Bispectral Index in ICU: correlation with Ramsay Score on assessment of sedation level

The assessment of sedation level in critically ill patient remains a challenge for the intensivists in order to avoid over- or under-sedation phenomena. Scoring systems commonly used still show some limitation; the introduction of Bispectral Index (an EEG parameter) could bring potential advantages in monitoring sedation. According to the reports, Bispectral Index correlates with levels of sedation on the Ramsay Scale. We report our personal experience in this topic.

Twenty patients, diagnosed with chronic obstructive pulmonary disease (COPD), were involved in the study. For an optimal adaptation to respiratory prothesis, they were sedated (with Propofol by continuous infusion at an initial dose of 2 mg/kg/h, which could be modulated with steps of 0.5 mg/kg/h), in order to maintain a Ramsay score of 4-5. BIS value was continuously recorded, and manually calculated on a mean average of a minute during the measuring of Ramsay score (T0) and every 30' for 24 hours on par with Ramsay score. EEG, SpO2, non invasive arterial pressure, ventilatory module, ETCO2, FIO2 were also recorded. For the statistic analysis, Friedman test and Spearman coefficient were utilized. Values of p < 0.05 were considered significant.

980 observations were carried out. The variation range of Ramsay Score was between 2 and 6. BIS range varied from 34 to 98. Statistic analysis of the data obtained pointed out some significative correlations, particularly between Ramsay Score and BIS (p < 0.01), and between BIS and dosage of Propofol (p < 0.01).

The results of the study are consistent with those found in the literature on this topic of study. In fact, this study demonstrates the utility of BIS to track levels of consciousness in ICU patients while still maintaining the use of the score systems to care for ICU patients.