Analysis of adenine nucleotides in tissue biopsies during normothermic machine perfusion of transplanted livers. (a) ATP concentration in liver biopsies. (b) Ratio of ATP to ADP. (c) Energy charge calculated as (ATP + 0.5∗ADP)/(ATP + ADP + AMP). Results are represented as median, interquartile range and min–max values. (∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001, ns = no significance; comparisons between time points, Kruskal–Wallis test).