Bispectal Index (BIS) correlates with Ramsay and Cook Sedation Scores in intensive care unit patients

Introduction

It is well known that the administration of sedation and analgesia constitute an inseparable section of the therapeutic approach of patients of the ICU. The follow-up and evaluation of the level of sedation has been considered indispensable, both for obtaining the desirable clinical objectives and, also, to avoid clinical complications. In an effort of creating a stable and objective system of evaluation of the level of sedation, we used various methods, the known scales and, recently the Bispectral Index (BIS) which constitutes a variable modification, a variant of the EEG. The aim of this study was to investigate the probable correlation between BIS and the Ramsay and Cook scales.

Material and methods

Twenty-six patients (18 males and 8 females) of a mean age of 55.46 ± 21.25, APACHE II Score 13.50 ± 5.21, who were hospitalized from August 4 to October 31, 2000 and were subjected to respiratory mechanical support were investigated. Patients who had damage of the neurological system or those who had received muscle relaxants were excluded from the study. All the patients, during evaluation and measurements were under stable sedation and analgesia (Fentanyl, Propofol or Myda-zolam) under continuous intravenous infusion. The evaluation of the level of sedation was carried out during the same time period by means of two different scales: The Ramsay (0–6), Cook's (4–19) and BIS (0–100). The BIS registration lasted 60 min and the final value was calculated from the average of the total recorded 10 min values. The measurements were taken under consideration if the SQI (Signal Quality Index) was higher than 80%. The statistical analysis was carried out by the Jonckheere-Terpstra test.

Results

The results are depicted analytically in Table 1. Between BIS and the Ramsay Scale, a correlation or a degree statistically significant (P = 0.012) were observed. The Cook Scale was not statistically significant (P = 0.091).

Table 1

Conclusions

BIS is satisfactory correlated with the Ramsay scale and its indications correspond to the clinical condition of the patient, where the sedation level is concerned, as opposed to the Cook scale for which no significant correlation was established. The BIS values in the ICU and the corroboration of our results require further study.