Brainstem death

Background

Brainstem death is a concept that was needed after intensive care units and ventilators were developed. People with no chance of recovery could be kept ‘alive’ indefinitely with IV therapy, nutrition and artificial ventilation.

Brainstem death is when 2 functions of the brainstem are irreversibly absent:

1. There is loss of consciousness due to damage to the reticular activating system in the pons
2. No spontaneous breathing is possible due to damage to the respiratory centre in the medulla

Note that this means other parts of the central nervous system (CNS) may be intact:

1. Cortical activity may be present on EEG. This is why EEG is irrelevant to diagnosing brain stem death in the UK.
2. Spinal activity may be present clinically. Deep tendon reflexes (biceps, etc) may be present because they do not involve the brain or brainstem.

The brainstem death criteria need a plausible cause, exclusion of reversible causes, and clinical testing of the brainstem reflexes and the respiratory centre. Most candidates forget about the first 2 points and talk about the brainstem reflexes!

Testing of reflexes involves all of the cranial nerves (CNs) from the 2nd to the 10th CNs, which covers the different parts of the brainstem. Remember the location of the CN nuclei:

• 3rd – 4th in the midbrain
• 5th – 8th in the pons
• 9th – 12th in the medulla

Brainstem death criteria

• Eligibility for assessment
• Patient is in a coma and is not breathing (ie. apnoea)
• There is irreversible brain damage from a known cause
• Coma is not due to drugs, hypothermia or reversible metabolic/endocrine factors
• Assessors
• Two doctors who have had full GMC registration for over 5 years
• One must be a consultant
• Neither must be members of the transplant team
• They must both test separately
• There is no time interval needed between the tests (often there is some interval though)
• Time of death is the time of the first test
• Brainstem tests (for Cranial Nerves II, III, V, VI, VII, VIII, IX, X)
• Pupils fixed and unresponsive to light (CN II & III)
• Corneal reflex absent (CN V & VII)
• Vestibulo-ocular reflex absent on injecting ice-cold water into ears (CN III, VI & VIII)
• Motor movements absent on stimulating the body eg. pressure on sternum (CN VII)
• Limb movements absent on supra-orbital pressure (CN V)
• Gag reflex absent (CN IX & X)
• Cough reflex absent on inserting suction catheter into the bronchi (CN X)
• Respiratory test
• There is no spontaneous breathing when PCO2 is >6.6kPa

Discussion points

• Explain that the patient is dead
• The ventilator is keeping the patient’s lungs moving and his/her heart beating
• There may be occasional reflex twitches or movement even after brainstem death. There may also be occasional but irregular, laboured gasps of breath (‘agonal breaths’).
• The pons and medulla, which have cranial nerve nuclei, also contain the reticular activating formation and the respiratory centre, responsible for consciousness and breathing.
• There is no legal definition of death in the UK, but since 1976, the courts have accepted brainstem death as death of an individual.
• No EEG or imaging is needed to diagnose brainstem death.

Ethical issues

• Should we use the criteria to define death?
• Beneficence: It could be argued that defining death may help preserve the dignity of the patient rather than continuing futile, invasive treatment indefinitely (intubation, IV access, catheterisation, etc).
• Non-maleficence: Tiny chance that the patient may be conscious despite brainstem death, as we cannot directly test the reticular activating system itself. Therefore we may be harming a person with the potential for consciousness (even though unlikely, and they would not be able to breathe unaided)
• Autonomy: There is no autonomy in this situation. Remember that even if a person has previously stated they would like ventilation or active treatment in all circumstances, the decision to continue treatment is a medical decision, only if it is considered to benefit the patient.
• Social justice: Defining brainstem death allows patients with no hope of recovery to be diagnosed and disconnected from ventilators more quickly, freeing up resources in intensive care. Also it allows the possibility of organ donation.

Further reading

For details on brainstem death criteria and testing:
A Code of Practice for the Diagnosis and Confirmation of Death by the Academy of Medical Royal Colleges. Available at: http://www.aomrc.org.uk/publications/reports-a-guidance/doc_download/42-a-code-of-practice-for-the-diagnosis-and-confirmation-of-death.html

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