The role of transcranial Doppler in confirming brain death: sensitivity, specificity, and suggestions for performance and interpretation

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.

Transcranial Doppler ultrasound: Clinical applications from neurological to cardiological setting

Transcranial Doppler (TCD) ultrasonography is a rapid, noninvasive, real-time, and low-cost imaging technique. It is performed with a low-frequency (2 MHz) probe in order to evaluate the cerebral blood flow (CBF) and its pathological alterations, through specific acoustic windows. In the recent years, TCD use has been expanded across many clinical settings. Actually, the most widespread indication for TCD exam is represented by the diagnosis of paradoxical embolism, due to patent foramen ovale, in young patients with cryptogenic stroke. In addition, TCD has also found useful applications in neurological care setting, including the following: cerebral vasospasm following acute subarachnoid hemorrhage, brain trauma, cerebrovascular atherosclerosis, and evaluation of CBF and cerebral autoregulation after an ischemic stroke event. The present review aimed to describe the most recent evidences of TCD utilization from neurological to cardiological setting.

Comparison of early- and late-phase CT angiography findings in brain death

BACKGROUND

Late-phase images on computed tomography angiography (CTA), traditionally used for assessing cerebral circulatory arrest in brain death, suffer from suboptimal diagnostic yield due to stasis filling. Herein, we assessed contrast filling in individual intracranial arteries and veins in the early and late phases of CTA in patients with clinically confirmed brain death.

METHODS

Contrast opacification within 28 arterial/venous segments was evaluated in both phases of CTA in 79 patients. This information was combined with reports in the literature to calculate prevalence of contrast filling in different intracranial vessels. Additionally, diagnostic sensitivity of 4-point, 7-point, and 10-point scores defined for brain death were compared among ratings based on early, late, and both phases (arteries rated on early, veins rated on late phase) of imaging.

RESULTS

The median (IQR) number of vessel segments with contrast opacification was 0 (0-2) in early phase and 6 (0-10) in late phase. All segments showed increased prevalence of opacification when evaluated in late phase (p < 0.05). The M4 segments of MCA, internal cerebral veins, and vein of Galen had the lowest percentage of opacification in both phases. The sensitivity of 4-, 7-, and 10-point scoring algorithms increased from 59-91% to 94-99% when ratings were performed using early-phase images rather than based solely on late-phase images.

CONCLUSIONS

The incorporation of early-phase images might be considered as a strategy to improve the sensitivity of CTA as an ancillary test in confirming brain death, especially in patients without missing or questionable elements in clinical examination.

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.

Addressing a Diagnosis of Brain Death in Hypernatremia Situation

Hypernatremia and the state of plasma hypertonia are part of the alterations of insipid diabetes that are integrated to the brain death (BD) syndrome. Hypernatremia should be corrected as early as possible to make the clinical diagnosis of BD and to avoid its potential deleterious effect on the subsequent operation of the liver graft. Transcranial Doppler is a very valuable tool for the diagnosis of cerebral circulatory arrest associated with BD. The correction of natremia is made through the use of hypotonic solutions, and using of pyrogen-free distilled water intravenously in special cases, which controls the possibility of hemolysis in the donor. In our study, isolated severe hypernatremia corrected before ablation was not associated with liver graft failure in the recipient.

Transcranial doppler ultrasonography cerebral blood flow dynamics study of neurosurgical patients in peri-agonal period with fixed dilated or non-reacting pupils

INTRODUCTION

Fixed dilated and unreactive pupils are a harbinger of imminent death in neurosurgical patients, signifying that the brainstem is not functioning. Transcranial Doppler (TCD) ultrasonography is a noninvasive, bedside method of determining the flow velocities in the basal cerebral arteries, used extensively in various neurosurgical conditions.

AIMS AND OBJECTIVES

To study the cerebral blood flow dynamics of neurosurgical patients in peri-agonal period with fixed dilated or non reacting pupils using TCD.

MATERIALS AND METHODS

Repeated TCD studies were done in patients with fixed dilated or unreactive pupils in a tertiary care, neurosurgical hospital over a year, recording the various waveforms and indices as Pulsatility Index (PI), Resistivity Index, Peak systolic flow velocity (PSV), End diastolic flow velocity (EDV), Mean cerebral blood flow velocity (MCBFV) of their middle cerebral artery in their peri-agonal period. The subsequent change in the indices as the patients died or improved was analyzed.

