Monday, 14 January 2013

Activity 3: What are some criteria the medical community uses to determine if one is “brain dead”?

What is Brain Death?


By definition, "brain death" is "when the entire brain, including the brain stem, has irreversibly lost all function." The legal time of death is "that time when a physician has determined that the brain and the brain stem have irreversibly lost all neurological function.

The concept of brain death can be very confusing because the person's heart is still beating and their chest will still rise and fall with every breath from the ventilator. Brain dead patients can be kept ‘alive’ by an automated ventilator. This machine mimics the action of breathing, causing the heart to continue to beat. Therefore, skin is warm and the person may appear to be resting comfortably, rather than critically ill and without brain function. This is because the worst of the physical damage is actually hidden in the brain, rather than visible on the body.
When the brain is injured, it responds like other injuries—it swells. However, the brain is confined in the skull and has no room to swell. This leads to brain death.

Once the brain is pronounced dead, the family has to decide whether to stop the ventilator from providing breathable air into the lungs and bury the patient or whether to continue and keep the heart pumping so that the patient can donate his organs to other people. 

There are 3 main types of Brain Death
- Cortical / cerebral death
- Brain stem death
- Whole brain death

How to test for Brain Death?

Criteria for Brain Dead
- Absence of reflexes
- Apnea (inability to breathe without a ventilator)

Various Tests for Brain Death
1) Patient has no response to commands- Verbal, visual or otherwise
2) The patient is flaccid, with areflexic extremities. The patient has no movements -- the arms and legs are raised and allowed to fall to see if there are adjacent movements, restraint or hesitation in the fall.
3) The pupils are unreactive (fixed). The patient's eyes are opened and a very bright light is shined into the pupil. The light will activate the optic nerve and send an impulse to the brain. In the normal brain, the brain will send an impulse back to the eye to narrow the pupil. In the non-viable brain, no message will be sent. This is performed in both eyes.
4) The patient has no oculocephalic reflex. The patient's eyes are opened and the head rotated from side to side. The active brain will allow a roving motion of the eyes; the non-functional brain will not. The eyes remain fixed.
5) The patient has no corneal reflexes. A cotton swab is pulled across the cornea while the eye is held open. The functioning brain will want the eye to blink. The dead brain will not. This is performed in both eyes.
6) The patient has no response -- either purposeful or posturing -- to supra-orbital stimulation.The patient's eyebrow ridge is compressed with the thumb. The resulting stimulation pressure will cause motion of the extremities, either purposeful or primitive posturing, in the living-brain patient, but none in the brain-dead patient.
7) The patient has no oculovestibular reflex. The patient's ear canal is checked to ensure an intact tympanic membrane and that the ear is free of wax. While holding the eyes open, ice water is injected into the ear canal. The sudden change in ear temperature will cause a violent eye twitching by the intact brain but no reaction in the brain-dead patient. This is performed in both ears.
8) The patient has no gag reflex. The movement of the breathing tube (in and out) or the insertion of a smaller tube down the breathing tube will cause a gag reflex in a comatose patient, but will not draw out a reflex in the brain-dead patient.
9) The patient has no spontaneous respiration. The patient is temporarily disconnected from life support. With the cessation of breathing by the machine, the body will immediately begin to build up metabolic waste of carbon dioxide in the blood. When the CO2 level reaches a level of 55 mm Hg, the normal brain will cause the patient to breathe spontaneously. The dead brain gives no response because for brain dead patients, the brain is unable to send the signal to breathe.

Done By: Jie Yi, Yi Chieh, Ada, Sylvia, Rui Zhi

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