Development of automatic infusion systems for sedatives and analgesics with surface EEGs and Auditory Evoked Potentials as Input Signals

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The aim of this project was to develop automatic infusion systems which were able to control a sedative and an analgesic independently. We chose surface EEG variables and auditory evoked potentials as input signals to quantify levels of sedation and analgesia. We have performed following sub-studies to complete this project.1) Development of target controlled infusion (TCI) systems for propofol and fentanylUsing published pharmacokinetic models, we made up TCI systems which were able to control blood or effect site concentration of propofol and fentanyl independently.2) Development of a computer system to integrate surface EEG variables and auditory evoked potentialsBispectral Index (BIS) and auditory evoked potential index (AEPindex) were involved as numerical variables for surface EEG and auditory evoked potentials, respectively. BIS and AEPindex values were automatically recorded in the system.3) Investigation of the interaction of propofol and fentanyl on EEG variablesWe studied interaction of propofol and fentanyl on EEGs to develop an algorithm which could quantify level of sedation and analgesia independently.4) Investigation of an algorithm to detect awareness using BIS and AEPindexWe could detect awareness more accurately using a combination of BIS and AEPindex5) Effects of profound hypothermia on EEG variablesWe investigated stability of EEG variables down to 22 degree centigrade. We found the AEPindex was most stable among the EEG variables studied during profound hypothermia.In conclusions, we found that the combination of the surface EEG and auditory evoked potentials were useful to detect awareness more accurately, however the combination did not have enough ability to quantify level of analgesia.