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

Objectives: Processed EEG monitoring has been suggested for sedation depth evaluation in intensive care unit (ICU) patients. The present study investi gated the efficacy of two processed EEG monitors using SEF90% or SEF95% and BIS to differentiate between conscious (Ramsay score 4) and unconscious se dation (Ramsay score 6). Design and setting: Prospective, randomized trial in a surgical ICU of a un iversity teaching hospital. Patients: Patients recovering from elective coronary bypass grafting. Intervention: One of two EEG analyzers was installed (A: Aspect A-1000 meas uring SEF95% and BIS; D: Drager pEEG measuring SEF90%). At ICU admission un conscious sedation (Ramsay score 6), and at three 30-min intervals consciou s 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 lar ge for all three processed EEG methods. SEF90% of analyzer D and BIS of ana lyzer A showed a statistically significant difference between unconscious a nd conscious sedation (11 +/- 3 and 17 +/- 6 Hz, p = 0.005; 74 +/- 10 and 8 3 +/- 10,p = 0.02). Positive and negative predictive values for SEF90% of a nalyzer D (0.57, 95% CI 0.34-0.77; and 0.92, 95% CI 0.64-0.99) and BIS of a nalyzer 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.