Brain-stem death and how it is confirmed

There is much confusion among people about three important medical terms -- coma (being comatose); persistent vegetative state and brain-death (brain-stem death).

The Sunday Times spoke to Consultant Anaesthetist Dr. Bhagya Gunetilleke of the Colombo North Teaching Hospital and Consultant Intensivist Dr. Manoj Edirisooriya of the NHSL to bring about clarity on these terms and also to find out what tests are performed to make sure that a person is brain-dead.

Coma or being comatose – This is a prolonged state of deep unconsciousness when a patient is unresponsive to his/her environment. The patient is alive and looks like he/she is sleeping but is deeply unconscious. Such patients are not braindead as the unconsciousness is potentially reversible.

Persistent vegetative state – This is when a patient’s brainstem is intact but the cortex is severely damaged. A patient in this condition is not brain-dead. Brain-death (brain-stem death) – This is when a patient is in a coma plus his/her brain-stem is dead. The brain-stem which is the link between the brain and the spinal cord comprises the midbrain, pons and medulla. It contains structures vital to sustaining life such as the cardiovascular and respiratory centres, cranial nerve nuclei and the ascending reticular activating system (RAS) which is essential for the maintenance of consciousness. In the absence of brainstem activity, a patient ceases to live.

Brain- stem death is confirmed after the determination of the absence of brain- stem function which must be due to a known cause such as major trauma like a very severe head-injury. In severe brain injury what usually happens is that the pressure within the skull rises to abnormal levels, pushing the brain and the brain stem out through an opening in the skull, which results in the cutting off of the blood supply to the brain- stem, causing its death. A massive irreversible head-injury which is not compatible with life should be confirmed through a CT scan by a Neurosurgeon.

Whether the brain- stem is dead is confirmed if there is irreversible apnoea (the patient’s incapacity to breathe on his/her own). Here, through a blood test, doctors will check whether the apnoea is being caused by drugs or muscle relaxants. More tests will be performed to exclude other causes for the non-functioning of the brain stem such as very low body temperature, abnormal electrolyte (sodium/potassium) levels and certain hormone levels.

After that they will perform the apnoea test to check for reversibility by allowing the carbon dioxide levels to rise, while not allowing the oxygen levels to drop. If the patient’s brainstem is not dead, this test will prod the patient to begin breathing.

There will also be cranial-nerve testing. These tests include checking the pupil and corneal reflexes, eye-ball movements, gag-reflexes and also facial responses such as grimacing to pain- stimuli to the forehead.

It is after all these measures that a patient is declared brainstem dead. A brain- stem dead person, the Sunday Times learns, even with full life- support will usually develop low blood pressure followed by multi-organ failure in 48-72 hours.