Transcranial Doppler ultrasonography to confirm brain death: a meta-analysis

The Approach to Altered Mental Status in the Intensive Care Unit

Altered mental status (AMS) is a syndrome posing substantial burden to patients in the intensive care unit (ICU) in both prevalence and intensity. Unfortunately, ICU patients are often diagnosed merely with syndromic labels, particularly the duo of toxic-metabolic encephalopathy (TME) and delirium. Before applying a nonspecific diagnostic label, every patient with AMS should be evaluated for specific, treatable diseases affecting the central nervous system. This review offers a structured approach to increase the probability of identifying specific causal etiologies of AMS in the critically ill. We provide tips for bedside assessment in the challenging ICU environment and review the role and yield of common neurodiagnostic procedures, including specialized bedside modalities of diagnostic utility in unstable patients. We briefly review two common etiologies of TME (uremic and septic encephalopathies), and then review a selection of high-yield toxicologic, neurologic, and infectious causes of AMS in the ICU, with an emphasis on those that require deliberate consideration as they elude routine screening. The final section lays out an approach to the various etiologies of AMS in the critically ill.

Role of Clinical and Multimodality Neuroimaging in the Evaluation of Brain Death/Death by Neurologic Criteria and Recent Highlights from 2023 Updated Guidelines

Purpose of Review: This review aims to provide a comprehensive overview of the diagnosis of brain death/death by neurologic criteria (BD/DNC) by emphasizing the clinical criteria established by the American Academy of Neurology (AAN) in light of their updated guidelines released in 2023. In this review, we will focus on the current implementation of ancillary tests including the catheter cerebral angiogram, nuclear scintigraphy, and transcranial Doppler, which provide support in diagnoses when clinical examination and apnea tests are inconclusive. Finally, we will also provide examples to discuss the implementation of certain imaging studies in the context of diagnosing BD/DNC. Recent Findings: Recent developments in the field of neurology have emphasized the importance of clinical criteria for diagnosing BD/DNC, with the AAN providing clear updated guidelines that include coma, apnea, and the absence of brainstem reflexes. Current ancillary tests, including the catheter cerebral angiogram, nuclear scintigraphy, and transcranial Doppler play a crucial role in confirming BD/DNC when the clinical assessment is limited. The role of commonly used imaging studies including computed tomography and magnetic resonance angiographies of the brain as well as CT/MR perfusion studies will also be discussed in the context of these new guidelines. Summary: BD/DNC represents the permanent cessation of brain functions, including the brainstem. This review article provides the historical context, clinical criteria, and pathophysiology that goes into making this diagnosis. Additionally, it explores the various ancillary tests and selected imaging studies that are currently used to diagnose BD/DNC under the newly updated AAN guidelines. Understanding the evolution of how to effectively use these diagnostic tools is crucial for healthcare professionals who encounter these BD/DNC cases in their practice.

Transcranial Doppler and Color-Coded Doppler Use for Brain Death Determination in Adult Patients: A Pictorial Essay

Transcranial Doppler (TCD) is a repeatable, at-the-bedside, helpful tool for confirming cerebral circulatory arrest (CCA). Despite its variable accuracy, TCD is increasingly used during brain death determination, and it is considered among the optional ancillary tests in several countries. Among its limitations, the need for skilled operators with appropriate knowledge of typical CCA patterns and the lack of adequate acoustic bone windows for intracranial arteries assessment are critical. The purpose of this review is to describe how to evaluate cerebral circulatory arrest in the intensive care unit with TCD and transcranial duplex color-coded doppler (TCCD).

Transcranial Ultrasound in the Neurocritical Care Unit

Ultrasound evaluation of the brain is performed through acoustic windows. Transcranial Doppler has long been used to monitor patients with subarachnoid hemorrhage for cerebral vasospasm. Transcranial color-coded sonography permits parenchymal B-mode imaging and duplex evaluation. Transcranial ultrasound may also be used to assess the risk of delayed cerebral ischemia, screen patients for the presence of elevated intracranial pressure, confirm the diagnosis of brain death, measure midline shift, and detect ventriculomegaly. Transcranial ultrasound should be integrated with other point-of-care ultrasound techniques as an essential skill for the neurointensivist.

Self-harm, suicide and brain death: the role of the radiologist

Suicide is a leading cause of death worldwide and takes many forms, which include hanging, jumping from a height, sharp force trauma, ingestion/poisoning, drowning, and firearm injuries. Self-harm and suicide are associated with particular injuries and patterns of injury. Many of these patterns are apparent on imaging. Self-harm or suicidal intent may be overlooked initially in such cases, particularly when the patient is unconscious or uncooperative. Correct identification of these findings by the radiologist will allow a patient's management to be tailored accordingly and may prevent future suicide attempts. The initial role of the radiologists in these cases is to identify life-threatening injuries that require urgent medical attention. The radiologist can add value by drawing attention to associated injuries, which may have been missed on initial clinical assessment. In many cases of self-harm and suicide, imaging is more reliable than clinical assessment. The radiologist may be able to provide important prognostic information that allows clinicians to manage expectations and plan appropriately. Furthermore, some imaging studies will provide essential forensic information. Unfortunately, many cases of attempted suicide will end in brain death. The radiologist may have a role in these cases in identifying evidence of hypoxic-ischaemic brain injury, confirming a diagnosis of brain death through judicious use of ancillary tests and, finally, in donor screening for organ transplantation. A review is presented to illustrate the imaging features of self-harm, suicide, and brain death, and to highlight the important role of the radiologist in these cases.

Promoting the process of determining brain death through standardized training

Objective

This study aims to explore the training mode for brain death determination to ensure the quality of subsequent brain death determination.

Methods

A four-skill and four-step (FFT) training model was adopted, which included a clinical neurological examination, an electroencephalogram (EEG) examination, a short-latency somatosensory evoked potential (SLSEP) examination, and a transcranial Doppler (TCD) examination. Each skill is divided into four steps: multimedia theory teaching, bedside demonstration, one-on-one real or dummy simulation training, and assessment. The authors analyzed the training results of 1,577 professional and technical personnel who participated in the FFT training model from 2013 to 2020 (25 sessions), including error rate analysis of the written examination, knowledge gap analysis, and influencing factors analysis.

