Pretransplant sequential hypo- and normothermic machine perfusion of suboptimal livers donated after circulatory death using a hemoglobin-based oxygen carrier perfusion solution

Abstract

Ex situ dual hypothermic oxygenated machine perfusion (DHOPE) and normothermic machine perfusion (NMP) of donor livers may have a complementary effect when applied sequentially. While DHOPE resuscitates the mitochondria and increases hepatic adenosine triphosphate (ATP) content, NMP enables hepatobiliary viability assessment prior to transplantation. In contrast to DHOPE, NMP requires a perfusion solution with an oxygen carrier, for which red blood cells (RBC) have been used in most series. RBC, however, have limitations and cannot be used cold. We, therefore, established a protocol of sequential DHOPE, controlled oxygenated rewarming (COR), and NMP using a new hemoglobin‐based oxygen carrier (HBOC)‐based perfusion fluid (DHOPE‐COR‐NMP trial, NTR5972). Seven livers from donation after circulatory death (DCD) donors, which were initially declined for transplantation nationwide, underwent DHOPE‐COR‐NMP. Livers were considered transplantable if perfusate pH and lactate normalized, bile production was ≥10 mL and biliary pH > 7.45 within 150 minutes of NMP. Based on these criteria five livers were transplanted. The primary endpoint, 3‐month graft survival, was a 100%. In conclusion, sequential DHOPE‐COR‐NMP using an HBOC‐based perfusion fluid offers a novel method of liver machine perfusion for combined resuscitation and viability testing of suboptimal livers prior to transplantation.

The efficacy of HBOC‐201 in ex situ gradual rewarming kidney perfusion in a rat model

“…Due to the lack of NADH‐dependent enzyme (methemoglobin reductase) in HBOC, the possibility of Met‐Hb production is a disadvantage associated with HBOC use and the gradual rise in Met_Hb level has been previously reported . Our experiments also revealed a slight increase in the Met‐Hb during rewarming and more extreme during reperfusion.…”

“…The use of HBOC in 2 discarded human liver studies reported the feasibility and safety of applying HBOC‐based perfusion media during normothermic machine perfusion (NMP) as an alternative to RBCs . A recent study by de Vries et al described the use of HBOC in a pretransplant combined dual oxygenate hypothermic machine perfusion (D‐HOPE) with controlled oxygenated rewarming (COR) to NMP in initially declined human liver grafts . The study presented promising results for further future use of HBOCs in clinical studies with the outcome of 100% patient survival in the first 3 months post‐transplant.…”

“…In general, the effects of temperature on oxygen affinity of HBOC are similar to the effects of temperature on native (corpuscular) Hb, which means that oxygen affinity increases by temperature decrease (low in hypothermic and higher in normothermic temperature). However, across all temperatures HBOC demonstrates high tendency to release oxygen which is still better than Hb in erythrocytes …”

“…([{ApO 2 −VpO 2 } × K /760] × total flow) + ([{AsO 2 −VsO 2 } × Hb × c × 0.0001] × flow)/Kidney weight × 100. In which pO 2 was in mm Hg, sO 2 in %, Hb in g/dL, Renal artery flow in mL/min and kidney weight in g. c the oxygen binding capacity of HBOC (1.26) and K was a constant (0.0225) …”

Synthetic hemoglobin-based oxygen carriers are an acceptable alternative for packed red blood cells in normothermic kidney perfusion

“…PRBC. However, the amount of HBOC reaching the recipient circulation in a clinical setting would be negligible, because the perfusion solution would be washed out prior to transplantation 26,27,38,39. Histology reveals glomerular tufts irregularly engorged with accumulated luminal red blood cells (black arrows), loss of the epithelial brush border, frequent cytoplasmic vacuolations (blue arrows), and rupture of some tubules with interstitial edema (red arrows).…”