Myocardial microvascular perfusion after transfusion of liposome-encapsulated hemoglobin evaluated in cross-circulated rat hearts using tracer digital radiography

The effect of hemodilution with Neo Red Cell (NRC, liposome-encapsulated hemoglobin) on myocardial perfusion was evaluated in cross-circulated rat hearts under 300-bpm pacing and 100-mmHg perfusion pressure. In NRC-transfused hearts (n = 5), NRC volume fraction and hematocrit were 9% ± 3% and 22% ± 4%, respectively; the latter decreased from 43% ± 3% before NRC transfusion. Coronary perfusion rate and left ventricular isovolemic developed pressure increased after NRC transfusion to 4.6 ± 1.0 ml/min/g and 127 ± 32 mmHg from basal values of 2.5 ± 0.3 ml/min/g and 115 ± 28 mmHg, respectively. In contrast, the flow increase during reperfusion following 30-s flow cessation decreased from 74% ± 24% to 64% ± 24%. The arteriovenous difference in O₂ saturation was slightly higher after NRC transfusion. Within-layer regional flow distributions from subepicardium to subendocardium assessed by tracer digital radiography (100-μm resolution) showed that coefficients of variation of flows in 400 X 400-μm regions were 0.41 ± 0.10 in NRC-transfused hearts and 0.54 ± 0.11 in nontransfused hearts (n = 5); i.e., the myocardial flow distribution was more uniform in NRC-transfused hearts. These results suggest that NRC is superior to erythrocytes in terms of the homogenization of O ₂ delivery, indicating its potential therapeutic value in myocardial microcirculatory failure.