A Study On Filter Flushing In Heparin-free Continuous Renal Replacement Therapy

Objectives This study investigated the use of filter flushing with normal saline in heparin-free continuous renal replacement therapy (CRRT) in terms of frequency and dosage. It was anticipated to extend the use of filters and shorten the discontinuousness of hemofiltration so to reduce patient cost and nursing workload but maintain the hemodynamic stability and the effectiveness of hemofiltration.Methods 240 hospitalized patients in this study were those who received heparin-free CRRT participated from October 2013 to August 2015 in a comprehensive first-class teaching hospital. All patients were divided into 12 groups (from Group A to Group L, alphabetically) in accordance with their sequence of admission. Filters were flushed with normal saline for all patients. The dosage and frequency of each normal saline flushing was arranged as follow:100 ml every 30 minutes in Group A,100 ml every 60 minutes in Group B,100 ml every 90 minutes in Group C,100 ml every 120 minutes in Group D,150 ml every 30 minutes in Group E,150 ml every 60 minutes in Group F,150 ml every 90 minutes in Group G,150 ml every 120 minutes in Group H, 200 ml every 30 minutes in Group I,200 ml every 60 minutes in Group J,200 ml every 90 minutes in Group K,200 ml every 120 minutes in Group L. The service life (i.e. the time duration of its use from the start to the end time point), trans-membrane pressure and other CRRT indexes in all groups were monitored and recorded. Changes in creatinine (CRE), urea nitrogen (BUN), blood platelet count (PLT), coagulation function (i.e. prothrombin time, PT; activated partial thromboplastin time, APTT), electrolytes (Na+, K+, Cl-), lactic acid (Lac), heart rate (HR), blood pressure (BP), central venous pressure (CVP) and brain-type natriuretic peptide (BNP) were tested and reported.Results A total of 214 valid data sheets were collected. Statistical analyses were performed using the SPSS 18.0 software. Results were reported as follows:1. The service life of filter was not significantly influenced (p>0.05) by flushing frequency and dosage, while post-12h trans-membrane pressure was affected by the flushing dosage of normal saline.2. Difference in the frequency and dosage could affect the clearance of CRE and BUN in this study. The increased flushing frequency and dosage of normal saline seems to have caused the decreased clearance of CRE and BUN (p<0.05).3. PLT, PT and APTT were not significantly different (p>0.05) between varies groups by the different flushing frequencies and dosages.4. Electrolytes (i.e. Na+, K+, Cl-) were not significantly influenced (p>0.05) by the different flushing frequencies and dosages.5. The different flushing frequencies and dosages could influence the HR (p<0.05), which was a sensitive index for hemodynamics.Conclusion Differences in frequency and dosage of normal saline for filter flushing have no significant effects on the service life of filters or the electrolytes concentration or coagulation function during heparin-free CRRT. However, the clearance of CRE and BUN as well as the hemodynamics may be affected when higher flushing frequency and dosage of normal saline being used.