Frequent Preservation of Neurologic Function in Brain Death and Brainstem Death Entails False-Positive Misdiagnosis and Cerebral Perfusion

Some patients who have been diagnosed as "dead by neurologic criteria" continue to exhibit certain brain functions, most commonly, neuroendocrine functions. This preservation of neurologic function after the diagnosis of "brain death" or "brainstem death" is an ongoing source of controversy and concern in the medical, bioethics, and legal literatures. Most obviously, if some brain function persists, then it is not the case that all functions of the entire brain have ceased and hence, declaring such a patient to be "dead" would be a false positive, in any nation with so-called "whole brain death" laws. Furthermore, and perhaps more concerning, the preservation of any brain function necessarily entails the preservation of some amount of brain perfusion, thereby raising the concern as to whether additional areas of neural tissue may remain viable, including areas in the brainstem. These and other considerations cast significant doubt on the reliability of diagnosing either "brain death" or "brainstem death."

AC, da Cruz Jr. LCH. The role of neuroimaging in the determination of brain death

Brain death is the irreversible cessation of all brain function. Although protocols for its determination vary among countries, the concept of brain death is widely accepted, despite ethical and religious issues. The pathophysiology of brain death is related to hypoxia and ischemia in the setting of extensive brain injury. It is also related to the effects of brain edema, which increases intracranial pressure, leading to cerebral circulatory arrest. Although the diagnosis of brain death is based on clinical parameters, the use of neuroimaging to demonstrate diffuse brain injury as the cause of coma prior to definitive clinical examination is a prerequisite. Brain computed tomography (CT) and magnetic resonance imaging (MRI) demonstrate diffuse edema, as well as ventricular and sulcal effacement, together with brain herniation. Angiography (by CT or MRI) demonstrates the absence of intracranial arterial and venous flow. In some countries, electroencephalography, cerebral digital subtraction angiography, transcranial Doppler ultrasound, or scintigraphy/single-photon emission CT are currently used for the definitive diagnosis of brain death. Although the definition of brain death relies on clinical features, radiologists could play an important role in the early recognition of global hypoxic-ischemic injury and the absence of cerebral vascular perfusion.

The intractable problems with brain death and possible solutions

Brain death has been accepted worldwide medically and legally as the biological state of death of the organism. Nevertheless, the literature has described persistent problems with this acceptance ever since brain death was described. Many of these problems are not widely known or properly understood by much of the medical community. Here we aim to clarify these issues, based on the two intractable problems in the brain death debates. First, the metaphysical problem: there is no reason that withstands critical scrutiny to believe that BD is the state of biological death of the human organism. Second, the epistemic problem: there is no way currently to diagnose the state of BD, the irreversible loss of all brain functions, using clinical tests and ancillary tests, given potential confounders to testing. We discuss these problems and their main objections and conclude that these problems are intractable in that there has been no acceptable solution offered other than bare assertions of an 'operational definition' of death. We present possible ways to move forward that accept both the metaphysical problem - that BD is not biological death of the human organism - and the epistemic problem - that as currently diagnosed, BD is a devastating neurological state where recovery of sentience is very unlikely, but not a confirmed state of irreversible loss of all [critical] brain functions. We argue that the best solution is to abandon the dead donor rule, thus allowing vital organ donation from patients currently diagnosed as BD, assuming appropriate changes are made to the consent process and to laws about killing.

Outcomes, Time-Trends, and Factors Associated With Ancillary Study Use for the Determination of Brain Death

OBJECTIVES

Brain death determination often requires ancillary studies when clinical determination cannot be fully or safely completed. We aimed to analyze the results of ancillary studies, the factors associated with ancillary study performance, and the changes over time in number of studies performed at an academic health system.

DESIGN

Retrospective cohort.

SETTING

Multihospital academic health system.

