Assessment of sedation level in critically ill mechanically ventilated patients: Is bispectral index correlated with Richmond agitation- sedation scale?

The intensivist should be avoided over or under sedation in mechanically ventilated patients. There are controversies in validity of bispectral index (BIS) in the management of intensive care unit (ICU) patients. The aim of this study was to evaluate sedation level in sedated and mechanically ventilated patients in our ICU using BIS and Richmond agitation–sedation scale (RASS, as a valid tool) and to determine the correlation between these two methods of evaluation. Following the institutional research committee approval, we prospectively determined the sedation level in 33 patients aged 20-75 years who were mechanically ventilated and sedated routinely using intravenous diazepam (0.05 – 0.1 mg/kg/6 hr) combined with intravenous morphine (0.05 – 0.1 mg/kg/6 hr) in central ICU of Al-Zahra hospital. In each patient, we assessed BIS (0 to 100) values and also RASS (-5 to +4) twice a day, two hours after receiving systemicsedation in the morning and evening during mechanical ventilation period. Appropriate sedation score was considered -2 and -3 on RASS and 70 to 80 in BIS. Lower or greater values were considered as under- or over-sedation, respectively. Data were analyzed using chi-square and spearman''s correlation tests. In this study, sedation level was assessed in patients using RASS (201 times) and BIS (201 times) methods. The frequency (percent) of under-sedated, appropriately sedated and over-sedated patients with BIS assessments were 121 (60.2%), 35 (17.4%) and 45 (22.4%), respectively. These values for RASS assessments were 196 (97.5%), zero, and 5 (2.5%), respectively. There was a weak correlation between BIS and RASS for determination of sedation level (P = 0, r = 0.245). This study showed that most of our ICU patients were under-sedated. BIS was poorly correlated with RASS in assessing the depth of sedation in mechanically ventilated patients.