Continuous renal replacement therapy (CRRT) is one of the essential treatments in the intensive care unit. CRRT is introduced in varieties of diseases, but its prognosis requires further investigation. We investigated the relationship between clinical parameters and prognosis. This is a retrospective observational study. We examined 121 patients who were introduced CRRT during hospitalization in our hospital from October 2016 to September 2019. We investigated clinical data at the time of introduction to CRRT and the diseases that caused CRRT and surgery during hospitalization. The outcome was all courses of death. Statistical analyses were performed using the Log-rank test and Cox regression model test. Data for 121 patients were available, 69 males and 52 females, mean age was 73.8 ± 13.7 years, and mean GFR was 25.4 ± 21.4 ml/min/1.73m2 at the time of CRRT introduction. The median observation period was 26 days [7.5-55.5 (interquartile range)]. All cases without one patient were introduced with CHDF in the intensive care unit. During the course, 60 patients were discharged from the hospital, 61 patients died. Forty-five patients who discharged and 15 patients who died were able to withdraw from CRRT, respectively. The most common cause disease of acute blood purification was coronary artery disease (n = 29), followed by aortic disease (n = 24) and sepsis (n = 24). Compared to cardiovascular disease, the initiation of acute blood purification due to sepsis had a poorer prognosis (log-rank p <0.05). Besides, there were 86 cases in which acute blood purification was introduced after invasive treatment, such as percutaneous coronary angioplasty or surgery. The classification was 47 cases of cardiovascular surgery, 18 cases of percutaneous coronary angioplasty, 14 cases of digestive surgery, and 8 cases of other operations. The prognosis was worse in the group without surgery compared to the group with surgery (log-rank p <0.05). To investigate risk factors for all-cause mortality, a multivariate analysis was performed based on age, sex, type of primary disease, whether or not surgery was performed, and whether or not acute blood purification was withdrawn. As a result, the group without surgery (HR 2.21 [1.14 to 3.37]) and the dialysis continued group(HR 1.8 [1.25 to 2.62]) had poor prognoses significantly. We have to be careful that the group in which CRRT was introduced without surgery, or the group in which CRRT could not be withdrawn, may have the severe pathophysiological conditions.