Age, splanchnic vasoconstriction, and heat stress during tilting
Age, splanchnic vasoconstriction, and heat stress during tilting
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DOI：
10.1152/ajpregu.1999.276.1.r203
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发表时间：
1999-01-01
影响因子：
2.8
通讯作者：
Kenney, WL
中科院分区：
文献类型：
--
作者：
Minson, CT;Wladkowski, SL;Kenney, WL
在直立倾斜过程中，血液转移到腿部的下垂静脉，需要进行代偿性循环调节以维持动脉压。为了检查年龄对这些反应的影响，七名年轻男子（23 +/- 1 岁）和七名老年男子（70 +/- 3 岁）在热中性条件下以及在穿着注水服被动加热期间将头部倾斜至 60 度。测量内容包括心率 (HR)、心输出量（(Q) over dot(c)；乙炔再呼吸技术）、中心静脉压 (CVP)、血压、前臂血流量（静脉闭塞体积描记法）、内脏和肾血流量（吲哚菁绿和对氨基马尿酸盐清除率）以及食道和平均皮肤温度。在热中性条件下倾斜时，年轻男性的 CVP 和每搏输出量下降幅度更大，但 HR 增加更多，因此直立姿势的两组中 (Q) 相对于点 (c) 的下降情况相似。老年男性的内脏血管阻力（SVR）增加幅度更大，但年轻男性的前臂血管阻力（FVR）增加程度比老年男性更大。与年长男性相比，在热应激和倾斜联合作用下，年轻人的 (Q) 相对于点 (c) 的下降幅度更大。只有四名年轻男子和六名老年男子能够完成第二次倾斜而不会出现晕厥。总之，老年男性依靠 SVR 的更大增加来补偿抬头倾斜期间收缩皮肤和肌肉循环的能力下降（由 FVR 的变化决定）。
During upright tilting, blood is translocated to the dependent veins of the legs and compensatory circulatory adjustments are necessary to maintain arterial pressure. For examination of the effect of age on these responses, seven young (23 +/- 1 yr) and seven older (70 +/- 3 yr) men were head-up tilted to 60 degrees in a thermoneutral condition and during passive heating with water-perfused suits. Measurements included heart rate (HR), cardiac output ((Q) over dot(c); acetylene rebreathing technique), central venous pressure (CVP), blood pressures, forearm blood flow (venous occlusion plethysmography), splanchnic and renal blood flows (indocyanine green and p-aminohippurate clearance), and esophageal and mean skin temperatures. In response to tilting in the thermoneutral condition, CVP and stroke volume decreased to a greater extent in the young men, but HR increased more, such that the fall in (Q) over dot(c) was similar between the two groups in the upright posture. The rise in splanchnic vascular resistance (SVR) was greater in the older men, but the young men increased forearm vascular resistance (FVR) to a greater extent than the older men. The fall in (Q) over dot(c) during combined heat stress and tilting was greater in the young compared with older men. Only four of the young men versus six of the older men were able to finish the second tilt without becoming presyncopal. In summary, the older men relied on a greater increase in SVR to compensate for a reduced ability to constrict the skin and muscle circulations (as determined by changes in FVR) during head-up tilting.