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Medical Surgical

Anemia, Megaloblastic (Vitamin B12 and Folic Acid Deficiency)

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The anemias caused by deficiencies of the vitamins B12 and folic acid show identical bone marrow and peripheral blood changes. Both vitamins are essential for DNA synthesis.

Pathophysiology

The two main vitamin deficiencies may coexist. In each case, hyperplasia of the bone marrow occurs, and the precursor erythroid and myeloid cells are large and bizarre in appearance. The RBC’s produced are abnormally large (megaloblastic). A pancytopenia (a decrease in all myeloid-derived cells) develops.

Vitamin B12 deficiency can occur from inadequate intake in strict vegetarians; faulty absorption from gastrointestinal tract; absence of intrinsic factor (pernicious anemia); disease involving the ileum or pancreas, which impairs B12 absorption; and gastrectomy. People with pernicious anemia have a higher incidence of gastric ulcer than the general public.

Folic acid deficiency occurs when intake of folate is deficicnet or the requirement is increased. People at risk include those who rarely eat uncooked vegetables or frutis, primarily elderly people living alone or people with alcoholism. Alcohol use, hemolytic anemia, and pregnancy increase folic acid requirements. PatientsĀ  with malabsoptive or small bowel disease may not absorb folic acid normally.

Clinical Manifestations

Symptoms are progressive and may be marked by spontaneous partial remissions and exacerbations.

  • Gradual development of signs of anemia (weakness, listlessness, and pallor)
  • Possible development of a smooth, sore, red, tongue and mild diarrhea (pernicious anemia)
  • Possible development of confusion, more often, paresthesias in the extremities ad difficulty keeping balance, loss of position sense
  • Lack of neurologic manifestations with folic acid deficiency alone
  • Vitiligo (patchy loss of skin pigmentation) and prematurely graying hair (often seen in pernicious anemia)
  • Without treatment, patients die, usually as a result of congestive heart failure from anemia

Assessment and Diagnostic Findings

  • Schilling test (primary diagnostic tool)
  • Complete blood count (Hgb value as low as 4 to 5 g/dl, WBC count 2,000 to 3,000/mm3, platelet count less than 50,000/mm3, MCV is very high, usually exceeding 110)
  • Serum levels of folate and vitamin B12 (folic acid deficiency and deficient vitamin B12)

Medical Management: Vitamin B12 Deficiency

  • Oral supplementation with vitamins or fortified soy milk (strict vegetarians)
  • Intramuscular injections of vitamin B12 for defective absorption or absence of intrinsic factor
  • Prevention of recurrence with lifetime vitamin B12 therapy for patient who has had pernicious anemia or non correctable malabsorption

Medical Management: Folic Acid Deficiency

  • Intake of nutritious die and 1 mg folic acid daily
  • Intramuscular folic acid for malabsorption syndromes
  • Folic acid taken orally as a separate tablet (except prenatal vitamins)
  • Folic acid replacement stopped when hemoglobin level returns to normal, with the exception of alcoholics, who continue replacement as along as alcohol intake continues

Nursing Management

  • Assess patients at risk for megaloblastic anemia for clinical manifestations (eg, inspect the skin, sclera, and mucous membranes for jaundice, note vitiligo or premature graying or smooth, red, sore tongue).
  • Perform careful neurologic assessment (eg, note gait and stability; test position and vibration sense).
  • Assess need for assistive devices (eg, cane, walkers) ans need for support and guidance in managing activities of daily living and home environment.
  • Ensure safety when position sense, coordination, and gait are affected.
  • Refer for physical or occupational therapy as needed.
  • When sensation is altered, instruct patient to avoid excessive heat and cold.
  • Advise patient to prepare bland, soft foods and to eat small amounts frequently.
  • Explain that other nutritional deficiencies, such as alcohol-induced anemia, can induce neurologic problems.
  • Instruct patient in complete urine collections for the Schilling test. Also explain the importance of the test and of complying with the collection.
  • Teach the patient about chronicity of disorder andĀ  need for monthly vitamin B12 injections when patient has no symptoms. Instruct patient how to self-administer injections, when appropriate.
  • Stress importance of ongoing medical follow-up and screening, because gastric atrophy associated with pernicious anemia increases the risk of gastric carcinoma.

