Comparison of five sedation scoring systems by means of auditory evoked potentials

Abstract

Objective: To review five sedation scoring systems and to determine their correlation with an objective method for assessing the level of sedation by means of auditory evoked potentials (AEP) in critically ill patients. Design: Prospective clinical study. Setting: Multidisciplinary intensive care unit in a university hospital. Patients: Ninety-five consecutive patients requiring sedation during intensive care therapy. Measurements and results: Previous studies have shown that auditory evoked potentials, especially latencies of the midlatency component N(b), could serve as an indicator of depth of anaesthesia. In the present study we used this electrophysiological method to evaluate sedation during intensive care therapy. Changes in latency of peak N(b) were compared with various levels of sedation assessed by five established sedation scoring systems. As in anaesthesia, latencies of N(b) increased with increasing depth of sedation. Among the scoring systems, the one developed by Ramsay correlated best with changes in N(b) latency (r2 = 0.68). The coefficient of determination, r2, of the other scores ranged from 0.56 to 0.61. Conclusion: For the assessment of sedation, several scoring systems have been introduced into clinical practice, but the differentiation of deeper sedation levels, especially, remains poor. In this study we compared auditory evoked potentials, as an objective method with which to assess the level of sedation, with five different sedation scoring systems. In comparison with changes in latency of the midlatency component N(b), Ramsay's sedation score showed the closest correlation. Objective electrophysiological monitoring is desirable during long-term sedation.