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Vitamin B12–Deficiency Anemia | 마이메르시 MyMerci
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Vitamin B12–Deficiency Anemia

NCLEX Review Guide: Vitamin B12-Deficiency Anemia

Pathophysiology & Etiology

Understanding B12-Deficiency Anemia

  • Vitamin B12 (cobalamin) is essential for DNA synthesis and red blood cell maturation, leading to megaloblastic anemia when deficient.
  • Most commonly caused by pernicious anemia - an autoimmune condition destroying parietal cells that produce intrinsic factor needed for B12 absorption.
  • Other causes include gastrectomy, Crohn's disease, strict vegan diet, and certain medications (metformin, PPIs).

Key Points

  • B12 deficiency develops slowly over 2-5 years due to large liver stores
  • Neurological symptoms can occur even with normal hemoglobin levels

Clinical Manifestations

Signs & Symptoms

  • Classic triad: Megaloblastic anemia, neurological symptoms, and glossitis (beefy red tongue).
  • Neurological symptoms: Paresthesias in hands/feet, ataxia, memory loss, depression, and potentially irreversible spinal cord degeneration.
  • GI symptoms include anorexia, weight loss, diarrhea, and abdominal pain.
  • General anemia symptoms: fatigue, weakness, pallor, and shortness of breath.

Memory Aid: "PALE NEURO"

Paresthesias, Ataxia, Loss of memory, Elevated MCV
Neuropathy, Elevated LDH, Unsteady gait, Red beefy tongue, Oval macrocytes

Diagnostic Studies

Laboratory Values

  • Serum B12 level < 200 pg/mL confirms deficiency; levels 200-300 pg/mL are borderline.
  • CBC shows macrocytic anemia with MCV > 100 fL and oval macrocytes on peripheral smear.
  • Elevated LDH, indirect bilirubin, and decreased haptoglobin indicate hemolysis of abnormal RBCs.
  • Schilling test (rarely used) or intrinsic factor antibodies help diagnose pernicious anemia.

B12 vs Folate Deficiency Comparison

FeatureB12 DeficiencyFolate Deficiency
Neurological symptomsPresentAbsent
Serum homocysteineElevatedElevated
Methylmalonic acidElevatedNormal
OnsetGradual (years)Rapid (weeks-months)

Nursing Management

Treatment & Interventions

  1. Administer B12 injections - typically cyanocobalamin 1000 mcg IM daily for 1 week, then weekly for 4 weeks, then monthly for life.
  2. Monitor for hypokalemia during initial treatment as rapid cell production depletes potassium.
  3. Assess neurological status regularly - document baseline and monitor for improvement or progression.
  4. Educate patient about lifelong treatment necessity for pernicious anemia.
  5. Monitor CBC, reticulocyte count, and B12 levels to assess treatment response.

Clinical Scenario

A 65-year-old vegetarian presents with fatigue, tingling in hands/feet, and a red, smooth tongue. Lab results show Hgb 8.5 g/dL, MCV 115 fL, and B12 level 150 pg/mL. Priority nursing action is to assess neurological status and prepare for B12 injection administration.

Key Points

  • Neurological damage may be irreversible if treatment is delayed
  • Oral B12 is ineffective in pernicious anemia due to lack of intrinsic factor
  • Response to treatment: reticulocytes increase in 3-5 days, Hgb normalizes in 6-8 weeks

Study Tips & Common Pitfalls

NCLEX Success Strategies

Quick Recognition Clues

  • Elderly patient + neurological symptoms + macrocytic anemia = Think B12 deficiency
  • Vegan diet + fatigue + high MCV = B12 deficiency likely
  • Post-gastrectomy patient with anemia = Consider B12 deficiency

Common Pitfalls to Avoid

  • Don't confuse with iron deficiency (B12 = macrocytic, Iron = microcytic)
  • Remember: Neurological symptoms can occur before anemia develops
  • Don't forget to monitor potassium during initial treatment
  • Oral B12 won't work for pernicious anemia - must be parenteral

Quick Check

Question: What is the priority assessment for a patient starting B12 injections?
Answer: Neurological assessment - document baseline function to monitor for improvement and prevent irreversible damage.

Self-Assessment Checklist

  • ☐ I can differentiate B12 deficiency from other anemias
  • ☐ I understand why neurological symptoms occur
  • ☐ I know the treatment protocol for B12 deficiency
  • ☐ I can identify priority nursing assessments
  • ☐ I understand the difference between pernicious anemia and dietary deficiency

Remember: You've got this! Focus on the neurological component that makes B12 deficiency unique among anemias. Understanding the pathophysiology will help you answer any NCLEX question about this condition. Stay confident and trust your knowledge!

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