HCO3 increment in arterial line can reveal significant vascular access recirculation in high‐flux hemodialysis: A preliminary report

AbstractWe report a new and simple way that can reveal the presence of vascular access recirculation (VAR) in patients undergoing hemodialysis (HD). Acid‐base and blood gas parameters (pH, pO2, pCO2, and HCO3) were measured in blood samples drawn from an arterial fistula needle before the initiation of HD and from arterial and venous lines simultaneously 5 min later, in 31 patients (group A). Vascular access recirculation was measured using the glucose infusion test (GIT) immediately after the withdrawal of the 5‐min samples. The same study was repeated in 30 patients in whom HD lines were reversed (group B). A comparison with baseline (predialysis) values of an analysis of the arterial line in group A at 5 min revealed that pCO2 increased by 1.14±2.5 mmHg and HCO3 by 0.6±0.6 mM/L (p<0.02 and p<0.00001, respectively). The corresponding pO2 and pH values did not show significant differences. Glucose infusion test at 5 min (GITa) was −0.058±0.03%. A comparison with baseline (predialysis) values of an analysis of the arterial line in group B at 5 min revealed that pCO2 increased by 7.7±3.5 mmHg and HCO3 by 2.9±1.0 mM/L (p<0.000001 in each case). The pH level was significantly lower in comparison with baseline values (p<0.00001), while pO2 did not show a significant difference. Glucose infusion test at 5 min (GITb) was 12.0±6.1% (p<0.000001 in comparison with GITa values). Clinically significant VAR was defined as HCO3 increment >1.8 mM/L, based on the receiver‐operating characteristics curve, which showed a threshold value of HCO3 increment >1.8 mmol/L as a predictor of GIT recirculation. Five minutes after the initiation of high‐flux HD with a 0 ultrafiltration rate, there is a small increment in arterial HCO3 values relative to predialysis values. Clinically significant VAR is present when this increment is higher than 1.8 mM/L.