RESULTS

A total of 104 TCD studies were done on 57 patients. Mean initial PI and MCBFV in the patients that died were 1.52 ± 0.76 and 28.55 ± 14.92 cm/sec respectively; and in the patients that showed neurosurgical recovery was 1.11 ± 0.28 and 36.52 ± 8.56 cm/sec respectively. Four out of 57 patients showed neurosurgical recovery and all of them had an initial PI less than 1.4 and they showed decrement in PI and increment in MCBFV on subsequent TCD study. The specificity and positive predictive value of the TCD waveform in predicting death was 100%, however, it had low sensitivity (47.17%) and negative predictive value (12.5%).

CONCLUSION

The various indices and waveforms of TCD can be useful in assessing the cerebral blood flow dynamics in patients with various traumatic and non-traumatic ailments in the peri-agonal period; and hence help in their management as well as in the confirmation of brainstem death.

Systodiastolic Separation Expresses Cerebral Circulatory Arrest?

There is a situation before the cerebral circulatory cessation phase, the systodiastolic separation in transcranial Doppler (TCD), which may raise doubts to the operator technician who performs it. A total of 266 studies were performed in 188 neurocritical patients over a 9-year period: 88 cases (77%) corresponded to cerebral circulatory arrest (CCA) which accompanies brain death (BD); 9 (5%) presented the systodiastolic separation pattern. In 1 of those 9 there was persistence of cough reflex and spontaneous breathing; in 5, CCA was not reached; only 3 evolved to CCA. The finding of a minimal persistent neurologic semiology is a categoric fact that would rule out the clinical correlation between this pattern and BD diagnosis.

Brain monitoring in severe head injury: a practical guide

There is, as yet, no specific therapy available for post-traumatic brain damage; the treatment of head injury is therefore aimed at limitation of secondary damage at the cellular, whole organ and systemic level.

The purpose of monitoring the injured brain is twofold:

1. to obtain a better understanding of the mechanisms by which pathophysiological processes further damage the injured brain

2. to continuously detect potentially harmful influences and allow them to be reversed before damage is done.

In this review, we provide a general overview of mechanisms of brain damage due to high intracranial pressure (ICP) and discuss the following ‘brain specific’ haemodynamic monitoring techniques:

• ICP/CPP (cerebral perfusion pressure) monitoring;

• jugular vein saturation (SjO2) monitoring;

• cerebral oxygen monitoring (PtiO2) and near infra-red spectroscopy (NIRS);

• brain temperature monitoring;

• cerebral blood flow (CBF) monitoring; and

• transcranial Doppler.

We also discuss the role of functional techniques such as electroencephalogram (EEG) and evoked potential monitoring. This article gives an overview of the techniques currently available in a rapidly expanding field within neuro-intensive care, mainly for the interest of trauma surgeons, intensivists, and others with a practical need to understand the monitoring of the injured brain.

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.

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.

A Review of Ancillary Tests in Evaluating Brain Death

The neurological determination of death (NDD) is primarily considered to be clinical. However, situations may arise where confounding factors make this clinical assessment difficult or impossible. As a result, ancillary tests have been developed in order to aid in the confirmation of brain death. As assessment of neuronal electrical activity; electroencephalography (EEG) is no longer recommended in this determination, tools assessing cerebral perfusion, as reflected by the presence or absence of cerebral blood flow (CBF), are the mainstay of NDD. The preferred ancillary test currently is Hexamethylpropylene amine oxime-single photon emission computed tomography (HMPAO SPECT) radionuclide angiography. When this is not available, or is equivocal, 4-vessel cerebral angiography can be used to determine the presence or absence of intracranial blood flow. However, as cerebral angiography has its own limitations, other techniques are sought by physicians in the Intensive Care and Neuro-intensive Care settings to replace cerebral angiography. In this article, we briefly review the history of diagnosis of brain death, pathophysiologic issues in making this determination, and currently available CBF imaging techniques, discussing each in turn with respect to their utility in the diagnosis of brain death.

Use of Transcranial Doppler (TCD) ultrasound in the Neurocritical Care Unit

Transcranial Doppler (TCD) is a portable device that uses a handheld 2-MHz transducer. It is most commonly used in subarachnoid hemorrhage where cerebral blood flow velocities in major intracranial blood vessels are measured to detect vasospasm in the first 2 to 3 weeks. TCD is used to detect vasospasm in traumatic brain injury and post-tumor resection, measurement of cerebral autoregulation and cerebrovascular reactivity, diagnosis of acute arterial occlusions in stroke, screening for patent foramen ovale and monitoring of emboli. It can be used to detect abnormally high intracranial pressure and for confirmation of total cerebral circulatory arrest in brain death.

