Clinical Pharmacy Hematologic Disorders Anemias Introduction

Anemia Introduction

• Anemia is a group of diseases characterized by a decrease in either hemoglobin (Hb) or the volume of red blood cells (RBCs), resulting in decreased oxygen-carrying capacity of blood.
• The World Health Organization defines anemia as Hb less than 13 g/dL in men or less than 12 g/dL in women.

Pathophysiology

• Functional classification of anemias is based on the underlying mechanism.
• Morphologic classifications are based on cell size:
  • Macrocytic cells are larger than normal and are associated with deficiencies of vitamin B12 or folic acid.
  • Microcytic cells are smaller than normal and are associated with iron deficiency.
  • Normocytic anemia may be associated with recent blood loss or chronic disease.

Iron-Deficiency Anemia (IDA)

• Characterized by decreased levels of ferritin (most sensitive marker) and serum iron, and decreased transferrin saturation.
• Can be caused by:
  • Inadequate dietary intake.
  • Inadequate gastrointestinal (GI) absorption.
  • Increased iron demand (e.g., pregnancy).
  • Blood loss.
  • Chronic diseases.

Vitamin B12- and Folic Acid-Deficiency Anemias

• Macrocytic in nature.
• Can be caused by:
  • Inadequate dietary intake.
  • Malabsorption syndromes.
  • Inadequate utilization.
• Deficiency of intrinsic factor causes decreased absorption of vitamin B12 (e.g., pernicious anemia).
• Folic acid-deficiency anemia can be caused by:
  • Hyperutilization due to pregnancy, hemolytic anemia, malignancy, chronic inflammatory disorders, long-term dialysis, or growth spurt.
  • Drugs can cause anemia by reducing absorption of folate (e.g., phenytoin) or through folate antagonism (e.g., methotrexate).

Anemia of Inflammation (AI)

• A newer term used to describe both anemia of chronic disease and anemia of critical illness.
• Associated with:
  • Malignant, infectious, or inflammatory processes.
  • Tissue injury.
  • Conditions associated with release of proinflammatory cytokines.
• Serum iron is decreased, but serum ferritin concentration is normal or increased.

Clinical Presentation

• Acute-onset anemia is characterized by:
  • Cardiorespiratory symptoms (e.g., palpitations, angina, orthostatic light-headedness, and breathlessness).
• Chronic anemia is characterized by:
  • Weakness, fatigue, headache, orthopnea, dyspnea on exertion, vertigo, faintness, cold sensitivity, and pallor.
• IDA is characterized by:
  • Glossal pain.
  • Smooth tongue.
  • Reduced salivary flow.
  • Pica (compulsive eating of nonfood items).
  • Pagophagia (compulsive eating of ice).
• Vitamin B12 deficiency may cause:
  • Neurologic effects (e.g., numbness and paraesthesisas).
  • Psychiatric findings (e.g., irritability, depression, and memory impairment).

Diagnosis

• Rapid diagnosis is essential because anemia is often a sign of underlying pathology.
• Severity of symptoms does not always correlate with the degree of anemia.
• Initial evaluation of anemia involves:
  • Complete blood cell count (CBC).
  • Reticulocyte index.
  • Examination of the stool for occult blood.
• The earliest and most sensitive laboratory change for IDA is decreased serum ferritin (storage iron).
• In macrocytic anemias, mean corpuscular volume is usually elevated.
• Vitamin B12 and folate concentrations can be measured to differentiate between the two deficiency anemias.
• In AI, serum iron is usually decreased, but serum ferritin is normal or increased.

Treatment

• Goals of treatment:
  • Return hematologic parameters to normal.
  • Restore normal function and quality of life.
  • Prevent long-term complications.
• Iron-deficiency anemia:
  • Oral iron therapy with soluble ferrous iron salts.
  • Daily dosage of 150–200 mg elemental iron in two or three divided doses.
  • Iron is best absorbed from meat, fish, and poultry.