Electroencephalogram (EEG) can be utilized in the measurement of the depth of anesthesia also during multidrug administration

Within the last few decades, electroencephalogram (EEG) has become a widely used tool for the automatic assessment of the depth of anesthesia.  The EEG-based depth of anesthesia measurement has been associated with several advantages, such as a decreased incidence of intra-operative awareness and recall, faster recovery, and reduced consumption of anesthetics.

The use of EEG for depth of anesthesia measurement is based on the changes in the electrical activity of the brain induced by the anesthetics. A small dose of an anesthetic drug in the blood generates high frequency beta activity indicating light anesthesia. As more of the drug is given, a progressive slowing to alpha, theta, and finally to delta frequencies is seen in the EEG. Simultaneously, the amplitude of EEG increases. The depth of anesthesia can be estimated by observing these kinds of changes in the signal characteristics. The measurement is challenged, however, by the simultaneous administration of different types of anesthetics, which is the common practice in the operating rooms today.

At the University of Oulu, Finland, a PhD study has been released on the EEG-based depth of anesthesia measurement. The focus of the work is on multidrug infusion in which the hypnotic drug (propofol) is supplemented with a short-acting opioid (remifentanil). In the study, the effects of remifentanil on EEG and depth of anesthesia during propofol infusion are described. It is found that the coadministration of remifentanil suppresses some of the propofol-induced EEG changes and produces some of its own. The effect on EEG is strongly dependent on the level of anesthesia. The opioid is also shown to significantly modify the mutual relations of the EEG changes and the clinical signs of the patient. Based on these findings, a technology is proposed for separating the effects of the two drugs.

“The thesis provides a framework for the EEG-based depth of anesthesia measurement during multidrug administration with propofol and remifentanil. Due to the similar mechanisms of action, the results are likely to be generalizable to other hypnotic-opioid drug combinations. The study thus offers potential for the development of more advanced systems for automatic monitoring of depth of anesthesia”, concludes Research Scientist, PhD Candidate (Computer Science and Engineering), and medical student Jukka Kortelainen.

Additional information and requests for an interview:

Research Scientist Jukka Kortelainen, tel. +358 50 447 4909, e-mail: jukka.kortelainen@ee.oulu.fi

Communication Officer Hannakaisa Aikio, tel. +358 400 142 293, e-mail: hannakaisa.aikio@ee.oulu.fi

The PhD thesis is available at: http://jultika.oulu.fi/Record/isbn978-951-42-9485-3

Last updated: 26.8.2011