Variables associated with circuit life span in critically ill patients undergoing continuous renal replacement therapy: a prospective observational study

One of the greatest problems in performing continuous renal replacement therapy (CRRT) is premature coagulation of the circuit. The aim of the current study was to monitor the circuit function prospectively and analyze patient-related variables that may affect circuit life. Critically ill patients admitted to the intensive care unit of a tertiary hospital between August 2010 and August 2011 receiving continuous veno-venous hemofiltration (CVVH) with systemic heparin anticoagulation were prospectively studied. Variables including body temperature, blood pH value, ionized calcium level, activated partial thromboplastin time (aPTT), prothrombin time (PT), platelet count, and heparin dose were collected and analyzed for their association with circuit life span. Fifty-four patients treated by CVVH were included, with 255 filters. The filter life was 29.7 ± 13.4 hours (mean ± standard deviation [SD]). Circuits with longer survival time appeared to have lower body temperature (37.80 ± 1.14 vs. 36.36 ± 1.09; p< 0.05), lower levels of serum ionized calcium (0.80 vs. 1.29; p< 0.05), and to be more acidic (7.233 vs. 7.377; p< 0.05). Cox regression showed that pH value and ionized calcium levels were significantly associated with circuit life. Other variables of hematocrit, albumin levels, platelet count, aPTT, PT, or dose of heparin were not significantly associated with circuit life.