Anzai Y, Nishikawa T
Department of Anesthesia, Obihiro Kousei General Hospital, Hokkaido, Japan.
Anesth Analg. 1991 Oct;73(4):385-90. doi: 10.1213/00000539-199110000-00002.
To evaluate whether low-pressure baroreceptors located in the right atrium could affect the heart rate (HR) during spinal anesthesia, the authors determined the effects of right atrial pressure changes associated with body tilt on HR in 40 unpremedicated patients. Ten-degree head-up body tilt produced significant increases in HR of 6 +/- 1 and 6 +/- 1 beats/min (mean +/- SE, P less than 0.01) and significant decreases in systolic arterial pressure of 2.8 +/- 0.9 and 6.6 +/- 1.7 mm Hg (P less than 0.01) during low (T-10 +/- 0.2, n = 20) and high (T-4 +/- 0.2, n = 20) analgesic levels of tetracaine spinal anesthesia, respectively. Ten-degree head-down body tilt caused significant decreases in HR without significant changes in systolic arterial pressure during spinal anesthesia. The reflex HR responses to body tilt were similar between low and high levels of spinal anesthesia and were preserved after administration of sedatives. The magnitudes of changes in right atrial pressure associated with body tilt were similar during spinal anesthesia and after sedation. These findings suggest that HR responses to head-up body tilt are mediated mainly by arterial baroreceptors even in the face of decreased venous return during low or high levels of spinal anesthesia and that light sedation does not impair this reflex HR response.
为评估位于右心房的低压压力感受器在脊髓麻醉期间是否会影响心率（HR），作者测定了40例未用术前药患者中，与体位倾斜相关的右心房压力变化对HR的影响。在丁卡因脊髓麻醉的低平面（T₁₀±0.2，n = 20）和高平面（T₄±0.2，n = 20）镇痛水平时，头高位倾斜10度分别使HR显著增加6±1次/分和6±1次/分（平均值±标准误，P<0.01），收缩动脉压显著降低2.8±0.9 mmHg和6.6±1.7 mmHg（P<0.01）。头低位倾斜10度在脊髓麻醉期间使HR显著降低，而收缩动脉压无显著变化。脊髓麻醉低平面和高平面时，对体位倾斜的反射性HR反应相似，且在给予镇静剂后仍保留。脊髓麻醉期间和镇静后，与体位倾斜相关的右心房压力变化幅度相似。这些发现表明，即使在脊髓麻醉低平面或高平面时静脉回流减少的情况下，对头高位倾斜的HR反应主要由动脉压力感受器介导，且轻度镇静不会损害这种反射性HR反应。
