Gadolinium-enhanced magnetic resonance angiography in brain death

Perfusion Pressure and the Histology of Brain Death: A Unique Case in an Infant Maintained on Life Support

Brain death is a not uncommon phenomena in the adult and pediatric population. Most cases are removed from life support soon after brain death is declared. Less commonly, systemic perfusion is maintained by life support for some time after neurologic function stops. These cases present uncommon opportunities to explore the histology of necrosis and autolysis in the context of global hypoxic ischemic damage. Here, we describe the unusual case of an infant maintained on life support for 2 weeks after brain death was declared with an emphasis on the resulting gross and histologic findings including a discussion of their underlying physiology.

Challenges in determining death by neurologic criteria in extracorporeal membrane oxygenation - A single center experience

INTRODUCTION

Apnea test (AT) in patients on extracorporeal membrane oxygenation (ECMO) support is challenging, leading to variation in determining death by neurologic criteria (DNC). We aim to describe the diagnostic criteria and barriers for DNC in adults on ECMO in a tertiary care center.

METHODS

A retrospective review of a prospective observational standardized neuromonitoring study was conducted in adult VA- and VV-ECMO patients at a tertiary center from June 2016 to March 2022. Brain death was defined according to the 2010 American Academy of Neurology guidelines and following the 2020 World Brain Death Project recommendations for performing AT in ECMO patients.

RESULTS

Eight (2.7%) ECMO patients (median age = 44 years, 75% male, 50% VA-ECMO) met criteria for DNC, six (75%) of whom were determined with AT. In the other two patients who did not undergo AT due to safety concerns, ancillary tests (transcranial doppler and electroencephalography) were consistent with DNC. An additional seven (2.3%) patients (median age = 55 years, 71% male, 86% VA-ECMO) were noted to have absent brainstem reflexes but failed to complete determination of DNC as they underwent withdrawal of life-sustaining treatment (WLST) before a full evaluation was completed. In these patients, AT was never performed, and ancillary tests were inconsistent with either neurological exam findings and/or neuroimaging supporting DNC, or with each other.

CONCLUSION

AT was used safely and successfully in 6 of the 8 ECMO patients diagnosed with DNC and was always consistent with the neurological exam and imaging findings, as opposed to ancillary tests alone.

Brain death: a clinical overview

Brain death, also commonly referred to as death by neurologic criteria, has been considered a legal definition of death for decades. Its determination involves many considerations and subtleties. In this review, we discuss the philosophy and history of brain death, its clinical determination, and special considerations. We discuss performance of the main clinical components of the brain death exam: assessment of coma, cranial nerves, motor testing, and apnea testing. We also discuss common ancillary tests, including advantages and pitfalls. Special discussion is given to extracorporeal membrane oxygenation, target temperature management, and determination of brain death in pediatric populations. Lastly, we discuss existing controversies and future directions in the field.

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.

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.

The use of apnea test and brain death determination in patients on extracorporeal membrane oxygenation: A systematic review

OBJECTIVE

To review practices of brain death (BD) determination in patients on extracorporeal membrane oxygenation (ECMO).

METHODS

A systematic search was applied to PubMed and 6 electronic databases from inception to May 22, 2019. Studies reporting methods of BD assessment in adult patients (>18 years old) while on ECMO were included, after which data regarding BD assessment were extracted.

RESULTS

Twenty-two studies (n = 177 patients) met the inclusion criteria. Eighty-eight patients (50%) in 19 studies underwent the apnea test (AT); most commonly through decreasing the ECMO sweep flow in 14 studies (n = 42, 48%), followed by providing CO₂ through the ventilator in 2 studies (n = 6, 7%), and providing CO² through the ECMO oxygenator in 1 study (n = 1, 1%). The details of the AT were not reported in 2 studies (n = 39, 44%). In 19 patients (22%), the AT was nonconfirmatory due to hemodynamic instability, hypoxia, insufficient CO₂ rise, or unreliability of the AT. A total of 157 ancillary tests were performed, including electroencephalogram (62%), computed tomography angiography (22%), transcranial Doppler ultrasound (6%), cerebral blood flow nuclear study (5%), cerebral angiography (4%), and other (1%). Forty-seven patients (53% of patients with AT) with confirmatory AT still underwent additional ancillary for BD confirmation. Only 21 patients (12% of all patients) were declared brain-dead using confirmatory ATs alone without ancillary testing.

