Institute of Physiology, Medical University of Graz, Austria.
Physiol Behav. 2012 Jun 25;106(4):569-73. doi: 10.1016/j.physbeh.2012.02.022. Epub 2012 Feb 25.
At orthostatic vasovagal syncope there appears to be a sudden decline of sympathetic activity. As mental challenge activates the sympathetic system, we hypothesized that doing mental arithmetic in volunteers driven to the end point of their cardiovascular stability may delay the onset of orthostatic syncope. We investigated this in healthy male subjects. Each subject underwent a head up tilt (HUT)+ graded lower body negative pressure (LBNP) up to presyncope session (control) to determine the orthostatic tolerance time, OTT (Time from HUT commencement to development of presyncopal symptoms/signs). Once the tolerance time was known, a randomized crossover protocol was used: either 1) Repeat HUT+LBNP to ensure reproducibility of repeated run or 2) HUT+LBNP run but with added mental challenge (2 min before the expected presyncope time). Test protocols were separated by 2 weeks. Our studies on five male test subjects indicate that mental challenge improves orthostatic tolerance significantly. Additional mental loading could be a useful countermeasure to alleviate the orthostatic responses of persons, particularly in those with histories of dizziness on standing up, or to alleviate hypotension that frequently occurs during hemodialysis or on return to earth from the spaceflight environment of microgravity.
在直立性血管迷走性晕厥中，似乎会突然出现交感神经活动的下降。由于精神挑战会激活交感神经系统，我们假设在自愿者到达心血管稳定的终点时进行心算可能会延迟直立性晕厥的发作。我们在健康男性受试者中对此进行了研究。每位受试者都进行了头高位倾斜（HUT）+分级下体负压（LBNP），直到出现晕厥前症状/体征（对照），以确定直立耐受时间（OTT，从 HUT 开始到出现晕厥前症状/体征的时间）。一旦知道了耐受时间，就可以使用随机交叉方案：1）重复 HUT+LBNP，以确保重复运行的可重复性，或者 2）进行 HUT+LBNP 运行，但增加精神挑战（在预计晕厥前时间前 2 分钟）。测试方案相隔 2 周。我们对五名男性受试者的研究表明，精神挑战显著提高了直立耐受能力。额外的精神负荷可能是缓解直立反应的有效对策，特别是对那些有直立时头晕史的人，或缓解在血液透析期间或从微重力的太空环境返回地球时经常发生的低血压。
