Patient blood management: where's the bottom?

B lood transfusion is the most common procedure performed during a hospitalization and is performed during 11% of all hospital stays. Variability in its use exists in hospitals performing the same procedures and by clinicians performing the same procedure and there is widespread inconsistency in blood use between countries. This variability suggests that there is widespread confusion in how to use allogeneic red blood cells (RBC) properly. Part of the problem is that there is no critical laboratory value below which ischemia or bleeding is guaranteed to occur, so the cautious physician would most likely err on the conservative side and over transfuse patients with a low hemoglobin (Hb) or platelet (PLT) count. In 1992 a study of 114 medical school faculty members was performed where 24 hypothetical patient vignettes were created and the participants’ decision making visa-vis transfusion was assessed. There was a remarkable lack of agreement between who should or should not be transfused. Thus, two physicians may look at the same clinical circumstances and develop quite different transfusion strategies. Over the past decade, significant clarity on RBC transfusion thresholds has been gained with the recognition that a more restrictive use of allogeneic RBCs results in no difference in patient outcome and leads to the avoidance of the complications associated with transfusion and does so at a reduced cost of care. These results have been demonstrated in a wide variety of patient populations including critically ill intensive care patients, orthopedic hip fracture, gastrointestinal bleeding, cardiac surgery, sepsis, pediatric critical care, geriatrics, and traumatic brain injury. A recent meta-analysis concluded that the restrictive strategy significantly reduced cardiac events, rebleeding, bacterial infections, and mortality. As the findings of these trials have been recognized in clinical practice, striking reductions in blood product use have been recorded. Over the past 3 years in our institution, we have seen a 13%, 16%, and now an 18% annual reduction in blood product use. These striking numbers raise several questions. First, where is the nadir in these reductions? Second, how do we make sure that our enthusiasm for reducing overtransfusion does not go too far and lead to undertransfusion and potential harm? Before we can address the latter question, we first have to resolve a semantic issue: How do we define undertransfusion? Undertransfusion has been defined in two ways. Given the powerful evidence from randomized controlled trials (RCTs) on Hb and PLT thresholds in a variety of different clinical situations, undertransfusion could be defined as a failure to provide a transfusion if a patient’s laboratory variables fall below those delineated in the aforementioned studies. This definition was used by Hibbs and colleagues in their article on the rates and reasons for not transfusing patients with low laboratory variables in this edition of TRANSFUSION. Alternatively, we may define undertransfusion operationally on the basis of outcome, such as “any adverse complication which may have been avoided by blood transfusion. ” The use of this second definition raises further questions as to how we might determine that the transfusion would have averted the adverse complications. The article by Hibbs and colleagues addresses the concept of undertransfusion through use of the first set of criteria proposed above. The results of this study, which was conducted in multiple hospitals across England, would suggest that at least these institutions have not reached the point of consistent undertransfusion. The authors identified 93 patients with Hb values that were less than 6 g/dL or whose PLT counts were fewer than 10 3 10/L and asked the following question: given that these are values at which most physicians would transfuse their patients, was a transfusion administered and if not, why not? Fifty-seven of these patients received a transfusion and 36 patients did not. Yet by their definition, these 36 patients were actually not undertransfused because their clinicians’ acumen prevailed—either most of these nontransfused patients had a spuriously low laboratory value that was rectified by a repeat measurement or else the clinician felt that the transfusion was not medically necessary as an alternative to transfusion was available. The relative rarity of identifiable undertransfusion has been reported previously in two other studies. One study examined 55 patients with Hb levels of less than 7 g/dL or PLT counts of fewer than 10 3 10/L. No cases of undertransfusion were found. The second study used a Hb of 5 g/dL and a similar PLT threshold. The authors found only two patients in 14 months—one with a low Hb value and the other with a low PLT count—who they concluded were undertransfused. Interestingly, both of these studies were conducted long before the recent publication of RCT data on transfusion triggers. This doi:10.1111/trf.13063