Reduced Baroreflex Sensitivity with Volume Loading in Conscious Dogs
Reduced Baroreflex Sensitivity with Volume Loading in Conscious Dogs
复制标题
意识清醒的狗的压力反射敏感性随着容量负荷的降低而降低
作者：
S. Vatner;D. Boettcher;G. Heyndrickx;R. McRitchie
班布里奇反射，即，快速输注生理盐水（1.1 ± 0.1）升对心率、动脉压和心房压的影响;平均动脉血压升高33 ± 3（SE）mm Hg，平均心房压升高14 ± 1 mm Hg，心率升高75 ± 9次/min。β受体阻滞后，心率上升幅度稍小（+49 ± 5次/min，P = 0.05）。胆碱能阻滞、胆碱能和β受体联合阻滞或迷走神经切断术后β受体阻滞可阻断心率对输注的反应。面对容量负荷的动脉血压升高，心率升高表明动脉压力感受器反射对动脉血压升高没有适当的反应。在清醒的狗去神经后的动脉压力感受器，增加的心率与容量负荷不大于那些狗与他们的动脉压力感受器完整，这表明压力感受器反射抑制心率在正常反应的容量负荷。在清醒犬静脉注射甲氧胺后，用脉搏间期（PI）与动脉收缩压（SAP）的关系来评价压力感受性反射的敏感性。在轻度容量负荷后，当心房压力为8 ± 2 mm Hg时，PI/SAP斜率较正常值显著降低。当容量负荷使心房压力进一步升高至28 ± 1 mmHg时，斜率进一步降低。因此，随着容量负荷升高心房压力，动脉压力反射敏感性逐渐降低，这一观察结果解释了心率如何在动脉血压升高时显著升高。
The Bainbridge reflex, i.e., the effect of rapid saline infusion (1.1 ± 0.1 liters) on heart rate and arterial and atrial blood pressures, was examined in 12 intact conscious dogs; mean arterial blood pressure rose by 33 ± 3 (SE) mm Hg, mean atrial pressure by 14 ± 1 mm Hg, and heart rate by 75 ± 9 beats/min. After beta-receptor blockade, heart rate rose slightly less (+49 ± 5 beats/min, P = 0.05). Cholinergic blockade, combined cholinergic and beta-receptor, or beta-receptor blockade after vagotomy blocked the heart rate response to the infusion. The rise in heart rate in the face of an increase in arterial blood pressure with volume loading suggested that the arterial baroreceptor reflex was not responding appropriately to the increase in arterial blood pressure. In conscious dogs after denervation of the arterial baroreceptors, the increase in heart rate with volume loading was no greater than that in those dogs with their arterial baroreceptors intact, suggesting that the baroreceptor reflex was not restraining heart rate in the normal response to volume loading. The relationship between the pulse interval (PI) and the systolic arterial blood pressure (SAP) following an intravenous injection of methoxamine was used to evaluate the sensitivity of the baroreceptor reflex in intact conscious dogs. After a mild amount of volume loading, when atrial pressure was 8 ± 2 mm Hg, the PI/SAP slope was significantly depressed from normal. When atrial pressure was elevated further to 28 ± 1 mm Hg by volume loading, the slope was further depressed. Thus, arterial baroreflex sensitivity is reduced progressively as atrial pressure is raised by volume loading, an observation that explains how heart rate can rise strikingly in the face of an elevated arterial blood pressure.