3.7 Vitamin B12 Deficiency

Vitamin B¹² deficiency is another common type of anemia that is caused by insufficient vitamin B¹² in the body. Vitamin B¹² is a water-soluble vitamin, so it is not stored in the body. Therefore, it must be consumed in adequate daily amounts for optimal functioning. Vitamin B¹² anemia is also referred to as megaloblastic or macrocytic anemia. The terms megaloblastic or macrocytic refer to the fact that the red blood cells in those with this disorder are abnormally large when compared to a healthy red blood cell.^[1],[2]

Vitamin B¹² is needed for a number of bodily functions: red blood cell formation, the synthesis of DNA and RNA, the formation of new cells, and nerve function.^[3]

There are three basic causes of vitamin B¹² anemia^[4],[5][6]:

• Dietary Deficiency: The body cannot produce vitamin B¹² so it must come from dietary intake. If one does not consume enough vitamin B¹² in their diet, they are at risk for vitamin B¹² anemia. Common sources of vitamin B¹² are animal products such as red meat and dairy. Therefore, individuals who are vegetarians or vegans are at risk for developing vitamin B¹² deficiency and the resulting anemia.
• Decreased Absorption of Vitamin B¹²: Some people may consume adequate amounts of vitamin B¹² but have issues with absorbing this vitamin. Risk factors for decreased absorption of vitamin B¹² are a gastric bypass, Crohn’s disease or other inflammatory bowel disorder, and chronic users of proton pump inhibitors (PPIs).
• Autoimmune Disorder: Pernicious anemia is a specific type of vitamin B¹² anemia. Pernicious anemia is an autoimmune disorder in which antibodies are formed that attack the stomach cells that produce intrinsic factor. Intrinsic factor is a protein produced by the parietal cells of the stomach that carry vitamin B¹² into the small intestine. Without intrinsic factor, vitamin B¹² cannot be absorbed by the gastrointestinal tract.

Specific populations who are at higher risk for developing vitamin B¹² anemia include the following^[7],[8],[9]:

• Lower Socioeconomic Status: Because animal proteins tend to be costly, lower socioeconomic status creates an increased risk for this anemia.
• Vegetarians and Vegans: Individuals who avoid eating animal products are more susceptible.
• Regular Consumption of Alcohol: Individuals who regularly consume alcoholic beverages may have issues absorbing vitamin B¹².
• Specific Medications: Proton pump inhibitors used to treat heartburn, as well as the diabetes drug metformin, can interfere with the absorption of vitamin B¹².
• History of an Autoimmune Disorder: Pernicious anemia is associated with other autoimmune disorders such as type 1 diabetes. Therefore, having an autoimmune disorder could put someone at risk for pernicious anemia.
• Age: A deficiency of vitamin B¹² is more common in the elderly than the general population, regardless of the etiology. People over 60 years of age are also at an increased risk of pernicious anemia.
• Ethnicity: Pernicious anemia is more common in Northern Europeans.

Pathophysiology

In healthy clients, when food sources containing vitamin B¹² are ingested, vitamin B¹² binds to an intrinsic factor, which is released from the parietal cells in the stomach. The vitamin B¹²-intrinsic factor complex is then able to bind to receptors on the ileum of the small intestine, and vitamin B¹² can be absorbed. If vitamin B¹² is not absorbed, neurological and hematological impairments will be seen as this vitamin plays a role in many chemical reactions throughout the body.^[10]

Vitamin B¹² is an important cofactor needed for DNA synthesis. Therefore, when vitamin B¹² is not available, not only are typical signs of anemia seen due to impaired red blood cell formation, but also other rapidly dividing cells are also affected. This also leads to elevated homocysteine (an amino acid that is broken down by vitamin B¹² in the process of DNA synthesis) levels, which can be useful for diagnostic purposes. Vitamin B¹² is also needed as a cofactor for enzymes in the Kreb’s cycle (a complex cycle that regulates cellular energy production). When B¹² is not present for this cycle, methylmalonic acid (MMA) accumulates, which can damage the myelin sheath that surrounds and insulates nerves. This can lead to the neurological symptoms that are seen with vitamin B¹² deficiency. MMA levels are also useful as a diagnostic tool.^[11]

Assessment

Physical Assessment

Clinical manifestations of vitamin B¹² anemia are related to the body’s inability to form red blood cells and other rapidly dividing cells, as well as the inability to properly regulate nerve function. See Table 3.7a for a summary of the clinical manifestations of vitamin B¹² anemia across body systems.

Table 3.7a. Clinical Manifestations of Vitamin B¹² Anemia^{[12],[13],[14],[15]}

Diagnostic Testing

A variety of lab tests may be ordered by a provider to diagnose vitamin B¹² deficiency. See Table 3.7b for a summary of common diagnostic tests.

Table 3.7b. Common Diagnostic Tests for Vitamin B¹² Anemia^[16]

Nursing Problems and Diagnoses

Nursing priorities for clients with vitamin B¹² anemia include promoting adequate tissue perfusion and oxygenation, providing adequate pain relief, preventing long-term neurological damage, preventing injury, enhancing nutrition (if applicable), improving fatigue and activity tolerance, and providing health teaching to help the client self-manage their disease.

