Faster Blood Flow Rate Does Not Improve Circuit Life in Continuous Renal Replacement Therapy: A Randomized Controlled Trial

Abstract

Objectives: To determine whether blood flow rate influences circuit life in continuous renal replacement therapy. Design: Prospective randomized controlled trial. Setting: Single center tertiary level ICU. Patients: Critically ill adults requiring continuous renal replacement therapy. Interventions: Patients were randomized to receive one of two blood flow rates: 150 or 250mL/min. Measurements and Main Results: The primary outcome was circuit life measured in hours. Circuit and patient data were collected until each circuit clotted or was ceased electively for nonclotting reasons. Data for clotted circuits are presented as median (interquartile range) and compared using the Mann-Whitney U test. Survival probability for clotted circuits was compared using logrank test. Circuit clotting data were analyzed for repeated events using hazards ratio. One hundred patients were randomized with 96 completing the study (150mL/min, n = 49; 250mL/min, n = 47) using 462 circuits (245 run at 150mL/min and 217 run at 250mL/min). Median circuit life for first circuit (clotted) was similar for both groups (150mL/min: 9.1hr [5.5–26 hr] vs 10hr [4.2– 17 hr]; p = 0.37). Continuous renal replacement therapy using blood flow rate set at 250mL/min was not more likely to cause clotting compared with 150mL/min (hazards ratio, 1.00 [0.60– 1.69]; p = 0.68). Gender, body mass index, weight, vascular access type, length, site, and mode of continuous renal replacement therapy or international normalized ratio had no effect on clotting risk. Continuous renal replacement therapy without anticoagulation was more likely to cause clotting compared with use of heparin strategies (hazards ratio, 1.62; p = 0.003). Longer activated partial thromboplastin time (hazards ratio, 0.98; p = 0.002) and decreased platelet count (hazards ratio, 1.19; p = 0.03) were associated with a reduced likelihood of circuit clotting. Conclusions: There was no difference in circuit life whether using blood flow rates of 250 or 150mL/min during continuous renal replacement therapy. (Crit Care Med 2017; 45:e1018–e1025)