Systematic reviews of guidelines and studies for single versus multiple unit transfusion strategies

Recent recommendations indicate that one red blood cell (RBC) unit should be transfused at a time, with reassessment after each transfusion, which may be extrapolated from literature supporting restrictive transfusion triggers rather than specific evidence. Therefore, two systematic reviews were performed to identify the following: 1) RBC transfusion guidelines and review articles to determine if single- or multiple-unit transfusion strategies are recommended and 2) studies comparing strategies for evidence of benefit.

MEDLINE, EMBASE, CINAHL, Web of Science, National Guideline Clearinghouse, and Trip Database were searched (inception to June 2017). For the first review, the proportion of articles with single/multiple-unit recommendations was assessed and stratified by article type. For the second review, the primary outcome was RBC use. Secondary outcomes included proportion of transfusion episodes using a single-unit strategy, length of stay, and mortality.

The first review identified 145 articles for analysis, with 51 transfusion guidelines. Only 14 guidelines (27%) made a recommendation, with most (93%) recommending single-unit transfusions. The second review identified seven cohort studies comparing preimplementation and postimplementation of a policy encouraging single-unit transfusion strategies. Meta-analysis could not be performed for outcomes given inconsistencies in reporting. RBC use decreased by approximately 10 to 41% across studies.

Transfusion guidelines lack recommendations to transfuse to a single-unit strategy. Mostly retrospective cohort studies (six of seven) are inconsistent in outcome reporting but suggest improved RBC use. Further high-quality studies could identify the benefits of a single-unit transfusion strategy, determine the applicability to different clinical settings, and inform future practice guidelines.