Cardiovascular Responses, Hemodynamics and Oxygen Transport to Tissue during Moderate Isovolemic Hemodilution in Pigs

As postulated, acute isovolemic hemodilution induces a decrease in systemic vascular resistance (SVR) almost parallel to the decrease in blood viscosity, whereas cardiac index (CI) increases significantly without increase in myocardial contractility, while oxygen affinity of hemoglobin is unaffected (Messmer et al., 1973). Over a wide range of hematocrit (Hct) levels, the rise in CI compensates for the decreased oxygen transport capacity, thereby maintaining oxygen transport to the tissue unaltered. Nearly all data in the literature about the effects of hemodilution are obtained from experiments in dogs. Dogs, however, differ from humans in anatomy, distribution of coronary arteries and in sympathetic responses (Weaver et al, 1986). Therefore in this study cardiovascular responses, hemodynamics, oxygen transport to tissue and the oxygen affinity of hemoglobin during normoxic acute isovolemic moderate hemodilution were studied in pigs. Ample evidence exist to demonstrate that the pig is closely related to the human both anatomically and physiologically. The cardiovascular system and metabolism show similarities with respect to the size and distribution of coronary vessels, blood pressure, heart rate, cardiac index, regional distribution of cardiac output and maximum oxygen consumption (Swindle, 1984; Mc Krinan et al, 1986; Weaver et al., 1986).