PRESERVATION OF INDIVIDUAL ORGANS AND TISSUES
Vascularized organs
Kidney
Simple hypothermic storage employs the following flush solutions: firstly, Collins' solution, with high concentrations of potassium, magnesium, phosphate, sulphate, and glucose. This extended preservation to 48 h, but precipitation of magnesium phosphate was a major problem. Subsequently, magnesium sulphate was omitted (EuroCollins solution) with no deleterious effect. Replacement of glucose by mannitol, sucrose, or raffinose improves function experimentally and in humans.
Citrate-based solutions, containing high concentrations of potassium, magnesium, citrate, sulphate, and mannitol were originally devised to overcome the limitations of Collins' solution. Both hypertonic and isotonic solutions are stable and provide successful clinical preservation for 48 h or more. High magnesium concentration is essential; magnesium citrate chelates provide the critical semipermeant component.
Recently, two other solutions have been shown to provide better renal preservation than the above which are nonetheless still widely used. These are phosphate buffered sucrose (PBS) and UW solution. The former is an isotonic solution containing only a phosphate buffer and sucrose, an impermeant solute. Clinically and experimentally this solution is highly effective. Preservation at 72 h was better with phosphate buffered sucrose than with Collins' or Citrate solutions.
UW solution was developed initially for pancreatic preservation. Subsequently, it was found to extend and improve preservation of the liver profoundly and became the preferred solution for multiorgan harvest, despite its higher cost. UW solution is highly effective in preserving dog kidneys for 72 h and rat kidneys for 48 h. Modifications of the solution, omitting the colloid (hydroxyethyl starch), are equally effective. High potassium concentration is not essential, and lactobionate can be replaced by gluconate. Clinically, a recent European Multicentre Trial indicated that kidneys preserved in UW solution produced a more rapid reduction of serum creatinine, higher creatinine clearance rate, and less dialysis when compared to EuroCollins (median preservation time 24 h, maximum 48 h). An additional advantage of use of UW solution was that sharing kidneys between centres to improve matching improved graft survival without any functional detriment for up to 48 h of storage. Other trials showed UW without HES to be equally beneficial.
Kidneys which have undergone more prolonged storage often exhibit poor early function for several days. Further extension of preservation requires additional resuscitative technology. Perfusion storage may resuscitate kidneys which have been subjected to adverse conditions before harvest or during storage. This could involve intermittent warm reperfusion with oxygen, nutrient amino acids, fatty acids, cofactors, and hormones. Normothermic reperfusion would be easier to apply clinically if a reliable synthetic perfusate could be developed.
Liver
Pancreas
Heart
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