Briefly discuss the information (including clinical features / investigations) that may help determine the prognosis of patients following cardiac arrest.
Answer and interpretation
Prognostication after cardiac arrest may be very difficult and involve a number of modalities.
It involves consideration of:
- Underlying cause of the arrest
- Use of therapeutic hypothermia
- Features of the arrest – down time, CPR, ROSC
- Timing:Neurological assessment timing will be determined by the use of therapeutic hypothermia and the duration and type of medication for sedation but is most reliably performed day 3 without therapeutic hypothermia – probably day 5 with TH. Suggestion is to wait 72 hours after return of normothermia.
With new TTM trial suggesting 36C then 72 hours post arrest may again be appropriate.
Clinical – off sedation and neuromuscular blocking agents
Cranial nerve abnormalities – absence of pupillary response and corneal reflexes are bad prognostic indicators.
Best Motor response at 72 hours with absent or extensor response associated with poor outcome.
Status / Generalised and repetitive myoclonus (as opposed to sporadic myoclonus)
- Nurone specific enolase >33mcg/L at days 1-3 indicates poor outcome
- S100, CSF CKBB not accurate enough for prognostication
- EEG: generalised suppression, burst suppression or generalised periodic complexes strongly associated with poor outcome.
- SSEPs: Bilateral absence of N20 component of SSEP with median nerve stimulation within 1-3 days is strongly associated with poor outcome.
- CT appearance – catastrophic changes with obvious pathology. Diffuse oedema has not been formally assessed as an indicator.
- MRI may be more sensitive
Predictors of better outcome are:
- Recovery of brainstem reflexes within 48 hours
- Return of purposeful response within 24 hours
- Hypothermia at the time of arrest
- Young age