Results

The total error rates for all four written examination topics were < 5%, at 4.13% for SLSEP, 4.11% for EEG, 3.71% for TCD, and 3.65% for clinical evaluation. The knowledge gap analysis of the four-skill test papers suggested that the trainees had different knowledge gaps. Based on the univariate analysis and the multiple linear regression analysis, among the six factors, specialty categories, professional and technical titles, and hospital level were the independent influencing factors of answer errors (p < 0.01).

Conclusion

The FFT model is suitable for brain death (BD) determination training in China; however, the authors should pay attention to the professional characteristics of participants, strengthen the knowledge gap training, and strive to narrow the difference in training quality.

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.

Diagnostic accuracy of ancillary tests for death by neurologic criteria: a systematic review and meta-analysis

PURPOSE

Ancillary tests are frequently used in death determination by neurologic criteria (DNC), particularly when the clinical neurologic examination is unreliable. Nevertheless, their diagnostic accuracy has not been extensively studied. Our objective was to synthesize the sensitivity and specificity of commonly used ancillary tests for DNC.

SOURCE

We performed a systematic review and meta-analysis by searching MEDLINE, EMBASE, Cochrane databases, and CINAHL Ebsco from their inception to 4 February 2022. We selected cohort and case-control studies including patients with 1) clinically diagnosed death by neurologic criteria or 2) clinically suspected death by neurologic criteria who underwent ancillary testing for DNC. We excluded studies without a priori diagnostic criteria and studies conducted solely on pediatric patients. Accepted reference standards were clinical examination, four-vessel conventional angiography, and radionuclide imaging. Data were directly extracted from published reports. We assessed the methodological quality of studies with the QUADAS-2 tool and estimated ancillary test sensitivities and specificities using hierarchical Bayesian models with diffuse priors.

PRINCIPAL FINDINGS

Overall, 137 records met the selection criteria. One study (0.7%) had a low risk of bias in all QUADAS-2 domains. Among clinically diagnosed death by neurologic criteria patients (n = 8,891), ancillary tests had similar pooled sensitivities (range, 0.82-0.93). Sensitivity heterogeneity was greater within (σ = 0.10-0.15) than between (σ = 0.04) ancillary test types. Among clinically suspected death by neurologic criteria patients (n = 2,732), pooled ancillary test sensitivities ranged between 0.81 and 1.00 and specificities between 0.87 and 1.00. Most estimates had high statistical uncertainty.

CONCLUSION

Studies assessing ancillary test diagnostic accuracy have an unclear or high risk of bias. High-quality studies are required to thoroughly validate ancillary tests for DNC.

STUDY REGISTRATION

PROSPERO (CRD42013005907); registered 7 October 2013.

Transcranial Doppler Ultrasonography-Related Research in the Caribbean Region

Transcranial Doppler (TCD) ultrasonography is a non-invasive ultrasound technique that uses high-frequency sound waves to measure blood flow velocities in the cerebral vasculature. This review analyzes TCD research in the Caribbean region using a bibliometric analysis of 29 articles from PubMed. The articles were analyzed using Microsoft Excel 2016 and the VOSviewer software (Van Eck and Waltman, Leiden University, Centre for Science and Technology Studies (CWTS), www.vosviewer.com) and characterized various aspects of TCD research, including countries, research themes, authorship, journals, affiliations, and keywords. The majority of the 29 publications came from Cuba (38%), followed by the French West Indies (22%) and Jamaica (20%). Most TCD research focused on sickle cell disease (SCD), accounting for 45% of the studies, followed by 21% of articles on vasospasm and subarachnoid hemorrhage. The use of TCD in brain death and neuro-intensive care was also explored, constituting 17% of the studies. Alternative TCD-monitored treatment options for SCD, such as stem cell transplantation and hydroxyurea, were also frequently investigated. The most productive institutions were Hospital Clínico-Quirúrgico Hermanos Ameijeiras in Havana, Cuba, the Sickle Cell Unit at the University of West Indies (UWI) Mona in Jamaica, the Medical-Surgical Research Center (CIMEQ) in Havana, Cuba, and the SCD Reference Center in Guadeloupe and Martinique in the French West Indies. TCD has been identified as a cost-effective tool for real-time monitoring of cerebral blood flow in many clinical settings, including stroke and SCD, which are prevalent in the Caribbean. Although there is an increase in the trend of using TCD for neuromonitoring in the Caribbean, gaps still exist. Capacity-building initiatives, such as training programs for healthcare providers and the development of local TCD research networks, can improve access to TCD in resource-constrained settings to treat and neuromonitor patients cost-effectively.

Success Rate of Transcranial Doppler Scanning of Cerebral Arteries at Different Transtemporal Windows in Healthy Elderly Individuals

This study measured the rates of success in applying transcranial Doppler (TCD) scanning at the middle, posterior and anterior temporal windows (MTW, PTW and ATW) in the elderly. A hand-held 1.6-MHz pulsed-wave TCD transducer was used to search for cerebral arteries at MTW, PTW and ATW locations. Physical attributes of the head, including head circumference and the distance between tragi on both sides ("tragus-to-tragus arc length"), were also measured to explore the associations with successful rates. Among 396 healthy elderly participants (aged 62.6 ± 6.0 y, 140 men), 81.1% (n = 321; 127 men) had one or more temporal windows penetrable by TCD ultrasound (n = 286 [72.2%] at MTW, n = 195 [49.2%] at PTW and n = 106 [26.8%] at ATW). Regression analysis revealed that successful scanning increased significantly in male participants at three window locations. Younger age significantly increased successful scanning at the MTW and ATW. Smaller tragus-to-tragus arc length increased successful scanning at the MTW, but unsuccessful scanning at the ATW. Our findings support using MTW as the first location when positioning the TCD transducer for the scanning of cerebral arteries in the elderly population. When performing TCD scanning on two temporal windows, we propose choosing the MTW and PTW.