PATIENTS

Consecutive adult patients declared brain dead between 2010 and 2020.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 140 brain death patients, ancillary studies were performed in 84 (60%). The false negative rate of all ancillary studies was 4% (5% of transcranial Doppler ultrasounds, 4% of nuclear studies, 0% of electroencephalograms, and 17% of CT angiography). In univariate analysis, ancillary study use was associated with female sex (odds ratio, 2.4; 95% CI, 1.21-5.01; p = 0.013) and the etiology of brain death being hypoxic-ischemic brain injury (odds ratio, 2.9; 95% CI, 1.43-5.88; p = 0.003), nontraumatic intracranial hemorrhage (odds ratio, 0.45; 95% CI, 0.21-0.96; p = 0.039), or traumatic brain injury (odds ratio, 0.22; 95% CI, 0.04-0.8; p = 0.031). In multivariable analysis, female sex (odds ratio, 5.7; 95% CI, 2.56-15.86; p = 0.004), the etiology of brain death being hypoxic-ischemic brain injury (odds ratio, 3.2; 95% CI, 1.3-8.8; p = 0.015), and the neurologists performing brain death declaration (odds ratio, 0.08; 95% CI, 0.004-0.64; p = 0.034) were factors independently associated with use of ancillary studies. Over the study period, the total number of ancillary studies performed each year did not significantly change; however, the number of electroencephalograms significantly decreased with time (odds ratio per 1-yr increase, 0.67; 95% CI, 0.49-0.90; p = 0.014).

CONCLUSIONS

A large number of ancillary studies were performed despite a clinical determination of brain death; patients with hypoxic-ischemic brain injury are more likely to undergo ancillary studies for brain death determination, and neurologists were less likely to use ancillary studies for brain death. Recently, the use of electroencephalograms for brain death determination has decreased, likely reflecting significant concerns regarding its validity and reliability.

South African guidelines on the determination of death

Summary

Death is a medical occurrence that has social, legal, religious and cultural consequences requiring common clinical standards for its diagnosis and legal regulation. This document compiled by the Critical Care Society of Southern Africa outlines the core standards for determination of death in the hospital context. It aligns with the latest evidence-based research and international guidelines and is applicable to the South African context and legal system. The aim is to provide clear medical standards for healthcare providers to follow in the determination of death, thereby promoting safe practices and high-quality care through the use of uniform standards. Adherence to such guidelines will provide assurance to medical staff, patients, their families and the South African public that the determination of death is always undertaken with diligence, integrity, respect and compassion, and is in accordance with accepted medical standards and latest scientific evidence. The consensus guidelines were compiled using the AGREE II checklist with an 18-member expert panel participating in a three-round modified Delphi process. Checklists and advice sheets were created to assist with application of these guidelines in the clinical environment (https://criticalcare.org.za/resource/death-determination-checklists/).

Key points

Brain death and circulatory death are the accepted terms for defining death in the hospital context.

Death determination is a clinical diagnosis which can be made with complete certainty provided that all preconditions are met.

The determination of death in children is held to the same standard as in adults but cannot be diagnosed in children <36 weeks’ corrected gestation.

Brain-death testing while on extra-corporeal membrane oxygenation is outlined.

Recommendations are given on handling family requests for accommodation and on consideration of the potential for organ donation.

The use of a checklist combined with a rigorous testing process, comprehensive documentation and adequate counselling of the family are core tenets of death determination. This is a standard of practice to which all clinicians should adhere in end-of-life care.

Determination of Brain Death/Death by Neurologic Criteria: The World Brain Death Project

IMPORTANCE

There are inconsistencies in concept, criteria, practice, and documentation of brain death/death by neurologic criteria (BD/DNC) both internationally and within countries.

OBJECTIVE

To formulate a consensus statement of recommendations on determination of BD/DNC based on review of the literature and expert opinion of a large multidisciplinary, international panel.

