Assesment of correlation between bispectral index and four common sedation scales used in mechanically ventilated patients in ICU

Abstract

Purpose: The aim of this study was to compare the correlation between bispectral index (BIS) monitor and four commonly used subjective clinical scales (Ramsay Sedation Scale (RSS), Richmond Agitation Sedation Scale (RASS), Sedation Agitation Scale, Adaptation to Intensive Care Environment scale) in mechanically ventilated patients in intensive care unit (ICU). In addition, comparison of responsiveness of the clinical scales in respect to BIS changes is another goal of this study.

Materials and methods: Mechanically ventilated thirty patients who required sedation for any reason were enrolled to study. Patients who needed neuromuscular blockade, patients with known hearing and visual problems, neurological diseases, anoxic encephalopathy, mental retardation and who developed hemodynamic instability (mean arterial pressure below 60 mmHg) and hypoxemia (sPO2 below 90%) during follow-up were excluded. Starting before the initiation of sedation, first BIS scores then clinical sedation scales were evaluated. This procedure is repeated every 2 hours for 24 hours.

Results: All of the four clinical scales were significantly correlated with BIS. BIS and clinical scale values, except Adaptation to Intensive Care Environment scale, showed significant changes compared to baseline after the initiation of sedation. Ramsay and Richmond scales showed the highest correlation with BIS (respectively, r = 0.758, r = 0.750). Adaptation to Intensive Care Environment revealed the lowest correlation (r = 0.565).

Conclusions: All of the scales were significantly correlated with BIS. RSS and RASS showed higher correlation than other scales. As a conclusion: RSS and RASS can be used for monitoring the depth of sedation in mechanically ventilated patients in ICU.