FUNCTIONAL CAPILLARY DENSITY CHANGES DURING BLOOD SUBSTITUTION WITH ALPHA-ALPHA-HB AND DEXTRAN-70 - INFLUENCE ON OXYGEN DELIVERY

The effectiveness of a blood substitute is ultimately determined by th e rate at which O-2 arrives to the capillaries and the functional capi llary density i.e., the number of flowing capillaries per unit volume of tissue. We use this rationale to analyze the effectiveness of isovo lemic blood substitution with alpha alpha Hb (3,5-bis(dibromosalicyl)f umarate) compared to isooncotic and isovolemic hemodilution with dextr an 70. Progressive hemodilution with each solution was performed in th e awake hamster skinfold model by simultaneous isovolemic exchange of blood until the systemic hematocrit was reduced to 30% of control. Sys temic hematocrit, blood pressure, heart rate were monitored. To determ ine O-2 delivery at the microcirculatory level, functional capillary d ensity, RBC velocity, RBC flux, capillary hematocrit were measured. Fu nctional capillary density was maintained during moderate hemodilution with dextran 70, whereas alpha alpha Hb exchange caused a gradual red uction in the number of flowing capillaries. O-2 delivery to tissue wa s calculated from total O-2 content (RBC and plasma Hb or RBC only), b lood now, and functional capillary density. Our findings suggest that augmentation of the O-2 content of blood with alpha alpha Hb substitut ion produces similar results in terms of capillary O, delivery and cap acity as isovolemic and isooncotic hemodilution with dextran 70.