Exclusive color-coded duplex sonography of extracranial vessels reliably confirms brain death: A prospective study

Background

Transcranial color-coded duplex sonography (TCCD) can be used as an ancillary test for determining irreversible loss of brain function (ILBF) when demonstration of cerebral circulatory arrest (CCA) is required. However, visualization of the intracranial vessels by TCCD is often difficult, or even impossible, in this patient cohort due to elevated intracranial pressure, an insufficient transtemporal bone window, or warped anatomical conditions. Since extracranial color-coded duplex sonography (ECCD) can be performed without restriction in the aforementioned situations, we investigated the feasibility of omitting TCCD altogether, such that the ILBF examination would be simplified, without compromising on its reliability.

Methods

A total of 122 patients were prospectively examined by two experienced neurointensivists for the presence of ILBF from 01/2019-12/2021. Inclusion criteria were (i) the presence of a severe cerebral lesion on cranial CT or MRI, and (ii) brainstem areflexia. Upon standardized clinical examination, 9 patients were excluded due to incomplete brainstem areflexia, and a further 22 due to the presence of factors with a potentially confounding influence on apnea testing, EEG or sonography. A total of 91 patients were enrolled and underwent needle-EEG recording for >30 min (= gold standard), as well as ECCD and TCCD. The sonographer was blinded to the EEG result.

Results

All patients whose ECCD result was consistent with ILBF had this diagnosis confirmed by EEG (n = 77; specificity: 1). Both ECCD and EEG were not consistent with ILBF in a further 12 patients. In the remaining two patients, ECCD detected reperfusion due to long-lasting cerebral hypoxia; however, ILBF was ultimately confirmed by EEG (sensitivity: 0.975). This yielded a positive predictive value (PPV) of one and a negative predictive value of 0.857 for the validity of ECCD in ILBF confirmation. TCCD was not possible/inconclusive in 31 patients (34%).

Conclusions

The use of ECCD for the confirmation of ILBF is associated with high levels of specificity and a high positive predictive value when compared to needle-electrode EEG. This makes ECCD a potential alternative to the ancillary tests currently used in this setting, but confirmation in a multi-center trial is warranted.

Trial registration

https://www.drks.de, DRKS00017803.

Loss of cerebral blood flow and cerebral perfusion pressure in brain death: A transcranial Duplex ultrasonography study

PURPOSE

We investigated cerebral perfusion pressure (CPP) at the time loss of cerebral blood flow (CBF) occurred during brain death (BD). We hypothesized that a critical closing pressure (CrCP) may be reached before CPP drops to 0 mmHg.

MATERIALS AND METHODS

14 patients with increasing intracranial pressure (ICP) leading to BD were included. Transcranial Duplex (TCD) ultrasonography was used to investigate CBF. Starting at a CPP of 30 mmHg, TCD was repeated until waveforms indicated loss of CBF. We then analyzed CPP by the time TCD indicated absent CBF and clinical BD was established.

RESULTS

In 12 patients, CPP was positive when clinical BD was manifest and TCD illustrated absent CBF. Across all patients, mean CPP at clinical BD manifestation was 10.0 mmHg (range 0-20 mmHg); mean CPP by the time CBF stopped was 7.5 mmHg (0-20 mmHg). In four patients, clinical BD preceded loss of CBF. Here, the mean CPP difference from clinical BD to loss of CBF was 8.8 mmHg (5-15 mmHg).

CONCLUSIONS

CrCP may be reached although CPP is still positive, resulting in complete loss of CBF and BD. By including bedside TCD, neuromonitoring may contribute to early identification of patients at risk to experience loss of CBF and subsequent BD.

Sonografisches Neuromonitoring auf der Stroke Unit und in der neurologischen Intensivmedizin

Hintergrund Der Artikel gibt einen Überblick über die aktuellen diagnostischen Einsatzmöglichkeiten sonographischer Anwendung in der neurologischen Intensivmedizin.

Methoden Selektive Literaturrecherche mit kritischer Beurteilung ab dem Jahr 1984 sowie nationaler und internationaler Leitlinien sowie Expertenmeinung.

Ergebnisse Neben der raschen validen Abklärung akuter Schlaganfälle bieten verschiedene neurosonografische Monitoring-verfahren gerade in der Intensivmedizin spezifische Vorteile wie die beliebig häufige Wiederholbarkeit am Patientenbett selbst und die Darstellung in Echtzeit. Innovative Entwicklungen machen die Neurosonografie auch wissenschaftlich zu einem interessanten Gebiet.

Schlussfolgerung Die neurosonografische Diagnostik nimmt seit Jahren einen wichtigen Stellenwert in der neurologischen Intensivmedizin ein. Weitere Anstrengungen sind notwendig, um die Verbreitung der Methode zu fördern und durch wissenschaftliche Evidenz zu stärken.

Clinical applications of transcranial Doppler in non-trauma critically ill children: a scoping review

BACKGROUND

Many applications of transcranial Doppler (TCD) as a diagnosis or monitoring tool have raised interest in the last decades. It is important that clinicians know when and how to perform TCD in this population, what parameter to assess and monitor and how to interpret it.

OBJECTIVE

This review aims to describe the emerging clinical applications of TCD in critically ill children excluding those suffering from trauma.

METHODS

Databases Web of Science, Cochrane and PubMed were searched in May 2020. We considered all publications since the year 2000 addressing the use of TCD as a prognostic, diagnostic or follow-up tool in children aged 0 to 15 years admitted to intensive care or emergency units, excluding neonatology and traumatic brain injury. Two independent reviewers selected 82 abstracts and full-text articles from the 2011 unique citations identified at the outset.

