Liver
Liver transplantation has been an established and effective treatment modality for end-stage liver disease since the early 1980s, but until recently livers were only able to be stored reliably for 12 h in Collins' or Citrate solutions. Preservation of the liver with EuroCollins or Citrate is less effective than preservation of the kidney for the hepatocyte is more permeable to glucose and mannitol, leading to reduced osmotic control and increased acidosis due to anaerobic glycolysis (EuroCollins). Pretreatment of the donor with chlorpromazine, or addition of chlorpromazine, diltiazem, or a stable prostacyclin analogue to the flush solution improves preservation.
A major advance in liver preservation occurred with introduction of UW solution. This solution provided effective preservation in the dog (48 h) and rat (30 h). Clinical preservation times have been safely extended to 24 h allowing procurement of liver grafts from distant cities, ample time for histopathological examination of the graft, more perfect recipient hepatectomy, and bench surgery of the graft to tailor adult grafts to fit one or more child recipients. The length of the preservation period within the range 4 to 24 h has not affected graft outcome in UW-preserved liver grafts. In contrast, the ischaemic period significantly affects EuroCollins livers preserved for this length of time.
Experimental studies have indicated that the essential ingredients of UW solution are the impermeant anion lactobionate, with additional osmolality provided by raffinose. Adenosine, allopurinol, and glutathione seem also beneficial. Omission of hydroxyethyl starch from UW solution is not detrimental to dog, rat, or human liver grafts. High potassium content has been shown to be unnecessary in 48-h preservation of the dog liver. Other buffers such as histidine can replace phosphate.
The hepatocyte is relatively insensitive to cold ischaemia; the primary damage is to the microvasculature and to the endothelial cells lining the sinusoid. Experimental studies indicate that although parenchymal cells remain viable during preservation for 48 h, a high proportion of endothelial cells are non-viable and this contributes to poor early function and mortality. UW solution helps to prevent cold-induced microcirculatory injury, but the mechanism of this protection is still speculative.
Prolonged preservation requires further refinement of solutions for static preservation, or development of perfusion preservation. Dog livers have been successfully stored for 72 h using continuous perfusion with modified UW solution: gluconate replaced lactobionate in this solution and calcium, adenine, glucose, and ribose were included.
Assessment of graft quality prior to implantation by measurement of ATP content, pH, energy charge, or morphology is not necessarily reliable; many of the detrimental changes occur after reperfusion. The volume and quality of bile flow, restoration of clotting, absence of lactate acidosis, blood amino acid clearance, and plasma concentration of bilirubin and aspartate aminotransferase can distinguish which grafts will recover.
During the recipient operation, it is advisable to replace the preservation fluid within the stored liver before releasing the suprahepatic caval clamp, by reflushing with balanced electrolyte solution, blood, or plasma, otherwise cardiac arrhythmias or arrest can occur due to the high concentrations of potassium, hydrogen ions, or pharmacological additives such as adenosine released into the circulation from the revascularized liver. Some centres use a warm rinse before release of the upper clamp; this avoids potential inhibition of cardiac activity from a large bolus of cold fluid.
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