Cerebrovascular compliance during progressive hypotension in patients with autonomic failure.

IF 3.3 3区 医学 Q1 PHYSIOLOGY
Journal of applied physiology Pub Date : 2025-02-01 Epub Date: 2025-01-15 DOI:10.1152/japplphysiol.00900.2024
Leena N Shoemaker, Aleena Sajid, Ronald Schondorf, J Kevin Shoemaker
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Abstract

The compliant nature of cerebral blood vessels may represent an important mechanical protection for sustained cerebral perfusion during reductions in arterial blood pressure (ABP). However, whether the rise in cerebrovascular compliance (Ci) with falling ABP persists and exhibits a threshold effect remains unknown. Therefore, we analyzed Ci changes during graded head-up tilt (HUT) in individuals with autonomic failure (AF), a group that tolerates graded and progressive reductions in ABP. Finger ABP and middle cerebral artery blood velocity (MCAv) were recorded from five patients with AF (61 ± 22 yr) at supine rest and during graded HUT. Tilt gradients increased incrementally between 30, 45, and 60° every 5 min until ABP reached a critically low value. The total time in HUT was 11 ± 4 min. Every 5 s during supine and HUT, individual ABP and MCAv waveforms were assessed for Ci and cerebrovascular resistance (CVR) using a modified Windkessel model. Pulse pressure (PP) was calculated as systolic ABP - diastolic ABP. A threshold value for the increase in Ci was determined using breakpoint analysis of the linear relationship between changes in Ci and PP or ABP across tilt periods. Graded HUT resulted in reduced ABP, PP, CVR, and mean MCAv, and increased Ci (all P < 0.01). Ci began to increase progressively after PP fell by 22 ± 6 mmHg and ABP fell by 20 ± 11 mmHg. In conclusion, the increase in Ci during progressive hypotension exhibited a threshold effect and persisted as ABP continued to fall.NEW & NOTEWORTHY We identify a threshold effect for the increase in cerebrovascular compliance (Ci) during progressive hypotension (baseline vs. end-tilt: 86 ± 18 vs. 50 ± 8 mmHg) in individuals with autonomic failure, such that Ci began to increase progressively after pulse pressure fell by 22 ± 6 mmHg and arterial blood pressure fell by 20 ± 11 mmHg.

自主神经衰竭患者进行性低血压时的脑血管顺应性。
脑血管的顺应性可能是动脉血压降低(ABP)期间持续脑灌注的重要机械保护。然而,脑血管顺应性(Ci)的上升是否随着ABP的下降而持续并表现出阈值效应仍然未知。因此,我们分析了自主神经衰竭(AF)患者在分级仰卧(HUT)期间的Ci变化,这是一组耐受分级和渐进式ABP降低的患者,记录了5名AF患者(61±22年)在仰卧休息和分级仰卧(HUT)期间的手指ABP和大脑中动脉血流速度(MCAv)。倾斜梯度每5分钟在30、45和60度之间逐渐增加,直到ABP达到一个临界低值。HUT总时间为11±4 min。仰卧和HUT期间,每隔5 s采用改良的Windkessel模型评估个体ABP和MCAv波形的Ci和脑血管阻力(CVR)。脉压(PP)以收缩期ABP -舒张期ABP计算,Ci升高的阈值通过对Ci与PP或ABP变化的线性关系的断点分析确定。分级HUT导致ABP、PP、CVR和平均MCAv降低,Ci升高(均P < 0.01)。PP下降22±6 mmHg, ABP下降20±11 mmHg后,Ci开始逐渐升高。总之,在进行性低血压期间,Ci的增加表现出阈值效应,并随着ABP的持续下降而持续。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
6.00
自引率
9.10%
发文量
296
审稿时长
2-4 weeks
期刊介绍: The Journal of Applied Physiology publishes the highest quality original research and reviews that examine novel adaptive and integrative physiological mechanisms in humans and animals that advance the field. The journal encourages the submission of manuscripts that examine the acute and adaptive responses of various organs, tissues, cells and/or molecular pathways to environmental, physiological and/or pathophysiological stressors. As an applied physiology journal, topics of interest are not limited to a particular organ system. The journal, therefore, considers a wide array of integrative and translational research topics examining the mechanisms involved in disease processes and mitigation strategies, as well as the promotion of health and well-being throughout the lifespan. Priority is given to manuscripts that provide mechanistic insight deemed to exert an impact on the field.
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