RESULTS

TCD provides crucial additional information at bedside about cerebrovascular hemodynamics. Many clinical applications include the diagnosis and management of various medical and surgical neurologic conditions (central nervous system infections, arterial ischemic stroke, subarachnoid hemorrhage and vasospasm, brain death, seizures, metabolic disease, hydrocephalus) as well as monitoring the impact systemic conditions on brain perfusion (hemodynamic instability, circulatory assistance).

CONCLUSION

To conclude, TCD has become an invaluable asset for non-invasive neuromonitoring in critically ill children excluding those suffering from trauma. However, the scope of TCD remains unclearly defined yet and reference values in critically ill children are still lacking.

Brain death and management of the potential donor

One of the first attempts to define brain death (BD) dates from 1963, and since then, the diagnosis criteria of that entity have evolved. In spite of the publication of practice parameters and evidence-based guidelines, BD is still causing concern and controversies in the society. The difficulties in determining brain death and making it understood by family members not only endorse futile therapies and increase health care costs, but also hinder the organ transplantation process. This review aims to give an overview about the definition of BD, causes, physiopathology, diagnosis criteria, and management of the potential brain-dead donor. It is important to note that the BD determination criteria detailed here follow the AAN’s recommendations, but the standard practice for BD diagnosis varies from one country to another.

Transcranial Doppler: A Useful Tool to Predict Brain Death Still Not Confirmed by Clinical Assessment

BACKGROUND

Diagnosing brain death (BD) with accuracy and urgency is of great importance because an early diagnosis may guide the clinical management, optimize hospital beds, and facilitate organ transplantation. The clinical diagnosis of nonreactive and irreversible coma can be confirmed with additional tests. Among the complimentary exams that may testify brain circulatory arrest, transcranial Doppler (TCD) can be an option. It is a real-time, bedside, inexpensive, noninvasive method that assesses cerebral blood flow. In patients with suspected BD, especially those who are under sedative drugs, early diagnosis is imperative. The aim of the present study was to evaluate the role of TCD in predicting BD.

METHODS

One hundred consecutive comatose patients with a Glasgow Coma Scale score of less than 5, owing to different etiologies, were included. TCD was performed in all patients. The TCD operator was blinded for clinical and neurologic data. This study is in compliance with the Declaration of Helsinki.

RESULTS

Sixty-nine patients with TCD-brain circulatory collapse were diagnosed later with BD. Of the 31 patients with brain circulatory activity, 8 (25.8%) were clinically brain dead and 23 (74.2%) were alive. TCD showing brain circulatory collapse had a sensitivity of 89.6%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 74.2%.

CONCLUSION

TCD is highly specific (100%) and sensitive (89.6%) as a method to confirm the clinical diagnosis of BD, even in patients under sedation. The possibility of patients presenting with cerebral circulatory activity and clinical diagnosis of BD was demonstrated to occur.

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.

Transcranial Doppler Use in Non-traumatic Critically Ill Children: A Multicentre Descriptive Study

Background: The use and perceived value of transcranial Doppler (TCD) scope in paediatric critical care medicine has not been extensively documented. Objective: To describe the use of TCD to assess non-traumatic brain injury in patients admitted to four paediatric intensive care units (PICUs) in France. Methods: We prospectively included all children (aged under 18) assessed with inpatient TCD between November 2014 and October 2015 at one of the four PICUs. The physicians completed a questionnaire within 4 h of performing TCD. Results: 152 children were included. The primary diagnosis was neurological disease in 106 patients (70%), including post ischemic-anoxic brain insult (n = 42, 28%), status epilepticus (n = 19, 13%), and central nervous system infection/inflammation (n = 15, 10%). TCD was the first-line neuromonitoring assessment in 110 patients (72%) and was performed within 24 h of admission in 112 patients (74%). The most common indications for TCD were the routine monitoring of neurological disorders (n = 85, 56%) and the detection of asymptomatic neurological disorders (n = 37, 24). Concordance between the operator's interpretation of TCD and the published normative values was observed for 21 of the 75 (28%) TCD abnormal findings according to the published normative values. The physicians considered that TCD was of value for the ongoing clinical management of 131 (86%) of the 152 patients. Conclusion: TCD is commonly used in French PICUs and tends to be performed early after admission on patients with a broad range of diseases. The physicians reported that the TCD findings often helped their clinical decision making. In view of the subjectivity of bedside interpretation, true TCD contribution to clinical care remains to be determined. Objective studies of the impact of TCD on patient management and clinical outcomes are therefore warranted.

Retrospective analysis of the apnea test and ancillary test in determining brain death

Objective

We investigated the frequency of apnea tests, and the use of ancillary tests in the diagnosis of brain death in our hospital, as well as the reasons for not being able to perform apnea testing and the reasons for using ancillary tests.

Methods

In this retrospective study, the files of patients diagnosed with brain death between 2012 - 2018 were examined. The preferred test was determined if an ancillary test was performed in the diagnosis of brain death. The rate and frequency of use of these tests were analyzed.

Results

During the diagnosis of brain death, an apnea test was performed on 104 (61.5%) patients and was not or could not be performed on 65 (38.5%) patients. Ancillary tests were performed on 139 (82.8%) of the patients. The most common ancillary test was computed tomography angiography (79 patients, 46.7%). Approval for organ donation was received in the meetings with the family following the diagnosis of brain death for 55 (32.5%) of the 169 patients.

Conclusion

We found an increase in the rate of incomplete apnea tests and concordantly, an increase in the use of ancillary tests in recent years. Ancillary tests should be performed on patients when there is difficulty in reaching a decision of brain death, but it should not be forgotten that there is no worldwide consensus on the use of ancillary tests.

The Role of Transcranial Doppler Ultrasonography in the Diagnosis of Brain Death

Ancillary tests can be used for the diagnosis of brain death in cases wherein uncertainty exists regarding the neurological examination and apnoea test cannot be performed. Transcranial Doppler ultrasonography (TCD) is a useful, valid, non-invasive, portable, and repeatable ancillary test for the confirmation of brain death. Despite its varying sensitivity and specificity rates with regard to the diagnosis of the brain death, its clinical use has steadily increased in the intensive care unit because of its numerous superior properties. The use of TCD as an ancillary test for the diagnosis of brain death and cerebral circulatory arrest is discussed in the current review.

