Categories
Medical Surgical

Anemia, Megaloblastic (Vitamin B12 and Folic Acid Deficiency)

www.nursingcrib.com

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. Patients  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 and  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
Introduction to Nursing Pharmacology Nursing Pharmacology

Drugs and The Body

Drugs and the Body

Pharmacodynamics

  • Pharmacodynamics is the science of dealing with interactions between living organisms and foreign chemicals
  • Chemical reactions occur continuously in the body of each living system
  • When other chemicals (drugs) are added to the body, additional effects occur

Drug Actions

  • To replace or act as substitutes for missing chemicals
  • To increase or stimulate certain cellular activities
  • To depress or slow certain cellular activities
  • To interfere with the functioning of foreign cells

Receptor Cells

  • Receptor site reacts to certain chemicals
  • The better the fit between receptor site and chemical, the more pronounced the reaction
  • Enzymes within the body are needed to break down the chemicals to open up the receptor site

Lock & Key

Drugs and The Body: Lock and Key
Drugs and The Body: Lock and Key

Enzymes

  • Drugs can interfere with the enzymes that may be catalysts for chemical reactions
  • Enzymes produce a cascade effect

Pharmacokinetics

  • Onset of drug action
  • Drug half-life
  • Timing of the peak effect
  • Duration of drug effects
  • Metabolism or biotransformation of the drug
  • Site of excretion

The Processes by Which Drugs Are Handled in the Body

The Processes by Which Drugs Are Handled in the Body
The Processes by Which Drugs Are Handled in the Body

Pharmacokinetics

  • Critical concentration
    • The amount of a drug that is needed to cause a therapeutic effect
  • Loading dose
    • A higher dose than that usually used for treatment
  • Dynamic equilibrium
    • The actual concentration that a drug reaches in the body

Dynamic Equilibrium

  • The actual amount of drug that reaches the body results in a dynamic equilibrium
  • Dynamic equilibrium is affected by:
    • Absorption
    • Distribution
    • Biotransformation
    • Excretion

Absorption

  • Administration
    • Affected by route of administration
    • Oral medications affected by presence of food in the stomach
  • First-pass effect
    • Medications are extensively metabolized by the liver

Factors Affecting Absorption

Factors That Affect Absorption of Drugs
Factors That Affect Absorption of Drugs

Distribution

  • Protein binding
  • Blood–brain barrier
  • Placenta/breast milk

Biotransformation

  • The liver is the single most important site for biotransformation (metabolism)
  • This process breaks down medications
  • It helps to prevent medications from causing adverse effects on the body

Excretion

  • Removal of drugs from the body
  • Kidneys play the most important role in the excretion of medication

Half-Life

  • Half-life is the time it takes for the amount of drug in the body to decrease to one-half the peak level
  • Half-life is affected by the absorption, distribution, metabolism, and excretion

Pharmacokinetics

Pharmacokinetics
Pharmacokinetics

Half-life

Half-Life
Half-Life

Calculating Half-Life

Focus on Calculations
Focus on Calculations

Factors Influencing Drug Effects

  • Weight
  • Age
  • Gender
  • Physiologic factors
  • Pathologic factors
  • Genetic factors
  • Immunologic factors
  • Psychological factors
  • Environmental factors
  • Drug tolerance
  • Cumulative effect

Drug-to-Drug Interactions

  • Can occur any time two or more drugs are taken together
  • Can occur at:
    • Site of absorption
    • During distribution
    • During biotransformation
    • During excretion
    • At the site of action

Drug–Food Interaction

  • Certain foods interact with drugs
  • Drugs are best taken on an empty stomach

Drug–Laboratory Test Interaction

  • Drugs may alter the results of lab testing
  • Laboratory tests may be used to monitor the effects of other medications