Low reticulocyte hemoglobin content is associated with a higher blood transfusion rate in critically ill patients: a cohort study.

BACKGROUND Intensive care unit (ICU) patients often need blood transfusion, but no reliable predictors of transfusion requirements are available at ICU admission. The authors hypothesized that ICU patients with functional iron deficiency may be at higher risk for developing anemia, requiring blood transfusion. Their objective was to determine whether low reticulocyte hemoglobin content (CHr) was associated with transfusion requirements in ICU patients. METHODS This is a prospective cohort study in a general ICU. The authors studied 62 patients, after excluding those transfused on or before ICU admission. The authors recorded age, diagnosis, severity score, presence of sepsis, ICU complications, ICU treatments, and transfusion-free interval. Threshold for low CHr was 29 pg. The authors also recorded ICU and hospital outcome. The statistical analysis included Cox proportional hazard function for transfusion. RESULTS Twenty-three patients (37%) presented with low CHr on ICU admission and tended to be sicker and more likely to have sepsis than those with normal CHr. They were also more prone to complications, particularly acute renal failure (39 vs. 13% P = 0.02) and ICU-acquired infection (30 vs. 10% P = 0.04). The overall transfusion rate was 22.6%, being higher in low-CHr patients than in normal-CHr patients (39.1 vs. 12.8%, P = 0.02). After adjusting for severity of illness, age, trauma, and hemoglobin level, low CHr remained significantly associated with transfusion, with a hazard ratio of 3.6 (95% CI, 1.2-10.7; P = 0.02). Median ICU stay was also longer in patients with low CHr (8 vs. 5 days, P = 0.01). Differences in mortality did not reach statistical significance. CONCLUSION Low CHr is common at ICU admission and is associated with higher transfusion requirements.