Anemias

SOURCE

Source: Cook K. Anemias. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146070326. Accessed January 30, 2017.

DEFINITION

• Decreased oxygen-carrying capacity of blood characterized by a decrease in hemoglobin (Hb) or red blood cells (RBCs)

• World Health Organization (WHO) definition.

  • Men: Hb <13 g/dL (<130 g/L; <8.07 mmol/L)

  • Women: Hb <12 g/dL (<120 g/L; <7.45 mmol/L)

ETIOLOGY

• Macrocytic anemias are a result of quantitative deficiency in hemoglobin synthesis, usually due to iron deficiency or impaired iron utilization.

  • Can be divided into megaloblastic and nonmegaloblastic anemias.

PATHOPHYSIOLOGY

• Hypoproliferative.

  • Marrow damage.

  • Iron deficiency.

  • Decreased stimulation (renal disease, inflammation, metabolic disease)

• Maturation disorders.

  • Cytoplasmic defects (thalassemia, iron deficiency, sideroblastic)

  • Nuclear maturation defect (folate deficiency, B₁₂ deficiency, refractory anemia)

• Hemorrhage/hemolysis.

  • Blood loss.

  • Intravascular hemolysis.

  • Autoimmune disease.

  • Hemoglobinopathy.

  • Metabolic/membrane defect.

EPIDEMIOLOGY

• 1.6 billion people in the world are anemic.

• Iron deficiency is the leading cause of anemia worldwide.

CLINICAL PRESENTATION

• May be asymptomatic or have vague complaints.

• Patients with B₁₂ deficiency may develop neurologic consequences.

SIGNS AND SYMPTOMS

• Symptoms.

  • Decreased exercise tolerance.

  • Fatigue.

  • Dizziness.

  • Irritability.

  • Weakness.

  • Palpitations.

  • Vertigo.

  • Shortness of breath.

  • Chest pain.

  • Neurological symptoms in vitamin B₁₂ deficiency.

• Signs.

  • Tachycardia.

  • Pale appearance.

  • Decreased mental acuity.

  • Increased intensity of some cardiac valvular murmurs.

  • Diminished vibratory sense of gait abnormality in vitamin B₁₂ deficiency.

• Manifestations of iron deficiency anemia (IDA) (Hgb ≤9 g/dL [90 g/L; 5.59 mmol/L])

  • Glossal pain.

  • Smooth tongue.

  • Reduced salivary flow.

  • Pica (compulsive eating of nonfood items)

  • Pagophagia (compulsive eating of ice)

• Folate deficiency is typically macrocytic but without neurological symptoms (unlike B₁₂)

DIAGNOSIS

MEANS OF CONFIRMATION AND DIAGNOSIS

• History.

• Physical examination.

• Laboratory test results

LABORATORY TESTS

• Complete blood count (CBC) (Table 1)

  • Focus on Hb, hematocrit (Hct), and RBC indices.

  • May initially be normal and then decrease as anemia progresses.

• Serum iron (low with IDA and anemia of inflammation (AI))

• Ferritin.

  • Low with IDA and normal to increased in AI

  • Earliest and most sensitive indicator of iron deficiency.

  • Interpret in conjunction with transferring saturation and total iron-binding capacity (TIBC)

• TIBC (high with IDA and low or normal in AI)

• Mean cell volume is elevated in vitamin B₁₂ deficiency and folate deficiency.

• Vitamin B₁₂ and folate levels are low in their respective types of anemia.

• Homocysteine is elevated in vitamin B₁₂ deficiency and folate deficiency.

• Methylmalonic acid is elevated in vitamin B₁₂ deficiency.