Anemia Risk Factor for AKI in Hospitalized Patients

Philadelphia—Anemia increases the risk of acute kidney injury (AKI) in hospitalized patients and the risk may be modified with correction of the anemia. Those were among the findings of research presented in a poster session during Kidney Week 2014 by Melanie Godin, MD, and colleagues. The poster was titled Anemia Is a Risk Factor for Development of Acute Kidney Injury in Hospitalized Patients.

Anemia, defined as hemoglobin <10 g/dL, is recognized as a risk factor for the development of AKI in patients undergoing cardiac surgery, but there are limited data on the prevalence of anemia in AKI on other settings. The researchers conducted the current study to test the hypothesis that anemia is common and is a predictor of AKI in hospitalized patients.

The study included 1946 patients hospitalized at an academic medical center over 24 months. Inclusion criteria included availability of sequential hemoglobin and creatinine values at admission, during hospitalization, and at discharge. Exclusion criteria were age <18 years, stay in the intensive care unit, hospital length-of-stay <48 hours or >35 days, and end-stage renal disease or dialysis. International Classification of Diseases, Ninth Revision discharge codes were used to record comorbidities and chronic kidney disease (CKD) status.

AKI was defined using Acute Kidney Injury Network criteria of serum creatinine increase >0.3 mg/dL within 48 hours. The study was designed to evaluate hemoglobin values at hospital admission, discharge, and average hemoglobin as predictors of AKI during hospital stay.

At admission, 26% of patients had anemia, defined as hemoglobin levels <10 g/dL, and 40.3% fit that definition during hospitalization. Of the 1946 patients in the study cohort, 348 (18%) developed AKI and, compared with those who did not develop AKI, had significantly lower levels of hemoglobin; there were more patients with average hemoglobin <10 g/dL (51.1% vs 20.7%; P<.001) in the group with AKI.

Worsening of anemia was more severe in the patients with AKI than in those without AKI (hemoglobin decline of 1.05 vs 0.69 g/dL between admission and discharge; P=.001).

In multivariate logistic regression models adjusting for age, sex, body mass index, diabetes, CKD, and heart failure, hemoglobin level <10 g/dL was identified as an independent predictor of AKI (odds ratio, 1.82; P<.001).

There was no correlation of hemoglobin levels with the severity of AKI. Further, while patients with pre-existing CKD had lower levels of hemoglobin at all time points during hospitalization, they did not have a worsening of anemia.

In conclusion, the researchers said, “Anemia is a risk factor for AKI in hospitalized patients. Correction of anemia could potentially modify this risk. Further studies are needed to define the cause of anemia and its relationship to AKI.”

The National Institute of Diabetes and Digestive and Kidney Diseases supported this study.