Effects of different hematocrits on the isolated working rabbit heart reperfused after ischemia

Increased blood viscosity has frequently been related to ischemic heart diseases. Since blood viscosity depends mainly on hematocrit (HTC), the effects of hemodilution have been studied on the isolated working rabbit heart perfused initially with 50% HCT, submitted to global ischemia for 10 min and reperfused with two different amounts of HCT: 50 and 30%. When the reperfusion was carried out with 50% HCT (N = 10) aortic flow failed to be restored in 4 hearts. When the reperfusion was performed with 30% HCT, all hearts recovered rapidly, reaching the preischemic cardiac output 20 min later. The ratio between cardiac output (C.O.) 20 min after reperfusion and C.O. before ischemia was 0.30 for the high hematocrit group (H.H.) as compared to 0.89 for the low hematocrit group (L.H.). The ratio of the coronary flow (C.F.) 20 min after reperfusion and that of C.F. before ischemia was 0.83 for the H.H. group as compared to 1.30 for the L.H. group. After reperfusion the myocardial oxygen consumption was not significantly different between both groups. The better recovery of heart performance after ischemia when the hearts were reperfused with a 30% HCT suggests that hemodilution results in a better oxygen distribution.