Department of Physiology, All India Institute of Medical Sciences, New Delhi, India.
Indian J Med Res. 2011 Oct;134(4):463-9.
BACKGROUND & OBJECTIVES: Patients of orthostatic hypotension may or may not have symptoms of the cerebral hypoperfusion despite fall in the blood pressure. The present study was done to quantify autonomic functions and cerebral autoregulation in patients of orthostatic hypotension with or without symptoms.
The study was conducted in 15 patients of orthostatic hypotension and 15 age, sex matched control subjects. The sympathetic reactivity was measured by diastolic blood pressure response to handgrip test (ΔDBP in HGT) and cold pressor test (ΔDBP in CPT). The parasympathetic reactivity was measured by E:I ratio during deep breathing test (DBT) and Valsalva ratio (VR) during Valsalva maneuver. The cerebral autoregulation was computed from the changes in the cerebral blood flow, cerebrovascular conductance and blood pressure measured during different time points during head-up tilt (HUT).
The sympathetic reactivity was lower in patients as compared to controls [ΔDBP in HGT: 10 (4 - 16) vs 18 (12 - 22) mmHg, P<0.01; ΔDBP in CPT : 10 (4-12) vs 16 (10-20) mmHg, P<0.01]. The parasympathetic reactivity was also lower in patients as compared to controls. The sympathetic and parasympathetic reactivity was comparable in the symptomatic and asymptomatic patients. The maximum fall in blood pressure during HUT was comparable between symptomatic and asymptomatic patients (29.14 ± 10.94 vs 29.50 ± 6.39 mmHg), however, the percentage fall in the cerebral blood flow was significantly higher in the symptomatic (P<0.05) compared to asymptomatics.
INTERPRETATION & CONCLUSIONS: Patients with orthostatic hypotension had deficits in sympathetic and parasympathetic control of cardiovascular system. Cerebral autoregulation was present in asymptomatic patients (increase in cerebrovascular conductance) during HUT while it was lost in symptomatic patients.
体位性低血压患者尽管血压下降，但可能存在或不存在脑灌注不足的症状。本研究旨在定量评估有症状和无症状体位性低血压患者的自主神经功能和脑自动调节。
该研究纳入了 15 例体位性低血压患者和 15 例年龄、性别匹配的对照组。通过手测血压试验（HGT）中的舒张压反应（ΔDBP in HGT）和冷加压试验（CPT）中的舒张压反应（ΔDBP in CPT）来测量交感神经反应性。通过深呼气试验（DBT）中的 E:I 比值和瓦尔萨尔瓦动作（Valsalva maneuver）中的瓦尔萨尔瓦比值（VR）来测量副交感神经反应性。通过在头高位倾斜（HUT）过程中不同时间点测量脑血流、脑血管阻力和血压的变化来计算脑自动调节。
与对照组相比，患者的交感神经反应性较低[HGT 中的 ΔDBP：10（4-16）与 18（12-22）mmHg，P<0.01；CPT 中的 ΔDBP：10（4-12）与 16（10-20）mmHg，P<0.01]。患者的副交感神经反应性也较低。有症状和无症状患者的交感神经和副交感神经反应性相似。在有症状和无症状患者中，HUT 期间血压的最大下降幅度相似（29.14±10.94 与 29.50±6.39mmHg），但在有症状患者中脑血流的下降百分比明显更高（P<0.05）。
体位性低血压患者的心血管系统自主神经控制存在缺陷。无症状患者在 HUT 期间存在脑自动调节（脑血管阻力增加），而有症状患者则丧失了脑自动调节。