PROCESS

Relevant international professional societies were recruited to develop recommendations regarding determination of BD/DNC. Literature searches of the Cochrane, Embase, and MEDLINE databases included January 1, 1992, through April 2020 identified pertinent articles for review. Because of the lack of high-quality data from randomized clinical trials or large observational studies, recommendations were formulated based on consensus of contributors and medical societies that represented relevant disciplines, including critical care, neurology, and neurosurgery.

EVIDENCE SYNTHESIS

Based on review of the literature and consensus from a large multidisciplinary, international panel, minimum clinical criteria needed to determine BD/DNC in various circumstances were developed.

RECOMMENDATIONS

Prior to evaluating a patient for BD/DNC, the patient should have an established neurologic diagnosis that can lead to the complete and irreversible loss of all brain function, and conditions that may confound the clinical examination and diseases that may mimic BD/DNC should be excluded. Determination of BD/DNC can be done with a clinical examination that demonstrates coma, brainstem areflexia, and apnea. This is seen when (1) there is no evidence of arousal or awareness to maximal external stimulation, including noxious visual, auditory, and tactile stimulation; (2) pupils are fixed in a midsize or dilated position and are nonreactive to light; (3) corneal, oculocephalic, and oculovestibular reflexes are absent; (4) there is no facial movement to noxious stimulation; (5) the gag reflex is absent to bilateral posterior pharyngeal stimulation; (6) the cough reflex is absent to deep tracheal suctioning; (7) there is no brain-mediated motor response to noxious stimulation of the limbs; and (8) spontaneous respirations are not observed when apnea test targets reach pH <7.30 and Paco2 ≥60 mm Hg. If the clinical examination cannot be completed, ancillary testing may be considered with blood flow studies or electrophysiologic testing. Special consideration is needed for children, for persons receiving extracorporeal membrane oxygenation, and for those receiving therapeutic hypothermia, as well as for factors such as religious, societal, and cultural perspectives; legal requirements; and resource availability.

CONCLUSIONS AND RELEVANCE

This report provides recommendations for the minimum clinical standards for determination of brain death/death by neurologic criteria in adults and children with clear guidance for various clinical circumstances. The recommendations have widespread international society endorsement and can serve to guide professional societies and countries in the revision or development of protocols and procedures for determination of brain death/death by neurologic criteria, leading to greater consistency within and between countries.

Controversies in Brain Death Declaration: Legal and Ethical Implications in the ICU

Purpose of review

This article provides a brief overview of the history and complexities of brain death determination. We examine a few legal cases that highlight some of the controversies surrounding the validity of brain death tests in light of varying state laws and institutional policy, the appropriateness of making religious accommodations, the dilemma of continuing organ-sustaining support in a pregnant brain-dead patient, and the issue of whether to obtain informed consent from surrogate decision makers before proceeding to testing.

Recent findings

In response to physician concerns about navigating these complex cases, especially with laws that vary from state to state, the American Academy of Neurology has published a position statement in January of 2019 endorsing brain death as the irreversible loss of all functions of the entire brain. It provides positions on the determination of brain death as well as guidance surrounding requests for accommodation.

Summary

Although death by neurologic criteria has been accepted as death medically for over 40 years, legal variance exists throughout the states, especially regarding religious accommodations and in pregnancy. Questions of whether to obtain informed consent from surrogate decision makers prior to brain death testing remain, and there is no guideline regarding obtaining ancillary testing. We expect to see continued cases that cause medical, legal, and ethical controversies in our ICUs. As such, uniform training in proper methodology in performing the brain death examination and appropriate use of ancillary testing is crucial, and there is a need for legal consistency in the acceptance of the medical standard.

