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ANESTHETIC PHARMACOLOGY

The Dynamic Relationship Between End-Tidal Sevoflurane Concentrations, Bispectral Index, and Cerebral State Index in Children

Ricardo Fuentes, MD^*, Luis I. Cortínez, MD^*, Michel M. R. F. Struys, MD, PhD, Alejandro Delfino, MD^*, and Hernán Muñoz, MD, MSc^*

From the *Departamento de Anestesiología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile; Department of Anesthesia, University Medical Center Groningen, Groningen, The Netherlands, and Department of Anesthesia, Ghent University, Ghent, Belgium.

Address correspondence and reprint requests to Dr. Luis I. Cortínez, Departamento de Anestesiología, Hospital Clínico U. Católica, Marcoleta 367, Santiago, Chile. Address e-mail to licorti{at}med.puc.cl.

BACKGROUND: To guide anesthetic administration with electroencephalogram monitors in children, an adequate characterization of the anesthetic effect measured by these monitors in this population is needed. We sought to quantify and compare the dynamic profile of sevoflurane’s effect measured with the cerebral state index (CSI) and the bispectral index (BIS) in children.

METHODS: Fifteen healthy children, aged 3–15 yr, scheduled to undergo minor surgery were prospectively studied. During the simultaneous recording of CSI and BIS, the sevoflurane vaporizer was set at 6 vol % for 5 min and then decreased. End-tidal concentrations (C_ET) were measured. The C_ET–sevoflurane effect–site concentration equilibration and pharmacodynamics were modeled. Goodness of fit between models was compared. Data are typical value (coefficient of variation).

RESULTS: Within the anesthetic depth range studied, the rate of change of sevoflurane’s effect expressed as the effect–site equilibration half-life (t_1/2 k_e0) was slower with the CSI [2.0 (14) min] than with BIS [1.2 (53) min] (P < 0.05). The estimated baseline effect of BIS and CSI before sevoflurane administration (E₀) was 84 (39) for CSI and 87 (7) for BIS (NS). The sensitivity to sevoflurane hypnotic effect expressed in the C₅₀ [steady-state C_ET eliciting half of the maximum response (E_max)] was 2.1 (68) % with CSI and 2.1 (16)% with BIS (NS). The E_max with CSI 45 (0) was higher than that with BIS 27 (39) (P < 0.05). The population prediction error was significantly better for BIS (–0.7 ± 26.9) than for CSI (–3.0 ± 178.6) (P < 0.05).

CONCLUSIONS: In children, the t_1/2 k_e0 of sevoflurane and the pharmacodynamics of sevoflurane were quantified and the results were entirely dependent on the monitor used to measure its hypnotic effect. Within the anesthetic depth range studied, the rate of change of sevoflurane’s effect was slower with the CSI. To adequately guide sevoflurane administration with these monitors in children, these differences should be considered.

Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999