Death is defined in the United States by the Uniform Determination of Death Act, proposed in 1981, as
The definition of brain death or irreversible coma as "loss of brain functions" was released by the Ad Hoc Committee of the Harvard Medical School in 1968. The American Academy of Neurology (AAN) guidelines of brain death determination ascertained this definition and released its first version in 1995. According to the AAN guidelines, brain death is clinically equivalent to the irreversible loss of all brain stem functions. Irreversibility in the definition refers to the impossibility of recovery, regardless of any medical intervention, which required clear elaboration. As with the advancement of mechanical ventilation and life support technologies during the 20th century, patients who suffered severe brain damage could be maintained physiologically for prolonged periods in the intensive care units (ICUs).
It is crucial to differentiate brain death from other forms of severe brain damage, which can cause vegetative states when some of the brain functions are maintained, and recovery can occur even after prolonged periods, especially in patients with traumatic brain injuries. Also, it is important to distinguish the term “brain death” from “coma” to the public, as a coma may imply a limited form of life. Understanding that brain death is equivalent to death helps both the physicians and patients’ families to decide about the withdrawal of care and prevents the unnecessary expenditure of resources. Another essential topic that evolved in parallel with brain death is the need of obtaining organs for transplantation. According to the “dead donor rule,” organ procurement can occur only after death. So for patients who are brain dead, the procurement of viable organs is allowed, even if they still have some circulatory and pulmonary functions. This concept is still causing an ongoing debate and controversy.
Brain death occurs as a result of an acute catastrophic brain injury. Abruption of cerebral perfusion occurs if a concomitant elevation of intracranial pressure is more than mean arterial pressure (Cerebral perfusion pressure= mean arterial pressure -intracranial pressure). This process was studied by monitoring brain tissue oxygenation in patients with brain death, and can occur in 2 different mechanisms:
A recent study of brain death determination protocols over the world in 91 countries showed high variability in the protocols in different countries and even the absence of protocols in most low-income countries. Another study in the United States showed variability in the protocols between various health institutions, and the performance of the apnea and the ancillary tests. Also, different states have different requirements for the examiner, including if one or two physicians are required to determine brain death. Some states (as Alaska) allow the authority to nurses to assess brain death with further certification by a physician. Another common requirement is if the patient is potential for organ procurement, the physician who declares brain death should not be a member of the procurement team.
Certain pre-requisites should be present before the determination of brain death, including:
Brain death can be assessed by doing a physical examination, the apnea test, and the ancillary tests.
I. Physical examination: which includes the response to pain and assessment of brain stem reflexes.
Loss of response to central pain occurs in brain death. Central pain assessment can be by the application of noxious stimuli to certain areas as the supraorbital notch, the ankle of the jaw, upper trapezius, the anterior axillary fold, and the sternum. Neither eye response nor motor reflexes are detectable in brain death. It’s important to note that some spinal reflexes can be present in patients with brain death. Saposnik et al. studied spinal reflexes in 107 patients with brain death and noted the following reflexes:
II. Apnea test:
The apnea test is used to assess the brain's ability to drive pulmonary function in response to the rise of CO2. Before the performance of the apnea test, the mechanical ventilator should be adjusted to obtain PCO2 within 35 to 45 mmHg and PO2 above 200 mmHg, with using a positive end-expiratory pressure (PEEP) of 5 to 8 cm H2O. During the test, oxygen should be supplemented using a cannula connected to the endotracheal tube at 6 L/min, or T piece at 12 L/min or using CPAP of 5 to 10 cm H2O. In the case of loss of respiratory drive, CO2 is expected to rise 5 mmHg every minute in the first 2 minutes, then by 2 mmHg every minute after. Repeat arterial blood gas (ABG) after 8 to 10 minutes showing CO2 of 60 mmHg or the rise of CO2 more than 20 mmHg above baseline is consistent with brain death. If the patient develops hypotension with SBP below 90 mmHg or cardiac arrhythmias, the test should terminate, and arterial blood gases are drawn. For patients on extracorporeal membrane oxygenation (ECMO) machines, oxygenation can be maintained while performing the apnea test by decreasing the gas sweep flow rate to 0.5 to 1.0 L/min and using an oxygenation source through the endotracheal (ET) tube.