Brazilian guidelines for the application of transcranial ultrasound as a diagnostic test for the confirmation of brain death

Neurosonological studies, specifically transcranial Doppler (TCD) and transcranial color-coded duplex (TCCD), have high level of specificity and sensitivity and they are used as complementary tests for the diagnosis of brain death (BD). A group of experts, from the Neurosonology Department of the Brazilian Academy of Neurology, created a task force to determine the criteria for the following aspects of diagnosing BD in Brazil: the reliability of TCD methodology; the reliability of TCCD methodology; neurosonology training and skills; the diagnosis of encephalic circulatory arrest; and exam documentation for BD. The results of this meeting are presented in the current paper.

Technical aids in the diagnosis of brain death: a comparison of SEP, AEP, EEG, TCD and CT angiography

BACKGROUND

The use of technical aids to confirm brain death is a controversial matter. Angiography with the intra-arterial administration of contrast medium is the international gold standard, but it is not allowed in Germany except in cases where it provides a potential mode of treatment. The currently approved tests in Germany are recordings of somatosensory evoked potentials (SSEP), brain perfusion scintigraphy, transcranial Doppler ultrasonography (TCD), and electroencephalography (EEG). CT angiography (CTA), a promising new alternative, is being increasingly used as well.

METHODS

In a prospective, single-center study that was carried out from 2008 to 2011, 71 consecutive patients in whom brain death was diagnosed on clinical grounds underwent recording of auditory evoked potentials (AEP) and SSEP as well as EEG, TCD and CTA.

RESULTS

The validity of CTA for the confirmation of brain death was 94%; the validity of the other tests was: 94% for EEG, 92% for TCD, 82% for SSEP, and 2% for AEP. In 61 of the 71 patients (86%), the EEG, TCD and CTA findings all accorded with the clinical diagnosis. The diagnosis of brain death was established beyond doubt in all patients.

CONCLUSION

In this study, the technical aids yielded discordant results in 14% of cases, necessitating interpretation by an expert examiner. The perfusion tests, in particular, can give false-positive results in patients with large cranial defects, skull fractures, or cerebrospinal fluid drainage. In such cases, electrophysiologic tests or a repeated clinical examination should be performed instead. CTA is a promising, highly reliable new method for demonstrating absent intracranial blood flow. In our view, it should be incorporated into the German guidelines for the diagnosis of brain death.

Clinical experience with transcranial Doppler ultrasonography as a confirmatory test for brain death: a retrospective analysis

BACKGROUND

Transcranial Doppler (TCD) ultrasonography to demonstrate cerebral circulatory arrest (CCA) is a confirmatory test for brain death (BD). The primary aim of this retrospective study was to evaluate the practical utility of TCD to confirm BD when clinical diagnosis was not feasible due to confounding factors. Secondary aims were to evaluate the reasons for inability of TCD to confirm BD and to assess the outcome of patients not brain dead according to the TCD criteria.

METHODS

TCD waveforms and medical records of all the patients examined to confirm suspected BD between 2001 and 2007, where clinical diagnosis was not possible, were analyzed. BD was diagnosed based on CCA criteria recommended by the Task Force Group on cerebral death of the Neurosonology Research Group of the World Federation of Neurology. Final outcome of patients and the use of other ancillary tests were noted.

RESULTS

Ninety patients (61 males), aged 40 ± 21 (range 3-84) years underwent TCD examination for confirmation of suspected BD. TCD confirmed BD in 51 (57%) patients and was inconclusive in 38 (43%), with no flow signals on the first examination in 7 (8%) patients and the waveform patterns in 31 (35%) being inconsistent with BD. Fourteen of the 19 patients who had CCA pattern in at least one artery but did not meet all the criteria for BD were subsequently found brain dead according to SPECT/clinical criteria or suffered cardiovascular death.

CONCLUSION

Using the conventional criteria, TCD confirmed BD in a large proportion, of patients where clinical diagnosis could not be made. The presence of CCA pattern in one or more major cerebral artery may be prognostic of unfavorable outcome, even when BD criteria are not satisfied.

Diffusion-weighted imaging findings in brain death

INTRODUCTION

The purpose of the present study was to determine the role of diffusion-weighted imaging (DWI) and to investigate the use of DWI in the diagnosis of brain death (BD).

