Over the last decade, a novel method of organ donation after circulatory death (DCD) known as normothermic regional perfusion (NRP) has come into widespread use in various European countries. Although DCD is well established in the U.S., NRP has generated significant controversy, and the American College of Physicians (ACP) has issued a statement recommending a freeze on its implementation until outstanding ethical concerns are more thoroughly resolved. At the center of the controversy is the contention that NRP kills the donor.
In its “controlled” form (cDCD), donation after circulatory death follows a request by a patient with a do-not-resuscitate order (DNR) or a surrogate decision-maker for such a patient to withdraw life-sustaining treatments (LSTs) due to a poor prognosis. Once LSTs are withdrawn and the patient sustains cardiac arrest, physicians wait for five minutes before declaring the patient dead based on circulatory criteria. In “standard” cDCD, surgeons rapidly retrieve organs and place them in cold storage. Unfortunately, however, organs tend to suffer damage during the five-minute “hands-off period” following cardiac arrest when they are deprived of oxygen. This is called “ischemic damage.” In response, various alternative methods of cDCD have been introduced, and cDCD-NRP (henceforth, NRP) is one of these. In NRP, following the five-minute hands-off period, surgeons occlude the arteries supplying the brain and reinitiate circulation in the chest and/or abdomen using an extracorporeal membrane oxygenation (ECMO) pump. Another alternative to standard cDCD is cDCD-normothermic machine perfusion (henceforth, NMP), in which organs are rapidly retrieved and stored in a machine called an organ care system (OCS) that perfuses them with oxygenated blood ex situ after a five-minute hands-off period. Both NRP and NMP help to reverse ischemic damage. But NRP has various advantages over NMP. It enables surgeons to more effectively monitor organ function prior to transplantation. It can also be used in conjunction with cold storage rather than machine perfusion, making it accessible in resource-limited countries where OCS machines are prohibitively expensive. It allows surgeons to retrieve both the heart and the liver from the same donor, whereas NMP typically does not permit this.
The most prominent objection to NRP is that it violates the so-called “dead donor rule” (DDR), which maintains that transplant surgeons may not (i) retrieve vital organs before death or (ii) cause death in the process of retrieving organs. The argument is that these donors are determined to be dead based on circulatory criteria, but to be dead based on such criteria according to U.S. state laws, one must have lost circulation irreversibly. Of course, however, NRP donors have not irreversibly lost circulation at the time that they are declared dead, since circulation is subsequently reinitiated. However, this objection seems to prove too much. It also implies that donors are still alive when their organs are retrieved in standard cDCD and NMP. The reason why physicians do not attempt to resuscitate cDCD or NMP donors is not that it would be technically impossible but rather that it would violate their DNR orders.
Opponents of NRP have a reply to this objection, which is that to be dead, it is sufficient to have lost circulatory function permanently, meaning that one has lost circulation and will never regain it. NRP donors do not meet this “permanence criterion,” whereas standard cDCD and NMP donors do.
Advocates of NRP have responded by arguing that what matters is not the permanent loss of circulation per se, but rather the permanent loss of circulation to the brain, since the brain is responsible for integrated bodily functioning and consciousness. Furthermore, it is argued that donors can be presumed to have permanently lost brain function following the five-minute hands-off period in NRP and other cDCD measures. Thus, it is argued that by occluding arteries leading to the brain before reinitiating circulation in the donor’s body, surgeons preserve the validity of the death declaration. Rather than resuscitating or “reanimating” the donor, it is argued, NRP merely perfuses organs in situ. Critics have responded by pointing out that U.S. state laws do not support the contention that donors die when they permanently lose cerebral circulation, stating only that they die when they lose circulation in general. They also observe that some residual brain function may persist five minutes after cardiac arrest when NRP measures commence.
Elsewhere, I have argued that the permanence criterion is implausible. It implies, for instance, that a patient with a DNR is dead once she has lost circulation, as long as she will not regain it on her own, even if she could be resuscitated to the point of regaining higher cognitive functions. Although such cases are undoubtedly rare in the cDCD context, partly because most donors have sustained devastating neurological injuries, the fact that they are possible, at least in other contexts, shows that the permanence criterion is conceptually problematic. If so, it is doubtful that it can be used to meaningfully distinguish between the validity of death declaration in standard cDCD and NMP on one hand and in NRP on the other. If NRP donors are alive when they are pronounced dead, standard cDCD and NMP donors must be as well, since death is determined at the same time and using the same criteria in all three procedures.
It is often taken more or less for granted that if NRP donors are alive when their vital organs are retrieved, then the retrieval process must kill them. For instance, the ACP suggests that, by occluding the donor’s arteries, transplant surgeons cause brain death to occur, but they do not defend this contention. The most plausible defense would maintain that occluding the donor’s arteries causes them to be occluded moments later when they reinitiate circulation in the body. However, once circulation is reinitiated, arterial occlusion prevents blood from reaching the brain, leading to brain death. Thus, it would be argued, by the transitivity of causation, occluding the donor’s arteries causes brain death.
Notice, however, that by occluding the donor’s arteries, surgeons do not cause the donor to suffer brain death any sooner than she would otherwise. By the time that they occlude the donor’s arteries, she has already lost circulation, and she will not regain it on her own. Nor would surgeons reinitiate circulation within her chest or abdomen without first occluding her arteries. Thus, by occluding the donor’s arteries, surgeons do not prevent any blood from reaching the brain that would have reached it otherwise. While they might cause brain death to occur by transitivity criteria, they do not cause it to occur by counterfactual criteria. They at most preemptively cause death to occur at the same time it would have otherwise, when the preempting cause is the arterial occlusion and the preempted cause is the absence of thoraco-abdominal blood flow due to cardiac arrest.
For these reasons, I have argued that the ultimate issue in the discussion of whether NRP kills the donor is whether transitivity-based or counterfactual criteria prevail when the two conflict. I argue that the counterfactual criteria prevail. In cases of alleged causal preemption, what actually causes the effect is neither the preempting nor the preempted cause, but the disjunction of the two. What causes the donor to suffer brain death is that either she never regains circulation or her arteries are occluded. Thus, I conclude, pace the ACP and many other critics of the procedure, NRP does not cause donors to die even if they are alive when they are determined to be dead. While NRP might violate the first condition of the DDR, stating that donors must be dead prior to vital organ retrieval, it does not violate the second and seemingly more significant condition, stating that organ retrieval must not cause death.
The debate surrounding NRP raises deep questions about the definition of death and the nature of causation. By doing so, it reveals how urgent practical matters in bioethics can be tightly bound up with fundamental philosophical problems.
Harrison Lee
Harrison Lee is a visiting assistant professor in the Department of Philosophy and Religion at the University of Mississippi, specializing in ethics and bioethics. His recent work has focused on the ethics of harm, intention, end-of-life care, and organ transplantation.
