Varying Perfusate Hemoglobin During Normothermic Ex Situ Heart Perfusion: Elevated Hemoglobin Exacerbates Functional Decline Through Hemolysis

Background. Ex-situ heart perfusion (ESHP) enables improved donor heart preservation, yet still suffers functional decline. The perfusate is 1 area that requires optimization, especially with regard to hemoglobin (Hb) content. We sought to compare performance of concentrated, physiologic, and dilute perfusates in minimally damaged hearts. Methods. Hearts of juvenile Yorkshire pigs (45–55 kg) were procured and subject to 11 h of working-mode ESHP in 1 of 4 groups varying in Hb: concentrated blood (CB, ~12 g/dL Hb, n = 4), whole blood (WB, ~8g/dL Hb, n = 6), plasma (~4g/dL Hb, n = 6, diluted with donor plasma), and control (~4g/dL Hb, n = 5, diluted with modified Krebs-Heinseleit). Functional, metabolic, and hemolytic markers were recorded and compared between groups statistically using appropriate statistical tests. Results. CB hearts exhibited worsened decline from baseline in cardiac index, dP/dT max/min, and stroke work ( P < 0.05) and had greater elevations in hemolytic markers by end perfusion. Preservation of baseline cardiac index did not differ significantly between controls, WB, or plasma groups over time ( P > 0.05). The CB group displayed elevated early oxygen consumption compared with controls ( P < 0.05), with WB and plasma groups trending toward increased oxygen consumption. Lactate elevated over time in all groups, however, was not comparatively elevated within the CB group; it was reduced in the plasma group during early perfusion compared with control. Conclusions. Hb dilution appears to lower absolute output but preserves baseline function. Supraphysiologic Hb elevation or sublethal blood cell damage exacerbates hemolysis, which contributes to functional decline during ESHP. Lactate evolution did not appear to associate with the degree of functional loss.