Normothermic Machine Perfusion

Ashley Sweet

A 61-year-old male with alcohol-associated cirrhosis is called in from home for liver transplantation. The liver is procured from a 69-year-old donor after declaration of circulatory death. The liver is then prepared on the backbench prior to being placed on a normothermic machine perfusion pump.

Which structures are cannulated and ligated during backbench preparation for ex-situ pumping?

Correct Answer:

A. The IVC, HA, PV, CBD are cannulated. The cystic duct is ligated.

What are the benefits of using normothermic machine perfusion during liver transplant?

Normothermic machine perfusion (NMP) is associated with decreased risk of early allograft dysfunction, postreperfusion syndrome, ischemia reperfusion injury, and ischemic biliary complications compared to static cold storage. The ability to evaluate graft function during perfusion has also expanded the use of more marginal allografts and decreased organ discard rates.

How do these devices work?

The graphics in Figures 1-3 depict how a liver is cannulated and connected to two commonly used NMP devices – the Transmedics® OCS Liver and the OrganOx metra®. In the Transmedics system, the suprahepatic inferior vena cava (IVC), portal vein (PV), hepatic artery (HA), and common bile duct (CBD) are cannulated prior to connection of the liver to the pump (Figure 2). In the OrganOx system, the infrahepatic IVC, PV, HA, and CBD are cannulated prior to connection, and the suprahepatic IVC is oversewn (Figure 3). Perfusion of the liver with warmed, oxygenated perfusate solution is begun and the perfusate recycles through the system.

Perfusate contents and perfusion parameters are summarized in Figure 1. In addition to the perfusion parameters, perfusate blood gas, lactate, and glucose are monitored during pumping. Adjustments can be made to meet the metabolic demands of the organ.

Back to the case…

After the liver is warmed to goal on the pump, serial ABGs are checked, which demonstrate a worsening acidosis and lactate. The liver is not making bile. What inspection should be undertaken?

Answer: Inspect all surfaces of the liver to ensure good global perfusion, and to ensure there is no major bleeding from the HA or PV which may require repair. Also to ensure there is no kinking of the vessels.

 

You note patchy perfusion of the liver and a kink in the hepatic artery, which is untwisted. The liver perfusion appears better, and it begins making bile. Serial ABGs demonstrate improving lactate but ongoing acidosis. What intervention could be provided?

Answer: Consider infusion of additional sodium bicarbonate into the perfusate

 

You note that the hepatic artery pressure remains high. What could be adjusted?

Answer: Consider infusion of Epoprostenol to encourage vasodilation

 

After several hours of perfusion, the pump parameters and pH remain within goal range. The lactate has normalized. Glucose is now <180. What infusion is needed?

Answer: TPN

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