4.2 Assessment of patients after red blood cell transfusion

Background question 2

When should a patient be retested after a transfusion to assess the response, guide whether further transfusions are required and avoid over transfusion?

When prescribing a RBC transfusion, deciding how many units to transfuse is as important as the transfusion decision itself, because each unit transfused carries additional risks (see Appendix B).

There is a growing body of literature covering appropriate Hb thresholds or triggers for RBC transfusion, both in the general population and in various clinical subgroups. However, these studies generally do not address the issue of over-transfusion and its attendant risks, which are of significant practical importance.172,173

When considering the decision to transfuse and the dosage, it is best to undertake careful clinical assessment of patients. A single-unit transfusion practice approach should be undertaken, with further clinical assessment after transfusion. Further transfusions are not required if the signs and symptoms are relieved. Clinical experience suggests that, in many patients, it may take 24 hours or more for patients to report an improvement in symptoms.

In some situations, prescribing more than one unit at a time may be appropriate; for example, where there is significant ongoing or anticipated blood loss, severe anaemia or the patient has chronic transfusion requirements (e.g. for bone marrow failure). The number of units prescribed, however, should still be carefully considered based on individual patient factors.

There is limited information in the literature about when to test the Hb level after a RBC transfusion. Where indicated, transfusion of a single unit of RBC followed by clinical reassessment is appropriate. This assessment will guide the decision on whether to retest the Hb level. One study reported a high correlation between Hb levels taken at 15 minutes, 1 hour and 2 hours after transfusion.174