Liver transplantation with grafts obtained after cardiac death-current advances in mastering the challenge

Table 2 Hypothermic vs normothermic machine perfusion of liver grafts

Hypothermic machine perfusion HMP	Normothermic machine perfusion NMP
Temperature 0 °C-4 °C	Temperature 37 °C
Logistically easier	Logistically demanding
Modest resumption of energy production with low perfusion rate
Improves the state of mitochondria during preservation	Recreates the physiological milieu by maintenance of normal temperature
Performed at sub-physiologic pressures[107]	Performed at physiological pressures[70,82]
Requires low perfusion rates[108]	Requires high perfusion rates[108]
No requirement for a specific oxygen carrier in the perfusate as demand for O2 is low[108]	Oxygen is provided by using blood, modified hemoglobin, or using a high oxygen tension in special preservation solutions[70,82,84,88,109]
Less occurrence of graft infection considering the hypothermic state More tendency for endothelial cell, kupffer cell, and macrophage cell damage due to shear stress and hypothermic activation[110-113]	Reduces IRI
When compared to SCS it decreases inflammatory cytokines but no difference in graft or patient survival was found[77,114]	Provides nutrients (glucose, amino acids, etc.), medications to prevent micro-circulatory failure (e.g., prostacyclin, heparin, antibiotics), and oxygen
May help protect marginal livers by converting PNF into allograft dysfunction[71]	Allows the assessment of organ viability (e.g., Galactose elimination, factor V production, bile flow)
	May allow the use of gene therapy prior to transplantation, to reduce the risk of rejection, or decrease the ischemia-reperfusion injury[115-117]

HMP: Hypothermic machine perfusion; SCS: Static cold storage; NMP: Normothermic perfusion.