Besarab A, Lubkowski T, Vu A, Aslam A, Frinak S
Department of Medicine, West Virginia University School of Medicine, Henry Ford Hospital, USA.
ASAIO J. 2001 Sep-Oct;47(5):501-6. doi: 10.1097/00002480-200109000-00021.
Absolute value of access flow (QA) and change in flow (deltaQA) over time are major determinants of access patency. However, QA may change in response to variation in systemic hemodynamics among dialysis sessions. We examined the effect of mean arterial pressure (MAP), cardiac output (CO), and segmental resistances (R) on QA. Access flow and CO (L/min) were determined by Transonic ultrasound dilution. Static intra-access pressures (mm Hg) at the arterial segment (AS) and venous segment (VS) were determined with the access unoccluded. During access occlusion (O), the AS pressure was equated to arterial pressure (MAPo), whereas the VS pressure reflected venous pressure (VP). Total and segmental vascular resistances (mm Hg-min/L) were calculated as deltaP/Q. We studied 58 arteriovenous (AV) grafts and 35 autologous AV fistulae (AVF) with measurements on two or more occasions in 43 grafts and 25 AVF. MAPC differed from MAPo by >20 mm Hg in 22% of patients. AS (58 +/- 2 vs. 31 +/- 2) and VS (40 +/- 1 vs. 25 +/- 2) were greater in grafts than in AVF, whereas VP was equal. Access flow (0.91 +/- 0.03 vs. 0.91 +/- 0.05 L/min), cardiac output (5.1 +/- 0.1 vs. 5.5 +/- 0.2 L/min), and total access resistance (115 +/- 5 vs. 11 +/- 6) were equal in grafts and AVF, but non-access systemic R was lower in patients with AVF that those with grafts (26 +/- 1 vs. 30 +/- 1). AS and VS resistances were greater in AVF than grafts (87 +/- 6 vs. 54 +/- 3 and 37 +/- 3 vs. 16 +/- 3). Multivariate analysis indicated that CO and ipsilateral MAPo affected flow in both access types. In grafts, all three access resistance elements, AS, VS, and total independently influenced flow, whereas in AVF, the VS did not. Unexpectedly, the ratio of systemic to access resistance also influenced access flow. The pressure in the venous system draining the access affected access flow in AVF but not grafts. We conclude that the hemodynamics of grafts and AVF differ. Cardiac output, MAP, and the arterial segment resistance influence QA in both access types and need to be considered when evaluating QA as part of the trend analysis for detecting access dysfunction.
随时间变化的通路血流量（QA）绝对值和血流量变化（ΔQA）是通路通畅性的主要决定因素。然而，QA可能会因透析疗程中全身血流动力学的变化而改变。我们研究了平均动脉压（MAP）、心输出量（CO）和节段性阻力（R）对QA的影响。通过Transonic超声稀释法测定通路血流量和CO（升/分钟）。在通路未闭塞的情况下，测定动脉段（AS）和静脉段（VS）的静态通路内压力（毫米汞柱）。在通路闭塞（O）期间，AS压力等于动脉压（MAPo），而VS压力反映静脉压（VP）。总血管阻力和节段性血管阻力（毫米汞柱·分钟/升）计算为ΔP/Q。我们研究了58例动静脉（AV）移植物和35例自体动静脉内瘘（AVF），对43例移植物和25例AVF进行了两次或更多次测量。22%的患者MAPC与MAPo相差>20毫米汞柱。移植物中的AS（58±2对31±2）和VS（40±1对25±2）高于AVF，而VP相等。移植物和AVF的通路血流量（0.91±0.03对0.91±0.05升/分钟）、心输出量（5.1±0.1对5.5±0.2升/分钟）和总通路阻力（115±5对11±6）相等，但AVF患者的非通路全身R低于移植物患者（26±1对30±1）。AVF的AS和VS阻力高于移植物（87±6对54±3和37±3对16±3）。多变量分析表明，CO和同侧MAPo影响两种通路类型的血流量。在移植物中，所有三个通路阻力要素，AS、VS和总阻力均独立影响血流量，而在AVF中，VS则不然。出乎意料的是，全身阻力与通路阻力之比也影响通路血流量。引流通路的静脉系统压力影响AVF的通路血流量，但不影响移植物的通路血流量。我们得出结论，移植物和AVF的血流动力学不同。心输出量、MAP和动脉段阻力影响两种通路类型的QA，在将QA作为检测通路功能障碍趋势分析的一部分进行评估时需要考虑这些因素。
