van Schelven Leonard J, Karemaker John M, Blankestijn Peter J, Oey P Liam
Department of Medical Technology and Clinical Physics, University Medical Center Utrecht, The Netherlands.
Clin Neurophysiol. 2008 Apr;119(4):869-79. doi: 10.1016/j.clinph.2007.12.009. Epub 2008 Feb 6.
Sympathetic baroreflex sensitivity (symBRS) can be defined as the maximum sensitivity of muscle sympathetic nerve activity (MSNA) to changes in arterial blood pressure. This sensitivity is the slope of the linear middle part of the sigmoid curve that relates blood pressure to MSNA. SymBRS is known to vary with conditions, for instance during cold pressor testing. We investigated whether symBRS is affected by infusions of phenylephrine and nitroprusside.
In 10 healthy subjects, vasoactive infusions were varied in slow steps, as customary in protocols to determine 'graded infusion symBRS' (symBRS(inf)). During each step, symBRS was estimated from spontaneous beat-to-beat fluctuations (symBRS(sp)). As a secondary goal, symBRS(inf) was compared to the symBRS(sp) without infusions.
The symBRS(sp) for MSNA burst area varied with infusions, augmenting with decreasing blood pressure, however the symBRS(sp) for burst occurrence was not affected. There were large differences between symBRS(inf) and symBRS(sp) at rest.
symBRS(sp) varies systematically with infusions during a symBRS(inf) protocol. This denotes a fundamental difference between these methods.
The relationship between 'slow' infusion effects (symBRS(inf)) and changes in symBRS(sp) is elucidated. The mathematical model that describes this relationship can also explain the increase of symBRS found with other sympathoexcitatory stimuli.
交感压力反射敏感性（symBRS）可定义为肌肉交感神经活动（MSNA）对动脉血压变化的最大敏感性。这种敏感性是将血压与MSNA相关联的S形曲线线性中间部分的斜率。已知symBRS会随条件变化，例如在冷加压试验期间。我们研究了苯肾上腺素和硝普钠输注是否会影响symBRS。
在10名健康受试者中，按照确定“分级输注symBRS”（symBRS(inf)）的方案中的惯例，以缓慢步骤改变血管活性输注。在每个步骤中，根据自发的逐搏波动估计symBRS（symBRS(sp)）。作为次要目标，将symBRS(inf)与未输注时的symBRS(sp)进行比较。
MSNA爆发面积的symBRS(sp)随输注而变化，随血压降低而增加，然而爆发发生的symBRS(sp)不受影响。静息时symBRS(inf)和symBRS(sp)之间存在很大差异。
在symBRS(inf)方案期间，symBRS(sp)随输注而系统变化。这表明这些方法之间存在根本差异。
阐明了“缓慢”输注效应（symBRS(inf)）与symBRS(sp)变化之间的关系。描述这种关系的数学模型也可以解释其他交感神经兴奋刺激下发现的symBRS增加。
