Hepcidin and Anemia of the Critically Ill Patient

Abstract

A NEMIA occurs frequently in critically ill patients, with 60–66% of them having anemia when admitted to the intensive care unit (ICU), and is associated with worse outcomes (such as increased length of stay and increased mortality). Anemia is only partially corrected during ICU stay because recent recommendations have led to a decrease in transfusion triggers. Today the prevalence of anemia in patients being discharged from the ICU is very high, being found in at least 75% of the patients upon final hemoglobin measurement. This common, and severe anemia at ICU discharge may also be prolonged after the ICU stay. The median time to recovery of anemia is 11 weeks. One observational study reports that more than half of such patients are still anemic at 6 months. Although the impact of anemia on rehabilitation after ICU discharge or quality of life has not been fully evaluated, it is well accepted that anemia is associated with worse outcomes for postoperative rehabilitation and for patients with chronic diseases such as cancer and thus should retain our interest at the bedside and in the research unit. Because blood transfusion is not an option for complete correction of this anemia, one may advocate the use of other treatments, such as erythropoiesis-stimulating agents (ESA) or iron. ESA efficacy has been studied in critically ill patients and has not proven to be indicated, at least according to the design of the studies. Iron is needed for erythropoiesis and thus may be indicated for the treatment of this anemia, but iron is also a toxic compound with the ability to induce oxidative stress or promote bacterial growth. A better understanding of iron metabolism regulation may help to define the place of iron in these indications. The recent discovery of hepcidin (i.e., the master regulator of iron metabolism) has shed new light on the regulation of iron homeostasis and has increased understanding of the physiopathology of anemia in complex clinical situations where several regulatory circuits interfere with iron metabolism, such as anemia of inflammation and anemia of critically ill patients. This article reviews the link between iron metabolism and anemia in critically ill patients and discusses therapeutic perspectives in this area.