Brain death Flashcards
Define what brain death is
Brain death exists when there is no demonstrable brain stem function in the presence of a diagnosis compatible with irreversible structural brain damage.
What are the 3 components of the brainstem?
Midbrain, pons and medulla.
What are the general functions of the brainstem?
- Respiratory drive and control of respiration.
- Regulation of cardiovascular function.
- Control of consciousness and the sleep/awake cycle.
- All motor output from the brain passes via the brain stem.
- Sensory input to higher centres of the brain.
- Cranial Nerve reflexes (readily tested).
What are the 3 commonest causes of brain death ?
- Head injury.
- Intracranial haemorrhage.
- Cerebral hypoxia.
What patients can the diagnosis of brainstem death only be considered in?
- It can only be considered in patients who have sustained acute, severe structural brain damage which has led to permanent coma with the permanent loss of the capacity to breath.
- AND whom have recieved prompt medical intervention that has ensured that artificial ventilation was commenced before the resulting hypoxia caused the heart to stop
What does the diagnosis of brainstem death rely on ?
It relies on the simple bedside demonstration of the absence of brain stem function in a patient with a known cause of severe and irreversible brain damage.
What are the mandatory pre-conditions & exclusions which are needed in the diagnosis of brain death ?
Preconditions:
- Patient is in coma and totally dependent on ventilatory support.
- No doubt that coma is due to irremediable structural brain damage.
- The diagnosis of the disorder that led to irreversible coma is fully established.
Exclusions (Other cause of apnoeic coma must be excluded) These are:
- Hypothermia. Core temperature must be >35C.
- Metabolic or endocrine causes of coma.
- CNS depression by drugs (medical or recreational).
- Exclude neuromuscular blocking (paralysing) agents as cause of apnoea.
Note - every single one of these must be confirmed
What are the clinical signs/bedside tests used to confirm the diagnosis of brain stem death alongside the mandatory pre-conditions and exclusions?
Absence of 5 brain stem reflexes:
- No pupillary response to light.
- Absent corneal reflexes.
- Absent caloric responses.
- No motor responses in the distribution of the cranial nerves.
- No cough or gag reflexes.
AND Apnoea - no attempt by the patient to breathe following ventilator disconnection despite the presence of an arterial partial pressure of Carbon Dioxide adequate to stimulate respiration. (PaCO2 > 6.65kPa).
Who can perform the tests to diagnose brain death?
- Tests performed by 2 senior doctors, fully registered with the General Medical Council for at least 5 years.
- One must be a Consultant (usually both).
- They must be competent to perform and interpret the tests.
- They must not be a member of a transplant team. (See notes on transplantation)
- Two sets of tests performed.
- Time of death is the time of completion of the 1st set of tests. 2nd set confirmatory.
- Written documentation of the preconditions and exclusions for testing as well as of the tests themselves is mandatory
When a diagnosis of brain stem death is confirmed what should then be considered ?
The possibility of organ donation.
- Ventilation and supportive care should be maintained to ensure continued cardiac function and tissue oxygenation.
- It is possible that the patient may carry a donor card and be registered on the NHS Donor register. Some relatives may highlight the subject of organ donation directly to staff. Other families may be unaware of the possibility of organ donation.
- All cases where a diagnosis of brain death is made should be discussed with the on-call Transplant Coordinator who will be able to advise on the suitability of donation in each particular case
