Death Study Reference

Death   The permanent cessation of the critical functions of the organism as a whole. Critical functions are those without which the organism as a whole cannot function: o Control of respiration and circulation. o Neuroendocrine and homeostatic regulation. o Consciousness. Brain-centred definition  Three formulations: o Whole brain. o Brainstem. o Neocortex.  Many areas of the brain (including the neocortex, thalamus and basal ganglia) cannot be accurately tested for clinical function in a comatose patient.  Most bedside tests for brain death (e.g. cranial nerve reflexes and apnoea testing) directly measure function of the brainstem alone.  The neocortical formulation of death is the irreversible loss of the capacity for consciousness and social interaction (e.g. permanent vegetative state; anencephalic infants). o Brain death is classically caused by a brain lesion that results in an intracranial pressure higher than MAP. o This causes intracranial circulation to cease and damage to the brainstem by herniation through the foramen magnum.  However, using the brainstem formulation of death, cases of catastrophic brainstem lesion (which spares the thalamus and cerebral cortex) can be declared brain dead in the absence of clinical brainstem function, despite intact intracranial circulation. Criteria for brain death (American Academy of Neurology)  Demonstration of coma.  Evidence for the cause of coma.  Absence of confounding factors (e.g. hypothermia, drugs, and electrolyte and endocrine disturbances).  Absence of brainstem reflexes and motor responses.  Apnoea.  A repeat evaluation after a further 6 hours is advised.  Confirmatory laboratory tests are only required when specific components of the clinical tests cannot be reliability evaluated. Assessment of brain death  The clinical set of tests for whole brain and brainstem death are identical.  There are two sets of tests that can be used to ascertain death. o Neurological. o Cardiopulmonary.   In mechanically ventilated patients: o Neurological tests are used to assure irretrievable absence of brain (in practice, just brainstem) function. In non-ventilated patients: o Physicians evaluate the irretrievable absence of heart beat and breathing. Vegetative state  Like brain death, the vegetative state “wakefulness without awareness”, is a clinical diagnosis that, when it becomes permanent, can be regarded as an artifact of modern technology (i.e. life support).  Unlike brain death, the vegetative state can be partially or totally reversible.  Persistent vegetative state: o 1 month after the occurrence of brain damage. o Does not mean that it is irreversible.  Permanent vegetative state: o Irreversible 3 months after a non-traumatic brain injury, and 12 months after traumatic injury. o Implies patient will not recover. Imagined movements  Asking a patient to imagine playing tennis, or to imagine walking around her house, activated the same areas as in controls.  Tennis: significant activity was observed in the supplementary motor area.  Walking through her home: significant activity was observed in the parahippocampal gyrus, the posterior parietal cortex, and the lateral premotor cortex.  Differences in activation patterns with motor imagery and spatial imagery can be used to communicate with patients in vegetative states. Criteria for vegetative state (US Multi-Society Task Force on Persistent Vegetative State)  No evidence of awareness of self or environment and an inability to interact with others.  No evidence of sustained, reproducible, purposeful or voluntary behavioural responses to visual, auditory, tactile or noxious stimuli.  No evidence of language, comprehension or expression.  Intermittent wakefulness manifested by the presence of the sleepwake cycle.  Sufficiently preserved hypothalamic and brainstem autonomic functions to permit survival with medical and nursing care.      Bowel and bladder incontinence. Variably preserve cranial and spinal reflexes. It is now recommended that persistent be omitted and patients be described as having been vegetative for a certain time. When there is no recovery after a specific period (3 – 12 months, depending on aetiology), the state can be declared permanent. Only then do the ethical and legal issues that surround withdrawal of treatment arise.