Multimodal Evaluation Strategy

The key recommendations are summarised below: 

1. Clinical examination

• Perform a daily neurological examination in patients who are unconscious after cardiac arrest
• It should be noted that clinical examination is prone to interference from sedatives, opioids or muscle relaxants, so potential confounding from residual sedation should always be considered and excluded.
• In unconscious patients at 72 h or later after ROSC, the following tests may predict a poor neurological outcome:
  • The bilateral absence of the pupillary light reflex.
  • The bilateral absence of corneal reflex
  • The presence of myoclonus within 96 h and, in particular, status myoclonus within 72 h.
• Guidelines also suggest to record an EEG in the presence of myoclonic jerks to detect any associated epileptiform activity or to identify EEG signs, such as background reactivity or continuity, that may suggest a potential for neurological recovery.

2. Neurophysiology

• EEG can be performed from day 1 after ROSC to predict outcome and detect seizure activity in comatose patients. Routine EEG or continuous EEG monitoring can also be considered though is not available in all units.
• Suppressed background with or without periodic discharges and burst suppression on EEG (i.e. ‘highly malignant’ patterns) are accurate indicators of a poor prognosis.
• The bilateral absence of somatosensory evoked cortical N20 potentials also indicates poor prognosis after cardiac arrest.
• EEG and somatosensory evoked potentials (SSEPs) results should always be assessed in the context of clinical examination findings and other tests.²

3. Biomarkers

• Biomarkers are released with different latency and speed following acute brain injury. The kinetics of neuron specific enolase (NSE) are not completely known however advice is to use serial measurements of NSE to predict outcome after cardiac arrest.
• Increasing values between 24 and 48 h or 72 h in combination with high values at 48 and 72 h indicate a poor prognosis.
• Conversely NSE levels tend to decrease over 72hrs in patients with favourable outcome.

4. Imaging

• Brain imaging studies should be used to help predict poor neurological outcome after cardiac arrest.
• The presence of a marked reduction in grey matter/white matter ratio on CT Brain within 72hrs after ROSC indicates generalised brain oedema and in the context of cardiac arrest usually suggests hypoxic ischaemic brain injury.
• The presence of extensive diffusion restriction on MRI Brain at 2-7 days after ROSC usually indicates the same, and correlates with poor outcome.
• A repeat CT Brain should be done if the patient remains unconscious at time of prognostication (72 h–96 h after ROSC) if the first CT Brain does not show signs of hypoxic ischaemic brain injury.²

It is strongly recommended that the above prognostication markers should be used in combination and not independently.