What are the UK diagnostic criteria of brain death?

The UK diagnostic criteria of brain death 

A. Preconditions for considering a diagnosis of brain death:

  • The patient is deeply comatose
    • There must be no suspicion that coma is due to depressant drugs, such as narcotics, hypnotics, tranquillizers
    • Hypothermia has been excluded-rectal temperature must exceed 35° C
    • There is no profound abnormality of serum electrolytes, acid-base balance or blood glucose concentration, and any metabolic or endocrine cause of coma has been excluded
  • The patient is maintained on a ventilator because spontaneous respiration has been inadequate or has ceased. Drugs, including neuromuscular blocking agents, must have been excluded as a cause of the respiratory failure
  • The diagnosis of the disorder leading to brain death has been firmly established. There must be no doubt that the patient is suffering from irremediable structural brain damage.

B. Test for confirming brain death:

  • All brain-stem reflexes are absent-
    • The pupils are fixed and non-reactive to light
    • The corneal reflexes are absent
    • The vestibulo-ocular reflexes are absent- there is no eye movement following the injection of 20 ml of ice-cold water into external auditory meatus in turn
    • There are no motor responses to adequate stimulation within the cranial nerve distribution
    • There is no gag reflex and no reflex response to a suction catheter in the trachea
  • No respiratory movement occurs when the patient is disconnected from the ventilator long enough to allow the carbon dioxide tension to rise above the threshold for stimulating respiration (PaCO2 must reach 6.7 kPa or 50 mmHg)

N.B: The diagnosis of brain death should be made by two doctors of a specified status and experience. The tests are usually repeated after a short interval to allow blood gases to normalize before brain death is finally confirmed


  • Davidson's Principles and Practice of Medicine 23rd Edition; page: 211

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