Evaluation of two processed EEG analyzers for assessment of sedation after coronary artery bypass grafting

Abstract

Objectives: Processed EEG monitoring has been suggested for sedation depth evaluation in intensive care unit (ICU) patients. The present study investigated the efficacy of two processed EEG monitors using SEF_90% or SEF_95% and BIS to differentiate between conscious (Ramsay score 4) and unconscious sedation (Ramsay score 6). Design and setting: Prospective, randomized trial in a surgical ICU of a university teaching hospital. Patients: Patients recovering from elective coronary bypass grafting. Intervention: One of two EEG analyzers was installed (A: Aspect A-1000 measuring SEF_95% and BIS; D: Dräger pEEG measuring SEF_90%). At ICU admission unconscious sedation (Ramsay score 6), and at three 30-min intervals conscious sedation (Ramsay score 4) were investigated. Measurements and results: Fourteen patients were monitored by A and 14 by D. The interindividual variability (coefficient of variation 32–69%) was large for all three processed EEG methods. SEF_90% of analyzer D and BIS of analyzer A showed a statistically significant difference between unconscious and conscious sedation (11±3 and 17±6 Hz, p=0.005; 74±10 and 83±10, p=0.02). Positive and negative predictive values for SEF_90% of analyzer D (0.57, 95% CI 0.34–0.77; and 0.92, 95% CI 0.64–0.99) and BIS of analyzer A (0.55, 95% CI 0.32–0.76; and 0.87, 95% CI 0.60–0.98) were too low for discrimination between conscious and unconscious sedation. Conclusions: The use of processed EEG monitoring cannot be recommended for assessing sedation depth after cardiac surgery.