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TECHNOLOGY, COMPUTING, AND SIMULATION

A Comparison of Bispectral Index and Rapidly Extracted Auditory Evoked Potentials Index Responses to Noxious Stimulation During Sevoflurane Anesthesia

A. Ekman, MD DEAA^*, L. Brudin, MD PhD, and R. Sandin, MD PhD^*

Departments of *Anesthesiology and Intensive Care and Clinical Physiology, Regional Hospital, Kalmar, Sweden

Address correspondence and reprint requests to Dr. Andreas Ekman, Department of Anesthesiology and Intensive Care, Regional Hospital, S-391 85 Kalmar, Sweden. Address e-mail to andrease{at}ltkalmar.se

In 21 patients given sevoflurane anesthesia, we simultaneously compared the abilities of Bispectral Index (BIS) and rapidly extracted auditory evoked potentials index (AAI) to display the effect of an increasing cerebral concentration of sevoflurane, with and without noxious stimulation. In addition to BIS/AAI, hemodynamic variables were monitored. After titrating sevoflurane to BIS = 50–55 during 15 min, the end-tidal concentration of sevoflurane (1.46% ± 0.20%) was doubled followed by a noxious stimulus, laryngoscopy, applied at random time points within the following 15 min. After the end-tidal concentration of sevoflurane was doubled, a substantial reduction in BIS was observed, whereas only a slight reduction in AAI was seen (P < 0.0001). BIS/AAI responses to laryngoscopy were not attenuated with increasing wash-in of sevoflurane. After noxious stimulation, AAI exceeded the highest recommended value, 25, in 3 cases, whereas BIS did not exceed the recommended threshold, 60, in any of the patients. Response times for BIS and AAI were 44.5 ± 26 and 47 ± 31 s, respectively. These results suggest that, at a hypnotic level associated with surgical sevoflurane anesthesia, BIS better displays drug-related alterations in the level of hypnosis than AAI or hemodynamic variables but there is no difference between BIS and AAI in the time to response to a noxious stimulus.

IMPLICATIONS: At a hypnotic level associated with surgical sevoflurane anesthesia, the data in this study suggest that Bispectral Index (BIS) better displays drug-related alterations in the level of hypnosis than auditory evoked potentials index (AAI) or hemodynamic variables and that there is no difference between BIS and AAI in the response time to a noxious stimulus.

This article has been cited by other articles:

				A. Ekman, E. Stalberg, E. Sundman, L. I. Eriksson, L. Brudin, and R. Sandin The Effect of Neuromuscular Block and Noxious Stimulation on Hypnosis Monitoring During Sevoflurane Anesthesia Anesth. Analg., September 1, 2007; 105(3): 688 - 695. [Abstract] [Full Text] [PDF]