Transcranial Doppler and brain death

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).

Computed tomography angiography in the diagnosis of brain death: Implementation and results in Germany

BACKGROUND

Computed tomography angiography (CTA) has been investigated as a confirmatory study (CS) for the diagnosis of brain death (BD). International consensus regarding its use, study parameters, and evaluation criteria is lacking. In the German BD guideline, a CTA protocol was first introduced in 2015.

METHODS

The authors obtained a comprehensive dataset of all BD examinations in adults from the German organ procurement organization to investigate implementation, results, and impact of CTA on BD determination during the first 4 years.

RESULTS

In 5152 patients with clinically absent brain function, 1272 CTA were reported by 676 hospitals. Use of CTA increased from 17.2% of patients in the first year to 29.7% in the final year. CTA replaced other CS such as electroencephalography without increasing overall CS frequency. Technical failure was rare (0.9%); 89.3% of studies were positive. Negative results (9.8%) were more frequent with secondary brain injury, longer duration of the clinical BD syndrome, or unreliable clinical assessment. Median time to diagnosis was longer with CTA (2.6 h) versus other CS (1.6 h). CTA had no differential impact on the rate of confirmed BD and did not improve access of small hospitals to CS for BD determination.

CONCLUSIONS

CTA expands the range of available CS for the diagnosis of BD in adults. Real-world evidence from a large cohort confirms usability of the German CTA protocol within the guideline-specified context.

Use of Transcranial Doppler in Intensive Care Unit

Use of transcranial Doppler has undergone much development since its introduction in 1982, making the technique suitable for general use in intensive care units. The main application in intensive care units is to assess intracranial pressure, confirm the lack of cerebral circulation in brain death, detect vasospasm in subarachnoid haemorrhage, and monitor the blood flow parameters during thrombolysis and carotid endarterectomy, as well as measuring stenosis of the main intracranial arteries in sickle cell disease in children.

This review summarises the use of transcranial Doppler in intensive care units.

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.

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.

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.

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.

Applications of transcranial Doppler in the ICU: a review

OBJECTIVE

Transcranial Doppler (TCD) ultrasonography is a technique that uses a hand-held Doppler transducer (placed on the surface of the cranial skin) to measure the velocity and pulsatility of blood flow within the intracranial and the extracranial arteries. This review critically evaluates the evidence for the use of TCD in the critical care population.

DISCUSSION

TCD has been frequently employed for the clinical evaluation of cerebral vasospasm following subarachnoid haemorrhage (SAH). To a lesser degree, TCD has also been used to evaluate cerebral autoregulatory capacity, monitor cerebral circulation during cardiopulmonary bypass and carotid endarterectomies and to diagnose brain death. Technological advances such as M mode, colour Doppler and three-dimensional power Doppler ultrasonography have extended the scope of TCD to include other non-critical care applications including assessment of cerebral emboli, functional TCD and the management of sickle cell disease.

CONCLUSIONS

Despite publications suggesting concordance between TCD velocity measurements and cerebral blood flow there are few randomized controlled studies demonstrating an improved outcome with the use of TCD monitoring in neurocritical care. Newer developments in this technology include venous Doppler, functional Doppler and use of ultrasound contrast agents.