METHODS

We prospectively evaluated 22 patients diagnosed with clinical BD (9 women, 13 men; mean age, 39.63 ± 15.1 years; age range, 9-66 years). All clinical criteria for BD were present in all 22 patients before magnetic resonance imaging, including a positive apnea test. For all cases, DW images, T2-weighted images, and fluid-attenuated inversion recovery were obtained. Thirteen distinct neuroanatomical structures were selected for analysis in all the cases. For each region of interest, the mean, standard deviation, and range of the average apparent diffusion coefficient (ADCav) values were obtained.

RESULTS

For BD patients, ADC values in all neuroanatomical structures were significantly lower than those for control subjects. We determined how ADC values in all structures were related to the diagnostic condition as well as the appropriate threshold ADC values to classify a subject as BD or control. The sensitivity, specificity, positive and negative predictive values, and correct classification rate of ADC cutoff values to distinguish BD from control groups were 100%.

CONCLUSIONS

DWI might be used as a noninvasive confirmatory test for the diagnosis of BD in the future.

The value of transcranial Doppler sonography with a transorbital approach in the confirmation of cerebral circulatory arrest

OBJECTIVE

Transcranial Doppler sonography (TCD) provides accurate confirmation of cerebral circulatory arrest (CCA) in brain death (BD), but is not feasible in patients with absent temporal bone windows. We added the transorbital approach in the TCD protocol for the diagnosis of CCA and compared findings with angiography. Furthermore, we evaluated whether reporting the angiographic and sonographic confirmation of CCA to relatives of brain-dead patients improves their comprehension and satisfaction with the medical information.

PATIENTS AND METHODS

Eighty-two clinically brain-dead patients underwent 4-vessel angiography, TCD of the basilar and middle cerebral arteries, and transorbital Doppler sonography (TOD) of the internal carotid arteries. Relatives were randomly allocated to 41 in whom BD was presented as a clinical diagnosis (group A) and to 41 in whom BD was presented as a clinical diagnosis confirmed by TCD and angiography (group B). Comprehension and satisfaction of the relatives were assessed using an interview and a questionnaire.

RESULTS

Both angiography and TCD verified CCA in all cases (k = 1). In 11 patients with failure of the transtemporal approach, CCA was confirmed by the transorbital recordings. The addition of TOD enabled 15.5% more cases of CCA to be diagnosed by TCD. Group B exhibited improved comprehension and satisfaction rates (P < .05).

CONCLUSIONS

The addition of TOD increases the efficacy of TCD in confirming CCA in BD. Reporting confirmation of CCA to families of brain-dead patients may improve their comprehension and satisfaction with the provided medical information.

Selective 4 vessels angiography in brain death: a retrospective study

BACKGROUND

In Canada, ancillary tests, such as selective four vessels angiography (S4VA), are sometimes necessary for brain death (BD) diagnosis when the clinical exam cannot be completed or confounding factors are present. Recent Canadian guidelines assert that brain death is supported by the absence of arterial blood flow at the surface of the brain and that venous return should not be considered. However, neuropathologic and angiographic studies have suggested that arteries might still be patent in BD patients. Current clinical practices in BD diagnosis following S4VA need to be better understood.

METHODS

We conducted a retrospective study of all S4VA performed for the determination of BD in a level 1 NeuroTrauma centre from 2003 to 2007. The objective of the study was to describe the prevalence of intracranial arterial, capillary (parenchymogram) and venous opacification in our study population. All tests were reviewed independently by two neuroradiologists. Disagreements were resolved by consensus.

RESULTS

Thirty two patients were declared BD following S4VA during the study period. Nine of these patients (28%) presented some proximal opacification of intracranial arteries (95% CI 15-45%). As opposed, none had a cerebral capillary and deep venous drainage opacification (95% CI 0-10%).

CONCLUSION

The absence of cerebral deep venous drainage or parenchymogram might represent a better objective marker of cerebral circulatory arrest for brain death diagnosis when the use of S4VA is required. These findings open the path for further research in enhancing our interpretation of angiographic studies for brain death diagnosis.

The relevance of early TCD monitoring in the intensive care units for the confirming of brain death diagnosis

Brain death (BD) diagnosis is the clinical assessment of the irreversible loss of function of the entire brain, including the brainstem. Transcranial Doppler (TCD) examination is used in several countries as a confirmatory test to assess cerebral circulatory arrest (CCA). A total of 1,400 TCD examinations were performed in 623 patients (pts) admitted to intensive care units (ICUs) of our hospital during the last 6 years. Oscillating flow, systolic spikes and the absence of any TCD signal were considered as diagnostic patterns of irreversible CCA. TCD patterns of CCA were detected in 56 pts. In 25 pts, deeply sedated with barbiturate therapy, TCD was employed as confirmatory test for BD diagnosis and 14 of them could become organ and/or tissue donors. TCD is a safe and inexpensive tool that can be performed at the bedside, and it allows to shorten the diagnostic process of BD, which is the prerequisite for organ donation.

