Anemia

 

Anemia is a very common global problem. It is defined as a reduction in red blood cell concentration, hematocrit, or hemoglobin, 2 SD below that of the normal hemoglobin. In men, this is below 140 g/L in men and 120 g/L in women.

 

Causes and Risk Factors

 

Signs and Symptoms

 

Obvious symptoms are not seen in younger people until hemoglobin has fallen below 70-80 g/L (hematocrit falls below 20-25%), or below 100-120 g/L in older folks.

 

  • history
  • physical exam
  • lab investigations

History

Common symptoms of various anemias include:

  • fatigue
  • weakness
  • shortness of breath, chest pain with exertion
  • presyncope
  • abdominal pain, flank bruising (retroperitoneal bleed)

With more pronounced anemia, exercise capacity becomes markedly reduced, and exertion is accompanied by palpitations, dyspnea, pounding headache, and rapid exhaustion.

Infants with anemia can have difficulty feeding, needing to break off or not able to fully draw all

 

past medical history

  • gastrointestinal bleeding past history, risk factors, and signs of blood in the stool.
  • prior history of anemia
  • medications
  • menstrual history

 

social history includes alcohol use and diet.

 

family history/past history, especially of anemia or other blood diseases

Some specific anemias also have specific symptoms:

  • iron deficiency - ice craving in adults, dirt eating in children
  • folate/B12 deficiency - sore mouth, difficulty swallowing
  • sickle cell anemia - lifelong, episodic bone and joint pain

 

Physical Exam

 

  • pallor, especially in conjunctiva, mucous membranes, nail beds, and palmar creases
  • mouth: glossitis, cheilosis
  • tachycardia
  • jaundice in extravascular hemolytic anemia
  • fingernail spooning

chronic anemia:

  • forceful apical impulse
  • wide pulse pressure
  • tachycardia with exertion
  • frequent flow murmurs secondary to blood turbulence as mid- or holosystolic murumrs at apex or along sternal border, with radiation to neck

lymph nodes

spleen

neurologic exam to assess for viamin B12/folate deficiency

Lab Investigations

Always look to past lab values to compare

  • CBC is the most important test to identify and evaluate anemia.
  • reticulocyte count can help distinguish between hypoproliferative and hyperproliferative causes.
  • iron studies identify iron deficiency and anemia of chronic disease.
  • thyroid
  • liver enzymes
  • serum B12 and RBC folate
  • haptoglobin and lactate dehydrogenase for hemolytic anemias
  • hemoglobin electrophoresis for sickle cell and thalassemias
  • peripheral blood smear to evaluate RBC shape
  • fecal occult blood testing (FOBT) if iron-deficiency is noted
  • bone marrow biopsy if indicated

University of Utah's WebPath provides microscope slides of various anemias.

 

Anemia detection in low-resource settings provides additional challenges (PATH, 1997).

 

 

hemolytic anemia workup

 

could also order free hemoglobin, urine hemosiderin

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Types of Anemia

The MCV, or mean corpuscular volume, is one of the most important RBC parameters in helping diagnose the cause of anemia, as described below. It is normally between 80-95 fl for men and  80-100 fl for women.

  • microcytic
  • normocytic
  • macrocytic
  • hemolytic

Microcytic

Many small RBCs (below 80 fl or so) results in microcytosis.

This is usually due to problems with heme or globin synthesis, remembered by the acronym TAILS:

  • Thalassemia
  • Anemia of chronic inflammation (can be slightly low or normal)
    • T 1/2 of RBC goes down as the pass through injured tissue
    • phagocytes hold onto iron
  • Iron deficiency anemia (can be very low, into the 40s)
  • Lead poisioning (often 50s)
  • Sideroblastic anemia - congenital or acquired problems with iron incorporation into heme (usually above 50s)

 

Normocytic

 

hyperproliferative (increased retic count) - appropriate BM response

  • acute blood loss
  • hemolytic anemia
    • G6PD deficiency
    • sickle cell anemia
    • spherocytosis, eliptocytosis

 

  • splenic pooling

hypoproliferative - inappropriate BM response, with lowered reticulocytes

  • anemia of chronic disease
  • bone marrow replacement (leukemia, myeloma, metastasis?)
  • chronic renal disease - loss of erythropoietin production
  • hypothyroidism
  • testosterone deficiency

Normocytic anemia can also be an early presentation of microcytic or macrocytic anemia, or a combination of the two.

Macrocytic

Macrocytosis occurs when MCV > 100 fL.

Problems

Megaloblastic anemia: due to vitamin B12/folate deficiency, leading to defective DNA synthesis.

    • also hypersegmented neutrophils
    • check RBC folate

     

  • ethanol abuse
  • liver and lipid disorders
  • drug-induced (antiretrovirals, antimetabolites, anticonvulsants)
  • reticulocytosis
  • endocrine disorders (ie hypothyroidism)
  • myelodysplastic syndrome

Hemolytic anemias

 

Immune-mediated

  • ABO-incompatibility
  • delayed
  • AIHA (cold IgM, warm IgG)
  • drug hapten-mediated

 

Micoangiopathic hemolytic anemia

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Pathophysiology

 

Anemia's effects on the body are determined by its severity, speed of onset, and state of the patient.

Exercise intolerance is a result of the oxygen-dissociation curve's ability to respond to modest reductions of hemoglobin, but not in situations of increased demand.

 

Anemia can result from disorders in RBC production, maturation, or destruction.

 

Disorders of red cell production can be due to bone marrow failure. This can occur with:

Impaired erythropoetin production is seen in

 

Impaired erythrocyte maturation can result from problems in the nucleus (vitamin B12 or folic acid deficiencies) or the cytoplasm (iron deficiency, thalasemia, sideroblastic anemia, lead poisoning).

 

 

disorders of red cell destruction can be seen with defects in hemoglobin or the RBC membrane. Problems of RBC metabolism can be due to many enzyme systems, ie G6PD. Destruction can be antibody mediated, ie following a viral infection, or due to mechanical or thermal injury or perturbation, ie mechanical heart valve.

 

 

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Treatments

 

Anemia should be identified and treated in the months before surgery is scheduled so that it can be corrected ahead of time.

 

Corrective therapy begins with adequate iron, folate, and B12 in the case of deficiency.

In patients with chronic renal disease, erythropoietin can be used.

Transfusion is indicated by hemodynamic instability - tachycardia and hypotension.

In patients with ischemic heart disease, anemia is especially tricky. However, the presence of cardiovascular disease is a serious risk for transfusion. As hematocrit drops, mortality increases. There is thus a trade-off between risk and benefit (Wu et al, 2001).

 

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Consequences and Course

 

Anemia can worsen ischemic complications, including angina and claudication, and can precipitate heart failure in patients with underlying heart disease.

 

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Patient Education

 

 

 

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Resources and References

 

PATH. 1997. Anemia Detection Methods in Low-Resource Settings: A Manual for Health Workers.

 

 

Wu et al. 2001. Blood transfusion in elderly patients with acute myocardial infarction. NEJM. 345(17):1230-6.

 

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