Normothermic Regional Perfusion: Why Isn't the Lactate Coming Down?

During normothermic regional perfusion (NRP), lactate is the most commonly used liver viability marker. Lactate production from pyruvate breakdown in erythrocytes is not suspended during pRBC storage. By transfusing blood at a variety of stored ages, variable amounts of lactate are added to the NRP circuit and may influence serial lactate measurements. Sixteen DCD donors undergoing NRP were enrolled in a prospective study. Samples were drawn from pRBC bags prior to use in the NRP circuit and were tested for lactate values. Lactate values of the NRP circuit perfusate were also assessed Q15 min. Lactate values of the pRBCs varied from 4.4 mmol/L to >20 mmol/L and were strongly correlated with the age of the stored blood (r² = 0.74). Donors in which the pRBCs were > = 20-days from expiration (Newer Blood group) had a significantly lower lactate at 60 min of NRP compared to donors in which pRBCs were <20 day from expiration (Older Blood group) (4.0±2.0 mg/dL vs. 6.3±2.3 mg/dL; p = 0.048). If the lactate is not decreasing as anticipated, transfusion of older pRBC should be entertained as one possible explanation. In cases where the liver seems acceptable for transplantation, additional lactate testing with longer time on NRP or sequential NRP/NMP should be considered in lieu of declining the liver outright.