Transcranial Doppler ultrasonography in the assessment of cerebral circulation arrest: improving sensitivity by transcervical and transorbital carotid insonation and serial examinations

INTRODUCTION

Transcranial Doppler (TCD) can detect the cerebral circulation arrest (CCA) in brain death. TCD is highly specific, but less sensitive because of false-negatives accounting for up to 10%. The aim of the study was to explore the diagnostic accuracy of TCD and to determine whether it can be augmented by strategies such as the insonation of the extracranial internal carotid artery (ICA) and sequential examinations.

METHODS

Data of 184 patients, who met clinical criteria of brain death, observed from 1998 through 2006, were retrospectively reviewed. The study of cerebral arteries was performed through the transtemporal approach, suboccipital insonation of the vertebro-basilar system, transorbital insonation of the ICA and ophthalmic artery, and transcervical insonation of the extracranial ICA. Repeated exams were performed in cases of persistent diastolic flow.

RESULTS

The specificity of the testing was 100%, no false-positive cases were recorded. The sensitivity of conventional TCD examination was 82.1%. The insonation of the extracranial ICA increased sensitivity to 88% allowing the detection of CCA in those patients lacking temporal windows; serial examinations further increased sensitivity to 95.6%.

CONCLUSIONS

The addition of insonation of the cervical ICA and of the siphon increased sensitivity of TCD. Nevertheless, a CCA flow patterns may appear later on those segments. Serial examinations, may be needed in those cases.

Transcranial Doppler for evaluation of idiopathic intracranial hypertension

OBJECTIVES

The value of transcranial Doppler (TCD) ultrasonography in assessing patients with Idiopathic Intracranial Hypertension (IIH) is uncertain. We sought to determine the contribution of TCD to their evaluation.

MATERIALS AND METHODS

Twenty-three patients with suspected IIH underwent TCD. Mean blood flow (BFV), peak systolic (PSV) and end-diastolic (EDV) velocities, and pulsatility (PI) and resistance (RI) indexes were obtained in the middle cerebral (MCA) and vertebral (VA) arteries and compared (Student's t-test) between patients with confirmed IIH and controls. IIH patients and controls were comparable in terms of age, gender and weight.

RESULTS

The mean +/- SD BFV(MCA), PSV(MCA), EDV(MCA) and PI(VA) in the 13 IIH patients were higher than in the ten controls (59 +/- 6.8, 94 +/- 28.5, 43 +/- 12.4, 0.86 +/- 0.16 and 50 +/- 8.6, 72 +/- 25.8, 32 +/- 11.5, 0.58 +/- 0.45 respectively, P < 0.05) but still within normal values. The mean +/- SD PI(MCA), RI(MCA) and RI(VA) values in the IIH patients and controls were similar.

CONCLUSIONS

TCD parameters had no useful unique features for monitoring IIH patients.

Kidney grafts from brain dead donors: Inferior quality or opportunity for improvement?

Major improvements in immunosuppressive treatment, surgical techniques, and treatment of post-transplant complications have contributed considerably to improved outcome in renal transplantation over the past decades. Yet, these accomplishments have not led to similar improvements in transplant outcome when the results of living and deceased donors are compared. The enormous demand for donor kidneys has allowed for the increase in acceptance of suboptimal donors. The use of brain dead patients as organ donors has had a tremendous positive influence on the number of renal transplants. Unfortunately, the physiologically abnormal state of brain death has a negative effect on transplant outcome. The fact that transplanted kidneys derived from brain dead donors have a decreased viability indicates that potential grafts are already damaged before retrieval and preservation. In this review, we present an overview of the current knowledge of (patho)-physiological effects of brain death and its relevance for renal transplant outcome. In addition, several options for therapeutic intervention during brain death in the donor with the goal to improve organ viability and transplant outcome are discussed.

Brain Death and Withdrawal of Support

The definition of death has evolved to include the concept of brain death. The brainstem is an indispensable central integrative unit for all vital functions. The clinical criteria for brain death consist of the demonstration of the absence of function of the brainstem. Confirmatory testing, which mostly evaluates higher clinical function, is usually not required for the diagnosis of brain death.

