• How are donor organs currently preserved?
• What are the limitations of current preservation methods?
• What can be done to improve organ status during preservation?

How Are Donor Organs Currently Preserved?

Since the advent of transplantation, the cornerstone of organ preservation has been cold ischemic storage. This has remained virtually unchanged for more than 25 years. Ischemic refers to an organ with no blood circulation. Organs without blood circulation are not able to function during storage. At normal temperatures, rapid cell death would occur in a donor organ in an ischemic state. Preserving the organ at sub-normal temperatures reduces metabolic demands and slows the rate of organ cell death. The organ is usually immersed in solutions in an effort to further reduce damage to cells. The cooled organ is transported in an ordinary beverage cooler from the donor site to the facility where the transplantation will be taking place.

What Are The Limitations Of This Preservation Method?

The three most critical limitations associated with cold ischemic storage include:

• The narrow window of time allowed for safe transport.
  Although cold ischemic storage helps reduce the extent of organ damage during transport, damage does occur. The more time that passes, the more damage occurs; if too much time elapses, the organ will become unusable. For example, we estimate that the majority of hearts are transplanted within four hours of retrieval from the donor.
  
  This greatly restricts the geographic distance allowed between donor and recipient. In fact, healthy donor organs sometimes go unused simply because there are no matched recipients within a close enough range to receive the organ in time.
  
  
• The potential for damage, even within "safe" time limits.
  Even when an organ can be transplanted within the narrow time frame allotted for safe storage, the organ invariably suffers some degree of damage, which can contribute to sub-optimal outcomes.
  
  Anticipated organ damage during ischemic storage has an impact on decisions about the usability of donor organs. Many organs are not used because of the potential for further damage during cold ischemic storage.
  
  
• Inability to test the organ for function.
  Because transplant organs are preserved in a "non-functioning" state during cold ischemic storage, during which they are extremely susceptible to damage, they cannot be further evaluated to determine the functional status. Thus, there is a risk of transplanting an organ with underlying disease that could not be detected during surgical removal.

What Can Be Done To Improve Organ Status During Preservation?

Many approaches to improving outcomes with cold ischemic storage have been explored, including different types of preservative solutions and mechanical perfusion; but none have demonstrated consistent clinical benefits over traditional cold storage. The fact remains, during the period of ischemia during preservation, the organ is at risk of being damaged.

The ability to maintain donor organs in a warm, "living" state outside the body could resolve many of limitations associated with cold ischemic storage. By pumping warm, oxygenated, nutrient-rich blood through the organ from the time of removal until it is implanted, the organ could potentially withstand longer periods of time outside of the body and be less vulnerable to damage during transportation to the recipient. More extensive testing for function and tissue matching might also be possible with a functioning organ.