Evaluation of Liver Grafts During Machine Perfusion at 20°C via Metabolization of 13C-Methacetin.

BACKGROUND: Evaluative measures, helping to decide whether a marginal graft can be used for transplantation or rather be discarded are of utmost importance but yet basically underdeveloped. Recent technical developments allow for the isolated detection of 13C-labelled carbon dioxide in the oxygenator exhaust of an isolated perfused organ. By adding a 13C-labelled tracer, its metabolism can be monitored by measuring the increase in 13C carbon in the exhaust air. Here we evaluated the potential of the technique to evaluate pig livers during machine perfusion. METHODS: Porcine livers (six per group) were subjected to 5, 20 or 45 min of warm ischemia and cold stored overnight. Evaluative machine perfusion was done with MPS at 20°C for 2 h. After injection of 13C-methacetin as a tracer, 13CO2 as metabolic end-product can be quantified by high precision laser-based spectroscopy in the gas outflow of the oxygenator. RESULTS: The 13CO2 test showed clear differences between all three groups, and provided superior discriminative potential when compared to conventional parameters (e.g., flow, transaminases, lactate). ROC curve analysis for discrimination between 5 and 20 min of warm ischemia revealed an area under the curve of 0.916 while comparison of 20 and 45 min of warm ischemia results in an area under the curve of 1.0 (p < 0.01). CONCLUSION: Thus, the 13C turnover test appears to have the potential of an objective, quantitative and valuable adjunct in the toolbox for pre-transplant evaluation of questionable liver grafts.