Misinterpretations of Guidelines Leading to Incorrect Diagnosis of Brain Death: A Case Report and Discussion

Guidelines describe the process necessary for the diagnosis of brain death. We present a case of a 3-month-old former 36-week-gestation infant after a prolonged out-of-hospital cardiac arrest of 37 minutes who was clinically diagnosed as brain dead at 120 hours after the event. Unusual findings included a normal slightly sunken anterior fontanelle, normal cerebral blood flow perfusion scan at 73 hours after the event, only localized parieto-temporal edema on the latest computed tomographic (CT) scan of the brain at 48 hours after the event, and discussion of whether nonconvulsive seizures could have confounded the examination for brain death. In light of these unusual findings, we discuss and highlight what may be common misinterpretations of brain death guidelines that led to the mistaken diagnosis of death (as opposed to severe neurologic injury) in this child.

Diagnostic Accuracy Studies

The medical community often assumes that the tests we use to diagnose various diseases are accurate, safe, and effective. However, the study designs traditionally used to determine whether such a diagnostic test is indeed accurate, safe, and effective are often at a higher risk of bias and are of lower methodological quality than those evaluating efficacy of therapeutic interventions. Several designs can be used to study diagnostic tests such as diagnostic accuracy cross-sectional studies, diagnostic accuracy case-control studies, and diagnostic accuracy comparative studies. Clinicians, researchers, and policy-makers may wish to consider moving toward higher quality study designs when studying new diagnostic modalities prior to their implementation in routine practice and diagnostic randomized trials are one such alternative.

How should we use imaging in the determination of brainstem death?

Brainstem death is defined as the "irreversible cessation of brainstem function", either due to primary intracranial events or extracranial factors such as hypoxia. The importance of accurate and timely diagnosis of brainstem death in critical care should not be understated, as it allows the withdrawal of treatment when it is no longer deemed to beneficial. Additionally, it may facilitate the process of organ donation. Overall, the diagnosis of brainstem death has four common principles across the world: (1) neurological criteria based on clinical assessment; (2) evidence of irreversible brain damage from known aetiology; (3) demonstrating an absence of a reversible cause; and (4) the use of ancillary studies. The latter in particular has been a controversial issue, with much debate continuing on how imaging should be used. We discuss three key questions surrounding the role of imaging in the diagnosis of brainstem death as well as important issues the radiology community should consider.

False-Positive Diagnosis of Brain Death Following the Pediatric Guidelines: Case Report and Discussion

A 2-year-old boy with severe head trauma was diagnosed brain dead according to the 2011 Pediatric Guidelines. Computed tomographic (CT) scan showed massive cerebral edema with herniation. Intracranial pressures were extremely high, with cerebral perfusion pressures around 0 for several hours. An apnea test was initially contraindicated; later, one had to be terminated due to oxygen desaturation when the Pco₂ had risen to 57.9 mm Hg. An electroencephalogram (EEG) was probably isoelectric but formally interpreted as equivocal. Tc-99m diethylene-triamine-pentaacetate (DTPA) scintigraphy showed no intracranial blood flow, so brain death was declared. Parents declined organ donation. A few minutes after withdrawal of support, the boy began to breathe spontaneously, so the ventilator was immediately reconnected and the death declaration rescinded. Two hours later, life support was again removed, this time for prognostic reasons; he did not breathe, and death was declared on circulatory-respiratory grounds. Implications regarding the specificity of the guidelines are discussed.

Confounding Brain Stem Function During Pediatric Brain Death Determination: Two Case Reports

A patient who has been declared brain dead is considered to be both legally and clinically dead. However, we report 2 pediatric cases in which the patients demonstrated clinical signs of brain stem function that are not recognized or tested in current Canadian or US guidelines.

Computed tomography angiography in the diagnosis of brain death: a systematic review and meta-analysis

BACKGROUND

Physiological instability and confounding factors may interfere with the clinical diagnosis of brain death. Computed tomography angiography (CTA) has been suggested as a potential ancillary test for confirmation of brain death, but its diagnostic accuracy remains unclear.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL for studies comparing CTA with other accepted methods of diagnosing brain death (clinical or radiographic). Summary estimates of diagnostic accuracy were computed using random effects models. Subgroup analyses and meta-regression were performed to assess associations between CTA sensitivity and study or patient characteristics.

