Organ Donation - Distribution

Distribution

The United States has two agencies that govern organ procurement and distribution within the country. The United Network for Organ Sharing and the Organ Procurement and Transplant Network (OPTN) regulate Organ Procurement Organizations (OPO) with regard to procurement and distribution ethics and standards. OPOs are non-profit organizations charged with the evaluation, procurement and allocation of organs whithin their Designated Service Area (DSA). Once a donor has been evaluated and consent obtained, provisional allocation of organs commences. UNOS developed a computer program that automatically generates donor specific match lists for suitable recipients based on the criteria that the patient was listed with. OPO coordinators enter donor information into the program and run the respective lists. Organ offers to potential recipients are made to transplant centers to make them aware of a potential organ. The surgeon will evaluate the donor information and make a provisional determination of medical suitability to their recipient. Distribution varies slightly between different organs but is essentially very similar. When lists are generated many factors are taken into consideration; these factors include: distance of transplant center from the donor hospital, blood type, medical urgency, wait time, donor size and tissue typing. For heart recipients medical urgency is denoted by a recipients "Status" (Status 1A, 1B and status 2). Lungs are allocated based on a recipients Lung Allocation Score (LAS) that is determined based on urgency and wait time. Livers are allocated using both a status system and MELD/PELD score (Model for End-stage Liver Disease/Pediatric End-stage Liver Disease). Kidney and pancreas lists are based on location, blood type, Human Leukocyte Antigen (HLA) typing and wait time. When a recipient for a kidney or pancreas has no direct antibodies to the donor HLA the match is said to be a 0 ABDR mismatch or zero antigen mismatch. A zero mismatch organ has a low rate of rejection and allows a recipient to be on lower doses of immunosuppressive drugs. Since zero mismatches have such high graft survival these recipients are afforded priority regardless of location and wait time. UNOS has in place a "Payback" system to balance organs that are sent out of a DSA because of a zero mismatch.

Location of a transplant center with respect to a donor hospital is given priority due to the effects of Cold Ischemic Time (CIT). Once the organ is removed from the donor, blood no longer perfuses through the vessels and begins to starve the cells of oxygen (ischemia). Each organ tolerates different ischemic times. Hearts and lungs need to be transplanted within 4–6 hours from recovery, liver about 8–10 hours and pancreas about 15 hours; kidneys are the most resilient to ischemia. Kidneys packaged on ice can be successfully transplanted 24–36 hours after recovery. Developments in kidney preservation have yielded a device that pumps cold preservation solution through the kidneys vessels to prevent Delayed Graft Function (DGF) due to ischemia. Perfusion devices, often called kidney pumps, can extend graft survival to 36–48 hours post recovery for kidneys. Research and development is currently underway for heart and lung preservation devices, in an effort to increase distances procurement teams may travel to recover an organ.