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

OBJECTIVE

Barbiturate therapy or hypothermia precludes proper diagnosis of brain death either clinically or by EEG. Specific intracranial flow patterns indicating cerebral circulatory arrest (CCA) can be visualized by transcranial Doppler ultrasonography (TCD). The aim of this study was to assess the validity of TCD in confirming brain death.

DESIGN

Meta-analysis of studies assessing the validity of TCD in confirming brain death.

METHODS

A systematic review of articles in English on the diagnosis brain death by TCD, published between 1980 and 2004, was performed. An oscillating or reverberating flow and systolic spikes were considered to be compatible with CCA. The quality of each study was assessed using standardized methodological criteria. The literature was searched for any article reporting a false-positive result.

RESULTS

Two high-quality and eight low-quality studies were included. Meta-analysis of the two high-quality studies showed a sensitivity of 95% (95% CI 92-97%) and a specificity of 99% (95% CI 97-100%) to detect brain death. Meta-analysis of all ten studies showed a sensitivity of 89% and a specificity of 99%. In the literature we found two false-positive results; however, in both patients brain-stem function did show brain death shortly thereafter.

CONCLUSIONS

CCA by TCD in the anterior and posterior circulation predicted fatal brain damage in all patients; therefore, TCD can be used to determine the appropriate moment for angiography. Further research is needed to demonstrate that CCA by TCD on repeated examination can also predict brain death in all patients.

Comparison between transcranial color Doppler ultrasonography and angiography in the confirmation of brain death

OBJECTIVE

Cerebral blood flow tests have increasingly been advocated for the confirmation of brain death (BD). Angiography has been considered the gold standard in the diagnosis of BD but is invasive. We validated transcranial color Doppler ultrasonography (TCD) to confirm BD by comparing it to angiography.

PATIENTS AND METHODS

Forty patients experienced the clinical diagnosis of brain death due to head injury in 19 cases (47.5%), cerebral hemorrhage in 11 (27.5%), subarachnoid hemorrhage in 7 (17.5%), and cerebral infarction in 3 (7.5%). Blood pressure, heart rate, SPO2, and PCO2 were monitored throughout the study. Patients were excluded if episodes of hypoxia, arrhythmia, and hypotension occurred during examinations, or if the TCD was not technically feasible.

RESULTS

Both angiography and TCD confirmed BD in all patients. The agreement between the above methods to confirm BD was 100%. Angiography showed the absence of filling of intracranial arteries, while TCD revealed: (1) brief systolic forward flow or systolic spikes and diastolic reversed flow (50%); (2) brief systolic forward flow or systolic spikes and no diastolic flow (25%); (3) no demonstrable flow in a patient in whom flow had been clearly documented on a previous TCD examination (12.5%). Five patients required repeated TCD examinations, because of initial detection of a diastolic to-and-fro flow pattern. BD was confirmed by TCD in the above patients after 30 hours of clinical BD.

CONCLUSION

TCD was a sensitive tool to diagnose BD, affording a reliable alternative examination to standard angiography.

Sensitivity of transcranial Doppler for confirming brain death: a prospective study of 270 cases

OBJECTIVE

The reported sensitivity of transcranial Doppler ultrasonography (TCD) for confirming brain death (BD) ranges from 91% to 100%. We assessed the frequency and causes of false-negative results in TCD examination in a series of patients with BD and in the literature.

METHODS

We carried out a prospective TCD examination of consecutive patients with the clinical diagnosis of BD.

RESULTS

In 204 (75.5%) of 270 patients, TCD showed a pattern compatible with BD. The causes of the false-negative results were persistent flow in the intracranial arteries in 47 (17.4%) patients and a lack of signal in 19 (7%). Absence of sympathomimetic drug use [odds ratio (OR) 5.4, 95% confidence interval (CI) 1.8-16.0, P = 0.003) and female gender (OR 3.7, 95% CI 1.1-12.5, P = 0.03) were associated with false-negative results. A review of 16 studies showed a sensitivity of 88% and a specificity of 98% of TCD for confirming BD.

CONCLUSIONS

The sensitivity of TCD for confirming BD may be lower than previously reported, but is probably similar to that of other non-invasive methods. The specificity of TCD is close to 100%. Uniform criteria are needed for the routine use of TCD as a confirmatory test for BD.

Time dependent validity in the diagnosis of brain death using transcranial Doppler sonography

OBJECTIVE

To evaluate the validity of transcranial Doppler (TCD) in confirming brain death from various pathological conditions.

