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Static cold storage has remained the gold standard for organ preservation worldwide. However, preservation injury due to classic cold storage causes injury to the liver graft, regardless of the length of the preservation period, only the degree of injury varies. Good quality grafts tolerate well storage times cumulating up to 12 hours, while grafts derived from so called “extended criteria” donors (ECD) have a much higher risk for dysfunction. ECD grafts include hepatic macrosteatosis (< 30 %), donation after cardiac death (DCD), long ICU stay before procurement, elevated liver enzymes and prolonged cold ischemia (> 12 hours). The combination of these factors in a donor puts a recipient at high risk of postoperative graft failure. The incentive to use these organs is, however, high, because of the severe organ shortage. Based on this, new strategies for the safer use of those grafts are urgently needed.
In this context, machine perfusion appears as an attractive dynamic method which was first suggested already 100 years ago, but has been abandoned because of the complexity associated with this technique and because of the emergence of simple and convenient cold storage. During the past decade, however, a number of promising data regarding machine liver perfusion have been reported.
We have developed during the past 15 years in several rat and pig liver models a cold oxygenated machine perfusion approach, which can be easily applied through the portal vein after conventional organ procurement and organ transport. Such concept, called hypothermic oxygenated perfusion (HOPE), is able to convert the hepatic cellular energy charge and results in subsequent less reperfusion injury. The mechanisms behind include a change in the mitochondrial electron transfer rate and a cleaning effect of the sinusoidal endothelium. Importantly, the optimal time of endischemic HOPE appears 1 to 2 hours. Practicability of this approach appears very high, due to the fact that machine perfusion could be performed after organ transport to the transplant center during recipient hepatectomy. Human application of this technique in DCD liver grafts is currently done in our center, showing promising preliminary results.