Spectral entropy as an objective measure of sedation state in midazolam-premedicated patients.

CONTEXT

Objective assessment of sedation depth is a valuable target. Spectral entropy is an anesthetic depth monitor based on the analysis of the electroencephalogram signal.

AIMS

To evaluate the performance of spectral entropy as an objective measure of sedation state in midazolam-premedicated patients and to correlate it with a clinically assessed sedation score.

SETTINGS AND DESIGN

This prospective double-blind placebo-controlled study was performed in King Fahd Hospital of the university.

METHODS

Eighty adult ASA I-II patients were randomly assigned into 4 groups. Patients were premedicated using 0.02, 0.04, or 0.06 mg/kg midazolam or saline intramuscularly. The effect of these doses on the Observer's Assessment of Alertness and Sedation (OAA/S) scale, hemodynamic variables, response entropy (RE), and state entropy (SE), was evaluated at 10, 20, and 30 min after premedication.

STATISTICAL ANALYSIS

Spearman Rank-order correlation analysis to examine the relation between OAA/S and entropy. The ability of spectral entropy to predict the depth of sedation was evaluated using Smith prediction probability.

RESULTS

Midazolam doses ≥0.04 mg/kg produced significant decreases in RE, SE, and OAA/S scores. There was a strong correlation between midazolam dose and OAA/S scale, RE, and SE since Spearman Rank R values were 0.792, 0.822, and 0.745, respectively (P<0.001). In addition, RE and SE were strong predictors of OAA/S level during midazolam sedation with no significant difference in prediction between the 2 entropy components.

CONCLUSIONS

Spectral entropy is a reliable measure for the sedative premedication. It may be used to objectively assess the adequacy of midazolam premedication and to determine the dose requirement.