College Answer

Preconditions

a) A known cause of coma (check terminology in new ANZICS guidelines)
b) Minimum of 4 hour period observation
c) neuro-imaging consistent with acute brain pathology which could result in brain death;

d) temperature > 35C;
e) normotension (as a guide, systolic blood pressure > 90 mmHg, mean arterial pressure (MAP) >
60 mmHg in an adult);
f) exclusion of effects of sedative drugs: the time taken for plasma concentrations of sedative drugs to fall below levels with clinically significant effects depends on
the dose and pharmacokinetics of drugs used, and on hepatic and renal function. If there is any doubt about the persisting effects of opioids or benzodiazepines, an appropriate drug antagonist should be administered;

g) absence of severe electrolyte, metabolic or endocrine disturbances. These include marked derangements in plasma concentrations of glucose, sodium, phosphate or magnesium, liver and renal dysfunction and severe endocrine dysfunction;

h) intact neuromuscular function. If neuromuscular-blocking drugs have been administered, a peripheral nerve stimulator or other recognised method (e.g. electromyography) should always be used to confirm that neuromuscular conduction is normal;

What are the indications for ancillary tests for brain death?

°     Inability to adequately examine the brain-stem reflexes. It must be possible to examine at least one ear and one eye;

°     Inability to perform apnoea testing. This may be precluded by severe hypoxic respiratory failure or a high cervical spinal cord injury.

What are the 2 imaging techniques  currently recommended by ANZICS for determining the absence of intracranial blood flow:

Four vessel intra-arterial catheter angiography, with digital subtraction; Tc-99 HMPAO SPECT radionuclide imaging

CT angio with certain caveats may be acceptable. Do not recommend MR angio

Discussion

This question resembles several other questions in the past papers:

• Question 17 from the second paper of 2012 and Question 12.1 from the second paper of 2010 ask about pre-conditions for brain death testing.
• Question 12.2 from the second paper of 2010 discusses imaging modalities to assess the intracranial blood flow.

The pre-conditions for clinical brain death testing are:

• Normothermia (over 35 degrees)
• Normotension( MAP >60)
• Not sedated
• Not paralyzed
• Not in a state of electrolyte or metabolic derangement (eg. hypoglycaemia)
• Possessing at least one intact eye and one ear (to examine brainstem reflexes)
• Able to breathe (to test for apnoea; i.e. high C-spine injury may disqualify you)
• Unresponsive coma
• A suitable explanation for why the patient is comatose, which would be consistent with the diagnosis of brain death

Otherwise, this current paper asks one original question: when must one resort to imaging?

Well. The ANZICS Statement on Death and Organ Donation suggests several distinct scenarios when one cannot perform clinical brain death testing:

• Inability to adequately examine the brain-stem reflexes:
  • One ear and one eye are not intact
  • Sedation, hypothermia, paralysis
• Inability to perform apnoea testing:
  • Severe hypoxic respiratory failure
  • High cervical spinal cord injury