Wide inter-individual variability of bispectral index and spectral entropy at loss of consciousness during increasing concentrations of dexmedetomidine, propofol, and sevoflurane

• Published in: British journal of anaesthesia : BJA Vol. 107; no. 4; pp. 573 - 580
• Main Authors: Kaskinoro, K., Maksimow, A., Långsjö, J., Aantaa, R., Jääskeläinen, S., Kaisti, K., Särkelä, M., Scheinin, H.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2011; Oxford University Press
• Subjects: Adult; anaesthetics i.v., propofol; anaesthetics volatile, sevoflurane; Anesthesia; Anesthesia Recovery Period; Anesthesia, General; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Anesthetics, Inhalation; Anesthetics, Intravenous; Biological and medical sciences; Consciousness Monitors - statistics & numerical data; Data Interpretation, Statistical; Dexmedetomidine; Dose-Response Relationship, Drug; Entropy; Humans; Hypnotics and Sedatives; Male; Medical sciences; Methyl Ethers; monitoring, bispectral index; monitoring, depth of anaesthesia; monitoring, spectral entropy; Propofol; Reproducibility of Results; Unconsciousness - chemically induced; Unconsciousness - physiopathology; Young Adult; anaesthetics i.v., propofol; anaesthetics volatile, sevoflurane; monitoring, bispectral index; monitoring, spectral entropy; dexmedetomidine; monitoring, depth of anaesthesia; Volatile compound; α2-Adrenergic receptor; Agonist; Nervous system diseases; Consciousness impairment; Variability; bispectral index; Entropy; Sevoflurane; depth of anaesthesia; anaesthetics i.v; General anesthetic; Dexmedetomidine; spectral entropy; Anesthesia; α-Adrenergic receptor agonist; Propofol; Neurological disorder; Faint; Monitoring; anaesthetics volatile; Halogen Organic compounds
• ISSN: 0007-0912; 1471-6771; 1471-6771
• DOI: 10.1093/bja/aer196

The bispectral index (BIS) and the spectral entropy (state entropy, SE, and response entropy, RE) are depth-of-anaesthesia monitors derived from EEG and have been developed to measure the effects of anaesthetics on the cerebral cortex. We studied whether they can differentiate consciousness from unconsciousness during increasing doses of three different anaesthetic agents. Thirty healthy male volunteers aged 19–30 yr were recruited and divided into three 10-volunteer groups to receive either dexmedetomidine, propofol, or sevoflurane in escalating concentrations at 10 min intervals until loss of consciousness (LOC) was reached. Consciousness was tested at 5 min intervals and after drug discontinuation at 1 min intervals by requesting the subjects to open their eyes. LOC was defined as unresponsiveness to the request and pre-LOC as the last meaningful response. The first meaningful response to the request after drug discontinuation was defined as regaining of consciousness (ROC). For the statistical analysis, pre-LOC and ROC values were pooled to represent the responsive state while LOC values represented the unresponsive state. Prediction probability (PK) was estimated with the jack-knife method. The lowest mean values for BIS, SE, and RE were recorded at LOC with all three drugs. The PK values were low for dexmedetomidine (BIS 0.62, SE 0.58, RE 0.59), propofol (BIS 0.73, SE 0.72, RE 0.72), and sevoflurane (BIS 0.70, SE 0.52, RE 0.62). Because of wide inter-individual variability, BIS and entropy were not able to reliably differentiate consciousness from unconsciousness during and after stepwise increasing concentrations of dexmedetomidine, propofol, and sevoflurane.