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.
Middle Aged Patients
|Study Design:||Endpoint Classification: Pharmacodynamics Study
Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Treatment
|Official Title:||Minimal Alveolar Concentration of Sevoflurane Inducing Isoelectric Electroencephalogram|
- MACie [ Time Frame: 30min ] [ Designated as safety issue: Yes ]Minimal Alveolar Concentration of sevoflurane inducing isoelectric electroencephalogram (EEG) in 50% of the subjects (MACie)
- MACbs [ Time Frame: 30 min ] [ Designated as safety issue: Yes ]Minimal Alveolar Concentration of sevoflurane inducing inducing burst suppression EEG (MACbs) in middle aged adults.
- Hemodynamic parameters [ Time Frame: 3 min ] [ Designated as safety issue: Yes ]Hemodynamic parameters 2 min before and 3 min after skin incision
- Use of phenylephrine [ Time Frame: 30 min ] [ Designated as safety issue: Yes ]Use of phenylephrine during induction and maintenance of anesthesia with sevoflurane.
|Study Start Date:||March 2012|
|Study Completion Date:||July 2012|
|Primary Completion Date:||May 2012 (Final data collection date for primary outcome measure)|
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.
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.
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.
|Department of Anaesthesiology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology|
|Wuhan, Hubei, China, 430030|
|Study Chair:||Yuke Tian, MD.||Department of Anaesthesiology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology|