Physiologic transfusion thresholds, better than using Hb-based thresholds?

Abstract

Transfusion guidelines recommend using hemoglobin (Hb)-based transfusion thresholds to decide whether to transfuse packed red blood cells. In most cases, even in restrictive transfusion strategies, these thresholds are above the theoretical limits of anemia tolerance, implying a potential risk for over-transfusion. Additionally, isolated hemoglobin or hematocrit values do not adequately reflect the balance between oxygen delivery and oxygen consumption and are, therefore, not suitable to detect impaired tissue oxygenation. As a consequence, physiologic transfusion triggers have been suggested as an alternative. Despite their intuitive physiologic rationale and the past efforts to scientifically investigate different physiologic transfusion triggers, most guidelines do not recommend their use in current clinical practice. Recent randomized controlled trials and prospective observational trials have shed new light on the possible benefits of using physiologic transfusion triggers in pRBC transfusion practice. Nevertheless, there is still a lack of solid scientific evidence supporting the feasibility, benefit, and safety of physiologic transfusion triggers to challenge the current gold standard of Hb-based transfusion practice. This commentary discusses the current literature and compares the concept of Hb-based transfusion triggers with alternative physiologic transfusion triggers.