The diagnosis, investigation and management of iron deficiency anaemia are discussed in more detail in Chapter 7. The underlying cause should be identified and treated if possible. In most cases, iron deficiency anaemia can be treated with oral iron. Safe intravenous iron preparations (see Chapter 6) are now available for patients who do not tolerate oral iron. In patients without acute blood loss, transfusion should only be considered if an immediate increase in Hb concentration is essential on clinical grounds – symptoms of severe anaemia such as chest pain or congestive heart failure. The minimum number of red cell units should be transfused with careful monitoring to ‘buy time’ for a response to iron therapy. One-unit transfusions are perfectly acceptable in this situation, especially for small, elderly patients at risk of TACO.
Deficiency of vitamin B12 or folate produces megaloblastic changes in bone marrow cells and anaemia with large (‘macrocytic’) red cells in the peripheral blood. Vitamin B12 deficiency is most often due to autoimmune pernicious anaemia with failure to absorb B12 in the terminal ileum. Folate deficiency usually results from dietary deficiency, consumption by increased red cell production (such as pregnancy or haemolytic anaemia) or malabsorption in coeliac disease. Patients may present with very low Hb concentrations. Treatment is with intramuscular B12 injections or oral folic acid. Severe megaloblastic anaemia causes impaired cardiac muscle function and red cell transfusion should be avoided wherever possible because of the risk of causing potentially fatal circulatory overload. Patients with severe symptomatic anaemia can often be treated with bed rest and high-concentration oxygen while a response to B12 or folate occurs (the Hb concentration starts to rise in 3 or 4 days). If red cell transfusion is essential, single units of red cells should be transfused over 4 hours with close monitoring and diuretic cover. Red cell exchange transfusion may also be considered.