Muscle sympathetic responses during orthostasis in heat-stressed individuals
Muscle sympathetic responses during orthostasis in heat-stressed individuals
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DOI：
10.1007/s10286-011-0126-6
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发表时间：
2011-12-01
影响因子：
5.8
通讯作者：
Crandall, Craig G.
中科院分区：
文献类型：
--
作者：
Cui, Jian;Shibasaki, Manabu;Crandall, Craig G.
全身热应激会损害直立性挑战期间的血压控制，尽管这种情况发生的程度在个体之间差异很大。导致这些不同反应的机制尚不清楚。该研究测试了以下假设：在热应激时最能耐受直立挑战的个体是在直立期间交感神经活动增加最多的个体，其由肌肉交感神经活动（MSNA）的记录来索引。记录11名健康志愿者在整个被动全身加热过程中以及在15分钟的60A度头高位倾斜（HUT）期间或直到预加热开始时的心率和心率。晕厥症状。全身加热显著增加核心温度（类似于0.9A摄氏度），仰卧心率和MSNA。11例受试者中有8例出现晕厥前症状，导致HUT提前终止。HUT耐受时间与HUT引起的MSNA升高呈正相关（R = 0.82，P = 0.01），表明直立倾斜时MSNA升高幅度最大的个体对热应激时立位挑战的耐受能力最强。
Whole-body heat stress compromises the control of blood pressure during an orthostatic challenge, although the extent to which this occurs can vary greatly between individuals. The mechanism(s) responsible for these varying responses remain unclear. This study tested the hypothesis that the individuals who are best able to tolerate an orthostatic challenge while heat stressed are the ones with the largest increase in sympathetic activity during orthostasis, indexed from recordings of muscle sympathetic nerve activity (MSNA).MSNA, arterial blood pressure, and heart rate were recorded from 11 healthy volunteers throughout passive whole-body heating and during 15 min of 60A degrees head-up tilt (HUT) or until the onset of pre-syncopal symptoms.Whole-body heating significantly increased core temperature (similar to 0.9A degrees C), supine heart rate and MSNA. Eight of 11 subjects developed pre-syncopal symptoms resulting in early termination of HUT. The HUT tolerance time was positively correlated (R = 0.82, P = 0.01) with the increase in MSNA by HUT.These data suggest that the individuals with the largest increase in MSNA during upright tilt have the greatest capacity to withstand the orthostatic challenge while heat stressed.