RESULTS

Twelve studies, involving 541 patients, were included. If the CTA criterion for brain death was complete lack of opacification of intracranial vessels, then the pooled sensitivity was 62 % (50-74 %) for venous phase and 84 % (75-94 %) for arterial phase imaging. The sensitivity of CTA was higher when the criterion for brain death involved absence of opacification of internal cerebral veins, either alone (99 %, 97-100 %) or in combination with lack of flow to the distal middle cerebral artery branches (85 %, 77-93 %). CTA sensitivity was not influenced by different reference standards (clinical vs. radiographic) or predominant diagnostic category (stroke vs. brain trauma). Specificity of CTA could not be adequately determined from the existing data.

CONCLUSION

Many patients who progress to brain death by accepted clinical or radiographic criteria have persistent opacification of proximal intracranial vessels when CTA is performed. The specificity of CTA in the diagnosis of brain death has not been adequately assessed. Routine use of CTA as an ancillary test in the diagnosis of brain death is therefore not recommended until diagnostic criteria have undergone further refinement and prospective validation. Absence of opacification of the internal cerebral veins appears to be the most promising angiographic criterion.

Clinical Brain Death with False Positive Radionuclide Cerebral Perfusion Scans

Practice guidelines from the American Academy of Neurology for the determination of brain death in adults define brain death as "the irreversible loss of function of the brain, including the brainstem." Neurological determination of brain death is primarily based on clinical examination; if clinical criteria are met, a definitive confirmatory test is indicated. The apnea test remains the gold standard for confirmation. In patients with factors that confound the clinical determination or when apnea tests cannot safely be performed, an ancillary test is required to confirm brain death. Confirmatory ancillary tests for brain death include (a) tests of electrical activity (electroencephalography (EEG) and somatosensory evoked potentials) and (b) radiologic examinations of blood flow (contrast angiography, transcranial Doppler ultrasound (TCD), and radionuclide methods). Of these, however, radionuclide studies are used most commonly. Here we present data from two patients with a false positive Radionuclide Cerebral Perfusion Scan (RCPS).

Brain death scintigraphy and pathology results in a rat model

OBJECTIVES

Brain scintigraphy with Tc-99m-labeled diethylenetriaminopenta-acetic acid is a sensitive diagnostic method showing loss of cerebral blood flow that occurs after brain death. Cerebral blood flow can be quantitatively estimated by this method. The aim of this study was to compare histopathologic changes occurring with the decrease of cerebral blood flow (as shown by Tc-99m-labeled diethylenetriaminopenta-acetic acid brain death scintigraphy) after brain death in an experimental model.

MATERIALS AND METHODS

The study included examination of cerebral blood flow by Tc-99m-labeled diethylenetriaminopenta-acetic acid brain scintigraphy in the 20 rats, 1 day before brain death, after producing brain death in 11 surviving rats. Tc-99m-labeled diethylenetriaminopenta-acetic acid brain scintigraphy was performed under intubation and monitored. The Mann-Whitney U test was performed to compare groups (scintigraphic quantification results before and after brain death).

RESULTS

In the time activity curves generated from the analysis of the scintigraphies, decreases in counts in the brain death group were obtained in the arterial phase (P < .01). Decreases of the cerebral blood flow between the first and the sixth minutes were statistically significant (P < .05). Common principal histopathologic changes of the brain death (ie, autolysis and color loss in the nerve cells, diffuse edema, petechial hemorrhage in the brain tissues) were observed in all subjects.

CONCLUSIONS

Quantitative findings of the brain scintigraphy by Tc-99m-labeled diethylenetriaminopenta-acetic acid was related with the histopathologic findings seen during the early brain death, with significant decreases of the cerebral blood flow. Quantification of Tc-99m-labeled diethylenetriaminopenta-acetic acid brain death scintigraphy as an easier and less-expensive scintigraphic method of cerebral blood flow might indicate a definite diagnosis of brain death and thus, potential donors can be determined earlier, leaving to increased transplant rates.