Death by neurologic criteria: pathophysiology, definition, diagnostic criteria and tests

Death by neurologic criteria is an irreversible sequence of events culminating in permanent cessation of cerebral functions. In this context, there are no responses arising from the brain, no cranial nerve reflexes nor motor responses to pain stimuli, and no respiratory drive. The diagnosis of death by neurologic criteria implies that there is clinical evidence of the complete and irreversible cessation of brainstem and cerebral functions. The diagnosis, confirmation, and certification of death are core skills for medical practitioners. The aim of this review is to discuss the pathophysiology and definition of death by neurological criteria, describing the clinical assessment, and the use of ancillary tests for the diagnosis of brainstem death.

Incorporation of Transcranial Doppler into the ED for the neurocritical care patient

INTRODUCTION

In the catastrophic neurologic emergency, a complete neurological exam is not always possible or feasible given the time-sensitive nature of the underlying disease process, or if emergent airway management is indicated. As the neurologic exam may be limited in some patients, the emergency physician is reliant on the assessment of brainstem structures to determine neurological function. Physicians thus routinely depend on advanced imaging modalities to further investigate for potential catastrophic diagnoses. Acquiring these tests introduces the risks of transport as well as delays in managing time-sensitive neurologic processes. A more immediate, non-invasive bedside approach complementing these modalities has evolved: Transcranial Doppler (TCD).

OBJECTIVE

This narrative review will provide a description of scenarios in which TCD may be applicable. It will summarize the sonographic findings and associated underlying pathophysiology in such neurocritical care patients. An illustrated tutorial, along with pearls and pitfalls, is provided.

DISCUSSION

Although there are numerous formalized TCD protocols utilizing four views (transtemporal, submandibular, suboccipital, and transorbital), point-of-care TCD is best accomplished through the transtemporal window. The core applications include the evaluation of midline shift, vasospasm after subarachnoid hemorrhage, acute ischemic stroke, and elevated intracranial pressure. An illustrative tutorial is provided.

CONCLUSIONS

With the wide dissemination of bedside ultrasound within the emergency department, there is a unique opportunity for the emergency physician to utilize TCD for a variety of conditions. While barriers to training exist, emergency physician performance of limited point-of-care TCD is feasible and may provide rapid and reliable clinical information with high temporal resolution.

Brain death

Declaration of brain death requires demonstration of irreversible injury to the whole brain including the brainstem. Current guidelines rely on bedside clinical examination to determine that the patient has irreversible coma, absent cranial nerve reflexes, and apnea. Neurophysiologic testing to support the clinical diagnosis of brain death has primarily consisted of EEG and evoked potentials-typically a combination of somatosensory evoked potential and brainstem auditory evoked potential. The diagnostic accuracy of these ancillary tests has been studied for the last few decades but the role of ancillary neurophysiologic testing in brain death continues to be a source of controversy. This chapter reviews the relevant studies and guidelines about EEG and evoked potentials in ancillary testing for brain death. Clinical scenarios in which neurophysiologic testing may aid the declaration of brain death include equivocal results of clinical examination findings, inability to perform some aspects of the neurologic examination, concern for residual sedative effects, suspected spinal cord or neuromuscular injury, and posterior fossa lesions with brainstem involvement. In these scenarios, EEG and evoked potentials may offer supportive evidence for irreversible injury to the whole brain. This chapter also discusses differences between current adult and pediatric guidelines for the role of ancillary testing in brain death.

Rapid Brain Death following Cardiac Arrest without Intracranial Pressure Rise and Cerebral Circulation Arrest

We describe here an unusual case of brain death following cardiac arrest. Brain electric activity had totally ceased, allowing the confirmation of brain death, despite normal cerebral blood flow (assessed by both transcranial doppler and tomodensitometry) and no evidence of intracranial hypertension. In our case, a residual electric activity was assessed at admission and lesions worsened on imaging during ICU stay, suggesting that part of the neuronal damage occurred after brain reperfusion. All these elements suggest BD rather by cellular toxicity than intracranial pressure elevation.

Point-of-care transcranial Doppler by intensivists

In the unconscious patient, there is a diagnostic void between the neurologic physical exam, and more invasive, costly and potentially harmful investigations. Transcranial color-coded sonography and two-dimensional transcranial Doppler imaging of the brain have the potential to be a middle ground to bridge this gap for certain diagnoses. With the increasing availability of point-of-care ultrasound devices, coupled with the need for rapid diagnosis of deteriorating neurologic patients, intensivists may be trained to perform point-of-care transcranial Doppler at the bedside. The feasibility and value of this technique in the intensive care unit to help rule-in specific intra-cranial pathologies will form the focus of this article. The proposed scope for point-of-care transcranial Doppler for the intensivist will be put forth and illustrated using four representative cases: presence of midline shift, vasospasm, raised intra-cranial pressure, and progression of cerebral circulatory arrest. We will review the technical details, including methods of image acquisition and interpretation. Common pitfalls and limitations of point-of-care transcranial Doppler will also be reviewed, as they must be understood for accurate diagnoses during interpretation, as well as the drawbacks and inadequacies of the modality in general.

Ancillary Studies in Evaluating Pediatric Brain Death

When confounding variables exist that inhibit the ability to diagnose brain death clinically in pediatric patients, ancillary tests may provide additional information for the practitioner in evaluating for the presence or absence of brain death. Multiple options exist but differ in availability, ease of administration, cost, safety profile, and reliability to accurately diagnose brain death. An important desirable quality of an ancillary test is eliminating false positives, which imply brain death when brain death is in fact not present. More commonly available ancillary studies include electroencephalograms, brain angiography through various modalities, brain stem auditory evoked potentials, and transcranial Doppler ultrasound. At this time, there is not an ancillary test with 100% reliability in diagnosing brain death that can replace the clinical brain death exam. Therefore, practitioners need to understand the strengths and limitations of the ancillary studies available at their hospital.

