Absence of brain-stem reflexes, motor responses, and respirations in a normothermic comatose patients with an irreversible brain lesion.
Irreversible loss of all brain function clinically demonstrates brain stem areflexia, and apnea.
Refers to the complete loss of brain function, including involuntary activity necessary to sustain life.
Brain death, according to neurologic criteria, accounts are approximately 2% of adult and 5% of pediatric in hospital deaths in the United States.
Brain death is a direct byproduct of the invention of mechanical ventilation:as previously a patient with a neurologic catastrophe would become apneic with subsequent hypoxemia and the heart would stop beating shortly thereafter.
The legal basis for brain death is described as irreversible cessation of all functions of the entire brain, including the brain stem.
In a persistent vegetative state, the person is alive and some autonomic functions remain.
With ordinary coma some brain and bodily activity and function remain.
BD is an indicator of legal death in many jurisdictions.
Its definition is inconsistent and often confusing.
Brain death includes cerebral and brainstem death.
Someone with a dead cerebrum but a living brainstem, can have spontaneous breathing unaided, whereas in whole-brain death, only life support equipment would maintain ventilation.
Patients classified as brain-dead can have their organs surgically removed for organ donation.
Brain death is an acceptable indication of death.
The legal and medical communities in the US use brain death as a legal definition of death, allowing a person to be declared legally dead even if life support equipment keeps the body’s metabolic processes working.
There must be definite clinical or neuro-imaging evidence of acute brain pathology consistent with the irreversible loss of neurological function.
With brain-death there are no clinical evidences of brain function upon physical examination: no response to pain, no cranial nerve reflexes, no
pupillary response, no oculocephalic reflex, no corneal reflex, no response to the caloric reflex test, and no spontaneous respirations.
With brain-death brain electrical activity can stop completely, or drop to such a low level as to be undetectable with most equipment: an EEG will be flat.
A flat EEG is not required to certify death.
A radionuclide cerebral blood flow scan that shows complete absence of intracranial blood flow must be considered with other exams
CT angiography is neither required nor sufficient test to make the diagnosis.
Cerebral angiography is considered the most sensitive confirmatory test in the determination of brain death.
Then diagnosis of brain death is the basis for the certification of death for legal purposes, but a very different state from biological death.
Continuing function of vital organs in the bodies of those diagnosed brain dead, provides optimal opportunities for their transplantation.
There is no evidence of arousal or awareness to maximal external stimulation, including noxious visual, auditory, and tactile stimulation, pupils are fixed in midsize or dilated position and are non-reactive to light, corneal, oculocephalic, and ocular vestibular reflexes are absent, there are no facial movement to noxious stimulation, the gag reflex is absent to bilateral posterior to pharyngeal stimulation, cough reflex is absent to deep tracheal suctioning, there is no brain mediated motor response to noxious stimulation of the limbs, spontaneous respirations are not observed when apnea test targets reach pH less than 7.3 and PaCO2 60 mmHg or greater.
The apnea test assesses the function of the medulla by allowing carbon dioxide levels to rise in the pH to fall to maximally stimulate medullary respiratory centers, and in the absence of respiratory effort in response to hypercarbia and acidosis is consistent with brain death.