For effective blood usage and reduction of unnecessary workload at blood banks, we established the maximum surgical blood order schedule (MSBOS) for major elective surgeries and evaluated indicators, including the rate of returned red blood cells (RBCs). Methods: During August 2016 and May 2017, MSBOS for neurosurgery, thoracic surgery, orthopedic surgery, and general surgery was established using two formulas: the mean units of transfusion per procedure (MSBOS 1) and the mean units of

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... on in transfused patients per procedure (MSBOS 2). The crossmatch to transfusion (C/T) ratio, transfusion probability, and rate of returned RBCs were calculated and analyzed. Results: Based on MSBOS 1, type and screen can be applied to all elective surgeries of the general surgery department. MSBOS 2 was higher than MSBOS 1 in most surgeries ranging from 1 to 3 units. The C/T ratio and transfusion probability of surgery exhibited similar tendencies, and the general surgery department was over-prescribed compared to the actual transfusion requirement. The rate of returned RBCs was the highest in thoracic surgery (32/101, 32%), and the total number of returned RBC unit was the highest in orthopedic surgery (276 of 1131 units). Conclusion: MSBOS 1 was the formula corresponding to the purpose of the maximum blood application protocol. Application of an appropriate MSBOS protocol and concurrent utilization of C/T ratio, probability of transfusion, and rate and number of returned units of RBCs will further aid the efficiency of blood bank resources. (Korean J Blood Transfus 2018;29:41-50)