TABLE 1.

Criteria used to determine viability during 2.5 h of NMP [Color table can be viewed at wileyonlinelibrary.com]

	Parameter	Green zone	Orange zone	Red zone
Hepatocytes	Bile production (ml)	≥ 10 a	5 to 10	< 5
	Perfusate lactate (mmol/L)	< 1.7	1.7 to 4.0	> 4.0
	Perfusate pH	7.35–7.45	7.25 to 7.35	< 7.25
Cholangiocytes	Bile pH	> 7.45	7.40 to 7.45	< 7.40
	ΔpH	> 0.10	0.05 to 0.10	< 0.05
	ΔHCO3 − (mmol/L)	> 5.0	3.0 to 5.0	< 3.0
	ΔGlucose (mmol/L)	< −5.0	−3.0 to −5.0	> −3.0

Viability criteria that needed to be reached within 2.5 h of normothermic machine perfusion. The green zone includes the four original viability criteria (perfusate pH, lactate, bile production, and bile pH) that had to be reached at any time point within 2.5 h after initiation of NMP. The other criteria were secondary criteria that emerged with increasing experience. Orange zone represents potentially acceptable values which are “on the border” and that could be accepted if the other viability criteria are “green.” Red zone indicates values that do not meet the viability criteria.

Abbreviations: NMP; normothermic machine perfusion.

^a Of which ≥4 ml in the last hour. ∆ indicates the bile value minus the perfusate value.