Transfusion medicine handbook

3. Guide to Good Transfusion Practice

3.5 Blood Stock Management: the Maximum Blood Order Schedule

The maximum blood order schedule (MBOS) is one way some blood banks may manage blood stock. For blood banks who predominately utilise electronic crossmatching the need for a MBOS may be minimal.

A MBOS commonly lists surgical, and other interventional procedures, along with the number of red cell units normally required in preparedness for transfusion in association with these procedures. The number of units is determined by analysis of historical blood usage figures. Many laboratories formulate a MBOS based on local surgical experience, while others adopt a generic schedule. An example of such a schedule is available in the 2020 Australian and New Zealand Society of Blood Transfusion (ANZSBT) Guidelines for Transfusion, and  Immunohaematology Laboratory Practice ANZSBT Guidelines - ANZSBT : ANZSBT.

The goal of the MBOS is to promote efficient use of red cells. It provides guidance to junior medical staff on the number of units of red cells likely to be required for various surgical procedures and is also a valuable guide for the blood bank, particularly those which routinely perform serological crossmatching (generally smaller facilities). For procedures where red cells are seldom required, the MBOS will simply recommend a group and screen performed, i.e. no units need to be crossmatched.  

If more red cells are ordered for a patient than required or they are held crossmatched unnecessarily, then these units may be unavailable for other patients and there is a chance that the red cells will expire before being used. The clinician therefore needs to have a valid rationale to order more units than is mandated by the MBOS.

If the patient has a positive antibody screen or special transfusion requirements the blood bank may adjust the number of red cells crossmatched (from what is specified in the MBOS) to avoid potential problems should transfusion be required.

Together, the MBOS, regular monitoring of crossmatch-to-transfusion (C:T) ratios for individual surgical procedures and adoption of a 'group and screen' policy are all helpful in ensuring maximum use of the available stock of red cell components.