Measuring System of Urea in Blood by Application in Recirculation for Hemodialysis Treatment

End stage renal disease (ESRD) is one of the most common life-threatening diseases. The number of patients accepted for renal replacement therapy including hemodialysis (HD), peritoneal dialysis, and kidney transplantation in developed and developing countries increases each year and imposes a major social and economic burden on these communities.(1) With an increasing number of elderly patients as well as patients with co-morbid conditions such as vascular disease and diabetes mellitus in the hemodialysis (HD) population, a well functioning mature arteriovenous fistula (AVF) is essential for the delivering HD in these patients. [1],[2] Malfunction of permanent vascular accesses remains a cause of frequent and costly morbidity among these patients. [3] Stenosis of the HD vascular access is common with an occlusion rate of 17–45% at one year. [4],[5] Therefore, periodic monitoring of the access is recommended; early detection and correction of stenotic lesions can reduce the frequency of thrombosis and the need for high-risk therapy, increase the life of the access and help to reduce the rate of access failure. [1],[5] A variety of techniques such as physical examination, venous pump pressure, percent access recirculation, transonic flow and others are helpful in detecting vascular access dysfunction and improve assessment of the vascular access site. [4],[6] There is currently no consensus as to the optimum method of screening for stenosis; the most widely used method of screening for stenosis has been the percent access recirculation (%AR) measurement. [4] Vascular access recirculation (AR) is defined as the return of dialyzed blood to the arterial segment of the access bypassing the systemic recirculation, thereby resulting in reducing the efficiency of dialysis. [7] High degrees of recirculation can lead to a significant discrepancy between the amount of HD prescribed and the amount of HD delivered.[8] Some investigators have suggested that AR of 15% or higher reliably suggests significant stenosis. [4] The usually method for recirculation measuring is the Doppler Effect and the different technical based in the circulation blood sense of through the needles. These procedures have the great advantage to be carried by the medical and infirmary personal. At the moment some automatic systems estimate the recirculation rate with used hemodilutión technical that consist in the administration of saline serum in the return line,