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DEPARTAMENT OF NEUROLOGY
AND NEUROSURGERY |
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DEPARTAMENT OF NEUROLOGY
AND NEUROSURGERY |
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Implications
of ischemic penumbra for the diagnosis of brain death:
Apnea testing may induce rather
than diagnose death
By
Cicero Galli Coimbra, M.D., Ph.D.
Laboratory for Brain Ischemia Research,
Head
Department of Neurology and Neurosurgery
Federal University of São Paulo
E-mail address: coimbracg.nexp@epm.br
Abstract
Background Irreversible damage of brain stem or whole brain is assumed when synapse-dependent phenomena (consciousness, cephalic reflexes, respiratory control, electrographic activity) remain absent for usually 6 hours.
Summary of Criticism Progressive intracranial hypertension due to cerebral edema may keep whole brain or vertebro-basilar blood flow within the range of ischemic penumbra for long enough as to fulfill current diagnostic criteria for brain death. Moreover, despite no angiographic evidence of intracranial circulation, secretory functions of the brain may be sustained for several hours, indicating that blood flow levels above the threshold of irreversibility may be consistent with absent vascular images on angiography. Furthermore, experimental and clinical data suggest that severe hypotensive episodes such as those observed in nearly 40% of patients subjected to the apnea test may irreversibly compromise brain circulation in victims of severe head trauma. In contrast, as recently reported, (1) whole body cooling induces rapid normalization of intracranial pressure, (2) moderate hypothermia (33ºC) sustained for a few hours efficiently reduces brain edema, as well as (3) largely increases the rate of good recovery following severe head trauma, and (4) intra-arterial thrombolysis may change the clinical course to death as to achieve good recovery in critical cases of basilar artery occlusion.
Conclusions Patients declared brain-dead may actually sustain global or regional (brain-stem) ischemic penumbra and respond to moderate hypothermia and/or thrombolysis. Time-consuming procedures currently in use may induce rather than diagnose irreversible brain damage. The 30-year old guidelines for diagnosis of brain death are to be urgently reconsidered.
Funding sources:
Brazilian Council for the Development
of Science and Technology (CNPq)
Foundation for Research Support in the
State of São Paulo (FAPESP)
Brazilian Program for Support of Centers
of Excellence in Research (PRONEX)
