Two-Operator Glucose Infusion Test (GIT2) for Vascular Access Recirculation Measurement during Hemodialysis

Vascular access recirculation rate (AR) monitoring is fundamental to guarantee treatment adequacy and to detect access failure early. We have evaluated the GIT2 test to measure AR unaffected by cardio-pulmonary recirculation (CPR), based on a short glucose infusion in place of the bolus and on a two-operator sampling, differently from the classical glucose infusion test (GIT). The GIT2 test is based on four steps: 1) basal (B) glucose arterial sample; 2) 10% glucose infusion for 1 min, by infusion pump at 600 ml/hr; (or 20% at 300 ml/hr); 3) simultaneous sampling at arterial (A) and venous (V) ports, after 35–40 sec from starting the infusion, taking care to avoid blood pump stop during the test; 4) AR=100*((A-B)/(V-B)). In vitro tests by dialysis on a 40 L tank containing a urea solution, with AR volumetrically simulated at 0, 5, 10, 20%, and in vivo comparison of GIT, GIT2 with stop-flow (SF) urea method. Our results have shown in vitro an almost perfect correspondence of SF urea method and a better reliability of GIT2 than GIT. The methylene-blue test has shown that a single color bolus in V reaches the A port after variable time, depending on blood flow and AR, while the continuous infusion determines a steady gradient after about 30″. In vivo tests (n=24) show good correspondence between GIT2 (4.37 ± 3.36) and SF (4.51 ± 3.62), while GIT data (1.01 ± 0.51) are significantly underestimated. In conclusion, our preliminary results have evidenced a good reliability of the new test, the continuous infusion causing a steady gradient in V and A that more precisely reflects the AR rate.