What is a MSBOS?
A ‘maximum surgical blood order schedule’ (MSBOS) indicates the number of units of red cells typically required by 80 - 90% of patients likely to need a transfusion when undergoing a specific surgical procedure. This information is presented as a table and can assist the clinician in ordering the appropriate number of red cell units for their patient.
Why is this important?
Each time a unit of red cells is reserved or crossmatched for a surgical patient, it is unavailable for other patients for a specified holding period. If the unit is not subsequently used, it can be returned to the blood bank inventory, but its remaining shelf life will have been reduced. Unfortunately, this practice increases the likelihood that units will expire before being used.
The adoption of policies such as the routine use of 'group and screen', electronic crossmatching, a MSBOS, and monitoring crossmatch-to-transfusion (C:T) ratios are all helpful in preventing unnecessary expiry of blood and reducing laboratory testing.
The ANZSBT guidelines for transfusion and immunohaematology laboratory practice provide a typical MSBOS. However, this is only an example and institutions should consider an MSBOS tailored to their local setting, including:
- Specific patient populations or demographics (which may have special transfusion requirements).
- Local surgical practices and experience, which may require adjustment to the recommended MSBOS for a procedure.
- Availability of transfusion support (consider alternative quantities in regional facilities).
- Complexity of surgery.
- Presence of red cell alloantibodies or autoantibodies.
For patients with a positive antibody screen, the hospital transfusion laboratory may need to have more units available than shown in the MSBOS. This will reflect the extra time required to find sufficient compatible units should the patient need transfusion.
Many large laboratories have moved to electronic crossmatching, which allows timely and on-demand issuing of blood. More efficient use of blood stocks enables the laboratory to hold a smaller inventory and reduces wastage due to expiration. If considering electronic crossmatching, the ANZSBT guidelines offer guidance.
Updated March 2025
