title: Increased urea kinetic modeling volume. Possible mechanisms and its significance.
abstract: The presence of access recirculation reduces delivered urea clearance and produces an increased volume/weight (V/M) ratio in three-point kinetic modeling. We measured R in 20 patients receiving conventional hemodialysis and correlated results with normalized intra-access venous pressure (PIA) and with angiographic or color-flow Doppler studies. Twenty patients were equally divided into those with and without persistently elevated modeled V/W ratios (0.64 vs 0.53), and subdivided into those with native and synthetic bridge graft accesses. Kinetic modeling parameters (Kt/V) and P1A did not differ between the two V/W groups. Modeled volume was quite accurately predicted by the equations in the normal group but deviated by 7.3 +/- 2.1 L in the high V/W ratio group. Three of 10 native and 4 of 10 graft accesses had trivial and hemodynamically insignificant abnormalities by color-flow Doppler or angiography. Recirculation was independent of V/W group and when measured by the slow flow/clamp technique was negligible (< 2.0%). Access flow always exceeded prescribed dialyzer blood flow by more than 300 ml/ min. Therefore, access recirculation was unlikely. In many of the high V/W patients, alternative explanations for falsely high modeled volume were found on follow-up modeling. Only one patient appeared to have a true high volume. The authors conclude that high urea volumes during kinetic modeling are unlikely to occur from access recirculation, but arise from other factors affecting the delivered urea clearance.
authors.affiliation: Department of Medicine, Henry Ford Hospital, Detroit, Michigan 48203, USA.
authors.forename: A
authors.initials: A
authors.lastname: Besarab
authors.forename: R
authors.initials: R
authors.lastname: Ross
authors.forename: S
authors.initials: S
authors.lastname: Frinak
authors.forename: G
authors.initials: G
authors.lastname: Zasuwa
mesh_terms: D000328:Adult; D000792:Angiography; D001794:Blood Pressure; D001806:Blood Urea Nitrogen; D001810:Blood Volume; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D002408:Catheters, Indwelling / Q000009:adverse effects / Q000592:standards*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007700:Kinetics; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012039:Regional Blood Flow; D006435:Renal Dialysis; D015203:Reproducibility of Results; D013927:Thrombosis / Q000209:etiology; D018615:Ultrasonography, Doppler, Color; D014508:Urea / Q000097:blood / Q000378:metabolism*; D014680:Veins / Q000502:physiology
chemical_list: D014508:Urea