A person who is brain dead is truly and unequivocally dead and will never wake up nor regain consciousness again.

Brain death occurs when there is total and irreversible cessation of all functions of the brain in a person. When a person is declared brain dead, he will not be able to breathe on his own and will need to be artificially supported by a ventilator. Once the ventilator is switched off, the person’s heart will cease to beat as his brain has already stopped functioning. 
 
Brain death is accepted as a legal definition of death in Singapore and in other advanced countries. It is determined based on a well-defined standard set of clinical criteria. This definition is similar to those used in countries such as Australia, Canada, Denmark, the United Kingdom and the United States.

There are very stringent safeguards and procedures in the certification of brain death. The clinical criteria for brain death must be observed to be met in the patient by two doctors before brain death can be certified. Both doctors must be experienced with specialist qualifications. Should the two doctors have differing opinions, brain death would not be certified. The two doctors who examine the patient must: 

1. not have been involved in the care or treatment of the patient being certified;
2. not belong to the team of medical practitioners who will remove the organ from the body;
3. not have been involved in the selection of the proposed recipient of the organ; and
4. not be involved in the care or treatment of the proposed recipient of the organ during his hospitalisation for the transplant.

There are seven clinical criteria for determining irreversible cessation of all functions of the brain. Brain death can only be certified if all seven clinical criteria are met. The seven clinical criteria are as follows:

1. Pupils do not constrict when exposed to direct, strong light. (Absent pupillary light reflex)             

Normal response: Pupils constrict when exposed to direct, strong light.         

 

2. There is no blink reflex when the corneas are stimulated. (Absent corneal reflex)   

Normal response: The eyelid blinks when the cornea (area over the pupils) is stimulated with a cotton wisp.

 

3. There is no response to painful stimulus, excluding spinal reflexes. (Absent pain response)        

Normal response: The subject will attempt to withdraw from, localise or remove  the painful stimulation.

 

4. The eye gaze follows the direction of the head when turned from side to side.  (Absent oculocephalic reflex)                     

Normal response: The eyes will remain fixed on forward gaze even when the head is turned from side to side.

5. There is no gag reflex in response to stimulation of the throat or upper air passages. (Absent gag reflex)                       

Normal response: Stimulation of the throat or the upper air passages will induce gagging.

 

6.         There is no eye response on instillation of 50 cubic centimetres of ice-cold water into each ear. (Absent vestibulo-ocular response)                       

Normal response: The eye will twitch when each ear is instilled with cold water.

           

7.         There is no spontaneous breathing when removed from the ventilator even with rising carbon dioxide concentration in the blood. (Positive apnea test)

Normal response: Spontaneous breathing will occur with rising carbon dioxide concentration (> 50 millimetres of mercury) in the blood.

Supplementary tests can be used to complement the clinical tests. These tests are carried out to demonstrate the presence or absence of blood flow in the brain. The absence of blood flow in the brain is confirmatory of brain death.

However, these tests are not substitutes for the clinical criteria. If six of the seven clinical tests can be performed, the criteria for these six tests must be fully met, before the doctor proceeds to carry out a supplementary test.

On 1 July 2004, the Interpretation (Determination and Certification of Death) Regulations were amended to allow two supplementary tests to be used for brain death certification:

1. Cerebral angiography: A contrast agent / dye is injected into the bloodstream and tracked in real-time by x-ray. The inability of the contrast agent to reach the brain will confirm the absence of blood flow in the brain; or

2. Radionuclide Perfusion Scan: A radioactive agent is injected into the bloodstream  and the presence of the radioactive agent in the brain is measured. Absence of the radioactive agent in the brain will confirm the absence of blood flow in the brain.

Cardiac death is when the heart irreversibly stops beating. Brain death is when the brain irreversibly stops functioning. At the point of cardiac death, all vital functions would stop, including the brain. Ordinarily, this occurs at the same time. When the brain stops functioning, the heart will also stop after a short while. Medical technology is now able to intervene such that the heart continues to beat even when the brain has stopped functioning. In such cases, the patient is dead, even though the heart continues to beat from the use of life-support technology. When these life support technologies are withdrawn, the heart and lungs would stop functioning after a short while.

Coma is a state where a person is unarousable but tests confirm that some brain functions are present. A comatose person may still recover or regain consciousness. Brain death is when a person is unarousable and tests confirm that all brain functions have irreversibly stopped. Persons declared brain dead cannot recover or regain consciousness.