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Effect of xenon on autonomic cardiovascular control--comparison with isoflurane and nitrous oxide
1Department of Anesthesia, Teikyo University School of Medicine, Ichihara Hospital, Chiba, Japan. yishigur@med.teikyo-u.ac.jp
Study Objectives:
To clarify the effect of xenon on the autonomic nervous system by comparing similar effects of isoflurane and nitrous oxide.
Design:
Prospective, randomized study.
Setting:
Operating room at a university hospital.
Patients:
39 ASA physical status I and II patients scheduled for general anesthesia.
Interventions:
Patients were randomly allocated into one of three groups and received one of the following inhalational anesthetics: 56% of xenon (Group X), 0.94% of isoflurane (Group I), or 70% of nitrous oxide and 0.15% of isoflurane (Group N). Phenylephrine (pressor test) and nicardipine (depressor test) were given to assess baroreflex sensitivity.
Measurements And Main Results:
Continuous blood pressure (BP) and electrocardiogram (ECG) were recorded before and during anesthesia to analyze heart rate (HR) variability and baroreflex sensitivity. Power spectrum of HR variability was calculated by fast Fourier transformation and power spectrum densities at low frequency (LF: 0.04-0.15Hz) and high frequency (HF: 0.15-0.40 Hz) were compared. Baroreflex sensitivity was calculated from the slope of regression for BP changes versus associated changes in R-R intervals. For HR variability, Group X showed lower power spectrum densities (ms(2).Hz(-1)) in LF and HF than did Group I (LF: 0.09 +/- 0.06 vs. 0.35 +/- 0.53; p < 0.05; HF: 0.40 +/- 0.34 vs. 0.98 +/- 0.68, p < 0.01). Group X had the lowest baroreflex sensitivity (ms.mmHg(-1)) via pressor test of the three study groups (Group X: 2.00 +/- 0.87, Group I: 3.53 +/- 2.14, Group N: 3.78 +/- 2. 17, p < 0.05).
Conclusions:
Xenon depressed both sympathetic and parasympathetic transmission more than isoflurane at 0.8 MAC. Xenon was also suggested to be relatively vagotonic.