Doppler Ultrasonography of the Central Retinal Vessels in Children With Brain Death

OBJECTIVE

The purpose of this observational study is to explore if bedside Doppler ultrasonography of the central retinal vessels has the potential to become an ancillary study to support the timely diagnosis of brain death in children.

DESIGN

Seventeen-month prospective observational cohort.

SETTING

Forty-four bed pediatric medical and surgical ICU in an academic teaching hospital.

PATIENTS

All children 0-18 years old who were clinically evaluated for brain death at Children's National Health Systems were enrolled and followed until discharge or death.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients had at least one ophthalmic ultrasound within 30 minutes of each brain death examination. The central retinal artery peak systolic blood flow velocity, resistive index, pulsatility index, and Doppler waveforms were evaluated in each patient. Thirty-five ophthalmic ultrasounds were obtained on 13 patients, 3 months to 15 years old, who each had two clinical examinations consistent with brain death. The average systolic blood pressure during the ultrasound examinations was 102 mm Hg (± 28), diastolic blood pressure 65 mm Hg (± 24), mean arterial pressure 79 mm Hg (± 23), heart rate 133 beats/min (± 27), temperature 36°C (± 0.96), arterial CO2 35 mm Hg (± 9), and end-tidal CO2 23 mm Hg (± 6). For all examinations, the average peak systolic velocity of the central retinal artery was significantly decreased at 4.66 cm/s (± 3.2). Twelve of 13 patients had both resistive indexes greater than or equal to 1, average pulsatility indexes of 3.6 (± 3.5) with transcranial Doppler waveforms consistent with brain death. Waveform analysis of the 35 ultrasound examinations revealed 11% with tall systolic peaks without diastolic flow, 17% with oscillatory flow, 29% showed short systolic spikes, and 23% had no Doppler movement detected. A rippling "tardus-parvus" waveform was present in 20% of examinations.

CONCLUSION

This study supports that the combination of qualitative waveform analysis and quantitative blood flow variables of the central retinal vessels may have the potential to be developed as an ancillary study for supporting the diagnosis of brain death in children.

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.

Use of Transcranial Doppler for Management of Central Nervous System Infections in Critically Ill Children

BACKGROUND

The primary objective of this study was to characterize changes in cerebral blood flow measured using transcranial Doppler in children with central nervous system infections. We hypothesized that children with central nervous system infections have abnormal cerebral blood flow, associated with a greater frequency of complications and poor neurological outcome.

METHODS

We conducted a single-center, retrospective study of children admitted to the neonatal or pediatric intensive care unit with central nervous system infection and undergoing transcranial Doppler as part of routine care between March 2011 and July 2015.

RESULTS

A total of 20 children with central nervous system infection underwent 35 transcranial Dopplers. The mean age was 8.2 ± 6.3 years, including 12 boys and eight girls. The most common infection was meningitis (n = 11, 55%), with the remainder comprising encephalitis (15%), meningoencephalitis (20%), and abscess or empyema (10%). Bacterial (n = 10, 50%) and viral (n = 6) sources were common with only one (5%) fungal infection and three (15%) unknown but presumed viral etiology. The patients underwent transcranial Doppler 4 ± 9 days after intensive care unit admission. Mean cerebral blood flow velocities were overall increased compared with reference values for age (healthy children and critically ill children) mostly because of hyperemia (n = 21, 60%) and vasospasm (6%). Hypoperfusion (cerebral blood flow velocity <1 S.D. of normal value) in at least one vessel was associated with morbidity (intubation, vasoactive medications, neurosurgery, cardiac arrest) (P = 0.04) and mortality (P = 0.03). Two patients had increased intracranial pressure and hyperventilation was safely achieved with transcranial Doppler monitoring to avoid ischemia. Serial transcranial Dopplers were used to guide blood pressure management.

CONCLUSIONS

Transcranial Doppler can be used in children with central nervous system infection as a tool to assess cerebral blood flow. In this retrospective study, cerebral hypoperfusion was associated with increased morbidity and mortality. If transcranial Doppler is to guide medical therapy and management of cerebral blood flow in children with central nervous system infections, these results will need to be validated in prospective studies with a more homogenous population of children with encephalitis or meningitis.

Revised CT angiography venous score with consideration of infratentorial circulation value for diagnosing brain death

BACKGROUND

Computed tomography angiography (CTA) is largely performed in European countries as an ancillary test for diagnosing brain death. However, CTA suffers from a lack of sensitivity, especially in patients who have previously undergone decompressive craniectomy. The aim of this study was to assess the performance of a revised four-point venous CTA score, including non-opacification of the infratentorial venous circulation, for diagnosing brain death.

METHODS

A preliminary study of 43 control patients with normal CTAs confirmed that the infratentorial superior petrosal vein (SPV) was consistently visible. Therefore, 76 patients (including ten with decompressive craniectomy) who were investigated with 83 CTAs to confirm clinical brain death were consecutively enrolled between July 2011 and July 2013 at a university centre. The image analysis consisted of recording non-opacification of the cortical segment of the middle cerebral artery and internal cerebral vein (ICV), which were used as the reference CTA score, as well as non-opacification of the SPV. The diagnostic performance of the revised four-point venous CTA score based on the non-opacification of both the ICV and SPV was assessed and compared with that of the reference CTA score.

RESULTS

The revised four-point venous CTA score showed a sensitivity of 95 % for confirming clinical brain death versus a sensitivity of 88 % with the reference CTA score. Non-opacification of the SPV was observed in 95 % of the patients. In the decompressive craniectomy group, the revised four-point CTA score showed a sensitivity of 100 % compared with a sensitivity of 80 % using the reference CTA score.

CONCLUSION

Compared with the reference CTA score, the revised four-point venous CTA score based on ICV and SPV non-opacification showed superior diagnostic performance for confirming brain death, including for patients with decompressive craniectomy.

