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Brain stem death

Created: 11/6/2005

 

BRAIN STEM DEATH (BSD)

  • Definition Irreversible loss of brain function as demonstrated by absence of brain stem function
  • Acceptance of BSD as a clinical and legal entity has taken 40 years is still developing.
  • The concept of BSD is important in minimising the burden on family members, facilitating transplant and preventing futile use of limited ITU facilities.
  • Survival
    • 30% of BSD patients survive >1 week.
    • Survival age dependant
    • Rare cases of children surviving 15 years

Evolution of BSD

  • Brain function more accurately represents life than cardio-pulmonary function
  • 1959 France - Coma Depasse (after coma) described-concept of irreversible loss of brain function
  • 1971 Finland first country to legally accept BSD
  • 1976 UK Royal Colleges define BSD based on purely clinical tests

DIAGNOSIS

Preconditions

  • Apnoea requiring ventilation.
  • Cause of coma shown to be irreversible
  • Rule out
    • Hypothermia
    • Metabolic/endocrine (? Na,? Ca,? glucose, ?T4, liver/renal failure)
    • Drugs (sedatives, narcotics, alcohol, anaesthetics)

Brain Stem Responses

1) Pupils fixed and unresponsive (direct and consensual). Usually dilated.

2) Absent corneal reflex.

3) Absent V and VII motor function in response to central or peripheral stimulus.

4) Absent occulovestibular reflex (caloric).

5) Absent oculocephalic (Dolls eye) reflex.

6) Absent cough and gag reflex.

7) No spontaneous movement.

8) Apnoea off ventilator (PCO2> 6.7 kPa)

UK BSD Testing Protocol

Two medical practitioners > 5 years post registration. One must be the patient’s consultant or ICU consultant. Neither can be in the transplant team

Two sets of tests with appropriate time interval (normally 6 hours, but > 24 hours if patient is a child)

First test > 6 hours after onset of apnoeic coma or >24 hours after CPR

Time of death first test, issue death certificate and inform Coroner second test.

Ancillary BSD Tests

Not compulsory in UK but useful

1) Speed up diagnosis (and transplant)

2) Difficult cases

Tests:

1) Absence of electrical activity (EEG)

2) Absence of cerebral blood flow (angio, CT/MRI, Doppler)

3) Cerebral Metabolism (PET)

Pitfalls of BSD Diagnosis

  • Spinal reflexes can be intact (Lazarus sign).
  • In N-M blockade must use nerve stim.
  • Apnoea test not reliable in high C-spine or phrenic nerve injury.
  • Pupillary reflexes can be affected by drugs, previous surgery or trauma.
  • Trauma or wax can affect caloric tests.
  • Avoid over testing corneal reflexes.

ArticleDate:20050611
SiteSection: Article
 
   
    
                                            



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