Table 4.

Utility and drawbacks of raw and processed electroencephalogram (EEG) in cardiac surgery

	Strengths	Weaknesses
Raw EEG	•Relatively available and inexpensive •Should not be affected by muscle relaxant •Artifact recognition •Specific patterns (e.g. isoelectricity) have clinical utility and can be appreciated	•Requires training to interpret •No well-designed studies evaluating its efficacy at reducing awareness
Common to both raw and processed EEG	•Might provide evidence with EEG features or with a numerical index that awareness is unlikely •Continues to provide useful information about the brain during CPB	•Does not reflect NMDA antagonism (e.g. ketamine, N2O) •Affected by underlying brain pathology
Processed EEG	•Reduces risk of awareness compared with standard care •Allows threshold-based alarms to be set •Interpretation under most clinical situations is simple	•Lag time between current state of EEG and pEEG index •Underlying algorithms may be poorly understood by those using it, hindering interpretation of artifactual readings •Cost

CPB, cardiopulmonary bypass; NMDA, N-methyl D-aspratate; pEEG, processed EEG