Abstract: Objective To investigate the affecting factors of perioperative red blood cell transfusions in patients with colorectal cancer, thus providing evidence for rational use of blood in clinic. Methods Data were collected from January, 2013 to January, 2020 regarding clinical records, laboratory tests and perioperative blood transfusions of 295 patients in our hospital. The main factors involved in the red blood cell transfusion process, i.e. patient's age, gender, preoperative hemoglobin level, preoperative coagulation, operation time, tumor location, tumor volume, tumor staging, hospital stay were classified and analyzed. Results Of the 295 patients, 106 (35.9%) had intraoperative blood loss greater than 600 mL, the intraoperative blood transfusion rate being 49.2%. The higher transfusion rate was associated with preoperative anemia (Hb <100 g/L) in 51.0% of patients. The volume of intraoperatively transfused red blood cells accounted for 52.1% of the blood perioperatively used. Multivariate logistic regression analysis showed the most influential factors that affected the volume of intraoperative red blood cells were patients'age（P<0.001）and cancer location (P=0.004 for colon cancer; P=0.003 for rectal cancer), which were statistically significant predictors. In terms of the perioperative red blood cell transfusion volume, the significantly associated variable was tumor size (P=0.037). Significant correlation was observed neither between patient age, gender and perioperative blood transfusion (P>0.05) nor between red blood cell volume and length of hospital stay (inter-operative P=0.428, perioperative P=0.604), surgical incision type（P=0.784）, or incision healing（P=0.056）. The ratio of red blood cell to plasma infusion was reasonable during the operation, and there was no need for "matched whole blood" infusion. Conclusion The main influencing factors of perioperative blood transfusions are tumor location and size instead of patients'age, sex, preoperative hemoglobin level, operation time and tumor staging. Perioperative blood management is essential to reduce blood transfusion and shorten hospital stay.

Key words: Colorectal neoplasms, Intraoperative blood transfusion, Perioperative blood transfusion, Patient blood management