Researchers at the Intensive Care Unit of Hospital Metropolitano Doutor Célio de Castro retrospectively analyzed 178 adult patients who completed brain death protocols between December 2017 and December 2023. Of these, 141 patients underwent transcranial Doppler ultrasonography, or TCD, as the complementary exam, while 37 were evaluated with electroencephalography or cerebral angiography. The findings, published in the journal Neurocritical Care, show that TCD use was independently associated with a 53.9 percent reduction in the median time needed to complete the brain death protocol, a difference so large that it reshapes the logistics of end-of-life care and organ procurement.

The numbers are striking. In the TCD group, the median protocol duration was nine hours, with an interquartile range of five to twenty-three hours. In the non-TCD group, the median stretched to thirty-five hours, with an interquartile range of twenty to sixty-six hours. After adjusting for age, sex, comorbidity burden measured by the Charlson Comorbidity Index, illness severity measured by the Simplified Acute Physiology Score III, calendar year, and whether the protocol was opened during business hours or after hours, TCD use carried an incidence rate ratio of 0.46, meaning the protocol took less than half as long. The only other independent predictor of protocol duration was whether the process began during business hours, underscoring how staffing availability shapes this delicate timeline.

Transcranial Doppler ultrasonography is a bedside technique that uses low-frequency ultrasound pulses through the temporal bone and other acoustic windows to measure blood flow velocity in the major arteries of the circle of Willis, including the middle cerebral, anterior cerebral, and basilar arteries. The technique was first described in 1982, when researchers demonstrated that flow velocity in the basal cerebral arteries could be recorded noninvasively. In the context of brain death, rising intracranial pressure progressively exceeds the perfusion pressure, producing a characteristic sequence of Doppler waveforms: first a blunting of diastolic flow, then oscillating or reverberating flow in which blood moves back and forth with each heartbeat without net forward perfusion, then tiny systolic contraction spikes, and finally the disappearance of detectable flow altogether. Demonstration of these arrest patterns in both anterior and posterior circulations, on two examinations separated by an interval defined by national guidelines, provides evidence of cerebral circulatory arrest.

The diagnostic credentials of the technique are well established. A meta-analysis published in Intensive Care Medicine in 2006 reported high specificity for confirming brain death, and a subsequent systematic review and meta-analysis in the American Journal of Neuroradiology reached similar conclusions, with reported sensitivity around 88 percent and specificity approaching 98 percent in pooled analyses. Brazilian guidelines issued in 2012 formally endorsed transcranial ultrasound as a confirmatory test for brain death, and the country’s Federal Council of Medicine incorporated it into the regulatory framework through Resolution 2,173 of 2017. Unlike angiography, TCD requires no transport to a radiology suite, no iodinated contrast, and no exposure of potentially donor organs to nephrotoxic agents. Unlike electroencephalography, it does not require prolonged recording sessions or interpretation delays, and it sidesteps the technical confounders of electrical artifacts in the intensive care environment.

The efficiency gains extended beyond the protocol itself. Length of stay in the intensive care unit after protocol initiation was significantly shorter in the TCD group, with a median of one day compared with two days in the non-TCD group, and an adjusted incidence rate ratio of 0.51. In a health system where intensive care beds are chronically scarce and expensive, each day of occupancy by a patient who has already died by neurologic criteria carries an opportunity cost measured in the patients waiting for that bed. The researchers also examined whether the choice of confirmatory exam influenced organ donation, and found that it did not: donation rates were statistically indistinguishable between the groups, at 35 percent in the TCD group and 38 percent in the non-TCD group. Faster protocols, in other words, did not come at the expense of donation outcomes, though they also did not visibly increase them in this cohort.

The study’s statistical approach was deliberately conservative. Because protocol duration and length of stay are skewed, count-like variables, the team used negative binomial regression rather than ordinary linear models, adjusting for the full panel of demographic, clinical, and logistical covariates. The groups were comparable at baseline in age, comorbidity, severity scores, and sex, with all baseline comparisons showing no significant differences. Supplementary correlation analyses reinforced the main findings: TCD use and business-hours protocol opening showed the strongest negative correlations with protocol duration, while illness severity, age, and comorbidity played smaller or negligible roles. Notably, the underlying diagnoses differed between groups, with subarachnoid hemorrhage more frequent among patients who did not receive TCD, at 49 percent versus 26 percent, and ischemic stroke more frequent in the TCD group, at 28 percent versus 11 percent. This pattern likely reflects a practical reality of neurosonology: adequate acoustic windows are harder to obtain in some patients, and certain clinical scenarios push teams toward angiography or electroencephalography instead.

The authors are careful about the limits of their conclusions. This was a single-center, retrospective study at a Brazilian tertiary hospital where confirmatory testing is mandatory, and they caution that generalizability to settings without such requirements is limited. In countries where confirmatory tests are optional, the operational calculus differs, since the protocol can sometimes be completed with repeated clinical examinations alone. The findings also hinge on the availability of trained practitioners; TCD interpretation in the setting of suspected brain death demands specific expertise in recognizing the arrest waveforms and in distinguishing them from technical limitations such as poor insonation windows. The authors argue that their results support broader implementation of TCD in countries with mandatory confirmatory testing, contingent on that trained practitioner availability being secured.

The implications ripple outward to two of the most pressing issues in critical care. The first is organ donation, where every hour of delay increases the risk of hemodynamic instability, cardiac arrest, and loss of viable organs, and where families awaiting a definitive answer endure prolonged uncertainty at the bedside. The second is intensive care capacity, where protocols that conclude in nine hours rather than thirty-five return beds to the queue of critically ill patients faster. A bedside ultrasound exam that costs a fraction of a digital subtraction angiography study and requires no patient transport may thus be one of the highest-leverage tools available in the delicate interval between devastating brain injury and the formal pronouncement of death. As brain death determination frameworks worldwide undergo revision, including the recent consensus guideline from American neurologic and critical care societies, this Brazilian dataset offers a reminder that the operational details of how death is confirmed can matter almost as much as the criteria themselves.

Subject of Research: Use of transcranial Doppler ultrasonography as a confirmatory exam in brain death determination protocols

Article Title: Transcranial Doppler Ultrasonography as a Complementary Exam in Brain Death Determination: Impact on Protocol Duration and ICU Length of Stay—A Single-Center Study in Brazil

Article References: de Freitas, M. R., de Lima, A. F., & Coutinho, C. F. A. (2026). Transcranial Doppler Ultrasonography as a Complementary Exam in Brain Death Determination: Impact on Protocol Duration and ICU Length of Stay—A Single-Center Study in Brazil. Neurocritical Care. https://doi.org/10.1007/s12028-026-02641-w

Image Credits: AI Generated

DOI: 10.1007/s12028-026-02641-w

Keywords: transcranial Doppler, brain death, brain death protocol, organ donation, intensive care unit, cerebral circulatory arrest, neurocritical care, TCD ultrasonography, ICU length of stay, Brazil, confirmatory testing, negative binomial regression