Dialysis

Abstract. The traditional method for measuring vascu-lar access recirculation has been questioned. We have compared methods based on samples from the femoral artery, a peripheral vein, and a slow flow technique. Seventeen patients on high-flux haemodialysis with blood flow 355 + 42 ml/min were examined after 60 min of treatment. Using urea as the marker solute, recircu-lation was 0.0 +1.8 % (femoral artery), 6.7 ± 2.7 % (peri-pheral vein), and 4.7 + 1.6 % (slow flow), and using creatinine 0.1 + 1-4 % (femoral artery), 7.8 + 3.0 % (peri-pheral vein) and 2.9 + 1.2 (slow flow). Access recircula-tion was non-existent among these patients when using the femoral artery sample: maximum 3.1%. In contrast, the traditional method (peripheral vein) produced values up to 13.5%. The observed differences can be explained by cardiopulmonary recirculation. Blood returning from the periphery mixes with blood returning from the dialyser, so that solute concentra-tion will be less in femoral artery than in peripheral vein. In conclusion, neither the traditional method nor slow-flow techniques accurately quantify access recir-culation. Cardiopulmonary recirculation must be con-sidered in kinetic studies, including routine dialysis prescription, where samples should be taken at least 2 min after termination of dialysis. Key words: haemodialysis; disequilibrium; kinetics; methodology; recirculatio