Minimal Alveolar Concentration of Sevoflurane Inducing Isoelectric Electroencephalogram

Sevoflurane can abolish movement or adrenergic response to noxious stimulus. In order to investigate the effect of sevoflurane on cerebral electrical activity, we determined the MAC of sevoflurane inducing isoelectric electroencephalogram (EEG) in 50% of the subjects (MACie) in middle aged subjects.

Study Overview

• Status: Completed
• Conditions: Sevoflurane; General Anesthesia; Middle Aged Patients
• Intervention / Treatment: Drug: Sevoflurane

Detailed Description

Patients received sevoflurane for anesthesia induction and maintenance at preselected concentrations according to an 'up and down' design, with 0.2% as a stepsize. General anesthesia was induced and maintained with sevoflurane, tracheal intubation was facilitated with cisatracurium. After a steady-state period of 30min without surgical stimulation, the state of isoelectric EEG was considered as significant when a burst suppression ratio of 100% last for more than 1 min. The haemodynamic responses to skin incision and the vasopressor requirement to maintain cardiovascular system were also analysed according to the EEG state.

• Study Type: Interventional
• Enrollment (Actual): 31
• Phase: Phase 4

Contacts and Locations

Study Locations

• China
  • Hubei
    • Wuhan, Hubei, China, 430030
      • Department of Anaesthesiology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 45 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• 45-65yr
• upper abdominal surgery in general anaesthesia
• ASA physical status classification of I or II

Exclusion Criteria:

• 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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Sevoflurane; Anaesthesia was induced by 8% sevoflurane. Cisatracurium 0.15mg 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 2L min-1. Gas concentrations were analysed using a gas analyser.The end-tidal concentration of carbon dioxide was maintained at 4.7kPa; an esophageal temperature probe was inserted and a warming unit was used if necessary to maintain normothermia (35.5°-38.5°). The surgical incision was performed at least 30min after tracheal intubation. When arterial blood pressure (MAP) decrease exceeding 20% of baseline values. Phenylephrine 0.1mg was administered intravenously if necessary to maintained MAP and recorded.

Drug: Sevoflurane; The design of experiment is referred to the "Dixon up-and-down" method. The first subject was designed to receive end-tidal sevoflurane concentration of 1.7%. For each subject, 30 min interval time was given. The isoelectric EEG was considered as significant when the isoelectric state last for more than 1min. The maximal burst suppression rate was recorded if isoelectric EEG was not reached. Heart rate and MAP, were recorded 2 and 1min before and 3 min after skin incision. Adrenergic reflexes positive cases were counted.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
MACie	Minimal Alveolar Concentration of sevoflurane inducing isoelectric electroencephalogram (EEG) in 50% of the subjects (MACie)	30min

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
MACbs	Minimal Alveolar Concentration of sevoflurane inducing inducing burst suppression EEG (MACbs) in middle aged adults.	30 min

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Hemodynamic parameters	Hemodynamic parameters 2 min before and 3 min after skin incision	3 min
Use of phenylephrine	Use of phenylephrine during induction and maintenance of anesthesia with sevoflurane.	30 min

Collaborators and Investigators

• Sponsor: Huazhong University of Science and Technology
• Collaborators: National Natural Science Foundation of China; Ministry of Health, China

Study record dates

Study Major Dates

• Study Start: March 1, 2012
• Primary Completion (Actual): May 1, 2012
• Study Completion (Actual): July 1, 2012

Study Registration Dates

• First Submitted: August 8, 2012
• First Submitted That Met QC Criteria: August 9, 2012
• First Posted (Estimate): August 10, 2012

Study Record Updates

• Last Update Posted (Estimate): August 14, 2012
• Last Update Submitted That Met QC Criteria: August 12, 2012
• Last Verified: August 1, 2012

More Information

Terms related to this study

• Keywords: sevoflurane; anaesthesia; middle aged; minimal alveolar concentration; isoelectric EEG
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Central Nervous System Depressants; Anesthetics, General; Anesthetics; Platelet Aggregation Inhibitors; Anesthetics, Inhalation; Sevoflurane
• Other Study ID Numbers: TJMZK20120301