We tested a new bedside method to determine the function of native arteriovenous fistula in 16 patients performed during hemodialysis without stopping the treatment. We initially measured vascular access flow (Q(a)) in each patient using the Transonic HD01(plus) device. We then measured the pressure in arterial and venous drip chambers at different blood pump flow rates (Q(bset)=0, 50, 100, 250, 300, 350 ml/min). The intravascular blood pressure gradient (P(f)) between arterial and venous puncture sites was estimated by a mathematical model. P(f) was positive for low Q(bset), but became negative when Q(bset) overcame the threshold value (Q(Inv)). Such critical flow showed a high correlation with Q(a), even if it was systemically lower. Computer analysis of fluid dynamics showed that when the blood pump flow overcame the Q(Inv) threshold, a critical transition from laminar flow to vortex circulation took place downstream of the venous needle, causing a dangerous shearstress on the vessel wall. Our results show that Q(Inv) provides an indication of the maximal blood pump flow rate needed to be reached to maximize blood flow supply in order to limit hemodynamic stress on the vascular access.

Background: The aim of our study was to evaluate laboratory data behaviour in two dialysis populations, with and without dialysis-related arthropathy and pain. Methods: We produced an elaboration of more than 160,000 items of biochemical data of 25 dialysis-related arthropathy patients with chronic articular pain, and 25 patients asymptomatic for joint pain and arthropathy. The pain visual analogue scale (VAS) was employed for pain intensity determination. Results: The serum level of β-2 microglobulin was similar in the two groups of patients, while ferritin values were significantly higher in symptomatic patients. We excluded the possibility that the ferritin difference between the two groups was due to different iron storage and to an inflammatory profile. Furthermore, the pain VAS mean value was higher in patients who had higher ferritin and pain than in asymptomatic patients. Conclusion:It is important to underline that the higher value of ferritin in patients with chronic pain due to dialysis--related arthropathy could represent a new stimulus for a deeper investigation of this indicator, setting a periodic revelation of pain intensity.