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:

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