Measuring depth of sedation in intensive care patients with the electroencephalographic Narcotrend Index

The electroencephalographic Narcotrend Index was evaluated as a measure of sedation in mechanically ventilated intensive care unit patients. Narcotrend Index and conventional electroencephalography parameter values were compared to the Richmond Agitation-Sedation Scale and a simplified three-level sedation scale.

In all, 100 mechanically ventilated patients, admitted to the cardiac surgical intensive care unit after open-heart surgery, were enrolled in this prospective observational study. The Narcotrend Index was recorded while patients were either sedated by propofol infusion or without sedative medication while being weaned off the ventilator. Clinical assessment of the patients' level of sedation was performed by means of the Richmond Agitation-Sedation Scale by a single observer who was blinded to the Narcotrend Index.

With the six-level Richmond Agitation-Sedation Scale, the prediction probability (PK) for the Narcotrend Index (0.81) was better than for all other electroencephalography parameters (P < 0.01) except for relative power in the beta band (PK 0.75). Using the three-level sedation scale instead, PK values for the Narcotrend Index (0.88) and all electroencephalography parameters improved (P < 0.01), and the Narcotrend Index was now superior to all electroencephalography parameters. Narcotrend Index values were distributed among the various sedation levels with significant overlap.

When used for assessment of propofol sedation in postsurgical cardiac intensive care unit patients, the Narcotrend Index can distinguish between very light and deep sedation. With respect to differentiation between light and moderate or moderate and deep sedation, the Narcotrend Index was not reliable in this study.