Comparison of electrophysiologic monitors with clinical assessment of level of sedation

OBJECTIVE: To assess the correlation between 2 clinical sedation scales and 2 electroencephalographic (EEG)-based monitors used during surgical procedures that required mild to moderate sedation. PATIENTS AND METHODS: Patients scheduled for elective surgery participated in this Institutional review board-approved study from March 2003 to February 2004. Level of sedation was determined both clinically using the Ramsay and the Observer's Assessment of Alertness/Sedation scales and with 2 EEG measures (the Bispectral Index version XP [BIS XP] or the Patient State Analyzer [PSA 4000]), Correlation between these 2 measures of sedation were tested using nonparametric statistical tests. RESULTS: The BIS XP monitor was used In 26 patients, and the PSA 4000 monitor was used in 24 patients. The Ramsay and Observer's Assessment of Alertness/Sedation scores correlated with each other (r=-0.96; P <.001) and with both the BIS XP (r=-0.89 and r=0.91, respectively; P <.001) and the PSA 4000 (r=-0.80 and r=0.80, respectively; P <.001) values. However, this correlation was strongest only at the extremes. Between the BIS XP and PSA 4000 values of 61 and 80, the clinical sedation scores varied greatly. CONCLUSION: On the basis of our results, these EEG-based monitors cannot reliably distinguish between light and deep sedation.