Diagnostic tests for confirmation of brain death

There are seven key diagnostic tests for the confirmation of brainstem death:

Tests involving the eye:

• pupils fixed, dilated, and unreactive to light: test of mid-brain
• absent oculo-cephalic reflex - test of mid-brain and pons
• absent corneal reflex - test of pons
• absent vestibulo-ocular reflex: using 20ml of ice cold water in each external auditory meatus - test of mid- brain and pons

Other non-ocular tests are:

• absent cough and tracheal reflexes: tested by passing a suction catheter passed down the trachea; test of pons
• no localising to pain: for example, to pin prick in the anterior nares; avoid sternal rub because of risk of bruising; test of mid-brain, pons and medulla
• no respiratory drive: no respiratory movements when disconnected from a respirator for long enough for the arterial PCO2 to rise above 50 mm Hg / 6.5 Kpa - the threshold for stimulation of respiration - test of medulla. If the patient has pre-existing chronic respiratory insufficiency then this particular criterion must be considered with care.

Note that:

• spinal reflexes are not a diagnostic test. They may be present and may cause alarm to attending relatives. It is essential to explain that they are a natural consequence of spinal cord hypoxia
• Electrocardiography is not among the criteria used for diagnosing brain death. However, brain death subjects frequently show ECG abnormalities
  • for example ECG abnormalities in brain death; and further explanation then click here