Question 14

College answer

1. Ensure severity of brain injury is compatible with brain death (i.e. sufficient intracranial pathology) by reviewing relevant imaging.

   Confirm that there has been a minimum of four hours observation and mechanical ventilation during which the patient has had unresponsive coma (GCS-3), no spontaneous breathing effort, absent cough/tracheal reflex. 

   Complete brainstem reflexes cannot be performed in this case and therefore brain death cannot be certified by clinical testing alone and will have to be determined by demonstrating absence of intracranial blood flow. However, the part of the clinical examination that can be undertaken should be performed.

   Ensure that the following pre-conditions have been met in order to do limited brain death testing-

   1. Normothermia (temperature > 35C); 

   2. Normotension (as a guide, systolic blood pressure > 90 mmHg, mean arterial pressure (MAP) > 60 mmHg in an adult); 

   3. Exclusion of effects of sedative drugs  

   4. Absence of severe electrolyte, metabolic or endocrine disturbances 

   5. Intact neuromuscular function   

   6. Ability to perform apnoea testing 

2. Undertake the clinical tests that can be done

   1. Response to painful stimulus to four limbs and trunk.

   2. Response to pain in trigeminal nerve distribution          

   3. Gag reflex

   4. Cough reflex

   5. Apnoea testing
      
      * Pupillary, corneal and cold caloric reflexes cannot be tested.

3. If all above reflexes absent, proceed to 4-vessel intra-arterial catheter angiography. Blood flow should not be demonstrable above the level of the carotid siphon in the anterior circulation, or above the foramen magnum in the posterior circulation 

   Alternatives- 

   Radionuclide imaging with Technetium -99m radiolabelled hexamethyl propylene amine oxime. (Tc-99mHMPAO)

   Contrast CT or CT-angiography subject to specific radiologic diagnostic guidelines. (Absent enhancement bilaterally of all of the following are likely to be the most reliable early CT indicators of brain death:  middle cerebral artery cortical branches — that is beyond the Sylvian branches; P2 segment of the posterior cerebral arteries; pericallosal arteries; and internal cerebral veins) 

   Brain death can then be certified by 2 medical practitioners (not including the practitioner who performed the imaging investigation) who have examined the patient and have knowledge of the circumstances of the coma

   Important points in the answer:

   Confirmation of a diagnosis compatible with brain death 

   Why clinical testing will not be sufficient 

   Preconditions satisfied 

   List of clinical tests that can be performed 

   Details of imaging test of choice + list of 2 alternatives 

   Detailed radiologic features required for diagnosis on contrast CT was not required, but an indication that specific radiologic criteria exist was expected.

   Confirmation with clinical testing alone was considered a fatal error.

Discussion

The diagnosis of brain death should be the bread and butter of an ICU specialist (as it is the thing that we do which is sufficiently unique to be the domain of intensivists alone). It is therefore surprising that only 43% of the candidates scored a passing mark. The college answer is remarkable in that it offers us a glimpse of the normally hidden marking rubric for an SAQ.

To break down this rubric into answerable components:

Confirmation of a diagnosis compatible with brain death 

• "Brain death cannot be determined without evidence of sufficient intracranial pathology". There must be an explanation for the coma which is consistent with the diagnosis of brain death.

Why clinical testing will not be sufficient 

• The patient has "significant bilateral ocular injuries resulting in a ruptured globe on the right and traumatic third nerve palsy on the left". This prevents one from performing clinical testing, which requires an opportunity to adequately examine brainstem reflexes.

Preconditions satisfied 

• A minimum period of 4 hours in which the patient is observed to have unresponsive coma, unreactive pupils, absent cough/tracheal reflex and no spontaneous respiratory effort
• Normothermia
• Normotension
• Exclusion of the effects of sedating drugs
• Absence of severe electrolyte, metabolic or endocrine disturbance
• Intact neuromuscular function
• Ability to perform apnoea testing

List of clinical tests that can be performed 

One needs to be reminded that the ANZICS statement recommends clinical testing should still be attempted: "If a complete examination is not possible (e.g. eye or ear trauma) or apnoea testing precluded (e.g. severe lung injury or high cervical trauma), then that part of the clinical examination that can be performed, should be undertaken".

• Painful stimulus in cranial nerve distribution, eg. supraorbital nerve pressure
• Painful stimulus in all 4 limbs, eg. nailbed pressure
• Painful stimulus over the supraorbital nerve. (CN V, VII)
• Gag reflex
• Cough reflex
• Apnoea testing

Details of imaging test of choice + list of 2 alternatives 

• Four-vessel intra-arterial angiography is the gold standard
• Tc-99 HMPAO SPECT scan is the next best option
• CT angiography is an "acceptable choice" but has significant limitations. Provided it fits the criteria of a technically adequate study ( contrast enhancement of external carotid artery branches). The college model answer offers a cut-and-pasted list of features from the ANZICS statement (p. 23); "Absent enhancement bilaterally of all of the following are likely to be the most reliable early CT indicators of brain death:
  •  middle cerebral artery cortical branches — that is beyond the Sylvian branches;
  • P2 segment of the posterior cerebral arteries;
  • pericallosal arteries; and
  • internal cerebral veins."