Early Detection of Hemodialysis Ateriovenous Fistula Dysfunction by Trend Analysis of Intra-access Pressure / 대한신장학회지

PURPOSE: To detect early arteriovenous fistula (AVF) dysfunction, we have developed a new method of intra-access total pressure (pT), and static pressure (pS) measurements. The purpose of this study is to assess the relationship between intra-access pressure and vascular stricture in order to establish the clinical validity of the method. METHODS: Total 46 of native AVFs were enrolled. They were measured intra-access pS and pT monthly. In initial angiography, 6 of 10 inflow stricture (As), 6 of 7 outflow stricture (Vs) and 2 having both lesions were taken PTA (percutaneous angioplasty) and compared pressure and ratio changes. If delta p (pT-pS) decreased more than 10% over 3 months or pT/MAP (mean arterial pressure) ratio dropped more than 10% over 3 months with below 0.8, then the patients were referred to angiography. Thirtyone patients were performed final angiography, and we compared the results with those of initial angiography. RESULTS: Although pT/MAP ratio and delta p were increased after PTA, there was no statistical significance in 6 As (+) patients (p>0.05). Six Vs (+) and 2 AS (+) and Vs (+) patients' delta p were increased significantly (p0.45). CONCLUSION: Intra-access stricture could be detected with pT/MAP ratio and delta p change. However, more careful MAP and pT measurement should be recommended for accurate diagnosis.

Early Detection of Hemodialysis Arteriovenous Fistula Dysfunction with Intra-access Static and Total Pressure Measurement / 대한신장학회잡지

PURPOSE: To detect the dysfunction of arteriovenous fistula (AVF) early, we have developed a new method to calculate the intra-vascular conduit flow rate based on the Bernoulli's theory. However, this method has limitation on detection of inflow stenosis. For detection of both in- and out-flow stenosis, we tried to measure intra-access static (pS) and total pressure (pT), and compared with angiographic findings. METHODS: From a total of 46 cases of native AVFs, of at least 3 months of construction, intra-access pS and pT were measured, before starting hemodialysis. deltap (pT-pS) and pT/mean arterial pressure (MAP) ratio were calculated, and compared with angiographic findings. RESULTS: Among 37 patients without outflow stenosis (Vs) in fistulogram, 10 patients with inflow stenosis (As) had significantly lower pT/MAP ratio and deltap than those without As patients (p<0.005). Among 34 patients without As, deltap was significantly lower in 7 patients with Vs than those 27 patients without Vs (p=0.001). CONCLUSION: pT/MAP ratio was correlated with As, and deltap reflects Vs in angiography. The measurement of pS and pT might be useful to predict inflow and outflow stenosis of AVFs.

Flow Measurement in the Hemodialysis Vascular Conduit for Surveillance of Internal Arteriovenous Fistula: A Trend Analysis

PURPOSE: We have already reported on a new method to calculate the intra-vascular conduit flow rate based on Bernoulli's theory for maintaining surveillance of the arteriovenous fistula (AVF) function. To assess the clinical validity of our methods, we examined a trend analysis on the calculated flow rate in hemodialysis vascular conduits. METHODS: From a total of 27 cases of native AVFs that were at least 3 months after construction, we measured the AVF flow rate (Q(D)) with Doppler ultrasonography first. When Q(D) was below 600 ml/min, a fistulogram was taken. The intra-vascular conduit static pressure (ps) was measured, and the flow rate (Q(a)) was calculated every month with using the mean arterial pressure. The patients with a decreased Q(a) of more than 10% over 3 months were referred for a diagnostic fistulogram. RESULTS: Twenty-seven AVFs were studied after 29.5+/-28.5 (4~120) months of operation. The mean Q(D) was 980.6+/-501.6 (144~2,230) ml/min. In 6 patients who showed a Q(D) less than 600 ml/min, 4 pathologic lesions were found on the diagnostic fistulogram: juxta-anastomosis stenosis (n=3) and a draining venous stenosis (n=1). Three patients who showed a Q(a) decrement were confirmed as having a draining venous stenosis. However, any unpredictable thrombosis with proximal stenosis (n=2) couldn't be detected. CONCLUSION: Q(a) represents the narrowing of the draining vein of an internal AVF. However, arterial or venous narrowing that is proximal to the arterial puncture site couldn't be detected with the calculated intra-conduit flow rate. The development of new methods that can detect proximal vascular stenosis and that can be used in combination with our method is anticipated in the near future.

Development of Simple Flow Measurement in the Vascular Access Conduit Based on the Bernoulli's Theory

PURPOSE: Early detection of arteriovenous fistula (AVF) dysfunction in hemodialysis patients and prompt corrective procedures reduces the AVF thrombosis rates and lengthens access survival. We tried to develop a new simple and cheap bedside measurement technique based on the Bernoulli's theory. METHOD: From a total of 20 case of vascular accesses for hemodialysis, of at least 3 months of construction, we twicely measured the AVF flow rate (QD) with Doppler ultrasonography and vascular conduit pressure. Four kinds of pressure were measured: tubing set free from dialysis machine and positioned on the patient's bed (PrF), two kinds of artificial stenosis made with tourniquet (PrS1, PrS2), pump flow rate at 100ml/min (Pr100), and pump off (Pr0). We calculated the flow rate of vascular conduit (QF) with PrF and mean arterial pressure on Bernouli's equation, and QF was compared with QD. RESULT: AVF was 26.0+/-28.6 (3~108) months after operation, with five cases (including 2 PTFE grafts) using brachial artery. PrF was closely correlated with Pr100 (R2=0.914), and inversely correlated with QD (R2=-0.026). QF was poorly correlated with QD (R2=0.003). There was no statistical difference in the double pressure measurement (P>0.05), but there was differenence in QD (P<0.05). When artificial stenosis was made, the pressures increased, and the calculated flow rates decreased in every patients. Thrombosis or stenosis was detected in all patients with decrement of QF, but not in all with decrement of QD. CONCLUSION: Pressure measurement and calculated flow rate in dialysis vascular conduit represent alterations of AVF flow rate. However its value in long-term follow up awaits further study with accurate constant number.