Understanding Brain Death
Implications of ischemic penumbra for the diagnosis of brain death
Current diagnosis of brain death may exclusively rely on testing for synaptic activity of brain tissue for a few hours. A 10-min. apnea testing usually follows clinical examination demonstrating absence of brain stem reflexes in a deeply comatose patient - Glasgow Coma Scale (GCS) score of 3. A flat electroencephalogram (EEG) may ultimately confirm brain death for procurement of transplantable organs. Therefore, the overall absence of neurologic function for usually 6 hours has been regarded as a consequence of irreversible whole brain or brain stem damage.
Since Harvard Ad Hoc Commission redefined death as brain death 1 the period advised for monitoring neurological status has been decreased from 24 to 6 hours 2 and, more recently, not required at all 3. Furthermore, apnea testing has been extended to 10 min., and associated with hyperbaric pre-oxygenation and intra-testing "passive oxygenation" through an endotracheal catheter 3. Other confirmatory tests have been proposed alternatively to EEG or angiography, but the reliability of neurological examination and apnea testing has been most considered, up to the point of regarding brain death as "a clinical diagnosis" 3.
