Types of Organ Donors
Most livers used for transplantation are obtained from patients that are brain dead. Brain death is usually due to a large stroke or massive trauma to the head from blunt injury (for example, impact to the head from a motor vehicle or a motorcycle accident) or penetrating injury (for example, a gun shot wound). The trauma has stopped all brain function although other organs including the liver may continue to function normally.
There are strict definitions as to what constitutes brain death based on the complete absence of any type of brain function. Because patients that meet criteria for brain death are legally dead, they are appropriate organ and tissue donors. In the United States, the family of someone who is brain dead must provide consent for organ and/or tissue donation. In other countries, such as France, consent for organ donation is presumed and allowed, unless the family objects.
Typically, transplant centers whose patients will be receiving organs from a particular donor will dispatch a team of surgeons to procure the relevant organ. The organ procurement procedure takes place in an operating room in the donor’s hospital. Organs are removed and preserved in a fashion to optimize their condition during the storage and transportation time period. Each procured organ is then transported to the hospitals where the designated recipient awaits.
Sometimes a patient suffers a devastating brain injury and carries a dismal neurological prognosis but fails to meet the strict criteria defining brain death in that there is still detectible brain function. In these circumstances, the patient’s family may decide to withdraw life-sustaining medical support with the intention of allowing the patient to die. In this scenario, death is not defined by brain death but rather cardiac death. Organ donation can occur after cardiac death but, again, only if the family gives consent.
Only AFTER the family’s decision to withdraw support may the patient be considered for organ donation after death. Under these circumstances, support is withdrawn, as desired by the family and managed by the patient’s physician, and the patient is allowed to expire. The patient’s physician, someone who is not involved in any aspect of organ transplantation, is present to determine when the heart stops beating and circulation has stopped such that the patient no longer has any signs of life. He or she then declares the patient’s death.
An urgent operation is then performed to preserve and remove organs for transplantation. This mode of cardiac death, in contrast to brain death, results in increased injury to the organs during two time periods. The first period is that between withdrawal of life support and death. As the donor’s breathing and circulation deteriorates, the organs may no longer be receiving sufficient oxygen. The second time period constitutes the minutes immediately after death and until the organs are flushed with preservation solution and cooled. As a result, livers procured from cardiac death donors are associated with an increased risk of primary non function or poor early organ function, hepatic artery thrombosis, and biliary complications.
Although each person has only one liver and would die without it, it is possible to donate a portion of the liver for transplantation into another individual. The segmental anatomy allows surgeons to create grafts of varying size, depending upon the recipient’s requirement for liver tissue. The partial livers in both the donor and the recipient will grow to provide normal liver function for both individuals.