METHODS

An observational case-control study over a 2.5 year period, in which transcranial Doppler (TCD) examinations were done on 101 comatose patients for confirmation of brain death. Between October 2002 to May 2005, 44 clinically diagnosed brain death cases (29 male, 15 female; mean (SD) age, 46.5 (19.5) years; Glasgow Coma Scale (GCS) score, 3.0 (0.0)) and 57 controls (36 male, 21 female; age 48.1 (16.5) years; mean GCS, 4.9 (1.7)) were examined. Reverse diastolic flow, very small systolic spikes, or no signals were considered characteristic of cerebral circulatory arrest.

RESULTS

The sensitivity and specificity of TCD examination of both the basilar artery and the middle cerebral arteries (MCAs) in confirming brain death were 77.2% and 100%, respectively. The sensitivity of TCD-diagnosed brain death increased with elapsed time. There was a trend for the basilar artery to have greater sensitivity (86.4% v 77.2%), higher positive predictive value (90.5% v 85.1%), and fewer false negatives (14% v 23.7%) than the MCAs for diagnosing brain death (all NS). The consistency of the basilar artery and the MCAs for diagnosing brain death was significant (kappa=0.877, p<0.001 and kappa=0.793, p<0.001, respectively).

CONCLUSIONS

TCD can be a confirmatory tool for diagnosing brain death. The validity of TCD diagnosed brain death depends on the time lapse between brain death and the performance of TCD. TCD of both the basilar artery and the MCAs showed significant consistency in brain death diagnosis.

Confirmatory tests in the diagnosis of brain death: Comparison between SPECT and contrast angiography

OBJECTIVE

Cerebral blood flow tests have increasingly been advocated for the confirmation of brain death (BD). Four-vessel angiography has been considered the most reliable investigation in the diagnosis of BD for >30 yrs, but it is invasive. (99m)Tc-HMPAO SPECT provides noninvasive, multiplanar imaging of brain tissue perfusion. The aim of this study was to check the reliability of SPECT compared with contrast angiography.

DESIGN

Prospective, blind study.

SETTING

Neurointensive care unit of a university hospital.

PATIENTS

Consecutive clinically brain dead patients with flat electroencephalogram.

INTERVENTIONS

BD was diagnosed according to Italian law. (99m)Tc-HMPAO SPECT and four-vessel angiography were performed in the same session; the rater of each investigation ignored the results of the other. Blood pressure, Sp(O2), and P(ECO2) were monitored throughout the study: any episode of hypoxia or hypotension caused exclusion of the patient from the study.

MEASUREMENTS AND MAIN RESULTS

Twenty brain dead patients were enrolled. The cause of BD was head injury in seven cases (35%), subarachnoid hemorrhage in seven (30%), spontaneous hemorrhage in one (10%), brain tumors in two (10%), stroke in two (10%), and thrombosis of the sagittal sinus in one (5%). Both angiography and SPECT confirmed BD in 19 of 20 patients: angiography showed the absence of filling of intracranial arteries, while SPECT showed a picture of "empty skull." For the remaining patient, angiography showed slight and late filling of left vertebral, basilar, and posterior cerebral arteries, while SPECT showed faint traces of uptake in the posterior fossa on the right side and on the midline. For this patient, the tests were repeated 48 hrs later, and both showed the arrest of intracranial circulation, thus confirming BD.

CONCLUSIONS

Our results confirm the reliability of SPECT in the diagnosis of BD; because SPECT is noninvasive, it is a good candidate for the "gold standard" of diagnosis.

Volume Measurement of Cerebral Blood Flow: Assessment of Cerebral Circulatory Arrest

BACKGROUND

Cerebral blood flow (CBF) volume can be measured at bedside by color duplex flowmetry of the extracranial cerebral arteries. In neurointensive care patients, we prospectively tested the hypothesis that a CBF volume <100 ml/min indicates imminent cerebral circulatory arrest.

METHODS

CBF volume was determined as sum of flow volumes in the internal carotid and vertebral arteries of both sides. In 192 neurointensive care patients, 829 measurements were taken. When CBF volume fell short of 100 ml/min, common carotid and external carotid artery flow volumes were also measured, and transcranial color-coded duplex sonography (TCCD) of basal cerebral arteries was performed. Results were compared with actual clinical conditions, outcome, and previously published reference data.

RESULTS

All 41 patients with CBF volume <100 ml/min (range, 0-89 ml/min) were officially declared brain dead 2-126 hours after the measurement (median, 23 hours). TCCD revealed signs of cerebral circulatory arrest in all patients with a patent acoustic bone window. External carotid artery flow volumes were normal. The lowest CBF volume rate recorded in a surviving patient was 208 ml/min.

