Clinical trial NCT01705743: Minimum Alveolar Concentration of Sevoflurane With Nitrous Oxide Inducing Isoelectric EEG
Official title: Minimum Alveolar Concentration of Sevoflurane With 60% Nitrous Oxide Inducing Isoelectric EEG in Mid-aged Adults
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: PHASE4
Conditions: Middle Aged Patients
General Anesthesia
Keywords: anaesthesia
middle aged
minimal alveolar concentration
sevoflurane
nitrous oxide
isoelectric EEG
Lead sponsor: Huazhong University of Science and Technology
Sponsor class: OTHER
First posted: 2012-10-12
Enrollment: 76
Sex: ALL
Minimum age (years): 45
Maximum age (years): 64
Standard ages: ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: 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: 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.

Eligibility criteria: 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

Primary outcomes:
measure: MACie
timeFrame: 30min
Secondary outcomes:
Other outcomes:
Locations:
city: Wuhan
country: China
facility: Department of Anaesthesiology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology
state: Hubei
Study officials:
affiliation: Department of Anaesthesiology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology
name: Yuke Tian, MD.
role: STUDY_CHAIR
References: