Hepcidine and Iron Deficiency in Critically Ill Patients

Anaemia is very frequent among critically ill patients, concerning more than 60 % of them at admission and more than 80% at intensive care unit discharge. Iron deficiency is also frequent at admission, with prevalence around 25 to 40%. During their stay in Intensive Care Unit, critically ill patients are exposed to repeated blood samples and to other blood losses (daily blood loss has been evaluated to be as high as 128 ml/day in median), this leads to direct iron loss. Prevalence of iron deficiency may thus be very important at Intensive Care Unit discharge. However, iron deficiency diagnosis is complicated in these patients, since inflammation induces an increase in plasma ferritin levels and a decrease in transferrin saturation, the two usual markers of iron deficiency. As a consequence, iron deficiency is usely under-diagnosed in these patients. Treatment of iron deficiency may be indicated to correct anaemia but also to improve patients fatigue and muscular weakness. The characterization of iron metabolism regulation by the hormone hepcidin opened new ways for the understanding and the follow-up of these complex clinical situations (combining inflammation and iron deficiency). Indeed, iron deficiency is associated with a decrease in hepcidin synthesis, while iron overload induces hepcidin synthesis. Furthermore, low hepcidin levels are required to mobilize iron from stores. Hepcidin has thus be proposed as a marker of iron deficiency in critically ill patients. To date, standard immunological methods of hepcidin quantitation are only proposed in the reasearch setting and could not be proposed in the clinical setting because it is too expensive. New approaches for hepcidin quantification, based on mass spectrometry are proposed and may be routinely implemented. We make the hypothesis that treating iron deficiency in critically ill anemic patients, diagnosed by hepcidin quantification, may improve the post-Intensive Care Unit rehabilitation, and may thus reduce p