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

Is a Second Transcranial Doppler Study Needed to Confirm Neurocirculatory Arrest?

BACKGROUND

In determining brain death, transcranial Doppler (TCD) is one of the recommended ancillary tests when clinical examinations and apnea tests are contraindicated. The American Academy of Neurology 2023 guideline updates and 2020 World Brain Death Project advise conducting two TCDs 30 min apart to diagnose neurocirculatory arrest. Our study aimed to evaluate whether a second TCD is necessary when the first TCD shows neurocirculatory arrest (no flow, oscillating flow, or systolic spikes).

METHODS

We conducted a single-center retrospective analysis of patients admitted to intensive care units from January 1, 2021, to February 1, 2025, at a community-based academic hospital. We included patients whose first study showed neurocirculatory arrest and who subsequently underwent a confirmatory TCD at least 30 min apart. A total of 48 patients were included in our final analysis. We compared the findings of the first TCD study with those of the second study and noted any differences.

RESULTS

In all 48 patients (100%), the second TCD confirmed the findings of the first TCD. Of these 48 patients, 44 patients (91.7%) had the same flow pattern on repeat TCD examination and 4 patients' (8.30%) TCDs showed different flow patterns, although still consistent with neurocirculatory arrest. Of the 44 patients with the same flow patterns found on first and repeat TCD examinations, 18 patients (40.9%) had both TCDs demonstrate brief systolic spikes; three patients (6.80%) had both TCDs demonstrate brief systolic spikes and oscillating flow; eight patients (18.2%) had both TCDs demonstrate no flow; seven patients (15.9%) had both TCDs demonstrate no flow and brief systolic spikes; one patient (2.30%) had both TCDs demonstrate no flow, brief systolic spikes, and oscillating flow; and, lastly, seven patients (15.9%) had both TCDs demonstrate oscillating flow.

CONCLUSIONS

We found that requiring two sequential TCD examinations to confirm neurocirculatory arrest may be unnecessary when the first TCD shows neurocirculatory arrest. Further investigation and studies such as ours in larger populations are warranted.

Technical Considerations in the TCD Evaluation of Cerebral Circulatory Arrest in Death by Neurological Criteria

BACKGROUND AND PURPOSE

Ancillary testing is essential for diagnosing brain death/death by neurologic criteria (BD/DNC) when clinical determination (neurologic exam and apnea testing) cannot be fully or safely performed. Transcranial Doppler ultrasound (TCD) has been recommended as an ancillary test; however, the technical descriptions have been heterogeneous. We aimed to consolidate the technical considerations related to the use of TCD as an ancillary test in the evaluation of BD/DNC.

METHODS

We performed a scoping review of the available literature from inception to December 2024. Articles describing TCD as an ancillary test for BD/DNC were included using appropriate Medical Subject Headings terms. The focus was on technical details and clinimetric properties of TCD (e.g., signal quality, frequency, gate, probe location, etc.). Technical categories were curated as full-text reviews were completed.

RESULTS

We reviewed 181 articles to extract technical descriptions of TCD under several categories. Image acquisition was divided into machine-related factors (59 studies, four questions), exam-related aspects (82 studies, 13 questions), and patient anatomical factors (19 studies, three questions). Image interpretation concerns were addressed in 50 studies (three questions). Patient-related clinical factors affecting TCD utility were addressed in 44 studies (seven questions). Legislative priorities were discussed in 19 studies; in 13 studies, authors commented on their recommendations for research priorities.

CONCLUSION

We found significant inconsistencies and a lack of technical details described in the literature. Next steps include a national survey of current TCD protocols for BD/DNC evaluation, and an expert consensus guidelines report on the technical use of TCD as an ancillary test.

Multi-Modal Assessment of Cerebral Hemodynamics in Resuscitated Out-of-Hospital Cardiac Arrest Patients: A Case-Series

We assessed the feasibility of concurrent monitoring of cerebral hemodynamics in adult, comatose out-of-hospital cardiac arrest (OHCA) patients admitted to the National University Heart Centre Singapore from October 2021 to August 2023. Patients underwent continuous near-infrared spectroscopy (NIRS) monitoring in the first 72 h after return of spontaneous circulation (ROSC) and 30-min transcranial Doppler ultrasound (TCD) monitoring at least once. With constant mechanical ventilatory settings and continuous electrocardiographic, pulse oximeter and end-tidal carbon dioxide monitoring, blood pressure was manipulated via vasopressors and cerebral autoregulation assessed by measuring changes in regional cerebral oxygenation (NIRS) and cerebral blood flow velocities (TCD) in response to changes in mean arterial pressure. The primary outcome was neurological recovery at hospital discharge. Amongst the first 16 patients (median age 61, 94% males), we observed four unique patterns: preserved cerebral autoregulation, loss of cerebral autoregulation, cardio-cerebral asynchrony and cerebral circulatory arrest. Patients with preserved cerebral autoregulation had lower levels of neuro-injury biomarkers (neurofilaments light and heavy) and the majority (86%) were discharged with good neurological recovery. Multi-modal assessment of cerebral hemodynamics after OHCA is feasible and derived patterns correlated with neurological outcomes. The between- and within-patient heterogeneity in cerebral hemodynamics calls for more research on individualized treatment strategies.

