[Use of the electroencephalographic spectral edge frequency 90 to monitor sedation of chronically ill patients]

Abstract

Introduction: The depth of sedation required for patients in critical care units varies over time and should be subject to control. The clinical assessment scales used at present are inadequate, and several electroencephalographic variables have been investigated in recent years with the aim of quantifying depth of sedation. One such variable is the spectral edge frequency 90 (SEF90).

Objectives: To establish the correlation between SEF90 and the Ramsay score as indicators of depth of sedation. To estimate the ability of SEF90 to predict sedation and a patient's hemodynamic response during aspiration of secretions through the orotracheal tube.

Patients and methods: Patients in a surgical intensive care unit. The ability of SEF90 to predict a certain Ramsay score was assessed by logistic regression. We also calculated the predictive probability (Pk) of SEF90 for the appearance of hemodynamic change and of movement in the event of endotracheal aspiration.

Results: When SEF90 was < 16 Hz, the probability of a Ramsay score >= 4 was >= 90% (Pk = 0.91). Neither SEF90 nor the Ramsay score predicted hemodynamic response to orotracheal aspiration.

Conclusions: SEF90 distinguishes superficial from deep sedation but does not differentiate further degrees of depth or the likelihood of hemodynamic instability or movement in response to aspiration.