Hemoglobin concentration, total hemoglobin mass and plasma volume in patients: implications for anemia

In practice, clinicians generally consider anemia (circulating hemoglobin concentration −1 in non-pregnant females and −1 in males) as due to impaired hemoglobin synthesis or increased erythrocyte loss or destruction. Rarely is a rise in plasma volume relative to circulating total hemoglobin mass considered as a cause. But does this matter? We explored this issue in patients, measuring hemoglobin concentration, total hemoglobin mass (optimized carbon monoxide rebreathing method) and thereby calculating plasma volume in healthy volunteers, surgical patients, and those with inflammatory bowel disease, chronic liver disease or heart failure. We studied 109 participants. Hemoglobin mass correlated well with its concentration in the healthy, surgical and inflammatory bowel disease groups (r=0.687–0.871, P P =0.11) and heart failure patients (r=0.312, P =0.16). Here, hemoglobin mass explained little of the variance in its concentration (adjusted R 2 =0.109 and 0.052; P =0.11 and 0.16), whilst plasma volume did (R 2 change 0.724 and 0.805 in heart and liver disease respectively, P