Association of hemoglobin levels with renal metabolism and function during normothermic machine perfusion of porcine kidneys
L. Annick van Furth1, Tobias M Huijink1, Hanno Maassen1, L. Leonie van Leeuwen1, Veerle A Lantinga1, Baran Ogurlu1, Tim L Hamelink1, Merel B F Pool1, Rianne Schutter1, Cyril Moers1, Henri G D Leuvenink1, Rene A Posma1, Leonie H Venema1.
1Surgery, organ donation and transplantation, University Medical Centre, Groningen, Netherlands
Introduction: Machine perfusion is widely studied as an opportunity to expand the kidney donor pool. Normothermic machine perfusion (NMP) of donor kidneys is increasingly implemented to preserve and assess renal function. However, the exact metabolic needs of an isolated perfused kidney are still unknown. Although all perfusion fluids are based on red blood cells or alternative oxygen carriers, hemoglobin levels are usually below physiological levels. It is unknown to which extent oxygen carrying capacity of hemoglobin is required to support kidney function during NMP. Therefore, the effect of hemoglobin levels on renal metabolism and function during NMP was retrospectively evaluated.
Methods: Using pooled data from our lab’s experimental work, slaughterhouse obtained porcine kidneys that underwent oxygenated NMP for four to six hours with a red blood cell-containing perfusion fluid between 2017 and 2022, were included in this study. All kidneys had a cold preservation period with either (oxygenated) hypothermic machine perfusion (HMP) or static cold storage (SCS). Kidneys were stratified according to arterial perfusate hemoglobin concentration at the start of NMP per 1 g/dL increment between 1,61 g/dL (= 1 mmol/L) and 12,89 g/dL (= 8 mmol/L). Outcome variables were fractional sodium excretion, creatinine clearance, oxygen consumption, lactate flux rates and adenosine triphosphate (ATP) levels during NMP.
Results: In total, 101 (75%) of 135 eligible kidneys were included. The mean hemoglobin level at the start of NMP was 8,17 g/dL (sd ±1,72 g/dL). A hemoglobin level ≥8.06 g/dL (= 5mmol/L) was associated with decreased fractional sodium excretion, indicative for improved tubular function. Moreover, oxygen consumption rates were higher and creatinine clearance appears to be higher in these groups as well. Other outcomes like lactate flux rates and ATP levels will be analyzed soon.
Conclusion: This preliminary study reveals that a minimum hemoglobin level of 8,17 g/dL (=5 mmol/L) may be important to support renal metabolism and function during NMP. Ultimately, these results can be translated to clinical NMP protocols.