III. Ancillary tests:
These tests are considerations if there is any uncertainty of diagnosis of brain death, or if the apnea test can’t be performed (as in cases of chronic CO2 retainers).
*Ancillary tests used for detection of cessation of cerebral blood flow:
*Ancillary tests used for detection of loss of bioelectrical activity of the brain:
Criteria of brain death determination are illustrated in detail in the guidelines of the American Academy of Neurology. However, it is still a topic of controversy and debate. A clear approach to brain death diagnosis is crucial, as mentioned in the following points:
Nursing should be supportive and continue to provide standard care until released by the diagnosis of brain death. The interprofessional healthcare team will function normally until making such determination.
Nurses should continue to monitor and treat the patient until the confirmation of brain death. No patient should experience deprivation of any treatment until this notification. Upon the determination of brain death, the appropriate provider should document it in the chart. The nurse should call the family and make all possible accommodations for religious preferences.
If there is any dispute with the family regarding brain death and treatment, nurses should not hesitate to call the ethics team to help with the situation. The key is to be supportive of the family and their wishes.
|||A definition of irreversible coma. Report of the Ad Hoc Committee of the Harvard Medical School to Examine the Definition of Brain Death. JAMA. 1968 Aug 5; [PubMed PMID: 5694976]|
|||Wijdicks EF, Determining brain death in adults. Neurology. 1995 May; [PubMed PMID: 7746373]|
|||Spinello IM, Brain Death Determination. Journal of intensive care medicine. 2015 Sep; [PubMed PMID: 24227449]|
|||Bernat JL, The natural history of chronic disorders of consciousness. Neurology. 2010 Jul 20; [PubMed PMID: 20554939]|
|||Capron AM, Brain death--well settled yet still unresolved. The New England journal of medicine. 2001 Apr 19; [PubMed PMID: 11309642]|
|||Truog RD,Miller FG,Halpern SD, The dead-donor rule and the future of organ donation. The New England journal of medicine. 2013 Oct 3; [PubMed PMID: 24088088]|
|||Machado C, Diagnosis of brain death. Neurology international. 2010 Jun 21; [PubMed PMID: 21577338]|
|||Palmer S,Bader MK, Brain tissue oxygenation in brain death. Neurocritical care. 2005; [PubMed PMID: 16174963]|
|||Wahlster S,Wijdicks EF,Patel PV,Greer DM,Hemphill JC 3rd,Carone M,Mateen FJ, Brain death declaration: Practices and perceptions worldwide. Neurology. 2015 May 5; [PubMed PMID: 25854866]|
|||Powell T,Zisfein J,Halperin J, Variability of brain death determination guidelines in leading US neurologic institutions. Neurology. 2008 Nov 25; [PubMed PMID: 19029529]|
|||Wijdicks EF,Varelas PN,Gronseth GS,Greer DM, Evidence-based guideline update: determining brain death in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2010 Jun 8; [PubMed PMID: 20530327]|
|||Shutter L, Pathophysiology of brain death: what does the brain do and what is lost in brain death? Journal of critical care. 2014 Aug; [PubMed PMID: 24930369]|
|||Saposnik G,Maurino J,Saizar R,Bueri JA, Spontaneous and reflex movements in 107 patients with brain death. The American journal of medicine. 2005 Mar; [PubMed PMID: 15745731]|
|||Kramer AH, Ancillary testing in brain death. Seminars in neurology. 2015 Apr; [PubMed PMID: 25839721]|
|||Lie SA,Hwang NC, Challenges of Brain Death and Apnea Testing in Adult Patients on Extracorporeal Membrane Oxygenation-A Review. Journal of cardiothoracic and vascular anesthesia. 2019 Aug; [PubMed PMID: 30765209]|