[Monitoring protocol of native vascular accesses for haemodialysis]

Vascular access failure is an important cause of morbidity and mortality for patients on haemodialysis. We have prospectively studied, with a 5 years follow up, a monitoring protocol of native vascular accesses, using the available methods in every haemodialysis unit. All the native vascular accesses, created from 1- 1998 to XII-2001, with a posterior follow up until XII-2002, were monitored. Monitoring was based on physical examination, dificulty for blood flow greater than 300 ml/min, and in a monthly basis: dynamic venous pressure, urea recirculation and urea kinetic model. Abnormalities suggestive of fistulogram were a priori defined. During the recruitment period, a total of 164 accesses were created in 144 patients. Of these only 3 were grafts, 28 native vascular accesses were never functioning (primary failure rate 17. 1%), and 127 native accesses created in 113 patients (age 63.3 +/- 12.4 years; 18 % diabetics), were monitored (83% cephalic vein). Monitoring findings indicated realization of fistulogram in 35% and percutaneus angioplasty in 25% of the accesses. In order to maintain patency, the surgical intervention rate was 0.03 procedures/patient/year, the radiological 0.10 and the total 0.13. During the 5 years of the study occurred 41 thrombosis episodes in 40 accesses (0.07 thrombosis/patient/year), with percutaneus repermeabilization in 30%. Primary (unassisted) survival was 30.3 months (Confidence Interval 95% 25.6, 35.0) and secondary (assisted) survival 42.8 months (Confidence Interval 95%: 38.7, 46.9). Logistic regression analysis showed that presence of a central catheter at the time of creating the vascular access posses a greater risk for thrombosis (Relative Risk 5.6 if in subclavian vein), whereas age, diabetes, time to canulation, number of previous accesses and anatomic type do not increase that risk. In conclusion, in an old haemodialysis population, with an important diabetes prevalence, it is possible to create functioning native vascular accesses in most of them. The monitoring protocol allowed the detection and posterior correction of stenosis in a great number of accesses. The main risk of thrombosis is the presence of a central catheter at the time of creating a vascular access.