Vascular access blood flow measured without indicator injection

Abstract

Since low access flow (Qa) signals access failure, periodic surveillance methods to measure Qa could increase access functionality and patency. Employing arterio-venous temperature changes caused by switching the extracorporeal blood lines we measured vascular access flow (TQa) without injection of indicator with the aim to detect low Qa and com pared that value to the Qa measured by the standard saline dilution method (HDQa) that requires indicator injection. In 15 patients (5 female, 55±12 years) using the Blood Temperature Monitor (BTM, Bad Homburg, Germany) and the Twister Combiset bloodlines (Fresenius Medical Care, Lexington, MA) two paired measurements were done within the first 15 min of hemodialysis (HD) and repeated twice in the first 90 min of treatment. Reversal of the extracorporeal blood lines was done between the BTM temperature sensors and the blood pump (distal switch). Patients were hemodynamically stable at a mean blood pressure (MAP) of 103±16 mmHg. Mean TQa was 995±396 mL/min and mean HDQa was 1020±366 mL/min. The absolute difference between techniques was larger at high Qa (-572 to 536 mL/min) and smaller at lower flows (-169 to 135 mL/min) and probably related to effects of variable environ mental temperature. The coefficient of variation at Qa below 1100 mL/min was comparable for both techniques and 3.3% and 2.7% for TQa and HDQa, respectively. Since surveillance methods should aim at detecting a low Qa the temperature gradient technique may be suitable for rapid and repeated measurement of Qa. Other arteriovenous gradients inherent to the HD procedure that do not depend on environmental conditions should be investigated. © 2009 Springer-Verlag.