Detection of Consciousness by EEG and Auditory Evoked Potentials

Study Overview
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Brief Summary
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The objective of the present investigation is to analyze EEG and auditory evoked potentials at the transition from consciousness to unconsciousness and vice versa. A set of electroencephalographic and auditory evoked potential parameters should be identified that allows separation of consciousness from unconsciousness (reflected by responsiveness/unresponsiveness to command). The study is based on data of 80 patients undergoing general anesthesia with remifentanil and either sevoflurane or propofol.

Detailed Description
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During the past years, monitoring of anesthetic effects on the main target of anesthesia, the brain, has gained increasing attention. Monitoring of the spontaneous electroencephalogram (EEG) and of auditory evoked potentials (AEP) has been suggested. Even if EEG and AEP reflect effects of anesthetic drugs, a visual interpretation is not expedient. As a consequence, several processing methods have been suggested that reduce the electroencephalogram to a numerical value. In the current study, a set of EEG- and AEP parameters based on different analysis methods is tested with respect to the parameters ability in separating consciousness (reflected by responsiveness to command) from unconsciousness at the transition between these stages. Therefore data of 80 unpremedicated patients undergoing general anesthesia with remifentanil and either sevoflurane or propofol is used. The study period is from induction of anesthesia until patients follow command after surgery and includes a reduction of the hypnotic agent after tracheal intubation until patients follow command. The isolated forearm technique is applied before muscle relaxants are given to maintain the ability to squeeze hand to command.

Official Title
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Detection of Consciousness by EEG and Auditory Evoked Potentials

Conditions
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Anesthesia, Electroencephalography/ Drug Effect

Intervention / Treatment
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* Drug: Propofol / Remifentanil
* Drug: Sevoflurane / Remifentanil


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists (ASA) physical status 1-2 Adult patients Exclusion Criteria: Patients with contraindications to the study drugs psychiatric or neurologic disease drug abuse or medication known to affect the central nervous system pregnancy indication for rapid sequence induction
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Propofol or Sevoflurane<br>General anesthesia | Drug: Propofol / Remifentanil<br>* General anesthesia: Loss of consciousness and standard clinical practice<br>Drug: Sevoflurane / Remifentanil<br>* General anesthesia: Loss of consciousness and standard clinical practice<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in EEG- and AEP-parameters during loss- and return of consciousness |  | 1 day | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Impact of muscle activity on EEG- and AEP-parameters |  | 1 day | 
| Influence of anesthetics on EEG- and AEP-parameters |  | 1 day | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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EEG, AEP, Propofol, Sevoflurane, Remifentanil, General anesthesia