Organ transplantation ranks as one of the success stories of modern technological medicine. From modest beginnings in the mid-twentieth century, transplantation has become a well-established treatment, able to prolong life and to improve the quality of life for many patients with end-stage organ failure. In the United States (US), both private and public health insurance cover the major types of organ transplants, and new transplant techniques and immunosuppressive therapies are under investigation. According to the latest update of the United Network for Organ Sharing (UNOS) Scientific Registry of Transplant Recipients, 22,170 organ transplants were performed in the United States in 1998, a 65% increase over the 1989 total of 13,473 [1]. Another indication of the success of organ transplantation is the rapidly growing demand for transplants. During the same period, the number of persons entered on the National Transplant Waiting List grew by 237%, from 19,095 at the end of 1989 to 64,423 at the end of 1998 [1].

The gradual increase in the number of US transplants performed in the 1990s has, in fact, been far too small to keep pace with the rapidly escalating demand. As a consequence of the increasing shortage of available organs, patients in need of a transplant must endure longer waiting times and a greater risk of death before an organ becomes available. The median waiting time for a liver transplant in the US, for example, increased from 34 days in 1988 to 477 days in 1997. The number of deaths of patients on the National Waiting List for all transplants nearly tripled during that period, from 1,494 in 1988 to 4,313 in 1997 [2].

Unlike most other medical treatments, the growth of organ transplantation depends on the availability of a specific scarce resource, namely, donor organs. Bridging the widening gap between organ supply and demand has become one of organ transplantation’s greatest challenges.

The most obvious response to the challenge of organ scarcity is to try to increase the number of transplantable organs. The goal of making the benefits of transplantation available to all patients in need is clearly laudable, but its achievement remains elusive. Because the giving and taking of organs for transplantation is a complex and morally sensitive process, new initiatives for organ procurement face significant moral, scientific and practical obstacles.

Several initiatives to increase the supply of donor organs have been implemented by transplant centers and organ procurement agencies in recent years, including the use of non-heart-beating cadaveric donors, new techniques for transplantation of liver and lung segments from living donors, and the encouragement of organ donation from unrelated living donors.

Despite continuing concerns about their moral justification, these initiatives have made a small contribution to increasing the supply of donor organs. Non-heart-beating cadavers comprised 1% of all cadaveric organ donors from 1994 to 1997 [2]. Similarly, living donors represented 1% of liver donors and 0.4% of lung donors from 1994 to 1997 [1]. Unrelated living donors increased from 4% of all living donors in 1988 to 15% in 1997, and the total number of living donors doubled during this ten year period [2]. None of these initiatives, however, comes close to keeping pace with the rapid increase in patients waiting for transplants.

Several other strategies for increasing US organ supplies have been proposed but not implemented. Some of these strategies recommend significant modifications of the current US organ procurement system. Such strategies include: (1) a shift to presumed consent for cadaveric organ donation, (2) a system requiring citizens to express prospectively a binding choice for or against donation of their organs after death, (3) provision of financial incentives for organ donation, and (4) revision of neurological criteria for the determination of death. Other strategies propose a major shift to an entirely new source of transplant organs, either animals or laboratory-engineered “bioartificial” organs.

The latter strategies offer the distinct advantage of bypassing the significant moral constraints we impose on the use of human organs. Despite years of research, however, major scientific obstacles still confront these strategies. In animal to human transplantation (xenotransplantation), for example, researchers must overcome significant immunological barriers to cross-species transplantation and also prevent zoonoses, the transmission of animal infectious agents into human populations by means of a transplanted organ. Studies using transgenic pigs have made progress in understanding and resisting hyperacute organ rejection, but additional problems remain, and xenotransplantation does not appear to be a short-term solution to the problem of organ supply [3].

The former group of strategies listed above proposes major changes in the current US system of cadaveric organ procurement. That system relies heavily on family consent to the donation of organs from heart-beating cadavers, that is, patients declared dead on the basis of neurological criteria whose heartbeat and respiration are being maintained by technological means. The motivation for consent to donation is primarily altruistic, since no financial incentives are provided. Each of the above strategies proposes a change in a basic feature of this system. Since roughly half of all families approached about organ donation do not consent, organ procurement rates might well improve if family consent were not required or if families were given financial incentives to consent. There are, however, significant moral and practical objections to each of these proposals. The rest of this article will focus on how recent proposals for revision of criteria for the determination of death might affect organ supply.

As noted above, most organs for transplantation in the U.S. are taken from heart-beating cadavers after a declaration of death based on neurological criteria. State “brain-death” statutes vary somewhat, but all are based on what has come to be known as the “whole-brain” standard or definition of death. According to this standard, death may be determined on the basis of “irreversible cessation of all functions of the entire brain, including the brain stem” [4].

Despite its longstanding legal recognition, the “whole-brain” approach to determining death has been criticized repeatedly over the past two decades. Two prominent recent examples of such critiques may be found in articles by Robert Veatch [5] and Robert Truog [6]. Both authors argue that the currently accepted neurological tests for determining death do not, in fact, correctly diagnose the death of the entire brain, because fulfilling these tests is compatible with continuation of several kinds of brain function, including electrical activity, cellular function and several neurohumoral regulatory functions. Both authors also challenge the conceptual coherence of identifying the death of a human being with the death of the whole brain.

