A 65-year-old man has surgery for gastric cancer and undergoes a total gastrectomy. Intrinsic factor, which is necessary for the absorption of vitamin $B_{12}$, is secreted by the parietal cells of the gastric mucosa. Postoperatively, the man lacks gastric mucosa and cannot secrete intrinsic factor, placing him at risk for vitamin $B_{12}$ deficiency (pernicious anemia).
- What are the signs and symptoms of pernicious anemia? What other body system is affected by a deficiency of vitamin $B_{12}$ ?
- The health care provider orders hydroxocobalamin $30 \mathrm{mcg}$ intramuscularly once daily for 5 days, then hydroxocobalamin $100 \mathrm{mcg}$ intramuscularly once monthly. Why is hydroxocobalamin ordered intramuscularly rather than orally? For what length of time will the man receive monthly injections of hydroxocobalamin?
- What teaching should the man receive in regard to self-administration of hydroxocobalamin intramuscularly?
- What adverse effects of hydroxocobalamin should the man be aware of?
- What laboratory tests are ordered to determine whether hydroxocobalamin therapy is effective?