Objective: To compare the reliability of bispectral index (BIS) with sedation agitation scale (SAS) in assessing the depth of sedation in ill patients on mechanical ventilation in intensive care unit (ICU).
Methods: Fifteen patients, aged 18-65 years old, who were receiving mechanical ventilation in ICU for longer than 72 hours and without brain dysfunction, were enrolled in this study. Sedatives and analgesics were suspended at 7:00 am. When patients fully woke up, propofol was infused till BIS score reaching 45-60. This was maintained for 10 minutes, then propofol dosage was decreased 10 microg . kg(-1) . min(-1) for every 10 minutes till all the drug was stopped. BIS was consecutively monitored and SAS was assessed in each interval.
Results: BIS score was markedly correlated with SAS (r=-0.6494, P<0.01). Although a significant correlation was still shown (r=-0.4566, P<0.01), there was wide variability in BIS scores when SAS reached 2-4. With decreasing of the propofol dosage, BIS score gradually increased. There was a satisfactory negative correlation between BIS scores and propofol dosage (r=-0.8076, P<0.01). SAS increased also following the decrease in propofol dosage, and a significant negative correlation was shown between SAS and the dosage of propofol (r=-0.6551, P<0.01).
Conclusion: SAS is well correlated with BIS in assessing the depth of sedation in patients treated with mechanical ventilation in ICU. BIS is an objective, efficient tool for monitoring the depth of sedation in ICU critical patients who are receiving mechanical ventilation, and it is more reliable than SAS, especially when sedated levels reaching SAS 2-4.