Transcranial Doppler ultrasonography: From methodology to major clinical applications

Non-invasive Doppler ultrasonographic study of cerebral arteries [transcranial Doppler (TCD)] has been extensively applied on both outpatient and inpatient settings. It is performed placing a low-frequency (≤ 2 MHz) transducer on the scalp of the patient over specific acoustic windows, in order to visualize the intracranial arterial vessels and to evaluate the cerebral blood flow velocity and its alteration in many different conditions. Nowadays the most widespread indication for TCD in outpatient setting is the research of right to left shunting, responsable of so called “paradoxical embolism”, most often due to patency of foramen ovale which is responsable of the majority of cryptogenic strokes occuring in patients younger than 55 years old. TCD also allows to classify the grade of severity of such shunts using the so called “microembolic signal grading score”. In addition TCD has found many useful applications in neurocritical care practice. It is useful on both adults and children for day-to-day bedside assessment of critical conditions including vasospasm in subarachnoidal haemorrhage (caused by aneurysm rupture or traumatic injury), traumatic brain injury, brain stem death. It is used also to evaluate cerebral hemodynamic changes after stroke. It also allows to investigate cerebral pressure autoregulation and for the clinical evaluation of cerebral autoregulatory reserve.

Use of Transcranial Doppler Ultrasound for Diagnosis of Brain Death in Patients with Severe Cerebral Injury

Background

The aim of this study was to investigate the use of transcranial Doppler (TCD) for diagnosis of brain death in patients with severe cerebral injury.

Material/Methods

This retrospective study enrolled 42 patients based on inclusion and exclusion criteria. All patients were divided into either the brain death group or the survival group according to prognosis. Blood flow of the brain was examined by TCD and analyzed for spectrum changes. The average blood flow velocity (Vm), pulse index (PI), and diastolic blood flow in reverse (RDF) were recorded and compared.

Results

The data demonstrated that the average speed of bilateral middle cerebral artery blood flow in the brain death group was significantly reduced (P<0.05). However, the PI of the brain death group increased significantly. Moreover, RDF spectrum and nail-like sharp peak spectrum of the brain death group was higher than in the survival group.

Conclusions

Due to its simplicity, high repeatability, and specificity, TCD combined with other methods is highly valuable for diagnosis of brain death in patients with severe brain injury.

Diagnostic Accuracy of Transcranial Doppler for Brain Death Confirmation: Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Transcranial Doppler is a useful ancillary test for brain death confirmation because it is safe, noninvasive, and done at the bedside. Transcranial Doppler confirms brain death by evaluating cerebral circulatory arrest. Case series studies have generally reported good correlations between transcranial Doppler confirmation of cerebral circulatory arrest and clinical confirmation of brain death. The purpose of this study is to evaluate the utility of transcranial Doppler as an ancillary test in brain death confirmation.

MATERIALS AND METHODS

We conducted a systematic review of the literature and a diagnostic test accuracy meta-analysis to compare the sensitivity and specificity of transcranial Doppler confirmation of cerebral circulatory arrest, by using clinical confirmation of brain death as the criterion standard.

RESULTS

We identified 22 eligible studies (1671 patients total), dating from 1987 to 2014. Pooled sensitivity and specificity estimates from 12 study protocols that reported data for the calculation of both values were 0.90 (95% CI, 0.87-0.92) and 0.98 (95% CI, 0.96-0.99), respectively. Between-study differences in the diagnostic performance of transcranial Doppler were found for both sensitivity (I(2) = 76%; P < .001) and specificity (I(2) = 74.3%; P < .001). The threshold effect was not significant (Spearman r = -0.173; P = .612). The area under the curve with the corresponding standard error (SE) was 0.964 ± 0.018, while index Q test ± SE was estimated at 0.910 ± 0.028.

CONCLUSIONS

The results of this meta-analysis suggest that transcranial Doppler is a highly accurate ancillary test for brain death confirmation. However, transcranial Doppler evaluates cerebral circulatory arrest rather than brain stem function, and this limitation needs to be taken into account when interpreting the results of this meta-analysis.

Latin American consensus on the use of transcranial Doppler in the diagnosis of brain death

Transcranial Doppler evaluates cerebral hemodynamics in patients with brain injury and is a useful technical tool in diagnosing cerebral circulatory arrest, usually present in the brain-dead patient. This Latin American Consensus was formed by a group of 26 physicians experienced in the use of transcranial Doppler in the context of brain death. The purpose of this agreement was to make recommendations regarding the indications, technique, and interpretation of the study of transcranial ultrasonography in patients with a clinical diagnosis of brain death or in the patient whose clinical diagnosis presents difficulties; a working group was formed to enable further knowledge and to strengthen ties between Latin American physicians working on the same topic. A review of the literature, concepts,and experiences were exchanged in two meetings and via the Internet. Questions about pathophysiology, equipment, techniques, findings, common problems, and the interpretation of transcranial Doppler in the context of brain death were answered. The basic consensus statements are the following: cerebral circulatory arrest is the final stage in the evolution of progressive intracranial hypertension, which is visualized with transcranial Doppler as a "pattern of cerebral circulatory arrest". The following are accepted as the standard of cerebral circulatory arrest: reverberant pattern, systolic spikes, and absence of previously demonstrated flow. Ultrasonography should be used - in acceptable hemodynamic conditions - in the anterior circulation bilaterally (middle cerebral artery) and in the posterior (basilar artery) territory. If no ultrasonographic images are found in any or all of these vessels, their proximal arteries are acceptable to be studied to look for a a pattern of cerebral circulatory arrest.

