Prognosis following cardiac arrest

A patient is admitted to the intensive care unit following an out-of-hospital ventricular

fibrillation cardiac arrest. He was sedated and cooled for 24 hours and is now

72 hours post event.Which of the following is NOT invariably associated with a poor

outcome (i.e. a Glasgow Outcome Scale score of three or less)?

a) Absent bilateral N20 response from the primary somatosensory cortex at 72 hours

post event

b) Extensor posturing to noxious stimulus at 72 hours post event

c) Absence of a corneal response at 72 hours post event

d) Myoclonic status epilepticus at 24 hours post event

e) Significantly elevated levels of S100 (glial protein) post cardiac arrest

Answer: e

Explanation

A patient’s outcome following cardiac arrest is improved by cooling post event.

However, a proportion of these patients still die or are left with a significant neurological

disability. A comatose state (otherwise known as anoxic-ischaemic encephalopathy)

post resuscitation is associated with poor prognosis, but within this group a

small proportion will make a good neurological recovery. Most studies that have

assessed predictors of outcome in this patient group have as an objective the reliable

prediction of an outcome better than a Glasgow Outcome Scale score of three or less.

This scale gives scores of one to five (one = dead; two = vegetative state; three = severe

disability; four = moderate disability; and five = a good recovery) and a score of three

or less is considered a poor prognosis. A number of clinical signs are associated with

poor prognosis and a subgroup of these are invariably associated with poor prognosis.

The latter group includes an absent pupillary response 72 hours post event (but not on

admission to hospital), a motor response to noxious stimuli that is no better than

extensor posturing (i.e. a decerebrate response or no response) at 72 hours and an

absent corneal response also at 72 hours. Myoclonic status epilepticus usually presents

as bilaterally synchronous twitches of limb, trunk, or facial muscles and is most

commonly detected at 24 hours. Its presence is, likewise, invariably a marker of a

poor outcome. The measurement of somatosensory evoked potentials (SSEPs), especially

the N20 response from the primary somatosensory cortex, has emerged as an

extremely accurate predictor of a poor outcome in patients with anoxic-ischaemic

encephalopathy. Bilateral absence of the N20 response 72 hours post event is again

invariably associated with poor outcome. Several chemicals are released from the brain

into the blood and cerebrospinal fluid after cardiac arrest, including neuron-specific

enolase and S100 (glial protein). The former shows a strong correlation with outcome,

the latter far less so. The measurement of other clinical variables has insufficient

predictive value to be as useful in clinical practice, i.e. they may be associated with

poor outcome but the correlation is less strong than those above. These include age,

sex, cause of cardiac arrest, type of arrhythmia, total arrest time, body temperature on

admission and duration of CPR.

Reference

Young G. Clinical practice. Neurologic prognosis after cardiac arrest. N Engl J Med

2009; 361(6): 605–11.