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Brain death

       Brain death is the complete loss of all brain functions including those of the brain stem like cardiac functions and spontaneous respiration.It differs from "persistent vegetative state" which results from damage to the cerebral cortex only and in which the person is in deep coma but he is capable of maintaining cardiac functions and respiration as the brain stem is not affected.In the former condition the person is truely and legally dead,while in the latter he is not considered dead at all.
   Criteria of brain death:
-the person must be in deep coma.
-he must be on a mechanical ventilator. 
-absence of response to painful stimuli.
-firm diagnosis of the cause of death,which must be irremediable and has been pesistent for at least 6 hours. 
-absence of brain stem reflexes
 Tests for brain stem reflexes:
-no pupillary response to light (i.e no miosis when eye exposed to light)
-absent corneal reflex ( reflex blinking on touching the cornea). 
-absent oculocephalic reflex (doll's eye): in functioning brain stem when the head is moved from one side to the other the eye is moved to the contralateral side (i.e fixing a point in the visual field) ,but if the brain stem is dead this movement is abolished.
Oculocephalic reflex
-vestibulo-ocular reflex is absent when ice-water is introduced in ears.
-pharyngeal and tracheal reflexes are also absent ( no gagging or coughing)
- the final test to be done if all previous tests are absent is the testing for apnea.
these tests should be done with body core temperature not less than 35.5 C to avoid hypothermia.
       Importance of brain death diagnosis:
-early determination of death is very important for prompt organ taking for transplantation purposes.
-the legality for discontinuation of life supporting equipments.
 -the determination of time of death which is important in criminal & civil problems.

-early death determination is favorable at the time of epidemics to dispose the dead body as early as possible to guard against the spread of infection.
-to differentiate between death & suspended animations(death like state) which can be induced by toxic doses of a hypnotic,sedative,narcotic...etc or in cases of "Yoga" practitioners. 
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