Using EEG to monitor anesthesia drug effects during surgery

Abstract

The use of processed electroencephalography (EEG) using a simple frontal lead system has been made available for assessing the impact of anesthetic medications during surgery. This review discusses the basic principles behind these devices. The foundations of anesthesia monitoring rest on the observations of Guedel with ether that the depth of anesthesia relates to the cortical, brainstem and spinal effects of the anesthetic agents. Anesthesiologists strive to have a patient who is immobile, is unconscious, is hemodynamically stable and who has no intraoperative awareness or recall. These anesthetic management principles apply today, despite the absence of ether from the available anesthetic medications. The use of the EEG as a supplement to the usual monitoring techniques rests on the observation that anesthetic medications all alter the synaptic function which produces the EEG. Frontal EEG can be viewed as a surrogate for the drug effects on the entire central nervous system (CNS). Using mathematical processing techniques, commercial EEG devices create an index usually between 0 and 100 to characterize this drug effect. Critical aspects of memory formation occur in the frontal lobes making EEG monitoring in this area a possible method to assess risk of recall. Integration of processed EEG monitoring into anesthetic management is evolving and its ability to characterize all of the anesthetic effects on the CNS (in particular awareness and recall) and improve decision making is under study.

How deep is your love: Awareness monitoring during general anesthesia

“…Also, various events (hypotension, hypercarbia, etc.) have the consequence of EEG changes 22 . Similar to this monitoring is the compressed spectral analysis (CSA).…”

Estimation the Depth of Anesthesia by the Use of Artificial Neural Network

“…The traditional monitoring of the DOA are based on automatic responses of patient body such as respiration pattern, blood pressure, body temperature, tearing, sweating and heart rate (Viertiö-Oja et al, 2004;Miller, 2005). However, considering the following major clinical problems at anesthesia discussion, i.e., sudden conscious during the surgery at the rate of 2-3% (in all under surgery patients) and the rate more than 4% for the patients with brain tumor and the patients under the heart surgery (Jameson & Sloan, 2006), and applying overdose anesthetic agents for the patients relying on the hemodynamic parameters as a criterion for the anesthesia conditions, encouraged the researchers to make an essential effort to introduce more reliable methods (Haddad et al, 2007). In this base, during the present two decades, some novel methods based on electroencephalogram (EEG) signal processing instead of the traditional methods based on hemodynamic parameters have been used by medical engineers to estimate DOA.…”

“…Bispectral index is a complex parameter, including a combination of time domain, frequency domain and higher order spectral (HOS) sub-parameters respectively named Burst Suppression Ratio (BSR as defined in subsection 3. are Bi-Spectrum value of the windowed signal in the ranges 0.5 to 47 Hz and 40 to 47 Hz respectively). This monitor integrates these three sub-parameters to produce BIS index, however, a detailed algorithm of this monitor is not published yet (Jameson & Sloan, 2006). Between 1990 and, approximately 450 peer-reviewed publications have been examined the clinical effectiveness and accuracy of the BIS™ monitor (Jameson & Sloan, 2006).…”

Quantification of Depth of Anesthesia by Means of Adaptive Calculation of Correlation Dimension Parameters

“…Several of the above methods are available that have recently been reviewed by Freye et al 3 and Jameson et al 4 The earliest methods were based on the FFT analysis of EEG signals. These approaches tend to find parameters that describe spectrum characteristics.…”

“…5 Approximately 450 peer-reviewed publications between 1990 and 2006 have been examined the effectiveness, accuracy and usefulness, both clinical and economical, of the BIS TM monitor. 4 The interpretation of the EEG is complex since it is a reflection of the brain state, the effects of the surgical procedure and the influence of anesthetic drugs. Anesthetic agents have different effects on the EEG and do not represent a straightforward solution concerning the monitoring of depth of anesthesia.…”