Pain Relief, Acceleration of Death, and Criminal Law

Field: Medicine (Health Sciences)

A New Look at Animal-to-Human Organ Transplantation Charles R. McCarthy (bio) The acute shortage of organs available for transplantation into human beings combined with a new scientific understanding of the immune systems of both humans and animals make it probable that animal-to-human solid organ transplants (xenografts) may soon be attempted at a frequency rate unknown in the past. 1 Optimism about successful animal-to-human organ transplantation is greater than at any previous time. The creation of a reliable supply of animal organs appears to be technically feasible. At least five major transplant centers in the United States are currently considering plans to pursue xenotransplantation. Although, at the time of this writing, no federal guidelines prohibit animal-to-human organ transplantation, the institutions considering such programs are awaiting deliberations on the subject by the Institute of Medicine (IOM), the Food and Drug Administration (FDA), and the Department of Health and Human Services (DHHS). The demand for organs suitable for transplantation into human beings greatly exceeds the supply. According to the United Network for Organ Sharing (UNOS 1996a), approximately 44,000 patients in the United states awaited organ transplantation at the end of 1995. In 1994, more than 3,000 patients died while on the transplant waiting list, and the demand for transplantable organs increases annually (UNOS 1996b). The figures do not include the hundreds or perhaps thousands of patients who could profit from a transplant, but who do not meet the requirements of the UNOS waiting list. Even if efforts to persuade persons to donate organs are redoubled, and even if the consent to donate organs should become a legal presumption, there is little prospect of developing a sufficient supply of transplantable human organs to meet the growing demand. As technical and biological barriers to successful animal-to-human xenografts are lowered, the prospect of raising dedicated colonies of animals, genetically altered to reduce the chances that human hosts will reject organs derived from them, is being seriously discussed. 2 Such colonies do not exist at the present time. [End Page 183] However, if new techniques for animal-to-human transplantation prove successful, it is likely that animal colonies will be established to provide a ready and predictable supply of organs for transplantation to humans. Some believe that commercial investment in colonies of purpose-bred animals to serve as a source of transplantable organs is close at hand (Leventhal 1994). New drugs and new combinations of existing drugs have improved the chances of successful medical outcomes for patients who receive solid organ transplants. It is now recognized that serial application of immunosuppressive drugs can reduce the likelihood of both short- and long-term organ rejection (Makowka 1994). Improved understanding of both human and animal immune systems, insights into histocompatibility, new agents to control graft-versus-host disease, animal breeding programs for the production of transgenic animals, and improved surgical techniques have opened, as never before, the possibility of successful transfer of organs from animals to humans. Some rate the chances of good patient outcomes (usually measured in terms of time of patient survival) as high, others make more conservative predictions, but virtually all experts believe that the chances for successful human patient outcomes resulting from xenotransplantation are improved. Because many patients face immanent death unless their organs can be replaced, there can be little doubt that many humans will readily consent to xenotransplantation. History Suggests Caution Despite the advances in immunosuppression, the frequency of failure in past animal-to-human xenograft attempts should temper the optimism of the transplant community. To date, all efforts to prolong human life by implanting solid organs from animals into human recipients have failed. The first attempts at animal-to-human xenotransplantation early in the twentieth century resulted in the early death of all recipients (Neuhof 1923). More sophisticated efforts at xenotransplantation occurred in the late 1960s and early 1970s, a period when anti-rejection drugs began to make allografts more feasible. Although one human recipient of a xenograft survived for nine months (with poor quality of life), most patients died within a matter of minutes, hours, or a few days following the transplantation of organs from chimpanzees or baboons (Starzl...