SBA 0683

Who should carry out brain stem death testing?
  • Carried out by two medical practitioners holding full GMC registration for more than five years:
    • One of whom should be a consultant
    • Experienced in interpreting the results
    • Independent of the transplant team (represents a conflict of interest)
  • The doctors may carry out the tests separately or together, but two sets of tests should always be performed to reduce the risk of observer error
FFICM / ICS Guidance

D

What are the essential components in assessing death by neurological criteria?

The Academy of the Medical Royal Colleges UK (AoMRC) code for the diagnosis of death by neurological criteria outlines three essential components:

1. Evidence of irreversible brain damage of known aetiology
2. Exclusion of reversible causes of coma and apnoea
3. Formal demonstration of coma, apnoea, and the absence of brainstem reflex activity

What are the reversible causes of coma and apnoea that must be excluded in brain death?

Coma

Specific criteria are laid out in guidance from the AOMRC

  • Metabolic or endocrine disturbance
  • Circulatory disturbance
  • Sedative/depressant drugs
  • Hypothermia
Apnoea

Rare but should be actively sought if the history or clinical examination suggests their presence

  • Severe neuromuscular weakness of any cause
  • Spinal cord injury following trauma – should be excluded through x-ray, CT or MRI imaging
  • Residual neuromuscular blockade - it is sensible to routinely use a nerve stimulator to confirm the absence of drug-related block

Which physiological criteria would exclude a patient from brainstem death testing?

Factor
Lower Limit
Upper Limits
Comments
Temperature Disturbance
34°c
-
Impaired consciousness can occur below 34°c
Biochemistry Disturbance
-
-
Derangements clearly the result of brainstem death (e.g. hyponatraemia of DI) may not require correction prior to testing

Sodium

115 mmol/l
160 mmol/l
-

Potassium

2 mmol/l
-
-

Magnesium

0.5 mmol/l
3.0 mmol/l
-

Phosphate

0.5 mmol/l
3.0 mmol/l
-

Glucose

3 mmol/l
20 mmol/l
-
Endocrine Disturbance
-
-
If there is any clinical reason to expect endocrine disturbances, hormonal assays should be undertaken.
Respiratory and Haemodynamic Disturbance
-
-
Requirement for cardiorespiratory stability is an important new prerequisite

pH

7.35
7.45
-

pCO2

-
6.0 kPa
-

pO2

10 kPa
-
-

MAP

60 mmHg
-
FFICM / ICS Guidance

D

How can sedative or depressant drug intoxication be excluded as a cause of coma in brainstem death?

  • May complicate assessment on occasions where:
    • Patient has received infusions of sedative drugs as part of their critical care treatment
    • Brain injury as a result of drug-induced self-harm – especially problematic when substance unknown
  • Possible approaches include:
    • A period of observation:
      • Should approximate four times the elimination half-life of the agent involved to allow effective drug elimination
      • Best suited to circumstances where short-acting agents such as propofol and alfentanil have been given to patients with normal hepatic and renal function
    • Administration of specific antagonists:
      • Flumazenil or naloxone may be used
    • Plasma analysis:
      • Can confirm that a suspected sedative is either not detected or at a subtherapeutic level
      • Particularly suited for agents with long or unpredictable half-lives such as thiopental or phenobarbital.
    • A confirmatory test to demonstrate the absence of cerebral blood flow/perfusion
      • For example, cerebral angiography