Is fetuin-A a biomarker of dialysis access dysfunction?

BACKGROUND: The arteriovenous (AV) access function of hemodialysis (HD) patients can be impaired by afferent artery stiffness due to preexisting microcalcification and by venous stenosis secondary to neointimal hyperplasia in whose development participates an upregulated local inflammatory process. Fetuin-A is a circulating potent inhibitor of vascular calcification and plays an important anti-inflammatory role. The aims of this prospective study were to investigate the relationship between baseline serum fetuin-A levels and: blood flow (QA) values at baseline, AV access failure (thrombosis or intervention for stenosis) during follow-up and primary unassisted AV access patency. METHODS: We measured baseline serum fetuin-A levels and QA values of the AV access in 64 HD patients under routine QA surveillance for stenosis. Patients were classified into tertiles according to their baseline fetuin-A levels (g/L): <0.5 (tertile-1), 0.5-1.20 (tertile-2), and >1.20 (tertile-3). RESULTS: Fetuin-A was positively correlated with QA (Spearman coefficient = 0.311, p = 0.012). Fourteen patients (21.9%) underwent AV access failure and they had lower fetuin-A (0.59 ± 0.32 g/L) and lower QA (739.4 ± 438.8 mL/min) values at baseline compared with the remaining patients (1.05 ± 0.65 g/L and 1273.0 ± 596.3 mL/min, respectively) (p = 0.027 and p < 0.001, respectively). The AV access failure rate was highest (34.8%) in tertile-1 (lowest fetuin-A level). Unadjusted Cox regression analysis showed a decrease in the risk of AV access patency loss by increasing fetuin-A concentration (hazard ratio 0.395 (95% confidence interval: 1.42-1.69), p = 0.044) but it was not confirmed in the adjusted model, although the hazard ratio was low (0.523). Kaplan-Meier analysis showed that patients in tertile-3 (highest fetuin-A concentration) had the highest primary unassisted AV access patency (λ2 = 4.68, p = 0.030, log-rank test). CONCLUSION: If our results are confirmed in further studies, fetuin-A could be used as a circulating biomarker to identify HD patients at greater risk for AV access dysfunction, who would benefit from much closer dialysis access surveillance.

The impact of pre-existing radial artery pathology by histological assessment on the maturation, function and patency of the radiocephalic fistula for hemodialysis.

BACKGROUND: We prospectively analyzed the effect of preexisting structural changes of the radial artery (RA) wall by histological examination on the wrist radiocephalic fistula (RCF) outcomes. METHODS: During RCF creation, one segment of the RA wall was collected and its histomorphometric analysis was performed. The RCF function was evaluated by measuring blood flow rate. RESULTS: At the end of follow-up, 75.7% of the thirty-seven patients enrolled were performing hemodialysis by using their successful RCF and 24.3% of them showed early RCF failure. Compared to patients with a healthy RA, the RCF of those with medial RA microcalcification reached up a lower flow and a shorter primary patency (P=0.005 and P=0.040, respectively). The RA microcalcification was predictive of the RCF function (coefficient -614.9, 95% CI: -994.7 to -235.1, P=0.003). Compared to patients with successful RCF, those with failed RCF had a greater frequency of weak RCF thrill after releasing the clamps (P=0.045). Dependence on hemodialysis during RCF placement was predictive of its early failure (OR: 23.2, 95% CI: 1.76 to 306.9, P=0.017). Both having at least one cardiovascular comorbidity (HR 4.30, 95% CI: 1.29 to 14.39, P=0.018) and a thicker media layer of the RA (HR 1.60, 95% CI: 1.87 to 2.15, P=0.002) were predictive of primary RCF patency. CONCLUSIONS: The function and survival of the successful RCF were related to preoperative RA abnormalities such as microcalcification and media layer thickness. Both dependence on hemodialysis during RCF placement and an attenuated RCF thrill were associated with early RCF failure.

Study of arteriovenous fistula function by the temperature gradient method using the Twister™ device.

INTRODUCTION: Periodic blood flow (QA) measurement is the preferred way for arteriovenous fistula (AVF) surveillance in chronic hemodialysis (HD) patients. Objectives. 1) Assess the efficacy of the temperature gradient method (TGM) on the QA determinations using the Twister™ device and to compare the functional results with the Delta-H method. 2) Evaluate the effect of blood pressure on the AVF function. Patients and method. We measured the QA non invasively in 30 AVF (24 radial and 6 brachial; mean duration 53.4 +/- 78.5 months) during HD in 30 stable patients (mean age 59.9 +/- 14.1 years, males 60 %, females 40 %; mean time on HD 37.4 +/- 40.6 months, diabetic nephropathy 20 %) by the TGM, described and validated by Wijnen et al (Kidney Int 2007;72:736). The QA was calculated from the temperature values obtained by means of the blood temperature monitor (BTM), integrated into the Fresenius Medical Care 4008-S machine, at normal and reverse configurations of the HD blood lines, with no need for a thermal bolus. The Twister™ device was used for reversing the blood lines without the need to disconnect them from the AVF lines nor to stop the blood pump. The QA was measured within the first hour of two consecutive HD sessions (the values were averaged). The mean arterial pressure MAP (diastolic pressure + 1/3 pulse pressure) was calculated simultaneous with the QA. In addition, the AVF blood flow was also determined during the same week in all patients by the Delta-H method using the Crit-Line III Monitor (ABF-mode, HemaMetrics, USA) during HD (manually switching lines). RESULTS: The mean QA was 1132.5 +/- 515.4 ml/min (range, 446-2233 ml/min). The mean coefficient of variation for duplicate QA measurements was 6.8 +/- 4.7 %; the MAP was not different when the reproducibility tests were performed (96.1 +/- 13.7 versus 96.6 +/- 12.8 mmHg, p = .72). No significant difference was found when comparing the mean QA between diabetic (n = 6, 966.4 +/- 340.7 ml/min) and nondiabetic (n = 24, 1174.4 +/- 548.3 ml/min) patients (p = .39). The mean QA was similar for patients with mean MAP < 100 mmHg (n = 18, 1101.0 +/- 552.7 ml/min) and for patients with mean MAP >_ 100 mmHg (n = 12, 1180.4 +/- 473.3 ml/min) (p = .69). No correlation was found between the mean QA and: age (r = 0.09, p = .62), time on HD (r = 0.06, p = .76), MAP (r = -0.21, p = .27), Kt/V index (r = 0.12, p = .51), distance between needles (r = - 0.17, p = .37) and AVF duration (r = -0.01, p = .96). The mean time required to measure QA with the TGM using the Twister™ device (5.9+/- 1.9 min) was significantly shorter compared with the Delta-H technique (26.8 +/- 1.9 min) or with the TGM (n = 35, 8.9 +/- 3.5 min, manually reversing lines) reported by Wijnen et al (Kidney Int 2007;72:736).) (for both comparisons, p < .001). The mean QA obtained by the TGM was not different when compared to mean ABF determined by the Delta-H method (1138.4 +/- 502.3 ml/min) (p=.83).The calculated values of AVF blood flow obtained by TGM were highly correlated with those determined by the Delta-H technique (r = 0.963, p < .001). CONCLUSIONS: 1) The TGM is a valuable and reproducible indicator of QA during HD. 2) The Twister™ device is useful to reduce the time for QA measurement by the TGM. 3) The AVF blood flow values obtained by the TGM and the Delta-H technique correlated highly with each other. 4) It has been shown the lack of relationship between the AVF function and the patient's blood pressure.