CONCLUSIONS

Performing AT for patients with ECMO was associated with high failure rate and hemodynamic complications. Our study highlights the variability in practice in regard to the AT and supports the use of ancillary tests to determine BD in patients on ECMO.

Confirmation of brain death using optical methods based on tracking of an optical contrast agent: assessment of diagnostic feasibility

We aimed to determine whether optical methods based on bolus tracking of an optical contrast agent are useful for the confirmation of cerebral circulation cessation in patients being evaluated for brain death. Different stages of cerebral perfusion disturbance were compared in three groups of subjects: controls, patients with posttraumatic cerebral edema, and patients with brain death. We used a time-resolved near-infrared spectroscopy setup and indocyanine green (ICG) as an intravascular flow tracer. Orthogonal partial least squares-discriminant analysis (OPLS-DA) was carried out to build statistical models allowing for group separation. Thirty of 37 subjects (81.1%) were classified correctly (8 of 9 control subjects, 88.9%; 13 of 15 patients with edema, 86.7%; and 9 of 13 patients with brain death, 69.2%; p < 0.0001). Depending on the combination of variables used in the OPLS-DA model, sensitivity, specificity, and accuracy were 66.7–92.9%, 81.8–92.9%, and 77.3–89.3%, respectively. The method was feasible and promising in the demanding intensive care unit environment. However, its accuracy did not reach the level required for brain death confirmation. The potential usefulness of the method may be improved by increasing the depth of light penetration, confirming its accuracy against other methods evaluating cerebral flow cessation, and developing absolute parameters for cerebral perfusion.

Organ donation protocols

Organ transplantation improves survival and quality of life in patients with end-organ failure. Waiting lists continue to grow across the world despite remarkable advances in the transplantation process, from the creation of public engagement campaigns to the development of critical pathways for the timely identification, referral, approach, and treatment of the potential organ donor. The pathophysiology of dying triggers systemic changes that are intimately related to organ viability. The intensive care management of the potential organ donor optimizes organ function and improves the donation yield, representing a significant step in reducing the mismatch between organ supply and demand. Different beliefs and cultures reflect diverse legislations and donation practices amongst different countries, creating a challenge to standardized practices. Maintaining public trust is necessary for continued progress in organ donation and transplantation, hence the urge for a joint effort in creating uniform protocols that ensure transparent practices within the medical community.

[Angiographic procedures for determination of cessation of cerebral circulation]

In several European countries catheter angiography is permitted as a confirmatory procedure for the determination of irreversible loss of brain function (brain death). In Germany catheter angiography requires the possibility of a therapeutic implication as a prerequisite. In the updated German guidelines computed tomography angiography (CTA) has been accredited as a new confirmatory procedure if a standardized protocol and predefined assessment parameters are adhered to. The CTA can be performed within a few minutes, even in situations with unstable intensive care patients. Magnetic resonance (MR) angiography has not yet been adequately validated and is not permitted in Germany as a confirmatory procedure for the determination of irreversible loss of brain function.

Portable Wideband Microwave Imaging System for Intracranial Hemorrhage Detection Using Improved Back-projection Algorithm with Model of Effective Head Permittivity

Intracranial hemorrhage is a medical emergency that requires rapid detection and medication to restrict any brain damage to minimal. Here, an effective wideband microwave head imaging system for on-the-spot detection of intracranial hemorrhage is presented. The operation of the system relies on the dielectric contrast between healthy brain tissues and a hemorrhage that causes a strong microwave scattering. The system uses a compact sensing antenna, which has an ultra-wideband operation with directional radiation, and a portable, compact microwave transceiver for signal transmission and data acquisition. The collected data is processed to create a clear image of the brain using an improved back projection algorithm, which is based on a novel effective head permittivity model. The system is verified in realistic simulation and experimental environments using anatomically and electrically realistic human head phantoms. Quantitative and qualitative comparisons between the images from the proposed and existing algorithms demonstrate significant improvements in detection and localization accuracy. The radiation and thermal safety of the system are examined and verified. Initial human tests are conducted on healthy subjects with different head sizes. The reconstructed images are statistically analyzed and absence of false positive results indicate the efficacy of the proposed system in future preclinical trials.