The purpose of preservation is to maintain the viability of the donor organ until it can be transplanted. Preservation methods are based on hypothermia and on the use of preservation solutions; these aim to avoid hypothermia-induced cell swelling. 
Hypothermia is induced by cooling the abdominal cavity of the donor with sterile ice and by flushing the vasculature of the organ with a cold solution (usually about 4°C) which lowers the temperature of the organ to 4 °C within 5 to 15 minutes. Hypothermia causes the suppression of hydrolytic enzymes (phospholipases, lysosomal enzymes, proteases) and of microorganism growth, and it reduces metabolism, including the requirements for a continual supply of nutrients, oxygen and energy. 
The energy (ATP) reduction is responsible for diminished activity of the membrane Na+-K+-ATPase pump, which normally maintains a high Na+ concentration outside the cells and a high K+ concentration inside the cells. Thus, there is a stoichiometric exchange between Na+ and K+ and an alteration of the membrane potential. As a consequence, Cl- diffuses inside the cells and causes an increased cell osmotic activity, with water pulling and cell swelling and dysfunction.
Preservation solutions are used to prevent cell swelling induced by hypothermia; they contain impermeants that exert sufficient osmotic force to counter the intracellular colloidal osmotic force. 
Collins preservation solution contains a high concentration of K+ and Mg+, a low concentration of Na+ (to resemble the intracellular milieu) and a high quantity of glucose that acts as impermeant.
EuroCollins preservation solution is identical to Collins solution except for the fact that it does not contain Mg+, to avoid its precipitation with phosphate. 
The University of Wisconsin solution (UW) contains penta starch as a colloid to counteract the hydrostatic pressure produced by the perfusion pump; gluconate as an impermeant anion, adenine and ribose as precursors of ATP synthesis, glutathione to suppress damage due to lipid peroxidation and oxygen-free radicals, high K+, low Na+.