Minimum Alveolar Concentration of Sevoflurane With Nitrous Oxide Inducing Isoelectric EEG

Study Overview
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Brief Summary
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In order to investigate the effect of a combination effect of sevoflurane and nitrous oxide on cerebral electrical activity, the investigators determined the MAC of sevoflurane combined with nitrous oxide inducing isoelectric electroencephalogram (EEG) in 50% of the subjects (MACie) in middle aged subjects.

Detailed Description
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Anaesthesia was induced by sevoflurane in oxygen. Cisatracurium 0.15 mg kg-1 was administered after loss of the lash reﬂex, then ventilated manually until the amplitude of T1 decreased to 0. Intubation was performed and switched to mechanical ventilation with a fresh gas flow of 2 L min-1. Anesthesia was maintained by sevoflurane or sevoflurane+60% nitrous oxide respectively. The surgical incision was performed at least 30 min after tracheal intubation, provided that the predetermined end-tidal sevoflurane concentration had been constant for at least 30 min and that the difference between inspired and end-tidal concentrations was less than 10%. Brain electrical activity was measured using Narcotrend Monitor and S/5 Compact Anaesthesia Monitor, which displayed unprocessed EEG and burst suppression ratio, respectively. The design of the experiment is referred to the Dixon up-and-down method. To avid anaesthesia awareness, the first subject was designed to receive end-tidal sevoflurane concentration of 2.5 %. The presence or absence of isoelectric EEG (Entropy Module) of the preceding patient determined the end-tidal concentration of sevoflurane given to the next patient (with an increment size of 0.2%). The isoelectric EEG was considered as significant when the isoelectric state last for more than 1 min. The maximal burst suppression rate was recorded if isoelectric EEG was not reached.

Official Title
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Minimum Alveolar Concentration of Sevoflurane With 60% Nitrous Oxide Inducing Isoelectric EEG in Mid-aged Adults

Conditions
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Middle Aged Patients, General Anesthesia

Intervention / Treatment
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* Drug: Sevoflurane+Nitrous oxide
* Drug: Sevoflurane


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: between 45 to 64 years old ASA physical status class 1 or 2 elective abdominal surgery Informed Consent Exclusion Criteria: history of neurological disease received central nervous system-active drugs cardiac ejection fraction less than 40% history of difficult intubation or anticipated difficult intubation daily alcohol consumption obesity, defined as a body-mass index of more than 30 without informed consent others judged inappropriate as subjects for the study by the Study Chair

Ages Eligible for Study
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Minimum Age: 45 Years
Maximum Age: 64 Years

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: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Group 1 Sevoflurane+Nitrous oxide<br> | Drug: Sevoflurane+Nitrous oxide<br>* 60% nitrous oxide +40% oxygen+ Sevoflurane<br>|
| Active Comparator: Group 2 Sevoflurane<br> | Drug: Sevoflurane<br>* 100% oxygen+ Sevoflurane<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| MACie | Minimal Alveolar Concentration of sevoflurane and NO inducing isoelectric electroencephalogram (EEG) in 50% of the subjects (MACie) | 30min | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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anaesthesia, middle aged, minimal alveolar concentration, sevoflurane, nitrous oxide, isoelectric EEG