Transcranial Doppler Ultrasound: Physical Principles and Principal Applications in Neurocritical Care Unit

Transcranial Doppler (TCD) ultrasonography is a noninvasive ultrasound study, which has been extensively applied on both outpatient and inpatient settings. It involves the use of a low-frequency (≤2 MHz) transducer, placed on the scalp, to insonate the basal cerebral arteries through relatively thin bone windows and to measure the cerebral blood flow velocity and its alteration in many different conditions. In neurointensive care setting, TCD is useful for both adults and children for day-to-day bedside assessment of critical conditions including vasospasm in subarachnoid hemorrhage, traumatic brain injury, acute ischemic stroke, and brain stem death. It also allows to investigate the cerebrovascular autoregulation in setting of carotid disease and syncope. In this review, we will describe physical principles underlying TCD, flow indices most frequently used in clinical practice and critical care applications in Neurocritical Unit care.

A Review of the Effectiveness of Neuroimaging Modalities for the Detection of Traumatic Brain Injury

The incidence of traumatic brain injury (TBI) in the United States was 3.5 million cases in 2009, according to the Centers for Disease Control and Prevention. It is a contributing factor in 30.5% of injury-related deaths among civilians. Additionally, since 2000, more than 260,000 service members were diagnosed with TBI, with the vast majority classified as mild or concussive (76%). The objective assessment of TBI via imaging is a critical research gap, both in the military and civilian communities. In 2011, the Department of Defense (DoD) prepared a congressional report summarizing the effectiveness of seven neuroimaging modalities (computed tomography [CT], magnetic resonance imaging [MRI], transcranial Doppler [TCD], positron emission tomography, single photon emission computed tomography, electrophysiologic techniques [magnetoencephalography and electroencephalography], and functional near-infrared spectroscopy) to assess the spectrum of TBI from concussion to coma. For this report, neuroimaging experts identified the most relevant peer-reviewed publications and assessed the quality of the literature for each of these imaging technique in the clinical and research settings. Although CT, MRI, and TCD were determined to be the most useful modalities in the clinical setting, no single imaging modality proved sufficient for all patients due to the heterogeneity of TBI. All imaging modalities reviewed demonstrated the potential to emerge as part of future clinical care. This paper describes and updates the results of the DoD report and also expands on the use of angiography in patients with TBI.

Electrophysiologic Study of a Method of Euthanasia Using Intrathecal Lidocaine Hydrochloride Administered during Intravenous Anesthesia in Horses

Background

An intravenous (IV) overdose of pentobarbital sodium is the most commonly used method of euthanasia in veterinary medicine. However, this compound is not available in many countries or rural areas resulting in usage of alternative methods such as intrathecal lidocaine administration after IV anesthesia. Its safety and efficacy as a method of euthanasia have not been investigated in the horse.

Hypothesis/Objectives

To investigate changes in mean arterial blood pressure and electrical activity of the cerebral cortex, brainstem, and heart during intrathecal administration of lidocaine. Our hypothesis was that intrathecal lidocaine affects the cerebral cortex and brainstem before affecting cardiovascular function.

Animals

Eleven horses requiring euthanasia for medical reasons.

Methods

Prospective observational study. Horses were anesthetized with xylazine, midazolam, and ketamine; and instrumented for recording of electroencephalogram (EEG), electrooculogram (EOG), brainstem auditory evoked response (BAER), and electrocardiogram (ECG). Physical and neurological (brainstem reflexes) variables were monitored. Mean arterial blood pressure was recorded throughout the study.

Results

Loss of cerebro‐cortical electrical activity occurred up to 226 seconds after the end of the infusion of lidocaine solution. Cessation of brainstem function as evidenced by a lack of brainstem reflexes and disappearance of BAER occurred subsequently. Undetectable heart sounds, nonpalpable arterial pulse, and extremely low mean arterial blood pressure supported cardiac death; a recordable ECG was the last variable to disappear after the infusion (300–1,279 seconds).

Conclusions and Clinical Importance

Intrathecal administration of lidocaine is an effective alternative method of euthanasia in anesthetized horses, during which brain death occurs before cardiac death.

The use of transcranial Doppler ultrasound in confirming brain death in the setting of skull defects and extraventricular drains

BACKGROUND

Transcranial Doppler ultrasound (TCD) has been used as a confirmatory test for the diagnosis of brain death (BD), but may be inaccurate in patients with a skull defect or extraventricular drain (EVD).

METHODS AND RESULTS

We report three cases of patients with a skull defect or EVD in whom TCD supported a diagnosis of BD but in which the clinical examination later refuted the diagnosis.

CONCLUSION

We caution against the use of TCD to confirm the diagnosis of BD in the presence of a skull defect or EVD.

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.

Cerebral and brainstem electrophysiologic activity during euthanasia with pentobarbital sodium in horses

Background

An overdose of pentobarbital sodium administered IV is the most commonly used method of euthanasia in veterinary medicine. Determining death after the infusion relies on the observation of physical variables. However, it is unknown when cortical electrical activity and brainstem function are lost in a sequence of events before death.

Hypothesis/Objectives

To examine changes in the electrical activity of the cerebral cortex and brainstem during an overdose of pentobarbital sodium solution for euthanasia. Our testing hypothesis is that isoelectric pattern of the brain in support of brain death occurs before absence of electrocardiogram (ECG) activity.

Animals

Fifteen horses requiring euthanasia.

Methods

Prospective observational study. Horses with neurologic, orthopedic, and cardiac illnesses were selected and instrumented for recording of electroencephalogram, electrooculogram, brainstem auditory evoked response (BAER), and ECG. Physical and neurologic (brainstem reflexes) variables were monitored.

Results

Loss of cortical electrical activity occurred during or within 52 seconds after the infusion of euthanasia solution. Cessation of brainstem function as evidenced by a lack of brainstem reflexes and disappearance of the BAER happened subsequently. Despite undetectable heart sounds, palpable arterial pulse, and mean arterial pressure, recordable ECG was the last variable to be lost after the infusion (5.5–16 minutes after end of the infusion).

Conclusions and Clinical Importance

Overdose of pentobarbital sodium solution administered IV is an effective, fast, and humane method of euthanasia. Brain death occurs within 73–261 seconds of the infusion. Although absence of ECG activity takes longer to occur, brain death has already occurred.