Nursing diagnoses for clients with vitamin B¹² anemia are created based on the specific needs of the client, their signs and symptoms, and their etiology of the disorder. These nursing diagnoses guide the creation of client specific care plans that encompass client outcomes and nursing interventions, as well the evaluation of those outcomes. These individualized care plans then serve as a guide for client treatment.

Possible nursing diagnoses for those with vitamin B¹² anemia include the following^{[17],[18],[19]}:

• Inadequate Tissue Perfusion
• Acute Pain
• Chronic Pain
• Risk for Falls
• Disturbed Sensory Perception
• Imbalanced Nutrition: Less Than Body Requirements
• Fatigue
• Decreased Activity Intolerance
• Readiness for Enhanced Knowledge

Outcome Identification

Outcome identification encompasses the creation of short- and long-term goals for the client. These goals are used to create expected outcome statements that are based on the specific needs of the client. Expected outcomes should be specific, measurable, and realistic. These outcomes should be achievable within a set time frame based on the application of appropriate nursing interventions.

Sample expected outcomes related to the previous nursing diagnoses are as follows^[20]:

• The client will demonstrate adequate perfusion as demonstrated by appropriate urine output, skin color appropriate for race, palpable peripheral pulses, and vital signs within normal limits for age.
• The client will engage in fall prevention activities as specified by the care plan.
• The client will accurately verbalize the presence of sharp and dull sensations on hands and feet.
• The client will include food sources high in vitamin B¹² with every meal.
• The client will describe two methods of energy conservation to manage fatigue.

Interventions

Medical Interventions

Medical Interventions for vitamin B¹² deficiency depend on the cause, as well as the severity of the disorder. Common medical treatments include the following^{[21],[22],[23],[24]}:

• Vitamin B¹² Supplements (Cyanocobalamin): Supplements are required to correct the deficiency, but the specific route is determined by the severity and the etiology of the anemia. For example, individuals with pernicious anemia must receive vitamin B¹² parenterally (IM), as they cannot absorb oral vitamin B¹² due to the lack of intrinsic factor. Additionally, this will be a life-long treatment. Those with a severe vitamin B¹² deficiency may also be initially treated with parenteral B¹². Vitamin B¹² is also available in oral, sublingual, subcutaneous, and intranasal forms. Clients should also be urged to increase their dietary intake of vitamin B¹² with food sources such as meat and dairy. For those who follow a vegan diet, fortified cereals and fortified vegan milk substitutes are good sources of vitamin B¹².
• Routine Monitoring of Vitamin B¹² Levels: Monitoring is especially important in those who are at risk due to malabsorption such as those with Crohn’s disease.
• Blood Transfusions: Blood transfusions may be necessary in severe cases of vitamin B¹² anemia. When clients have extreme symptoms or their hemoglobin levels fall below 7 g/dL, a transfusion may be prescribed.

Nursing Interventions

Common nursing interventions for those suffering from vitamin B¹² anemia include the following^{[25],[26],[27],[28]}:

• Monitor vitals because anemia can cause tachycardia and tachypnea.
• Perform comprehensive neurological assessments due to the neurological effects of vitamin B¹² deficiency. If the client has been deficient in vitamin B¹² for a prolonged amount of time, neurological symptoms may not be completely reversed even with adequate treatment.
• Administer vitamin B¹² via enteral or parenteral routes per provider order and provide related health teaching. The RN should also monitor for potential side effects and allergic reactions. Hypokalemia is a common side effect of cyanocobalamin and would manifest as muscle cramping/weakness and/or irregular heartbeat. Cyanocobalamin contains cobalt and may need to be avoided in those with a cobalt sensitivity/allergy.
• Encourage a diet rich in vitamin B¹². The recommended daily intake for vitamin B¹² for adults is 2.4 mcg and more for those who are pregnant or breastfeeding.
• Initiate fall precautions such as a bed/chair alarm and a low height bed. Those with vitamin B¹² anemia frequently exhibit dizziness, lightheadedness, paresthesia, vision changes, or confusion. Any of these symptoms put the client at increased risk for falls.
• Monitor input and output. Due to the potential for glossitis and impaired taste, the client may have a decreased appetite. Decreased appetite could also worsen the dietary intake of vitamin B¹². Diarrhea can also put the client at risk for dehydration. Decreased urine output can also indicate ineffective peripheral tissue perfusion due to decreased red blood cells production.
• Assess pain because paresthesia and peripheral neuropathy may be painful.
• Teach energy management techniques such as setting priorities, assigning tasks to others, and balancing rest with activity.

Evaluation

During the evaluation stage, nurses determine the effectiveness of nursing interventions for a specific client. The previously identified expected outcomes are reviewed to determine if they were met, partially met, or not met by the time frames indicated. If outcomes are not met or only partially met by the time frame indicated, the nursing care plan is revised. Evaluation should occur every time the nurse implements interventions with a client, reviews updated laboratory or diagnostic test results, or discusses the care plan with other members of the interprofessional team.