Ancillary testing
The consensus statement also reviews ancillary testing, which the authors recommend be required when the minimum clinical examination, including the apnea test, cannot be completed and when it is in the presence of confounding conditions that cannot be resolved.
The authors recommended digital subtraction angiography, radionuclide studies, and transcranial Doppler ultrasonography as ancillary tests based on blood flow in the brain. However, CT angiography and magnetic resonance angiography not be used.
A lack of guidance makes performing an apnea test in patients receiving extracorporeal membrane oxygenation (ECMO) challenging, according to the authors. Nevertheless, they recommended that the same principles of BD/DNC be applied to adults and children receiving ECMO.
They further recommended a period of preoxygenation before the apnea test, and the document describes in detail the method for administering this test to people receiving ECMO.
Another potentially challenging situation pointed out in the consensus document is the determination of BD/DNC in patients who have been treated with targeted temperature management. Therapeutic hypothermia, particularly if it is preceded or accompanied by sedation, can temporarily impair brain stem reflexes, thus mimicking BD/DNC.
The new document includes a flowchart and step-by-step recommendations as well as suggestions for determining BD/DNC under these circumstances.
Among document limitations acknowledged by the authors is the lack of high-quality data from randomized, controlled trials on which to base their recommendations.
In addition, economic, technological, or personnel limitations may reduce the available options for ancillary testing, they added. Also, the recommendations do not incorporate contributions from patients or social or religious groups, although the authors were mindful of their concerns.
To promote the national and international harmonization of BD/DNC criteria, “medical societies and countries can evaluate their own policies in relation to this document and fix any deficiencies,” Dr. Sung said.
“Many countries do not have any BD/DNC policies and can use the documents from this project to create their own. There may need to be discussions with legal, governmental, religious, and societal leaders to help understand and accept BD/DNC and to help enact policies in different communities,” he added.
Divergent definitions
The determination of death is not simply a scientific question, but also a philosophical, religious, and cultural question, wrote Robert D. Truog, MD, director of the Harvard Center for Bioethics, Boston, and colleagues in an accompanying editorial. Future research should consider cultural differences over these questions.
“Most important is that there be a clear and logical consistency between the definition of death and the tests that are used to diagnose it,” Dr. Truog said.
The concept of whole brain death was advanced as an equivalent to biological death, “such that, when the brain dies, the body literally disintegrates, just as it does after cardiac arrest,” but evidence indicates that this claim is untrue, Dr. Truog said. Current tests also do not diagnose the death of the whole brain.
Another hypothesis is that brain stem death represents the irreversible loss of consciousness and the capacity for spontaneous respiration.
“Instead of focusing on biology, [this definition] focuses on values and is based on the claim that when a person is in a state of irreversible apneic unconsciousness, we may consider them to be dead,” said Dr. Truog. He and his coeditorialists argued that the concept of whole brain death should be replaced with that of brain stem death.
“This report should be a call for our profession, as well as for federal and state lawmakers, to reform our laws so that they are consistent with our diagnostic criteria,” Dr. Truog said.
“The most straightforward way of doing this would be to change U.S. law and adopt the British standard of brain stem death, and then refine our testing to make the diagnosis of irreversible apneic unconsciousness as reliable and safe as possible,” he concluded.
The drafting of the consensus statement was not supported by outside funding. Dr. Sung reported no relevant financial relationships. Dr. Truog reported receiving compensation from Sanofi and Covance for participating in data and safety monitoring boards unrelated to the consensus document.
A version of this article originally appeared on Medscape.com.
