Irreversibility is consistent with legal
The determination of death affects all physicians, and modern medical technology has complicated this process. The availability of life-sustaining interventions such as CPR, mechanical ventilation, heart-lung support machines, ventricular assist devices, and organ transplantation has obscured our ability to distinguish between the seemingly discrete states of life and death.
Explore This IssueACEP News: Vol 29 – No 09 – September 2010
The ethical norm for organ donation is the “dead donor rule,” which states that living patients must not be killed by organ retrieval. For transplantation to be successful, the arrest of circulation and resulting warm ischemic injury must be minimized. This is partially overcome when death is determined using neurologic criteria because the brain dead donor remains on a ventilator and circulation persists until surgical removal of organs.
Brain dead donors continue to be the preferred source of transplantable organs, but the persistent shortage of organs has led to the reemergence of donation after cardiac death (DCD). DCD programs account for the largest incremental increase in organ donation in active U.S. programs. Accompanying this renewed emphasis on DCD is the requirement to determine death as rapidly as possible following cardiac arrest, to minimize ischemic organ injury.
Death is generally understood to be based on the irreversible cessation of either brain or circulatory/respiratory functions. The language and notion of irreversibility is problematic, and the Uniform Determination of Death Act did not define the term. Its interpretation has evolved, given the advances in the technical ability to sustain vital functions.
Hospital deaths are almost always preceded by a decision to forego some form of life-sustaining intervention. So does “irreversible” mean “cannot be reversed under any circumstances” or “will not be reversed” in accordance with appropriate care?
DCD has enhanced the rigor of the determination of death after cardiac arrest. However, there is a lack of consensus on how long circulation must cease for a person to be determined dead. Internationally, this period varies from 75 seconds to 10 minutes.
Irreversibility of circulation after cardiac arrest is defined as a state in which vital functions cannot return on their own and will not be restored by medical interventions. This applies to the setting of a legally valid refusal of CPR by the patient directly, through advance directive, or via the patient’s decision maker. In this way, irreversible is defined as not physically possible to reverse without violating the law on consent.
The existing practices for determining death during controlled DCD, where a consensual decision has been made to withdraw life support and withhold CPR, are consistent with medical, ethical, and legal standards permitting organ donation.
Dr. Shemie is a pediatric critical care physician and director of the Extracorporeal Life Support program at the Montreal Children’s Hospital, McGill University; the Bertram Loeb Chair in Organ Donation Research at the University of Ottawa; and medical director of tissue and organ donation for the Canadian Blood Services.
The circulatory standard is full of flaws.
Cardiac mechanical asystole (or absent arterial pulse) lasting anywhere from 75 seconds to 5 minutes is the U.S. circulatory standard of declaring death in donation after cardiac death (JAMA 2009;301:1902-8). At that point, mechanical ventilation and hemodynamic support are both discontinued in the operating room, and surgical procurement begins after an absent arterial pulse or mechanical contraction of the heart.
However, the current circulatory standard of death used for organ donation has scientific flaws.
First, it is based on expert opinion of a zero chance of spontaneous recovery of heart and brain functions (autoresuscitation) after 65 seconds of mechanical asystole. Scientific evidence is based on observations inferred from published case series (1912 and 1970) and one retrospective study of 12 patients in non-heart-beating donation (Crit. Care Med. 2000;28:1709-12; Philos. Ethics Humanit. Med. 2007;2:28). The sample size needed to rule out any autoresuscitation after 65 seconds in fewer than 1 in 1,000 donors is more than 10,000 patients.
Second, procured hearts have normal native mechanical and electrical functions after transplantation (N. Engl. J. Med. 2008;359:709-14; Eur. J. Cardiothorac. Surg. 2010;37:74-9), demonstrating that mechanical asystole is reversible and does not constitute an acceptable standard for irreversibility. For example, when artificial circulation is restarted with cardiopulmonary bypass for preserving organs (ASAIO J. 2006;52:119-22), donors with normal brains before mechanical asystole can recover neurologic functions.
Third, the extent of recovery of integrated brain functions during surgical procurement is unknown. A preliminary report of EEG recordings during the dying process indicate sharp increases in brain electric activities in pulseless patients (J. Palliat. Med. 2009;12:1095-100).
No neurophysiologic monitoring studies of donor brains have been done to exclude residual and clinically relevant pain or awareness during surgical procurement. Neither are there any histopathologic examinations of brains from DCD donors that validate the claim that 2-5 minutes of mechanical asystole will inevitably result in complete destruction or necrosis of the whole brain and irreversible cessation of neurologic functions (Crit. Care Med. 2010;38:963-70; J. Clin. Ethics 2006;17:122-32).
Transplantation advocates reinterpret the Uniform Determination of Death Act of 1981 to mean that determination of death can also be based on intent and action not to resuscitate. Procuring transplantable organs then becomes an active intervention of ending a human life, bringing up the ethical and legal questions of whether this approach requires sanctioning utilitarian homicide.
Dr. Verheijde is an associate professor in the departments of biomedical ethics, physical medicine, and rehabilitation at the Mayo Clinic in Arizona. Some of these comments will appear as a letter in response to a paper coauthored by Dr. Shemie (Crit. Care Med. 2010 March 11 [doi:10.1097/CCM.0b013e3181d8caaa]).