The number of needed blood unites usually is decided by each hospital based on a policy called (MSBOS), which stands for the maximum surgical blood order schedule. The number and type of ordered blood units, therefore, would rely on the classification of that procedure, the number of patients in the hospital, median estimated blood loss and transfusion index (Frank 2013), this policy was developed in the late 1970's. There have been many attempts to revolutionise (MSBOS) since: