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Quasiperiodic oscillations of electroencephalgram during induction of general anesthesia with thiopental

Quasiperiodic oscillations of electroencephalgram during induction of general anesthesia with thiopental A. Sekulic, V. Isgum, B. Mazul Sunko, M. Matas Department of Anaesthesiology and Intensive Care, KBC Zagreb, Zagreb, Croatia Background and Goal of Study: Quasiperiodic oscillations were observed in coupled neuronal oscillators (1). Nonlinear dynamics of electroencephalogram (EEG ), with wide variety of changes, was observed during emergence from sevoflurane anesthesia (2). The aim of our work was to detect quasiperiodic EEG during induction of general anesthesia with thiopental. Materials and Methods: A group of 46 patients (20 males, age range 42 – 54 years, ASA I ), scheduled for lumbar diskectomy, recieved 5 mg / kg of thiopental intravenously, for induction of general anaesthesia. All the patients were premedicated with midazolam. EEG was recorded with four channels MEDELEC 81996 apparatus. Silver disc electrodes were palced in according with 10-20 International system on C3, C4, T5, T6. Cz ref., Fz ground. Sampling rate was 200 Hz. Recording of EEG lasted from awake state to loss of eyelid reflex. Analysis of electroencephalogram was performed off – line with in home made software. Criteria for quasiperiodicity in EEG were adopted from (3). Results and Discussion: Quasiperiodic oscillation in EEG were detected in 12 of 46 (26 %) patients. Our results are pointing toward nonlinear dynamics of EEG during induction of general anestesia. Biological meaning of these results is not clear. Conclusion(s): Quasiperiodic oscillations of EEG are present during induction of general anestesia with thiopental. References: 1 Del Negro CA et al. Biophysical Journal 2002. 2 Waling PT, Hicks KN. Anesthesiology 2006 ; 105:927-35. 3 Steyn-Ross ML et al. Phys Rev E Stat Nonlin Soft Matter Phys. 2003 ; 68(2 Pt 1):021902.

thiopental; anesthesia; quasiperiodic oscillation; electroencephalogram

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