Wilcox C S, Puritz R, Lightman S L, Bannister R, Aminoff M J
J Lab Clin Med. 1984 Sep;104(3):331-9.
Blood pressure in patients with progressive autonomic failure falls during salt restriction or orthostasis. We contrasted the regulation of plasma volume in patients with progressive autonomic failure with that of controls to determine whether hypovolemia contributes to this hypotension. When sitting, the plasma volume (measured from distribution of human serum albumin) was normal. During 1 week of low Na+ intake, patients with progressive autonomic failure lost three times as much body weight as controls; however, changes in plasma volume were strictly comparable. Therefore, the extra fluid lost in the patients must have derived primarily from the interstitial space. During alteration in Na+ intake, mean blood pressure values were closely related to plasma volume in the patients (r = 0.80, p less than 0.01) but not in controls. Changes in plasma volume in the head-up tilt position were assessed from the hematocrit values. During tilting, the blood pressure in controls was unchanged, but their plasma volume fell by 10.3% +/- 1.8% (p less than 0.001). In contrast, the mean blood pressure of the patients with progressive autonomic failure fell by 40 +/- 6 mm Hg; yet, their plasma volume was unchanged. Thus, in progressive autonomic failure, plasma volume measured during sitting is normal, but dynamic regulation of plasma volume during salt restriction or orthostasis is abnormal and hypovolemia is offset by partitioning of interstitial fluid into the plasma. Also, because the blood pressure is unusually dependent on volume, this fluid redistribution could be an important defense against severe hypotension in patients lacking cardiovascular reflex control.
进行性自主神经功能衰竭患者的血压在限盐或直立位时会下降。我们对比了进行性自主神经功能衰竭患者与对照组的血浆容量调节情况，以确定血容量不足是否导致了这种低血压。坐着时，血浆容量（通过人血清白蛋白分布测量）正常。在低钠摄入的1周内，进行性自主神经功能衰竭患者体重减轻量是对照组的3倍；然而，血浆容量的变化严格可比。因此，患者额外丢失的液体一定主要来自间质间隙。在改变钠摄入期间，患者的平均血压值与血浆容量密切相关（r = 0.80，p<0.01），而对照组则不然。通过血细胞比容值评估头高位倾斜位时的血浆容量变化。倾斜期间，对照组血压未变，但其血浆容量下降了10.3%±1.8%（p<0.001）。相比之下，进行性自主神经功能衰竭患者的平均血压下降了40±6 mmHg；然而，他们的血浆容量未变。因此，在进行性自主神经功能衰竭中，坐着时测量的血浆容量正常，但限盐或直立位时血浆容量的动态调节异常，间质液向血浆的分配抵消了血容量不足。此外，由于血压异常依赖于容量，这种液体再分布可能是缺乏心血管反射控制的患者抵御严重低血压的重要防御机制。
