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Types of donor

Organ donors may be living or may have died of brain death or circulatory death. Most deceased donors are those who have been pronounced brain dead. Brain dead means the cessation of brain function, typically after receiving an injury (either traumatic or pathological) to the brain, or otherwise cutting off blood circulation to the brain (drowning, suffocation, etc.). Breathing is maintained via artificial sources, which, in turn, maintains heartbeat. Once brain death has been declared, the person can be considered for organ donation. Criteria for brain death vary. Because less than 3% of all deaths in the US are the result of brain death, the overwhelming majority of deaths are ineligible for organ donation, resulting in severe shortages. It is important to note currently that patients that have been pronounced brain dead are one of the most common and ideal donors, since often these donors are young and healthy, thus leading to high quality organs.

Organ donation is possible after cardiac death in some situations, primarily when the person is severely brain-injured and not expected to survive without artificial breathing and mechanical support. Independent of any decision to donate, a person's next-of-kin may decide to end artificial support. If the person is expected to expire within a short period of time after support is withdrawn, arrangements can be made to withdraw that support in an operating room to allow quick recovery of the organs after circulatory death has occurred.

Tissues may be recovered from donors who die of either brain or circulatory death. In general, tissues may be recovered from donors up to 24 hours past the cessation of heartbeat. In contrast to organs, most tissues (with the exception of corneas) can be preserved and stored for up to five years, meaning they can be "banked." Also, more than 60 grafts may be obtained from a single tissue donor. Because of these three factors – the ability to recover from a non-heart-beating donor, the ability to bank tissue, and the number of grafts available from each donor – tissue transplants are much more common than organ transplants. The American Association of Tissue Banks estimates that more than one million tissue transplants take place in the United States each year.