• Syozo Hidaka, Masashi Kawamoto, Shigeaki Kurita, and Osafumi Yuge.
• Department of Anesthesiology and Critical Care, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 737-8551, Japan. hidakas@k3.dion.ne.jp
• J Clin Anesth. 2005 Feb 1;17(1):36-43.

Study ObjectiveTo investigate the effect of propofol and midazolam on cardiac autonomic nervous system (CANS) activity during combined spinal-epidural anesthesia.DesignProspective, clinical study.SettingOperating room of a university hospital.PatientsForty ASA physical status I and II patients scheduled for knee surgery.InterventionPatients were randomized to receive sedation with either propofol or midazolam.MeasurementsHeart rate (HR), HR variability (HRV), systolic arterial pressure (SAP), and SAP variability (SAPV) were used for the analysis. These values were measured at the preanesthetic period, after intrathecal injection for spinal anesthesia, after sedation with propofol or midazolam, and just before the end of surgery with sedation. Cross-spectral analyses of the HR and SAP data were assessed to quantify the frequency-related coherence spectra and phase spectra.Main ResultsSpinal anesthesia itself had no effect on power spectral changes in both groups. After sedation, as for HRV, high-frequency (HF) power (HF, 0.15-0.40 Hz) did not change, whereas low-frequency (LF) power (LF, 0.04-0.15 Hz) and LF/HF, an indicator of CANS balance, significantly decreased with propofol. Further, coherence in cross-spectra presented depression in the LF band area after sedation with propofol. Before the end of surgery with sedation, LF and LF/HF in both HRV and SAPV were correlated with age in those with propofol; however, scarce relation was observed in those who received midazolam.ConclusionsPropofol was more potent than midazolam in causing CANS activity to be sympatholytic during combined spinal and epidural anesthesia and which was correlated with age only with propofol.

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