242 - HEMOLYTIC BYPRODUCTS DURING EX-SITU HEART PERFUSION ASSOCIATE WITH FUNCTIONAL DECLINE DURING EXTENDED PRESERVATION

Background: Ex-situ heart perfusion (ESHP) is an improved method of transport for donor hearts for transplantation, which can improve the duration and quality of preservation in comparison to cold storage. Despite facilitating lengthier ex-vivo transportation of the donor heart, cardiac function and myocardial oxygen consumption (MVO2) are known to deteriorate during prolonged perfusion periods, precluding longer distance transport and raising concern for post-transplant success. The mechanism regarding functional decline remains unclear. Perfusion solutions for ESHP typically utilize a buffer to supplement blood volume, leading to reduced hematocrit. It has been postulated that lack of oxygen delivery to the organ due to low hematocrit within the ESHP apparatus may contribute to functional decline. Therefore, the objective of our study was to investigate varying perfusate hematocrit during ESHP.

METHODS AND RESULTS: The hearts of yorkshire pigs weighing 45-55kg were procured and subject to ESHP for 12 hours using various mixtures of donor whole blood (DWB) in 3 groups: dilute whole blood (DB) group (n=5), perfused with a 1:1 mixture of DWB with Krebs Heinseleit buffer with 8% albumin (Hb ~4g/dL); whole blood (WB) group (n=6), perfused with entirely DWB (Hb ~8g/dL); and concentrated blood (CB) group, perfused with DWB supplemented with donor packed red blood cells obtained via cell saver (final Hb ~13g/dL). During perfusion, cardiac index and myocardial oxygen consumption (using arterial blood gas) were measured alongside arterial blood gas analysis every two hours.
Interestingly, compared to DB group and WB group the decrease in cardiac index from baseline was significantly greater in the CB group by late perfusion (p < 0.05). While MVO2 was significantly raised in the CB group compared to WB group at baseline (p < 0.05), it declined the most rapidly from baseline out of all groups. Concomitantly, perfusate potassium in both the WB and CB groups increased significantly compared to DB group. Cell-free hemoglobin was significantly elevated in CB group compared to WB and DB groups (p < 0.05) by mid and late perfusion.


Conclusion: Hemolysis appears to highly associated with functional decline during ESHP, suggesting that efforts to combat hemolytic byproduct accumulation or toxicity mediated by hemolytic byproducts can bolster functional preservation over extended periods of perfusion. Conversely, perfusate hemoglobin as low at 4g/dL appears to be safe for perfusion, and may be cardioprotective over prolonged perfusion.