الفهرس 
ANEMIA DEFINITIONOnly 14 pages are availabe for public view
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Abstract
Anemia is commonly prevelant in ICU. Anemia is defined by WHO as hemoglobin(Hb) concentration that is below the normal range regarding age,gender and other factors that may change relation between plasma volume and hemoglobin concentration with pregnancy as a good example(Nelson et al., 2006).
Many studies were done to show prevelance of anemia in icu course .the most famous are CRIT study and TRICC studies which showed that many people suffer from anemia at icu admission.But because of differences in case mix and study methodology, the prevalence of anemia at ICU admission varies, but it appears that 20–30% of patients have moderate to severe anemia (hemoglobin concentration <9 g/ dL) Corwin et al., 2004).
During icu stay despite differences in case mix and transfusion practice the prevalence of moderate to severe anemia (hemoglobin concentration <9 g/dL) at some time during ICU stay appears to be 40–50% among most ICU populations. If anemia is not present at the time of ICU admission it develops rapidly during the first 2–3 days in most patients. Once present anemia tends to persist until ICU discharge unless modified by blood transfusions(Corwin et al., 2004).
There are currently few data concerning anemia during the recovery phase of critical illness. The data available indicate that anemia may persist for many weeks in some patients.
To know anemia in icu ,we also have to know the critical Hb concentration and acceptable Hb concentration. The critical hemoglobin concentration is defined as the concentration below which oxygen consumption is supply-dependent assuming normo volemia is maintained.This is unlikely to be a fixed value, but varies between organs and is dependent on the metabolic activity of the tissue and oxygen extraction capabilities(Cook et al., 2001).
The physiological responses to normovolemic anemia maintain tissue oxygenation as the Hb concentration falls. Eventually a point is reached where cardiac output and oxygen extraction are maximal and cannot increase anymore. Further reductions in Hb will lead to a decrease in oxygen delivery, and in turn oxygen consumption . This point is called the critical DO2, it is the point at which energy production in cells becomes limited by the supply of oxygen i.e., oxygen consumption is supply dependent.Many factors can increase the critical Hb concentration like reduced oxygen delivery caused by decreased cardiac out put ,pre morbid disease (e.g. ischemic heart disease, valvular heart disease ),acute respiratory failure and pulmonary embolism. An acceptable hemoglobin concentration is the degree of anemia that is the best balance between the risks of red cell transfusion and the risks of low hemoglobin concentration .the acceptable hemoglobin concentration differs in patients with ischemic heart diseases,patients with AMI ,or after PCI,patients with SAH,where these patients have higher values of acceptable hemoglobin concentration.The aetiology of anemia is multifactorial. It may be caused by decrease production or caused by increase destruction or loss of RBCS .Decrese production mostly caused by decrease iron stores, EPO production or response to EPO caused by inflammatory mediators e.g.TNF,IL-1.RBCs destruction is caused by hmolytic anemia. Blood loss is caused by phlebotomy,or GIT bleeding.Diagnosis depends on history taking,clinical features which not specific ,blood indices ,iron profile and auto immune investigations.Mangement of anemia in ICU.includes decrease of blood loss by decreasing blood sampling,decrease GIT bleedings,giving iron preparetion with different doses,blood transfusion which has many complications despite safety measures nowadays,like transmission of infection e.g.transmission of infections(e.g HIV,HCV).,transfusion related acute lung injury and auto immune ractions.the new lines of management of anemia in icu include EPO use and oxygen carriers .Many studies did not show the appropriate dose of EPO,dose intervals,duration of course of EPO use or side effects of EPO.