Reference: Joyce Young Johnson, Brunner & Sudddarth’s Textbook of Medical-Surgical Nursing 11th edition Lippincott Williams & Wilkins pp. 45-48

Categories
Chemotherapeutic Agents Nursing Pharmacology

Anti-infective Agents

Anti-infective Agents

Drug Therapy Across the Lifespan

Drug Therapy Across the Lifespan
Drug Therapy Across the Lifespan

Development of Anti-infective Therapy

  • 1920s
    • Paul Ehrlich worked on developing a synthetic chemical effective against infection-causing cells only
    • Scientists discovered penicillin in a mold sample
  • 1935
    • The sulfonamides were introduced

Mechanisms of Action

  • Interfere with biosynthesis of the bacterial cell wall
  • Prevent the cells of the invading organism from using substances essential to their growth and development
  • Interfere with steps involved in protein synthesis
  • Interfere with DNA synthesis
  • Alter the permeability of the cell membrane to allow essential cellular components to leak out

Mechanism of Anti-infective Agents

Mechanism of Anti infective Agents
Mechanism of Anti infective Agents

Anti-infective Activity

  • Anti-infectives vary in their effectiveness against invading organisms
  • Some are selective: they are effective only for a small number of organisms
  • Bactericidal: kill the cell
  • Bacteriostatic: prevent reproduction of the cell

Narrow Spectrum vs Broad Spectrum

  • Narrow spectrum of activity
    • Effective against only a few microorganisms with a very specific metabolic pathway or enzyme
  • Broad spectrum of activity
    • Useful in treating a wide variety of infections

Human Immune Response

  • Goal of anti-infective therapy is reduction of the population of the invading organism
  • Drugs that eliminate all traces of any invading pathogen might be toxic to the host as well
  • Immune response is a complex process involving chemical mediators, leukocytes, lymphocytes, antibodies, and locally released enzymes and chemicals

Problems With Treating Infections in Immunosuppressed Patients

  • Anti-infective drugs cannot totally eliminate the pathogen without causing severe toxicity in the host
  • These patients do not have the immune response in place to deal with even a few invading organisms

Resistance

  • Anti-infectives act on a specific enzyme system or biological process; many microorganisms that do not act on a specific system are not affected by the particular drug
  • This is considered natural or intrinsic resistance to that drug

Acquired Resistance

  • Microorganisms that were once sensitive to the particular drug have begun to develop acquired resistance
  • This results in serious clinical problems

Ways Resistance Develops

  • Producing an enzyme that deactivates the antimicrobial drug
  • Changing cellular permeability to prevent the drug from entering the cell
  • Altering transport systems to exclude the drug from active transport into the cell
  • Altering binding sites on the membranes or ribosomes, which then no longer accept the drug
  • Producing a chemical that acts as an antagonist to the drug

Preventing Resistance

  • Limit the use of antimicrobial agents to the treatment of specific pathogens sensitive to the drug being used
  • Make sure doses are high enough, and the duration of drug therapy long enough
  • Be cautious about the indiscriminate use of anti-infectives

Identification of the Pathogen

  • Identification of the infecting pathogen is done by culture
  • A culture of a tissue sample from the infected area is done
    • A swab of infected tissue is allowed to grow on an agar plate
    • Staining techniques and microscopic examination identify the bacterium
  • Stool can be examined for ova and parasites

Sensitivity of Pathogen

  • Shows which drugs are capable of controlling the particular microorganism
  • Important to be done for microorganisms that have known resistant strains
  • Along with a culture, identifies the pathogen and appropriate drug for treatment

Factors Affecting Prescribing Anti-infective Agents

  • Identification of the correct pathogen
  • Selection of the right drug
    • One that causes the least complications for that particular patient
    • One that is most effective against the pathogen involved

Combination Therapy

  • Use of a smaller dosage of each drug
  • Some drugs are synergistic
  • In infections caused by more than one organism, each pathogen may react to a different anti-infective agent
  • Sometimes, the combined effects of the different drugs delay the emergence of resistant strains

Adverse Reactions to Anti-infective Therapy

  • Kidney damage
  • Gastrointestinal (GI) tract toxicity
  • Neurotoxicity
  • Hypersensitivity reactions
  • Superinfections

Prophylaxis of Anti-infective Agents

  • People traveling to areas where malaria is endemic
  • Patients who are undergoing gastrointestinal or genitourinary surgery
  • Patients with known cardiac valve disease, valve replacements, and other conditions requiring invasive procedures