Hepcidin in trauma: linking injury, inflammation, and anemia.

BACKGROUND: Anemia is almost universal in trauma patients admitted to the intensive care unit (ICU). Hepcidin is a liver-derived peptide that is a negative regulator of iron stores. Hepcidin synthesis is suppressed by erythropoiesis and iron deficiency and upregulated by iron overload and inflammation. Hepcidin has been shown to have an important role in the anemia of chronic inflammatory diseases but has not been previously studied in the setting of trauma. We sought to define the link between traumatic injury, hepcidin, and inflammation.
METHODS: One hundred fifty trauma patients admitted to the ICU were prospectively enrolled in the study. Urine was collected at regular time points for hepcidin measurement. Serum for iron studies and measurement of those cytokines associated with acute inflammation was also collected.
RESULTS: The study population comprised 73% men. Mean age was 46 years, with a median Injury Severity Score (ISS) of 27. The mean lactate level was 2.9 mmol/L, and mean hemoglobin was 12.4 g/dL. More than 50% of patients were anemic on ICU admission, and nearly all were anemic by postinjury day 10. Urinary hepcidin levels were among the highest reported to date and had a rightward skew. Iron studies confirmed functional iron deficiency. Log hepcidin values were positively correlated with ISS and negatively correlated with admission Pao₂/FiO₂. Every increase in ISS by 10 was associated with a 40% increase in hepcidin. Initial hepcidin levels were positively correlated with duration of anemia.
CONCLUSIONS: Hepcidin levels rise to extremely high but variable levels after trauma and are positively correlated with injury severity measured by ISS and duration of anemia and negatively correlated with hypoxia. Hepcidin is likely a key factor in the impaired erythropoiesis seen in critically injured trauma patients.