Impact of body weight on hemoglobin increments in adult red blood cell transfusion

Background: Though weight is a major consideration when transfusing blood in pediatric patients, it is generally not considered when dosing transfusions in adults. We hypothesized that the change in hemoglobin (Hb) concentration is inversely proportional to body weight when transfusing red blood cells (RBC) in adults. Methods: A total of 13,620 adult surgical patients at our institution were assessed in this retrospective cohort study (2009–2016). Patients were stratified based on total body weight (kg): 40–59.9 (16.6%), 60–79.9 (40.4%), 80–99.9 (28.8%), 100–119.9 (11.3%), and 120–139.9 (2.9%). The primary outcome was the change in Hb per RBC unit transfused. Subgroup analyses were performed after stratification by sex (male/female) and the total number of RBC units received (1/2/≥3 units). Multivariable models were used to assess the association between weight and change in Hb. Results: As patients' body weight increased, there was a decrease in the mean change in Hb per RBC unit transfused (40–59.9 kg: 0.85 g/dL, 60–79.9 kg: 0.73 g/dL, 80–99.9 kg: 0.66 g/dL, 100–119.9 kg: 0.60 g/dL, 120–139.9 kg: 0.55 g/dL; p <.0001). This corresponded with a 35% difference in the change in Hb between the lowest and highest weight categories on univariate analysis. Similar trends were seen after subgroup stratification. On multivariable analysis, for every 20 kg increase in patient weight, there was a ~6.5% decrease in the change in Hb per RBC unit transfused (p <.0001). Conclusions: Patient body weight differentially impacts the change in Hb after RBC transfusion. These findings justify incorporating body weight into the clinical decision-making process when transfusing blood in adult surgical patients.