Brief review: the role of ancillary tests in the neurological determination of death.

PURPOSE: The acceptance of brain death by society has allowed for the discontinuation of "life support" and the transplantation of organs. In Canada we accept the clinical criteria for brain death (essentially brain stem death) when they can be legitimately applied. Ancillary tests are needed when these clinical criteria cannot be applied or when there are confounders. Ancillary tests include tests of intracranial blood circulation, electrophysiological tests, metabolic studies and tests for residual vagus nerve function. The ideal confirmatory test is one which, when positive, would be incompatible with recoverable brain function (i.e., has no false positives), is not influenced by drugs or metabolic disturbances and which can be readily applied. A critical review of the various ancillary tests used to support the neurological determination of death (brain death) was undertaken.

METHODS: A literature review based on a MEDLINE search of relevant articles published between January 1966 to January 2005 was undertaken.

RESULTS: Tests of whole brain perfusion/intracranial blood circulation are the only ones that meet stated criteria.

CONCLUSIONS: At present only cerebral angiography and nuclear medicine tests of perfusion are accepted by Canadian standards, but computed tomography and magnetic resonance angiography should prove to be suitable. Transcranial Doppler studies may be suitable for specific cases once appropriate guidelines are established.