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

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 SEF90% or SEF95% and BIS to differentiate between conscious (Ramsay score 4) and unconscious sedation (Ramsay score 6).

Prospective, randomized trial in a surgical ICU of a university teaching hospital.

Patients recovering from elective coronary bypass grafting.

One of two EEG analyzers was installed (A: Aspect A-1000 measuring SEF95% and BIS; D: Drager pEEG measuring SEF90%). At ICU admission unconscious sedation (Ramsay score 6), and at three 30-min intervals conscious sedation (Ramsay score 4) were investigated.

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. SEF90% 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 SEF90% 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.

The use of processed EEG monitoring cannot be recommended for assessing sedation depth after cardiac surgery.