EEG spectral analysis during surgical procedure under anesthesia with Ketamine

Abstract

Maintaining an adequate level of anesthesia during a surgical procedure has been proofed to be of great importance for both intraoperative and postoperative safety of the patient. Depth of anesthesia monitors are trustworthy tools to assist anesthesiologist inducing general anesthesia. These monitors are based on the processing of the electroencephalogram (EEG) signal to obtain an indicator of the level of consciousness. However, not all anesthetics have the same effects on the EEG, and so under some drugs these monitors can be misled and provide a result not consistent with the clinical state of the patient. This is the effect produced by Ketamine, a dissociative anesthetic. In order to determine its effects to the brain activity, the EEG energy spectrum and three depth of anesthesia indexes (qCON, qNOX and BIS) have been analyzed in the different clinical states of a surgery. The results obtained are compared providing boxplots with other two anesthetics, Propofol and Desflurane, to see the differences between anesthetic drugs. Statistical analyses are performed, as Mann-Whitney U and Wilcoxon tests, to find differences between the groups. Significant differences between anesthetics and also between different clinical states have been obtained for all the parameters considered. However, it has been determined that Ketamine has its greatest effect during the first twenty minutes after its administration as a bolus, where high frequency bands as beta (14-30 Hz) and gamma (30-40 Hz) increase until they reach values related to an awake state. It is presumed that the depth of anesthesia monitors interpret the activity of this bands as if the patient is recovering consciousness.