Although their critiques of current “whole-brain” determination of death criteria are similar, Veatch and Truog offer very different proposals for resolving the problem. Despite their differences, however, either proposal could, if adopted, significantly increase the number of potential cadaveric organ donors. Veatch argues that neurological criteria for the determination of death focusing on the irreversible loss or absence of higher brain functions are preferable to the current “whole-brain” criteria. He asserts that it is not the irreversible loss of all brain functions, but of those higher brain functions that support conscious experience, that should be used to identify the end of a human life. He argues further that loss of the capacity for mental function provides a clear conceptual distinction between human life and death, and that this criterion can be accurately measured.

Veatch does not discuss the implications of his approach for organ procurement. Adoption of a “higher-brain” criterion for death could have a significant effect on procurement, however, because it would create two new categories of heart-beating cadavers, anencephalic infants and individuals in a persistent vegetative state. A recent review article cites estimates of between 14,000 and 35,000 patients with persistent vegetative state in the US [6]. According to Centers for Disease Control estimates, about 1,050 infants with anencephaly are born each year in the US, although perhaps half of these are stillborn [7]. These two groups could, therefore, potentially provide a significant number of additional organ donors.

Truog considers the higher brain criterion for determining death, but does not embrace it. He argues that “higher brain death” cannot be diagnosed with certainty and that many people could not accept the consequence of this criterion that some spontaneously breathing patients could be declared dead. As an alternative, Truog proposes a return to the traditional cardiorespiratory standard for determining death. The main obstacle to this alternative, Truog notes, is that it would block access to heart-beating cadavers for organ donation. Truog argues that this obstacle can be overcome if, in addition to abandoning brain-oriented criteria for determining death, we also abandon the “dead donor rule,” that is, the requirement that donors be declared dead before their organs can be removed. Truog proposes instead that vital organs be taken from still-living patients when appropriate consent is given and when the donation would not harm the patient. This approach would, he notes, permit expansion of organ donation to patients in a persistent vegetative state and anencephalic infants, as well as current cadaveric donors.

An illustration of the controversial nature of Truog’s proposal for abandonment of the “dead donor rule” can be found in the fate of a recent report of the American Medical Association’s Council on Ethical and Judicial Affairs regarding the use of anencephalic infants as organ donors [9]. In that report, the Council recommended that organ donation from anencephalic infants be permitted as a “limited exception” to the dead donor rule. At the request of the AMA’s House of Delegates in June 1995, however, the Council on Ethical and Judicial Affairs reconsidered and “suspended” this recommendation, citing concerns “about certain diagnoses of anencephaly and understanding of consciousness in these neonates” [10].

While there are both scientific and philosophical reasons for reconsidering the current “whole brain” criteria for determining death, then, there are also significant practical and moral barriers to change in this area. Because the US organ procurement system relies so heavily on public acceptance and willingness to participate, organ procurement agencies have a strong interest in avoiding controversial issues and in preventing any appearance of deception or exploitation of potential donors and families. Expanding brain death criteria or abandoning the dead donor rule, without strong public consensus in favor of those changes, might well result in a public backlash and a subsequent decrease in organ donation.

(Note: This article is based in part on Moskop J. Current ethical aspects of organ procurement and transplantation in North America. Balliere’s Clinical Anaesthesiology 1999:13;195-210, which includes fuller discussion of, and additional references to, a variety of organ procurement proposals.)

REFERENCES

1.UNOS. Critical data (www.unos.org/Newsroom/critdata_main.htm) accessed February 2, 2000.

2.UNOS. 1998 Annual Report of the US Scientific Registry of Transplant Recipients and Organ Procurement and Transplantation Network (http://www.optn.org/data/annualReport.asp) accessed February 2, 2000.

3.Weber M, Deng S. Olthoff K et al. Organ transplantation in the twenty-first century. Urol Clin North Am 1998: 25; 51-61.

4. President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research. Defining Death. Washington, DC: U.S. Government Printing Office, 1981.

5. Veatch RM. The impending collapse of the whole brain definition of death. Hastings Cent Rep 1993:23, no. 4; 18-24.

6. Truog RD. Is it time to abandon brain death? Hastings Cent Rep 1997: 27, no. 1: 29-37.

7. Multi-Society Task Force on PVS. Medical aspects of the persistent vegetative state (first of two parts). N Engl J Med 1994: 330; 1499-1508.

8.Medical Task Force on Anencephaly. The infant with anencephaly. N Engl J Med 1990: 322; 669-674.

9.Council on Ethical and Judicial Affairs, American Medical Association. The use of anencephalic neonates as organ donors. JAMA 1995: 273; 1614-1618.

10.Plows CW. Reconsideration of AMA opinion on anencephalic neonates as organ donors. JAMA 1996: 275; 443-444.