Factors associated with urea reduction ratio in acute renal failure.

Prescription and delivery of hemodialysis (HD) in acute renal failure (ARF) may be affected by patient- related factors such as hemodynamic instability, catabo- lism, variable extracellular fluid volume, and coagulation disturbances. This study was undertaken in a cohort of patients with ARF requiring HD, to quantify patient- and dialysis-related variables that influence dialysis delivery. The urea reduction ratio (URR) was calculated for each HD session. Patient-related variables included age, gender, weight, mean arterial pressure, and Acute Physiological and Chronic Health Evaluation (APACHE) II and Multi- ple Organ Failure (MOF) scores. Dialysis-related variables were dialyzer characteristics (membrane type, surface area, KoA, and K UF ), blood flow rate (Qb), session length, anti- coagulant use, vascular access, and ultrafiltration volume. The analysis of factors associated with URR was performed using mixed linear statistical models. The cohort consisted of 81 adult patients with ARF who underwent 419 consec- utive dialysis sessions. Mean ( ± SD) age was 60 ± 18 years; 57% were male. At dialysis initiation, APACHE II score was 23 ± 8 and MOF score 2 ± 1. The number of HD treat- ments averaged 5.5 ± 6.1/patient and 0.8 ± 0.2/patient/day, mean URR was 54 ± 15%, and session length 3.2 ± 1.1 h; 58% used a femoral venous catheter, and 92% polysulfone dialyzers. Among patient-related variables, the only inde- pendent predictor of delivered dose of dialysis, as measured by URR was the predialysis weight ( P < 0.01). Among the dialysis-related variables, treatment time ( P < 0.01), dia- lyzer surface area ( P < 0.01), dialyzer K UF ( P = 0.04), blood flow rate ( P < 0.01), and the use of a femoral venous cath- eter ( P < 0.01) were also independently associated with URR. An interaction between vascular access site and blood flow rate was also found to be significant ( P < 0.01). This study underscores the importance of the dialysis pre- scription parameters and vascular access site in influencing the dialysis dose in critically ill patients, and argues against the importance of patient-related characteristics such as disease severity. Key Words: Acute renal failure— Dialysis—Dose—Urea kinetic modeling.