[Arteriovenous fistula stenosis: diagnosis and radiotherapy]

Dialysis outcome is strongly affected by the function of the vascular access (VA). Thrombosis occurs as a result of decreased vascular access flow caused by a progressive stenosis of the access venous outflow tract. Applying a periodic measurement of recirculation with Blood Temperature Monitor (BTM-Fresenius Medical Care) every three months is it possible to prevent thrombosis and to avoid unnecessary expenses and a time-consuming procedure.

Using BTM, incorporated in Fresenius 4008 S machines, during dialysis procedure, we measured the recirculation on AV fistulas. The temperature bolus (thermodilution method) is produced by a temporary change in dialysate temperature (typically about 2,5 degrees C for 2,5 minutes). The measurement is initiated by pressing a single key. The result is available in 5-6 minutes. When recirculation measurement was greater than the threshold of 10%, we repeated the measurement on two next consecutive dialysis. If they were positive, a patient referred for Doppler evaluation, to elective fistulogram, or both. The patients with hemodynamically significant stenosis undergo angioplasty.

Over the period of 42 months 591 measurements were obtained in 44 patients (22M; 22F), mean patient age 62,3 (61,5M; 63,3F) years. All patients (100%) are having native AVF at their arms. In the observed period we found 22 suspected AVE After further evaluation we found 20 stenosis in 11 patients (4M; 4F). We performed 13 PTA without and 7 with stent placement. In 2 fistulas angiographies didn't confirm our suspicion, but they thrombosed after 3,7 (1-6,5) months, in average. Three fistulas thrombosed, in spite of a normal recirculation, two after the collapse caused by symptomatic hypotension, and one after the intensive physical work. In 4 patients (2M; 2F) we found 1-4 restenoses after percutaneous procedures. Restenoses were treated by PTA again. They occurs after 9,4 (2,5-17,5) months, in average.

Our results in finding stenosis and restenoses confirm that with three months measurements only a few stenoses will be unrecognised and rapidly progressed into a thrombosis. BTM is easy, quick and could be done by existing staff during every dialysis procedure, non-invasive, without blood sampling or indicator injections, without treatment interruption and discomfort or stress for the patient. Venography or Duplex sonography was used to confirm the lesions. PTA with or without stent placement is safe, simple, and efficacious, with rare complications.

BTM measurements are sufficiently reproducible and offer the opportunity to extend access monitoring to all haemodialysis patients. We propose to screen well functioning accesses every three months, accesses that are problematic or had a history of previous stenosis every 4 weeks. For now, accesses detected by BTM can be then examined by Venography or Duplex sonography. Screening with recirculation appears to enable earlier detection and therapy.