluoroche mical-dissolved oxygen is an effective temporary substitute for the us e of hemoglobin-bound oxygen during cardiopulmonary bypass. Perfluoroc hemical-dissolved oxygen may be particularly beneficial in the setting of multiple hypoxic stresses.