Permanent cessation of all vital functions. The classic indicators of death are the permanent cessation of heart and lung function, and, in almost all cases, these remain the criteria by which death is certified. Brain death is the irreversible cessation of all functions of the entire brain, including the brainstem. The diagnosis of death under normal circumstances, when the individual is not on a ventilator, is based on the absence of breathing, absence of heartbeat, and on the pupils being fixed wide open and unresponsive to light. When an individual is on a ventilator, the criteria for diagnosing brain death are based on clear evidence of irreversible damage to the brain; persistent deep coma; no attempts at breathing when the patient is taken off the ventilator; and lack of brainstem function. (See also death, sudden; mortality.)


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