• Itsuo Nakatsuka, Ryoichi Ochiai, and Junzo Takeda.
• Department of Anesthesiology, School of Medicine, Keio University, Tokyo, Japan.
• J Clin Anesth. 2002 May 1;14(3):196-200.

Study ObjectiveTo quantify the effects of sevoflurane on autonomic nerve function by analyzing changes in heart rate (HR) variability in sevoflurane anesthesia; and to investigate the effects of anesthetic depth and apnea on HR variability.DesignProspective study.SettingOperating room (OR) of a university medical center.Patients7 ASA physical status I and II patients scheduled for elective surgery.InterventionsPatients were premedicated with ranitidine 150 mg. Anesthesia was induced with thiopental sodium 4 mg/kg intravenously (IV) and succinylcholine 1 mg/kg IV, and maintained with nitrous oxide (N(2)O) 67% and sevoflurane in oxygen. Patients were ventilated mechanically at a rate of 15 breaths/min.MeasurementsR-R interval of electrocardiography (ECG), electroencephalogram (EEG), noninvasive arterial blood pressure (BP), and end-tidal sevoflurane concentration were recorded. Measurements were performed 1) after patients arrived at the OR and were placed in the supine position, 2) a stable period after inhalation of 2% sevoflurane, and 3) following the appearance of an isoelectric EEG at a higher concentration of sevoflurane. At times 2) and 3), data were recorded during mechanical ventilation and during apnea.Main ResultsThere were decreases in both the low-frequency (LF; 0.04 to 0.15 Hz) and high-frequency (HF; 0.15 to 0.4 Hz) components of HR variability during anesthesia compared with the awake state. HF decreased during apnea at 2% sevoflurane, but LF did not change. Neither LF nor HF changed in response to the absence or presence of respiration during isoelectric EEG.ConclusionsAutonomic nerve activity was attenuated by sevoflurane. Parasympathetic input to the heart by respiration was markedly suppressed following the appearance of isoelectric EEG.

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