non-heart-beating donation non-heart-beating donation prior to the introduction of brain death into law in the mid to late 1970s, all organ transplants from cadaveric donors came from non-heart-beating donors (nhbds). donors after brain death (dbd) (beating heart cadavers), however, led to better results as the organs were perfused with oxygenated blood until the point of perfusion and cooling at organ retrieval, and so nhbds were generally no longer used except in japan, where brain death was not legally or culturally recognized, until very recently. however, a growing discrepancy between demand for organs and their availability from dbds has led to a re-examination of using non-heart-beating donations, dcd (donation after circulatory death, or donation after cardiac death), and many centres are now using such donations to expand their potential pool of organs. tissue donation (corneas, heart valves, skin, bone) has always been possible for nhbds, and many centres now have established programmes for kidney transplants from such donors. a few centres have also moved into dcd liver and lung transplants. many lessons have been learnt since the 1970s, and results from current dcds transplants are comparable to transplants from dbds. maastricht classification non-heart-beating donors are grouped by the maastricht classification: developed at maastricht in the netherlands. in 1995 during the first international workshop on non-heart‐beating donors. i brought in dead } uncontrolled ii unsuccessful resuscitation iii awaiting cardiac arrest controlled iv cardiac arrest after brain-stem death uncontrolled v cardiac arrest in a hospital inpatient uncontrolled (added in 2000) categories i, ii, iv and v are termed uncontrolled and category iii is controlled. as of yet, only tissues such as heart valves, skin and corneas can be taken from category i donors. category ii donors are patients who have had a witnessed cardiac arrest outside hospital, have cardiopulmonary resuscitation by cpr-trained providers commenced within 10 minutes but who cannot be successfully resuscitated. category iii donors are patients on intensive care units with nonsurvivable injuries who have treatment withdrawn; where such patients wished in life to be organ donors, the transplant team can attend at the time of treatment withdrawal and retrieve organs after cardiac arrest has occurred. maastricht definitions were reevaluated after the 6th international conference in organ donation held in paris in 2013 and a consensus agreement of an established expert european working group on the definitions and terminology were standardized, and later the word "retrieved" (organ) was substituted for "recovered" throughout the text. organs that can be used kidneys can be used from category ii donors, and all organs except the heart can potentially be used from category iii, iv and v donors. an unsuccessful kidney recipient can remain on dialysis, unlike recipients of some other organs, meaning that a failure will not result in death. kidneys from uncontrolled (category ii) donors must be assessed with care as there is otherwise a high rate of failure. many centres have protocols for formal viability assessment. relatively few centres worldwide retrieve such kidneys, and leaders in this field include the transplant units in maastricht (the netherlands), newcastle upon tyne and leicester (united kingdom), madrid and barcelona (spain), pavia (italy) and washington, dc (united states). livers and lungs for transplant can only be taken from controlled donors, and are still somewhat experimental as they have only been performed successfully in relatively few centres. in the united kingdom, nhbd liver transplants are currently performed in addenbrooke's hospital cambridge, queen elizabeth hospital birmingham, king's college hospital london, st. james's university hospital, leeds, newcastle upon tyne and the scottish liver transplant unit in edinburgh. in other countries such as spain, currently up to one-third of transplants are performed with nhbd. the international meeting on transplantation from non-heart-beating donors is organised in the uk every two years and brings together specialists in transplantation including transplant physicians, surgeons, fellows, nurses, coordinators, intensive care physicians, perfusion technicians, ethicists, and researchers interested in the aspects of retrieval, preservation and transplantation of dcd thoracic and abdominal organs and cells. lectures are held by experts on the most challenging themes such as clinical outcomes of transplantation of controlled and uncontrolled dcd organs, progress made on machine perfusion of kidneys, livers, lungs and hearts and ethics and legal issues regarding donation after cardiac death. procedure for uncontrolled donors following declaration of death, cardiopulmonary resuscitation (cpr) is continued until the transplant team arrive. a stand-off period is observed after cessation of cpr to confirm that death has occurred; this is usually from 5 to 10 minutes in length and varies according to local protocols. once the stand-off period has elapsed, a cut down is performed over the femoral artery, and a double-balloon triple-lumen (dbtl) catheter is inserted into the femoral artery and passed into the aorta. the balloons are inflated to occlude the aorta above and below the renal arteries (any donor blood specimens required can be taken before the top balloon is inflated). a pre-flush with streptokinase or another thrombolytic is given through the catheter, followed by 20 litres of cold kidney perfusion fluid; the opening of the lumen is between the balloons so that most of the flush and perfusion fluid goes into the kidneys. another catheter is inserted into the femoral vein to allow venting of the fluid. once full formal consent for organ donation has been obtained from relatives, and other necessary formalities such as identification of the deceased by the police and informing the coroner (in the uk), the donor is taken to the operating room, and the kidneys and heart valves retrieved. procedure for controlled donors if the liver or lungs are felt to be suitable for transplantation, then the donor is usually taken directly to the operating room after cardiac arrest, and a rapid retrieval operation is performed once a 10-minute stand-off period has elapsed. it seems this stand-off period has been reduced to as short as 75 seconds based on a recent article by the cbc. this is now causing an ethical debate as to whether physicians will declare death sooner than is currently required. this is similar to a normal multi-organ retrieval, but prioritises rapid cannulation, perfusion and cooling with ice, with dissection following later. if only the kidneys are suitable for retrieval, either rapid retrieval or cannulation with dbtl catheter can be used. use of a dbtl catheter allows relatives of the deceased to see them after death, but the donor must be taken to the operating room as soon as possible. category iv donors (who are already brain-stem dead), should either proceed as for a normal multi-organ retrieval—if this has already started—or should be managed as a category ii or iii as appropriate to the circumstances of cardiac arrest. ethical issues certain ethical issues are raised by nhbd transplantation such as administering drugs which do not benefit the donor, observance of the dead-donor rule, the decision-making surrounding resuscitation, the withdrawal of life-support, the respect for a dying patient and the dead body, as well as proper information for the family. in 2016 author dale gardiner issued a report called "how the uk overcame the ethical, legal and professional challenges in donation after circulatory death". actions prior to consent in category ii uncontrolled donors, the donor may die and the transplant team arrive before the donor's next-of-kin can be contacted. it is controversial whether cannulation and perfusion can be started in these circumstances. on one hand, it can be considered a violation of the potential donor's autonomy to cannulate before their in-life wishes are known. on the other hand, delay in cannulation may mean that a patient's strongly held wish to be donor cannot be respected. many ethicists also feel that a doctor's duty of care to the still living outweighs any duty of care to the dead. the compromise reached is usually to cannulate if there is any evidence of a wish to donate (such as a donor card or registration as a donor) even in the absence of next-of-kin. for category iii donors, treatment is being withdrawn from a living person, who will then die and become a donor. important factors for assessment include a) that the decisions regarding nonsurvivable injuries are correct, b) continued treatment is futile and c) that withdrawal is in the patient's best interests be made completely independently of any consideration of suitability as an organ donor. only after such decisions have been firmly made should a patient be considered as a potential organ donor. although such treatment can be continued until the transplant team arrives, no additional treatment should be started to improve the organs—until the point of death, the patient should be treated exactly as any other dying patient. the standard recommendation to ensure this is to require a complete separation of the treatment and organ procurement teams. it is not, however, clear how complete this separation can be in those jurisdictions that require hospitals to report the names of candidates for organ donation to an organ procurement organization (opo) before life support has been withdrawn so that organ donation can be discussed with surrogates. this forces treating physicians to view their patients partly as potential organ donors, and even absent an opo, it is unrealistic to think treating physicians are not aware of benefits to others of transplantation, and sometimes weigh this against the benefit of continued treatment to the patient. as one author puts it: "if the person in need of organ transplantation is younger, more attractive, or in some way more deserving than another critically ill patient"—and there are always such patients awaiting transplants—"then the conclusion that one patient's condition is hopeless can be tainted by an understanding of the tremendous hope organ availability holds for another." factored into this is the element of judgement that physicians bring to evaluating the "best interest" of patients. there is considerable variability among physicians in determining from whom to withdraw life-sustaining treatments in the icu. bias has been demonstrated on the part of medical professionals against patients who are perceived as disabled or are otherwise stigmatized. studies have shown that, when evaluating the quality of life of severely disabled patients, physicians consistently apply much poorer rating than do the patients themselves. this raises the question: would prejudice about vulnerable patients, such as disabled people, lead medical professionals to approach such individuals and families for nhbd more than others with higher "quality of life" ratings? thus, as doig puts it: "…the possibility of conflicted decision-making in a controlled dcd program is more than a theoretical possibility." the upshot is that the mere existence of a nhbd program in a hospital potentially compromises the care of patients. few have rejected those programs on this basis, but the question of how to protect against it is ongoing. dead donor rule the so-called "dead donor rule" (ddr) requires that persons be dead before their organs can be taken, and this rule is basic to all dcd programs. also common to all dcd programs is that death is determined by cardiocirculatory criteria according to which life-support is withdrawn, an interval of the monitored absence of pulse, blood pressure, and respiration observed, and then death declared. programs differ, however, on the length of the interval. the pittsburgh protocol requires 2 minutes, the institute of medicine (iom) and canadian council for donation and transplantation (ccdt) 5 minutes, the 1981 president's commission 10 minutes, and recently boucek et al. have proposed that it can be shortened to 75 seconds. these times are based on estimates of when autoresuscitation (i.e., the spontaneous recovery of circulatory activity) becomes impossible. the scientific validity of all these times, however, has been questioned. the iom in 2000 concluded that "existing empirical data cannot confirm or disprove a specific interval at which the cessation of cardiopulmonary function becomes irreversible." in addition, none of these intervals precludes the possibility of cpr restoring cardiocirculatory activity. to preclude that, brain death is required. the exact interval at which that occurs is likewise not known, but it is known to be more than 10 minutes. in light of this we can now raise the question of whether patients declared dead by cardiocirculatory criteria are really dead. it is generally agreed that death occurs when the patient is in an irreversible state. whether patients declared dead by cardiocirculatory criteria are really dead thus depends on what is meant by "irreversible," and the term