Preservation solutions in liver transplantation: what are the options?

Alexis Carrel took the initial steps in the area of organ preservation by successfully preserving an artery for several days using chilled Locke’s solution, although this effort was largely overshadowed by his work in vascular surgery and organ transplantation. With the increased interest in clinical organ transplantation in the 1960s, the transplant community soon realized the need for preservation solutions and techniques to procure and store organs in “as-optimal” condition and to provide maximally safe times to transport organs to potential recipients. This became achievable by; 1) preventing graft damage in the donor by decreasing warm ischemia time; 2) minimizing cellular changes during the cold storage time; and 3) minimizing reperfusion injury to the organ after restoration of the blood supply in the recipient. Induction of hypothermia to reduce metabolic requirements of the organ is the mainstay of all clinically utilized preservation methods. Simple surface cooling with ice slush in the donor was used by Moore, while Starzl introduced the concept of core cooling by flushing abdominal organs by cold solution through an aortic cannula. The development of machine perfusion by Belzer and simple cold storage by Collins in the late 1960s were the original options in the rapidly expanding field of organ preservation and transplantation and are still in use today. Belzer and coworkers conceptualized the use of impermeant molecules, added to the preservative solution, with the goal to prevent cell swelling during hypothermic storage, which were incorporated into the preservation solution developed at the University of Wisconsin (UW, also known as Viaspan) in the mid1980s. With the burgeoning liver transplant activity in the United States in the 1990s, UW soon became the gold standard for preservation of the liver and other intraabdominal organs. However, in spite of the clinical success of the solution, several alternative solutions have been introduced and utilized in liver allograft preservation with potential benefits. Histidine-tryptophane-ketoglutarate (HTK) solution was originally developed for cardiac preservation and was subsequently utilized in organ transplantation. Its preservative function is also based on a principle of different buffers and electrolyte composition, i.e., extracellular-based electrolyte composition with low potassium content, compared to UW solution. The use of HTK in liver transplantation can be traced to European efforts in the late 1980s, where it was shown to be efficacious and safe in liver preservation when compared to UW. The solution was not utilized in the United States until 2002, when it was first used at the University of Pittsburgh in cadaveric and living donor liver transplantation. The lower viscosity of HTK and potentially better penetration in the microcirculation of liver prompted the program to use HTK with the main focus to evaluate long-term outcome of liver transplantation and biliary problems, especially in the setting of non-heart-beating donation after cardiac death donors. In addition, the expansion of the living donor program, utilizing a piggyback venous reconstruction, benefited from the low potassium content, obviating the need for in situ flush prior to revascularization. In this issue of Liver Transplantation, Mangus et al. compared HTK vs. UW in a large series of cadaveric adult liver transplantations at Indiana University. They examined the outcome of 174 livers preserved with HTK and compared the results with a historical control