Kawamoto M, Tanaka N, Takasaki M
Department of Anaesthesiology, Miyazaki Medical College, Japan.
Br J Anaesth. 1993 Oct;71(4):523-7. doi: 10.1093/bja/71.4.523.
Power spectral analysis of heart rate (HR) variability is a useful tool with which to assess cardiac autonomic activity. The low frequency bands have been considered as both sympathetically and parasympathetically mediated components, while the high frequency bands have been assumed to be the parasympathetically mediated respiratory components. It has been anticipated that spinal anaesthesia to the thoracic level may modulate cardiac autonomic activity to reduce HR and arterial pressure by blocking cardiac sympathetic activity. In order to quantify the alterations in cardiac autonomic activity, we have analysed the power spectra of HR variability for 30 min after subarachnoid administration of hyperbaric amethocaine. Using 256-s R-R interval data obtained from continuously recorded ECG, low frequency (Lo: 0.04-0.15 Hz) and high frequency (Hi: 0.15-0.40 Hz) band widths were integrated and their serial alterations were computed by shifting subjected R-R intervals at 60-s intervals. After the subarachnoid injection, arterial pressure, HR and Lo decreased and Hi and the Hi:Lo ratio increased. These changes were observed within 15-20 min. Ventilatory frequency did not change throughout the study. These findings suggest that the decrease in HR and arterial pressure after subarachnoid administration of hyperbaric amethocaine reflect decreased sympathetic activity and increased parasympathetic activity in the cardiac autonomic nervous system.
心率（HR）变异性的功率谱分析是评估心脏自主神经活动的一种有用工具。低频段被认为是交感神经和副交感神经介导的成分，而高频段被假定为副交感神经介导的呼吸成分。预计胸段脊髓麻醉可能通过阻断心脏交感神经活动来调节心脏自主神经活动，从而降低心率和动脉压。为了量化心脏自主神经活动的变化，我们分析了蛛网膜下腔注射高比重丁卡因后30分钟内心率变异性的功率谱。使用从连续记录的心电图中获得的256秒R-R间期数据，对低频（Lo：0.04 - 0.15Hz）和高频（Hi：0.15 - 0.40Hz）带宽进行积分，并通过以60秒间隔移动受试R-R间期来计算它们的连续变化。蛛网膜下腔注射后，动脉压、心率和低频段降低，高频段和高频：低频比值增加。这些变化在15 - 20分钟内观察到。在整个研究过程中呼吸频率没有变化。这些发现表明，蛛网膜下腔注射高比重丁卡因后心率和动脉压的降低反映了心脏自主神经系统中交感神经活动的降低和副交感神经活动的增加。
