Phenotyping Acute Non-Severe Anemia in the Emergency Department

Anemia is traditionally diagnosed and managed using circulating hemoglobin concentration (\[Hb\]). However, \[Hb\] is influenced by plasma volume and may not accurately reflect the total amount of hemoglobin available for oxygen transport. Total hemoglobin mass (Hbmass), measured using the optimized carbon monoxide rebreathing method, provides a direct assessment of the body\'s oxygen-carrying capacity but has never been extensively investigated in patients presenting to the emergency department with non-life-threatening anemia. The hypothesis of the PHENOEMEMIA study is that routine blood hemoglobin concentration is only moderately correlated with Hbmass and therefore does not fully reflect the physiological severity of anemia. PHENOEMEMIA is a prospective single-center interventional physiological study including adults presenting to the emergency department with non-life-threatening anemia. Each participant undergoes routine clinical assessment, standardized symptom questionnaires, additional blood sampling for biological and hemorheological analyses, focused transthoracic echocardiography, near-infrared spectroscopy assessment of tissue oxygenation, and Hbmass measurement using the optimized carbon monoxide rebreathing technique. The primary objective is to evaluate the correlation between blood hemoglobin concentration and Hbmass normalized to body weight. Secondary objectives include describing the relationships between Hbmass, biological markers of anemia, clinical symptoms, cardiac adaptation, blood rheology, tissue oxygenation, and physiological phenotypes of anemia.