BIS and Ramsay score in critically ill patient: what future?

The recent introduction of BIS has improved the concept of utilizing it as a method for the assessment of the sedation level, thus opening new frontiers in critically ill patients care. Its validity in measuring the hypnotic drug effects has been repeatedly proved, but it has rarely been used in ICU. The aim of this paper is to evaluate the correlation between BIS and Ramsay score and its fluctuations with the sedative dosage variations, as a possible utilization in ICU.

In this study, 20 patients with severe lung disease requiring ventilator support, were recruited. All patients were sedated with propofol and/or midazolam to maintain a Ramsay score of 4. Continuous infusion techniques were commonly used. At time 0 and every half an hour, the patients were evaluated by 2 investigators, using the Ramsay score and the BIS simultaneously. The BIS was calculated by a 1-min recording every time that the sedation score was recorded, for a total of 960 observations. In addition BIS was continuously recorded to establish a baseline value, when the patient was not stimulated. Ventilator settings, medications and vital signs were also recorded.

With the increase of the Ramsay score there was a progressive decrease in the BIS score (Ramsay score=2, BIS=88 +/- 15.1; Ramsay score=6, BIS=52.2 +/- 10.7); between BIS and Propofol dosages and between Ramsay score and systolic pressure.

The data obtained show a good correlation between Ramsay score and BIS.