Scintigraphic confirmation of brain death

The concept of brain death has gained importance in the past few decades to prevent futile attempts to sustain ventilation and blood circulation when the brain has lost all function and to procure beneficial tissues or life-saving organs for transplantation. However, differences remain among professional societies and various study group recommendations, as well as among individual legal statutes, in how brain death is defined and the methodology for which the diagnosis is attained. Furthermore, reports have appeared both in the medical literature and the lay press concerning quality assurance measures in brain death documentation. Scintigraphy is a commonly used technique in the evaluation of brain death and can be performed with the use of either nonspecific tracers, such as Tc99m diethylene triamine pentaacetic acid, or brain-specific tracers, such as Tc99m hexamethylpropyleneamineoxime (HMPAO). Planar imaging, with or without radionuclide angiography, continues to be the mainstay for the scintigraphic confirmation of brain death. Flow with multiprojection static planar imaging with the use of Tc99m HMPAO can be used to evaluate the cerebral hemispheres, basal ganglia, thalamus, and cerebellum. Single-photon emission computed tomography (SPECT) can provide cross-sectional information but can be difficult to perform in the context of brain death. The current use of SPECT primarily is supplemental to help differentiate overlying scalp from intracerebral activity. The reliability of SPECT to exclude flow and metabolism in the brainstem remains to be scientifically validated.

The apnea test: rationale, confounders, and criticism

The apnea test is recommended for the diagnosis of brain death. There are several reasons this test should be reconsidered. Confounding factors for performing the test are vaguely and poorly specified. The following 2 confounders are usually present and not considered: potentially reversible high cervical spinal cord injury and central endocrine failure of adrenal and thyroid axes. There are case reports of breathing at a higher partial pressure of arterial carbon dioxide threshold and cases of recovery of breathing after brain death is diagnosed. The test is dangerous for an injured brain in the setting of high intracranial pressure. It can convert viable penumbral brain tissue to irreversibly nonfunctioning tissue via a transient increase in intracranial pressure and no-reflow phenomena. Hyperoxia during the apnea test can further suppress the function of medullary respiratory rhythm centers. Finally, the philosophical rationale for the need to show lack of spontaneous breathing in brain death is lacking.

Brain death and the cervical spinal cord: a confounding factor for the clinical examination

STUDY DESIGN

This study is a systematic review.

OBJECTIVES

Brain death (BD) is a clinical diagnosis, made by documenting absent brainstem functions, including unresponsive coma and apnea. Cervical spinal cord dysfunction would confound clinical diagnosis of BD. Our objective was to determine whether cervical spinal cord dysfunction is common in BD.

METHODS

A case of BD showing cervical cord compression on magnetic resonance imaging prompted a literature review from 1965 to 2008 for any reports of cervical spinal cord injury associated with brain herniation or BD.

RESULTS

A total of 12 cases of brain herniation in meningitis occurred shortly after a lumbar puncture with acute respiratory arrest and quadriplegia. In total, nine cases of acute brain herniation from various non-meningitis causes resulted in acute quadriplegia. The cases suggest that direct compression of the cervical spinal cord, or the anterior spinal arteries during cerebellar tonsillar herniation cause ischemic injury to the cord. No case series of brain herniation specifically mentioned spinal cord injury, but many survivors had severe disability including spastic limbs. Only two pathological series of BD examined the spinal cord; 56-100% of cases had upper cervical spinal cord damage, suggesting infarction from direct compression of the cord or its arterial blood supply.

CONCLUSIONS

Upper cervical spinal cord injury may be common after brain herniation. Cervical spinal cord injury must either be ruled out before clinical testing for BD, or an ancillary test to document lack of brainstem blood flow is required in all cases of suspected BD. BD may not be a purely clinical diagnosis.