Abstract
Introduction
Neurologic Outcome
A challenge in interpreting the literature on AIE is the varying or imprescise use of the phrase “poor neurologic outcome.” The American Academy of Neurology practice parameter paper defines poor outcome as: death, persistent unconsciousness (such as a vegetative state), or severe disability requiring full nursing care after 6 months. This is the definition used in this Fast Fact.
Predictors of Neurologic Outcome
A review of the current literature reveals that data obtained by careful neurologic examination, electrophysiologic studies, and biochemical markers are most predictive of outcome (see below). Other factors not strongly predictive of outcome include: age, gender, cause of arrest, type of arrhythmia, total arrest time, duration of CPR, geographic location of arrest, elevated body temperature, elevated intracranial pressure, concurrent respiratory failure, and brain imaging findings.
Note: the data below assume patients are not receiving medications that would significantly confound their neurologic examination such as high-dose barbiturates. In all cases, specialist neurologic examination and input is advised.
Strong Indicators of Poor Outcome (false-positive rates of 0% based on current literature)
Moderate Predictors of Poor Outcomes (these all predict a poor outcome, but not as invariably as the above factors based on current literature)
The Therapeutic Hypothermia Protocol
The majority of the evidence for prognosis in the comatose patient after CPR predates the widespread use of therapeutic hypothermia in patients after cardiac arrest. It remains unclear how this intervention will change prognostication. While the above factors will likely still indicate poor prognosis, the timing of when the evaluations should be done, as well as if they will predict a uniformly poor outcome is uncertain. One European study advises that patients have an initial neurological assessment as soon as possible, but that the second assessment occurs no earlier than 48–72 hours after resumption of normothermia. Zandbergen et al suggest that serum NSE > 33 μg/L occurring while hypothermic still consistently predicts poor outcomes accurately. Initial data on the predictive value of SSEPs in patients who underwent hypothermia confirmed that bilateral absent N20 responses is highly predictive of a poor outcome. There has been a case report of a single patient with absent N20 responses who made a full recovery, highlighting the importance of ongoing investigation into the impact of the hypothermia protocol on the prognosis of AIE.
