PERSONAL BLOG

Brain Death Criteria

Brain Death Criteria


A quick recap on brain death criteria


  • It is important to distinguish brain death from a vegetative state.
  • In vegetative states, part of the brain is still functional and the condition is reversible in certain cases.
  • While being brain dead is considered the diagnosis to declare death (WHO 2012).
  • First, reversible causes of brain damage need to be ruled out such as metabolic, infectious, endocrine, drug effects and hypothermia.

The following must then be present to declare a person brain dead:


Loss of brainstem reflexes:


Cranial nerve

Result

CN II

  • No pupillary reflex
  • A fixed dilated pupil that does not react to light

CN III, IV and VI

  • No eye movement in relation to head position

CN V

  • No corneal reflex

CN VIII

  • No oculovestibular reflex
  • Also known as the caloric test. Ice cold water is irrigated in each ear which usually should move the eyes towards the irrigated ear but this reflex is lost in brain death.

CN IX

  • No gag reflex
  • Stimulation of both posterior pharyngeal membranes and the trachea causes no gag reflex.

CN X

  • No cough reflex after stimulation of the trachea


When all of the above are present, the person can be declared brain dead. In some instances, spinal reflexes can still be present despite brain death. 




Apnea test


  • The role of the apnea test is to prove an absence of respiratory reflex in the setting of a ventilatory stimulus (respiratory acidosis).
  • A negative test is a respiratory effort under hypercapnic or acidotic conditions while a positive test is no respiratory reflex under these conditions.
  • Before the test mechanical ventilation is set to:

    • pCO2 35-45 mmHg
    • PaO2 > 200 mmHg
    • PEEP 5-8 cm H2O

  • A loss of respiratory drive will cause CO2 to rise at 60 mmHg or >20mmHg above baseline.
  • This is detected by an arterial blood gas and is consistent with brain death. 


Ancillary test


  • These are done when there are uncertainties following clinical evaluation. Ancillary tests are performed to confirm if there is cerebral blood flow.
  • The gold standard remains cerebral angiography. It includes CT brain angiography and MR angiography.
  • Others include transcranial ultrasound and radionuclide brain imaging. 


By Karishma Toolsee

I- Medics Ambassador

About the author

The i-medics Editorial Team consists of Doctors, Medical Students, Professional Content writers, i-medics Ambassadors and Freelance workers.