Dehydration reduces stroke volume and cardiac output during exercise because of impaired cardiac filling and venous return, not left ventricular function
Dehydration reduces stroke volume and cardiac output during exercise because of impaired cardiac filling and venous return, not left ventricular function
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DOI：
10.14814/phy2.14433
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发表时间：
2020-06-01
影响因子：
2.5
通讯作者：
Gonzalez-Alonso, Jose
中科院分区：
文献类型：
--
作者：
Watanabe, Kazuhito;Stohr, Eric J.;Gonzalez-Alonso, Jose
在高温下长时间剧烈全身运动时产生的脱水会损害外周血流量和心输出量（（Q）超过点）。每搏输出量（SV）显著减少是脱水引起的心血管紧张的一个关键特征，但心脏输出量降低是否由外周或心脏因素介导仍不清楚。因此，我们反复量化左心室（LV）容积、LV力学（LV扭转，收缩肌功能的标志物，LV解扭率，LV肌肉松弛的独立标志物），左心室内压差，在高温和无脱水情况下2小时自行车期间的血容量和外周血流量（分别为DEH：4.0 +/- 0.2%体重减轻和EUH：正常水化对照）。与2小时后的EUH相比，DEH组的肱动脉和颈动脉血流量、血容量、SV、LV舒张末期容积（LVEDV）、心脏充盈时间、全身血管传导性和（Q）过点减少，LV扭转和解扭转率倾向于更高（分别为p = 0.09和0.06），两种情况下的心室内压差无差异（p = 0.22）。此外，DEH中的LVEDV与血容量（r = 0.995，p <0.01）、头部和前臂搏动量（r = 0.98，p <0.05）和舒张期LV充盈时间（r = 0.98，p <0.05）密切相关。这些结果表明，运动性脱水导致的钝化（Q）过点的SV下降是由LV充盈和静脉回流受损引起的，而不是固有的收缩或舒张LV功能。
Dehydration accrued during intense prolonged whole-body exercise in the heat compromises peripheral blood flow and cardiac output ((Q) over dot). A markedly reduced stroke volume (SV) is a key feature of the dehydration-induced cardiovascular strain, but whether the lower output of the heart is mediated by peripheral or cardiac factors remains unknown. Therefore, we repeatedly quantified left ventricular (LV) volumes, LV mechanics (LV twist, a marker of systolic muscle function, and LV untwisting rate, an independent marker of LV muscle relaxation), left intra-ventricular pressure gradients, blood volume and peripheral blood flow during 2 hr of cycling in the heat with and without dehydration (DEH: 4.0 +/- 0.2% body mass loss and EUH: euhydration control, respectively) in eight participants (three females and five males). While brachial and carotid blood flow, blood volume, SV, LV end-diastolic volume (LVEDV), cardiac filling time, systemic vascular conductance and (Q) over dot were reduced in DEH compared to EUH after 2 hr, LV twist and untwisting rate tended to be higher (p = .09 and .06, respectively) and intra-ventricular pressure gradients were not different between the two conditions (p = .22). Furthermore, LVEDV in DEH correlated strongly with blood volume (r = .995, p < .01), head and forearms beat volume (r = .98, p < .05), and diastolic LV filling time (r = .98, p < .05). These findings suggest that the decline in SV underpinning the blunted (Q) over dot with exercise-induced dehydration is caused by compromised LV filling and venous return, but not intrinsic systolic or diastolic LV function.