Vitamin B 12 /Folate Deficiency

5–10% of adults over the age of 65 have vitamin B ₁₂ or folate deficiency.

Vitamin B ₁₂ (cobalamin) deficiency is associated with a strict vegan diet, pernicious anemia, gastrectomy procedures, exposure to nitrous oxide, HIV infection, H. pylori infection, certain medications, and ileal resections.

Folate deficiency is associated with chronic alcoholism and malnutrition.

Intraop:

• Increased risk of vitamin B ₁₂ deficiency after the exposure to nitrous oxide anesthesia due to the irreversible inhibition of vitamin B ₁₂ activity.

• Homocysteine levels can be elevated after the use of nitrous oxide. The risk of coronary artery and cerebrovascular complications are increased in patients with high total plasma homocysteine levels.

Postop:

• Increased risk of postop MI.

• Risk of neurologic symptoms including peripheral neuropathy, paresthesias, and subacute combined degeneration of spinal cord following nitrous oxide anesthesia.

Limited oxygen carrying capacity due to megaloblastic anemia caused by vitamin B ₁₂ and folate deficiency.

Delayed onset of hematologic and neurologic abnormalities seen after nitrous oxide exposure; several wk may elapse before symptoms develop.

Vitamin B ₁₂ and folate have interdependent and essential roles in DNA synthesis.

Vitamin B ₁₂ is needed for

• Synthesis of methionine from homocysteine via methionine synthase.

• Conversion of methylmalonyl coenzyme A to succinyl coenzyme A via methylmalonyl-CoA mutase.

• Development and myelination of the CNS and its maintenance.

Folate has multiple metabolic roles including purine synthesis and amino acid metabolism.

Deficiencies of vitamin B ₁₂ and folate lead to increased serum homocysteine levels, which is associated with cardiovascular disease.