The following is the summary of “Prognostication after cardiac arrest: how EEG and evoked potentials may improve the challenge” December 2022 Issue of Intensive Care By Benghanem, et al.
About 80% of CA patients who are resuscitated enter the intensive care unit (ICU) in a coma, and nearly half of those who survive do not regain consciousness until 72 hours later. It is crucial to accurately predict neurological outcomes in these patients to provide accurate information to patients’ loved ones, prevent overtreatment of patients with irreversible hypoxic-ischemic brain injury (HIBI), and prevent premature withdrawal of care in patients with a possible favorable neurological recovery. Unfortunately, only 32% can be classified as having a “poor outcome likely” using the ERC/ESICM 2021 algorithm, with the outcome remaining “indeterminate” in the remaining 68%. The most important thing is to figure out how to better evaluate both negative and positive outcomes. Electroencephalography (EEG) and evoked-potentials (EPs) are examples of neurophysiological tests that can be performed noninvasively at the bedside.
The electroencephalogram (EEG) records electrical activity in the brain with great temporal resolution but poor spatial resolution. In a recent survey examining how neuro-prognostication is currently done, EEG was found to be the most commonly used tool. Extreme HIBI is associated with “highly malignant” EEG patterns, such as suppression or burst suppression, correlated with the predominant frequency and background continuity of EEG. In contrast to EEG signals, continuously recorded from the brain, EPs are elicited by external stimuli and represent the aggregate activities of large populations of neurons firing in synchrony. A variety of EPs can be evaluated in the intensive care unit, each with its onique brain generators and prognostic values. These include somatosensory EPs (SSEPs), brainstem auditory EPs (BAEPs), middle latency auditory EPs (MLAEPs), and long latency EPs (ERPs) with mismatch negativity (MMN) and P300 responses.
In this article, researchers provide a concise summary of the various neurophysiological tools available, including signal generators, recording modalities, interpretations, and prognostic values for EEG and EPs. Investigators conclude by evaluating the potential for further neurophysiological studies to clarify the prognosis of CA patients who are comatose or suffering from disorders of consciousness (DoC).