Abstract: OBJECTIVE To explore the influence of frequency of flushing of in vitro pipelines with normal saline on bloodstream infections in patients undergoing heparin-free continuous renal replacement therapy (CRRT). METHODS A total of 384 patients who received the CRRT in the hospital from Jan 2015 to Dec 2016 were enrolled in the study and randomly divided into the observation group and the control group, with 192 cases in each group.Both groups of patients were treated with heparin-free CRRT; the frequency of flushing of in vitro pipelines with normal saline was 100 ml/6 h in the observation group, 100 ml/h in the control group; the blood coagulation function indexes of the two groups of patients were recorded on the day of use of filters; the average time of use of filters for treatment, average time of use of filters and average time of use of pipelines were compared between the two groups of patients, and the incidence of bloodstream infections of the two groups of patients was recorded. RESULTS There was no significant difference in the fibrinogen degradation products, fibrinogen, thrombin time, prothrombin time, international normalized ratio or activated partial thrombin time between the two groups of patients on the days of use of filters.The continuous veno-venous hemofiltration (CVVH) therapy was completed for 396 times in the observation group, 404 times in the control group.There was no significant difference in the average treatment time, average time of use of filters or average time of use of pipelines between the two groups.Totally 2 patients had bloodstream infections in the observation group, 12 patients in the control group, the infections rate was 1.04% in the observation group, 6.25% in the control group, and there was significant difference in the infection rate between the two groups (P＜0.05). CONCLUSION The high frequency of flushing with normal saline may not improve the blood coagulation function but lead to the increase of risk of bloodstream infections, and the necessity of its clinical application is worthy to be discussed.