Ancillary Testing in Brain Death

Abstract

Despite worldwide acceptance of the concept of brain death, there is marked variability in the use of ancillary testing. In most countries, ancillary tests are used primarily when confounding factors interfere with reliable completion of a clinical assessment, or physiologic instability precludes performance of an apnea test. Alternatively, in some countries, confirmatory ancillary tests are routinely required before brain death can be diagnosed. Ancillary tests assess brain function (e.g., electroencephalography) or blood flow (e.g., cerebral angiography). Evaluation of blood flow is affected less by confounding clinical factors and is now preferred in most jurisdictions. With angiographic techniques, a significant proportion of patients meeting clinical criteria for brain death have some opacification of proximal intracranial arteries. Consequently, the sensitivity of angiography is strongly influenced by the particular criteria that are used to define intracranial circulatory arrest. Lack of enhancement of the great cerebral and internal cerebral veins has the highest sensitivity. Worldwide experience with newer tests, such as computed tomography and magnetic resonance angiography, is growing. Radionuclide imaging has the advantage of not requiring use of potentially nephrotoxic contrast material. Transcranial Doppler ultrasonography can be brought to the bedside to demonstrate lack of brain blood flow. The specificity of imaging techniques in the detection of intracranial circulatory arrest has not been as well studied as their sensitivity.

Identification of separation phenomenon during brain death determination of potential organ donor and analysis of relative factors

“…Further multivariate analysis showed that age, systolic blood pressure, primary brain stem injury, spontaneous respiration arrest time ≤72 h and decompressive osteotomy (unilateral / bilateral) were independent risk factors for "separation phenomenon" (Table 2). 6,7 Therefore, the choice of EEG and CBF evaluation as the confirmatory test of brain death determination is conducive to the implementation of DBD.…”

“…9 It can be seen that EEG and TCD can be selected as the confirmatory test method to ensure the accuracy of brain death determination and keep consistent with the international standard of brain death determination. 6,7 Therefore, the correct cognition and countermeasures to the "separation phenomenon" of EEG silence and CBF arrest can ensure the accuracy of brain death determination and the successful implementation of DBD.…”

Critical synopsis and key questions in brain death determination

“…In many (~ 30%) countries, ancillary tests are required by law and interpreted as confirmatory [9], and it seems hard to give up tests we never really trusted in the first place. Ancillary tests in a clinically declared patient may, inconveniently, show equivocal results in one of five patients; results depend on test used, timing of test, and mechanism of brain death-more often false negative if intracranial pressure is not markedly elevated [10]. Ancillary tests may confuse physicians, lead to more tests, delay closure, and block the usual pathways.…”

Confirmation of brain death using optical methods based on tracking of an optical contrast agent: assessment of diagnostic feasibility

“…Ancillary tests used to prove blood flow cessation, such as four-vessel angiography or radionuclide imaging, are currently the most recommended methods 13 – 15 . However, there are numerous limitations to these tests.…”