CONCLUSIONS

Early confirmation of cerebral circulatory arrest is of decisive importance if the patient is a potential organ donor. CBF volume measurement allows confirming the arrest of cerebral circulation even in patients without a patent acoustic bone window for TCCD. Because the critical lower threshold for survival appears to lie at 200 ml/min, bedside monitoring of CBF volume in neurointensive care patients may indicate a therapeutic window before irreversible circulatory arrest occurs.

Difficulties in assessing brain death in a case of benzodiazepine poisoning with persistent cerebral blood flow

Assessing brain death may sometimes be difficult, with isoelectric EEG following psychotrope overdoses or normal cerebral blood flow (CBF) persisting despite brain death in the case of ventricular drainage or craniotomy. A 42-year-old man, resuscitated after cardiac arrest following a suicidal ingestion of ethanol, bromazepam and zopiclone, was admitted in deep coma. On day 4, his brainstem reflexes and EEG activity disappeared. On day 5, his serum bromazepam concentration was 817 ng/ml (therapeutic: 80-150). The patient was unresponsive to 1 mg of flumazenil. MRI showed diffuse cerebral swelling. CBF assessed by angiography and Doppler remained normal and EEG isoelectric until he died on day 8 with multiorgan failure. There was a discrepancy between the clinically and EEG-assessed brain death, and CBF persistence. We hypothesized that brain death, resulting from diffuse anoxic injury, may lead, in the absence of major intracranial hypertension, to angiographic misdiagnoses. Therefore, EEG remains useful to assess diagnosis in such unusual cases.

Cadaveric donors

The diagnosis of brain death describes the final catastrophic state of a person for whom, except for ventilators and pharmacology, death would surely have already intervened. Although we think of death as an ending, if the patient becomes an organ donor it is also a beginning. For, at the moment we lose one patient, we potentially gain others in the fortunate recipients of viable grafts.

Difficulty in brainstem death testing in the presence of high spinal cord injury

In the UK, when the standard brain death criteria are met, further investigations are not necessary. Confirmatory tests can be useful, however, when it is not possible to carry out all of the brainstem tests. We report the case of a patient with multiple trauma and a high spinal cord injury who was apnoeic. Confirmatory tests (EEG, brainstem, auditory evoked potential) were essential in supporting the diagnosis of brainstem death to allow withdrawal of artificial ventilation, as organ donation was being considered.

Utility of transcranial doppler ultrasonography for confirmatory diagnosis of brain death: two sides of the coin

BACKGROUND

Although the clinical examination and documentation of the clinical signs of brain death are very uniform, there are significant differences in the guidelines for using technical confirmatory tests to corroborate the clinical signs. The current study examined the utility of transcranial Doppler ultrasonography (TCD) for confirmation of brain death.

METHODS

After 19 patients were excluded from the study because of lack of bone window or because an apnea test could not be performed because of desaturation, 100 patients (61 patients with clinical brain death, and 39 control patients with Glasgow Coma Score<5) were included in the study. The following TCD findings were accepted as confirmatory of brain death when they were found bilaterally or in at least three different arteries for at least 3 minutes within the same examination: (1) brief systolic forward flow or systolic spikes and diastolic reverse flow, (2) brief systolic forward flow or systolic spikes and no diastolic flow, or (3) no demonstrable flow in a patient in whom flow had been clearly documented in a previous TCD examination.

RESULTS

The sensitivity and specificity of the first TCD examination for confirmation of brain death were 70.5% and 97.4%, respectively. Eighteen patients with clinical brain death required repeat TCD examinations because of detection of forward systolo-diastolic flow or a diastolic to-and-fro flow pattern, which were not confirmatory for the diagnosis of brain death. Brain death was confirmed ultrasonographically in 12 of 18 patients in a second examination after 12.6 +/- 8.3 hours of clinical brain death, in 2 patients in a third TCD examination, and in 1 patient in a fourth examination. Three clinically brain-dead patients had died before the diagnosis was confirmed by repeat TCD examinations. The sensitivity of TCD reached 100% in our study population after the fourth examination.

CONCLUSION

The sensitivity of TCD is increased with repeat examinations and should be repeated in cases in which systolo-diastolic forward flow is demonstrated after the first TCD. TCD may prolong or shorten the time to declaration of brain death. The necessity of demonstrating cerebral circulatory arrest in patients with clinical brain death is debatable.