Impact of anemia on outcome in critically ill patients with severe acute renal failure

Objective: To evaluate the prognostic value of hemoglobin levels in critically ill patients with acute renal failure (ARF) requiring dialysis. Design and setting: A prospective observational cohort study in two adult medical ICUs. Patients: 206 consecutive patients with ARF who required dialysis. Overall 28-day mortality was 48%. Measurements and results: At ICU admission mean hemoglobin level was 9.1 +/- 2.1 g/dl. By ROC curve analysis the threshold value of hemoglobin with the highest sensibility/specificity was 9 g/dl. At baseline 63% of patients had anemia, defined as initial hemoglobin below 9 g/dl. Kaplan-Meier analysis showed that these patients had lower survival rate than those with hemoglobin above 9 g/dl. By multivariable analysis three factors were independently associated with 28-day death: hemoglobin lower than 9 g/dl (adjusted odds ratio 2.4, 95% CI 1.1-5.2), age, and SOFA score. Based on age and SOFA a matched cohort analysis of 67 pairs of ARF patients with or without anemia found similar results regarding the negative impact of anemia on outcome. Finally, a multivariable logistic regression analysis on matched cohort identified hemoglobin level below 9 g/dl (adjusted odds ratio 1.32, 95%CI 1.15-1.46), continuous renal replacement therapy, and vasoactive therapy as independent predictors of 28-day death. Conclusions: These results suggest that initial hemoglobin level could be helpful in identifying patients with ARF requiring dialysis at high risk of death.