Monitoring of Neuroendocrine Changes in Acute Stage of Severe Craniocerebral Injury by Transcranial Doppler Ultrasound Image Features Based on Artificial Intelligence Algorithm

This study was aimed at exploring the application value of transcranial Doppler (TCD) based on artificial intelligence algorithm in monitoring the neuroendocrine changes in patients with severe head injury in the acute phase; 80 patients with severe brain injury were included in this study as the study subjects, and they were randomly divided into the control group (conventional TCD) and the experimental group (algorithm-optimized TCD), 40 patients in each group. An artificial intelligence neighborhood segmentation algorithm for TCD images was designed to comprehensively evaluate the application value of this algorithm by measuring the TCD image area segmentation error and running time of this algorithm. In addition, the Glasgow coma scale (GCS) and each neuroendocrine hormone level were used to assess the neuroendocrine status of the patients. The results showed that the running time of the artificial intelligence neighborhood segmentation algorithm for TCD was 3.14 ± 1.02 s, which was significantly shorter than 32.23 ± 9.56 s of traditional convolutional neural network (CNN) algorithms (P < 0.05). The false rejection rate (FRR) of TCD image area segmentation of this algorithm was significantly reduced, and the false acceptance rate (FAR) and true acceptance rate (TAR) were significantly increased (P < 0.05). The consistent rate of the GCS score and Doppler ultrasound imaging diagnosis results in the experimental group was 93.8%, which was significantly higher than the 80.3% in the control group (P < 0.05). The consistency rate of Doppler ultrasound imaging diagnosis results of patients in the experimental group with abnormal levels of follicle stimulating hormone (FSH), prolactin (PRL), growth hormone (GH), adrenocorticotropic hormone (ACTH), and thyroid stimulating hormone (TSH) was significantly higher than that of the control group (P < 0.05). In summary, the artificial intelligence neighborhood segmentation algorithm can significantly shorten the processing time of the TCD image and reduce the segmentation error of the image area, which significantly improves the monitoring level of TCD for patients with severe craniocerebral injury and has good clinical application value.

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.

Effects of one-lung flooding on porcine haemodynamics and gas exchange

Background and aim: We established a porcine model of one-lung flooding (OLF) that can be used for research on the use of ultrasound for lung tumour detection, ultrasound-guided transthoracic needle biopsy, and tumour ablation. However, OLF requires one-lung ventilation (OLV) and eliminates the recruitment strategies of the nonventilated lung. During thoracic surgery, OLV alone can be associated with hypoxia, hypercapnia, and right ventricular overload. Here, we examined whether OLF influences haemodynamics and gas exchange indices during and after OLV/OLF compared with OLV/apnoea and two-lung ventilation (TLV) following deflooding. Methods: Fourteen pigs were included in this study: five were allocated to the control group (CO) and nine were assigned to the OLF group (OLF). Assessments of haemodynamics, gas exchange, and lung sonography were performed after baseline measurements, during OLV/apnoea, OLV/OLF, and after deflooding and TLV. The volume of extravascular lung water was also measured. Results: OLF induced no significant deterioration of oxygenation or ventilation during OLF or after deflooding and TLV. Color-coded duplex sonography of the pulmonary artery in the flooded lung demonstrated an oscillating flow that corresponded to intrapulmonary circulatory arrest. After flooding of the nonventilated lung, the partial pressure of O₂ in the arterial blood increased and the shunt fraction decreased significantly compared to OLV/apnoea conditions. After deflooding and TLV, haemodynamics and gas exchange indices showed no differences compared to the CO group and baseline values, respectively. Conclusions: OLF is safe to use during acute animal experimentation. No clinically relevant deterioration of haemodynamics or gas exchange occurred during or after OLF. Due to the circulatory arrest in the flooded lung, the right-to-left shunt volume in the nonventilated lung was minimized. Survival experiments are necessary to further assess the utility of this method.

Confirmation of Brain Death with Positron Emission Tomography

After recent advances regarding organ transplantation, accurate and timely diagnosis of brain death has gained importance. In the diagnosis of brain death, in addition to clinical findings, various ancillary tests are very crucial. In this study, the scintigraphic imaging of the brain death of an 8-year-old girl with both Tc-99m diethylenetriaminepentaacetic and 18F-fluorodeoxyglucose (FDG) has been presented. This case study shows that 18F-FDG positron emission tomography-computed tomography imaging can be a useful technique in evaluating brain death in patients.

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.

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.