The criteria for determining death play a prominent role in the acceptability of DCD. The recovery of viable organs for successful transplantation must be achieved with the donor already dead at the time of procurement in order to comply with the dead donor rule. Whereas some have considered a person dead after 2 minutes of apnea, unresponsiveness, and absent arterial pulse , the Institute of Medicine recommended waiting for 5 minutes of absent consciousness, respiration, and mechanical pump function of the heart (zero pulse pressure through arterial catheter monitoring), irrespective of the presence of electric activity of the heart (evident on electrocardiographic monitoring) . In 2001, the American College as well as the Society of Critical Care Medicine concluded in a position statement that a waiting period of either 2 minutes or 5 minutes was physiologically and ethically equivalent and therefore either was an acceptable timeline for beginning the process of organ retrieval . Waiting for longer than 5 minutes can cause warm ischemia and detrimentally affect the quality of procured organs and impair their suitability for transplantation. However, critics have argued more than a decade ago that the waiting time to determine death by respiratory and circulatory criteria is based on insufficient scientific evidence . The spontaneous return of circulation and respiration (i.e., the Lazarus phenomenon or autoresuscitation) has been reported to occur in humans as long as 10 minutes after cessation of circulation and respiration. Autoresuscitation appears to validate previous concerns that viable organs may be procured from persons who are in the process of dying yet are not truly dead [16–18].
According to the Uniform Determination of Death Act (UDDA) of 1981, a person is determined dead after having sustained either irreversible cessation of circulatory and respiratory functions or irreversible cessation of all brain function, including that of the brain stem, and the determination of death must be made in accordance with accepted medical standards . The President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research defined the statute for the determination of death so that ""Death is a Single Phenomenon" . The statute is intended to address the question "how, given medical advances in cardiopulmonary support, can the evidence that death has occurred be obtained and recognized". The President's Commission defined the cessation of circulation to be irreversible for death determination " [i]f deprived of blood flow for at least 10–15 minutes, the brain, including the brainstem, will completely cease functioning". A 4–6 minute loss of blood flow – caused by, for example, cardiac arrest – typically damages the cerebral cortex permanently, while the relatively more resistant brainstem may continue to function."
The challenge in determining death for organ procurement is twofold: (1) the use of an arbitrary set of criteria and time frames to define irreversible cessation of circulatory and respiratory functions without evidence of the uniformity for death determination and (2) the variability of the criteria used by different institutions for organ procurement protocols [14, 21].
The notion of irreversibility of cessation of circulatory and respiratory functions has been a contentious medical and ethical issue. Tomlinson proposed a definition of irreversibility as "a requirement that arises only at the level of the criteria for the determination of death, rather than at the level of the concept of death, just as 'beyond reasonable doubt' is not a part of the concept of 'guilty', but instead is a requirement for the legitimate determination of guilt within a judicial system." . The requirement for irreversibility therefore depends on the context in which, and the purposes for which, the concept of death is being used . The notion of irreversibility is commonly understood as meaning either that the heart cannot be restarted spontaneously (a weaker construal) or that the heart cannot be restarted despite standard cardiopulmonary resuscitation (a stronger construal). The stronger construal of irreversibility as meaning "can never be reversed" implies in its extreme that at no time can organ procurement ever be permissible because future possibilities of resuscitation can never be fully ruled out. In practical terms, the weaker definition of "not reversible now" implies that a person is considered irreversibly dead based on that person's moral choice to forego resuscitative interventions; thus, as long as the probability of autoresuscitation is negligible, the dead donor rule is not violated. On the basis of that argument, the notion of irreversibility depends on the person's choice to forego resuscitative interventions after spontaneous cessation of circulatory and respiratory functions. However, the argument that irreversibility can be understood as a moral choice is flawed. First, the issue is not whether there are good reasons not to resuscitate a person but whether the person is truly dead . Second, resuscitative interventions are performed during the procurement process to keep organs viable for transplantation after the cessation of vital functions. The use of artificial cardiopulmonary bypass machines, external mechanical cardiac compression devices, and reinflation of the lungs to preserve organs for procurement also results in the resuscitation of the heart and the brain after the formal declaration of death. Resuscitation of the brain with a return of consciousness is particularly problematic because the Institute of Medicine announced in its 2006 report that expansion of the organ donor pool by procuring organs from living persons with normal brain function who sustain sudden cardiac death is morally acceptable .
Longer than 10 minutes of absent circulation is required for irreversible cessation of the entire human brain, including brain stem function. The administration of medications to suppress heart and brain functions is therefore required when the procurement process begins within 5 minutes of cessation of circulation [12, 24].
The use of resuscitative methods and medications to suppress heart and brain functions during organ procurement raises a host of additional ethical and legal questions. Organ donors consent to the withholding of all resuscitative interventions after cessation of circulatory and respiratory functions through a do-not-resuscitate (DNR) directive. Under such conditions, the use of resuscitative methods for organ procurement violates not only the dead donor rule but also the person's health directives. The strong probability of a return of heart and brain functions during procurement also means that the act of organ removal is the immediate and proximate cause of death for that person.
The need for criteria to sharpen "the indeterminate boundary between life and death" for death determination has been widely recognized . The dependence on both circulatory and respiratory criteria only for the determination of death in DCD is problematic and conceptually inconsistent because of (1) there is a likelihood of spontaneous reversibility of circulatory and respiratory functions when organ procurement begins, and (2) the possibility for the brain to recover function long after circulatory arrest, particularly when artificial circulation is used for organ procurement. Therefore, the practice of DCD conflates a prognosis of death with a diagnosis of death [12, 26]. The application of criteria for irreversible cessation of neurologic, circulatory and respiratory functions requires a waiting time well in excess of 10 minutes to sharpen the determination of death for organ procurement [27–32]. However, that waiting time can also make it more difficult to recover viable organs for transplantation. The simultaneous determination of total cessation of the activity of the entire brain, including the brain stem, is required for the determination of death when respiration and circulation are artificially supported during organ procurement. Capron and Kass emphasized in the President's Commission when defining death "A person will be considered dead if in the announced opinion of a physician, based on ordinary standards of medical practice, he has experienced an irreversible cessation of respiratory and circulatory functions, or in the event that artificial means of support preclude a determination that these functions have ceased, he has experienced an irreversible cessation of total brain functions".