Chaotic analysis of autonomic nervous activities during anesthesia

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The mechanism of action of inhalational anesthetics is unknown, but neuronal membrane alteration with chaotic purturbations caused by anesthetics is a favored hypothesis. In order to evaluate whether or not HRV have both periodic and deterministic-chaotic properties in conscious and anesthetized states, we analyzed HRV by power spectral analysis and methods of deterministic chaos.A predominant deterministic-chaotic structure of HRV with high fractal correlation dimension during conscious states altered to a more periodic structure and lower correlation dimension during general anesthesia with sevoflurane or halothane. In addition, major thoracic surgery, such as esophagectomy or pulmonary resection, diminished fractal features of HRV,suggestiong that fractal component could be an estimate of recovery state from surgical invasion.Neural control of cardiovascular system, thus, shows featrues associated with deterministic chaos by analyzing HRV changes. These results indicated the dynamic cardiovascular system that are partly characterized by non-linear natures typical for chaotic systems.