Introduction: Variation in red blood cell (RBC) transfusions persists across providers, and is thought, in part, to be attributed to a lack of consensus regarding thresholds to support transfusion decision-making. We developed standardized clinical vignettes to assess differences in inclinations to transfuse RBCs among surgeons, anesthesiologists and perfusionists in the setting of coronary artery bypass grafting (CABG) surgery.
Methods: We surveyed operating room transfusion decision-makers across all 33 non-federal cardiac surgery programs in the state of Michigan. Respondents were asked for their transfusion threshold (hematocrit “trigger”). Ten clinical vignettes were developed to elicit a provider’s inclination to transfuse (on a 6-point Likert Scale) in situations having moderate (Class IIa) or weak (Class IIb) evidence to support a transfusion. Hierarchical generalized linear models were used to estimate the effect of provider type and hematocrit trigger on the inclination to transfuse across clinical vignettes.
Results: There was a 45% (186 of 413) response rate. Of the respondents, 75.3% (140 of 186) reported having a hematocrit trigger, with a mean of 20.4 (SD 2.2). For every 1-unit increase in a hematocrit trigger, the inclination to transfuse increased by 0.19 points on the Likert scale (p<0.001). Inclination to transfuse differed by provider type: anesthesiologists vs. perfusionists (difference: 0.71, p<0.001); surgeons vs. perfusionists (difference: -0.11, p=0.51). After accounting for a provider’s transfusion trigger, the magnitude and significance of the effect diminished for anesthesiologists (difference: 0.30, p=0.06), while strengthening for surgeons (difference: -0.29, p=0.05) (Figure). Twenty-seven percent of the variation in a provider’s inclination to transfuse was accounted for by the transfusion trigger, while 15% of the variation was explained by the provider type.
Conclusion: In our statewide survey of intra-operative transfusion decision-makers, a provider’s hematocrit trigger was the strongest predictor of variation in blood transfusions. Reducing variation in provider hematocrit triggers may serve as an effective
blood management target, especially in clinical situations less well supported by evidence.