The main rule of thumb is to be sure that your contact at the bedside does not lead to increased agitation, which can occur if the patient is semi-aware and frustrated by their inability to communicate or express themselves. If this occurs, it is probably best to leave the patient alone. Persistent vegetative state describes the chronic condition that almost invariably emerges after coma. While these patients look awake and often alert they have no discernable meaningful interaction with their environment. Recovery of conscious awareness after one year in a vegetative state is exceedingly rare.
Brain death is defined as irreversible cessation of all brain functions, including the brain stem.
Death may be declared in an individual who has sustained brain death. This means no behavioral or reflex responses mediated above the spinal cord. Brainstem functions must be absent. This includes unreactive pupils, the absence of ocular responses, facial sensation and motor responses, and lack of cough and gag reflexes. The patient must be apneic.