BJA Advance Access originally published online on August 23, 2008
British Journal of Anaesthesia 2008 101(5):653-658; doi:10.1093/bja/aen245
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Validation of the index of consciousness during sevoflurane and remifentanil anaesthesia: a comparison with the bispectral index and the cerebral state index
1 Anaesthesia Research Group, Cardiac Anaesthesia and Postoperative Intensive Care Unit, Hospital Santa Creu i Sant Pau, Antonio Maria Claret 167, 08025 Barcelona, Spain
2 Center of Research in Biomedical Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain
* Corresponding author. E-mail: mrevuelta{at}santpau.cat
Background: The purpose of this study was to validate a new level of consciousness monitor derived from the EEG, called the index of consciousness (IoC), by comparing it with the bispectral index (BIS) and the cerebral state index (CSI) during general anaesthesia for cardiac surgery using sevoflurane, remifentanil, and atracurium.
Methods: After ethical committee approval and written patient consent, data from 35 patients [31 males, four females, age 55 (10) yr] were recorded during general anaesthesia for elective cardiac bypass surgery. All patients were induced with sevoflurane 8%, until the Observer's Assessment of Alertness and Sedation (OAAS) scale level 1 was reached, and then was set at a 1% end-tidal sevoflurane concentration. Subsequently, remifentanil and atracurium were administered, the trachea was intubated, and the procedure continued as usual. To assess accuracy, the prediction probability (Pk) was calculated both during induction and during maintenance.
Results: The Pk values [mean (SE)] for IoC, BIS, and CSI during induction were 0.90 (0.01), 0.90 (0.01), and 0.88 (0.01), respectively, whereas the corresponding Pk values during maintenance were 0.95 (0.01), 0.94 (0.01), and 0.60 (0.01).
Conclusions: The three indices performed equally well during the induction phase and were able to predict the level of consciousness of the patients satisfactorily. During maintenance, the IoC and the BIS showed good agreement with the clinical signs. The CSI was significantly influenced by the administration of atracurium; therefore, the agreement with the OAAS scale during the maintenance phase was significantly less for CSI than for IoC and BIS.
Keywords: anaesthesia, depth; anaesthetics volatile, sevoflurane; analgesics opioid, remifentanil; monitoring, electroencephalogram
Declaration of interest. H. L. has been a non-paid consultant for both the CSM (Danmeter) and the IoC-view (Morpheus Medical) devices and he is a shareholder in Morpheus Medical, the manufactures of the IoC.