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

BACKGROUND: 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. STUDY DESIGN AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.