Insulin Flashcards

Insulin

What is Insulin?

  • A hormone secreted by the beta cells of the pancreas.
  • Release stimulated by increased blood glucose levels after meals.
  • Main function is to lower blood sugar levels.

How Insulin Works (Mechanism of Action)

Insulin lowers blood sugar by:

  • Increasing glucose transport into cells.
  • Promoting glucose conversion to glycogen (storage form).
  • Promoting the uptake and conversion of glucose, amino acids, and fatty acids into storage within body cells.
  • Limiting lipolysis (breakdown of fat) and proteolysis (breakdown of protein).
  • Promoting the movement of potassium from extracellular fluid into cells.

When is Insulin Used? (Indications)

Insulin is indicated for:

  • Type 1 Diabetes Mellitus (DM).
    • Absolute lack of insulin.
    • Autoimmune disease.
    • Often seen in individuals who are normal weight or thin.
    • Used to treat Diabetic Ketoacidosis (DKA).
  • Type 2 DM unresponsive to dietary measures and oral hypoglycemics.
    • Often adult onset.
    • Common in individuals who are obese.
    • Involves insulin resistance.
    • Used when other methods fail or are contraindicated.
  • Elevated blood glucose levels during emotional or physical stress.
  • When other antidiabetic drugs are contraindicated.
  • Treatment of complications of DM.

Types of Insulin

  • Animal insulin: Made from bovine and porcine sources.
  • Human insulin: Manufactured by recombinant DNA technology.

When NOT to Use Insulin (Contraindications)

Insulin is contraindicated in cases of:

  • Hypersensitivity.
  • Hypoglycemia (low blood sugar).

Major Classes of Insulin (Grouped by Onset, Peak, Duration)

Important Note: Clear insulin is injected before cloudy, unless specifically instructed otherwise.

Long-acting insulin analogues cannot be mixed with other insulins.

  1. Rapid Acting

    • Clear/colorless.
    • Agents: Lispro (Humalog), Aspart (Novolog), Glulisine (Apidra).
    • Onset: 10-15 minutes.
    • Peak: 1 hour.
    • Duration: 2-4 hours.
    • Nursing Implication: Instruct patients to eat no more than 5-15 minutes after injection. Given immediately before a meal. Not eating after injection can cause hypoglycemia.
    • Uses: Basal bolus regimen, in combination with intermediate and long-acting analogues, or with OHAs (oral hypoglycemic agents), or in insulin pumps. The first hour after injection and 2-3 hours after exercise are other peak times for hypoglycemia.

  2. Short Acting

    • Also called Regular insulin.
    • Clear/colorless.
    • Agents: Regular (Humalog R, Novolog R, Actarapid).
    • Onset: 20-30 minutes.
    • Peak: 2-3 hours.
    • Duration: 4-6 hours.
    • Frequency: Can be given two to four times per day.
    • Uses: In combination with intermediate or long-acting insulins. Only insulin that can be administered IV. The solution in the vial should be clear.

  3. Intermediate Acting

    • Cloudy.
    • Mixing: Must be mixed gently before use (rotate the vial; don't shake).
    • Agents: Hypurin (isophane), Humulin N, Novolin N (NPH).
    • Onset: 2-3 hours.
    • Peak: 4-12 hours
    • Duration: 12-18 hours.
    • Uses: Commonly with short-acting insulin. Can be used alone for patients sensitive to short-acting insulin or in combination with oral hypoglycemic agents. Regular insulin can be mixed with NPH or lente insulins.

  4. Long Acting

    • Agents: Ultralente (UL), Glargine (Lantus).
    • Onset: 1-2 hours, described as peakless or steady.
    • Duration: 18-24 hours.
    • Mixing: Cannot be mixed with other insulin or injected into the same site.

Pharmacokinetics (How the Body Handles Insulin)

  • Absorption: Administered parenterally (IV, SQ). Absorption greater at deltoid (upper arm) and abdomen sites. SQ absorption rate is slow. Heat and massage could increase absorption.
  • Distribution: Widely in the body.
  • Metabolism: Metabolized in the liver and kidneys.
  • Excretion: Excreted in urine and feces.

Types of Insulin Delivery

  • Subcutaneous Injection: Standard method using an insulin syringe (calibrated in units). Injection angle is typically 45-90 degrees.
  • Insulin Pen: Resembles a fountain pen. Contains a disposable needle and an insulin-filled cartridge. Increases compliance due to convenience. Examples include Humulin NPH 70/30, Lantus.
  • Implantable Insulin Pumps: Surgically implanted in the abdomen. Delivers a basal infusion and bolus doses with meals. Administered intraperitoneally or IV. Results in fewer hypoglycemic reactions and better blood glucose control.

Complications of Insulin Therapy

  • Local Allergic reactions: Redness, swelling, tenderness, induration (a hard area, 2-4 cm). An antihistamine may be given 1 hour before injection.
  • Systemic allergic reactions: Urticaria (hives), edema (swelling), anaphylaxis (severe allergic reaction).
  • Insulin Lipodystrophy: Localized reactions at the injection site.
    • Lipoatrophy: Loss of subcutaneous fat.
    • Lipohypertrophy: Development of fibrofatty masses.
    • Rotation of injection sites is important to prevent this.
  • Resistance to injected insulin: Immune antibodies develop and bind insulin, decreasing available insulin.
  • Morning Hyperglycemia (High blood sugar in the morning) caused by:
    • Somogyi effect: Normal or elevated blood glucose at bedtime, drops to hypoglycemic levels (low) at 2-3 am, followed by a rebound high blood sugar in the morning.
      • Treatment: Decrease the evening (pre-dinner or bedtime) dose of intermediate-acting insulin, or increase the bedtime snack.
    • Dawn Phenomenon: Normal blood glucose until about 3 am, then hyperglycemia (high) on awakening. (More common in diabetic patients).
      • Management: Change the time of injection of evening intermediate-acting insulin from dinner to bedtime.
    • Insulin Waning: Progressive rise in blood glucose from bedtime to morning.
      • Treatment: Increase the evening (pre-dinner or bedtime) dose of intermediate or long-acting insulin, or add a dose of insulin before the evening meal if not already part of the regimen.

Nursing Considerations

  • Cannot be given PO (by mouth) as GI secretions destroy insulin.
  • Given SQ (subcutaneously) at a 45-90-degree angle.
  • Use only insulin syringes calibrated in units.
  • Before withdrawing insulin, rotate the vial between palms (do not shake) to mix, especially for cloudy insulins.
  • When mixing two insulins, draw up the regular (clear) insulin dose first to prevent contamination.
  • Regular insulin is the only insulin that can be administered IV.
  • Insulin injection sites should be rotated (1.5 inches apart, not used again for 2-3 weeks) to prevent lipodystrophy.
  • Monitor for signs of hypoglycemia (low blood sugar) at the peak time of insulin. Signs include: apprehension, chills, perspiration, confusion, double vision, drowsiness, inability to concentrate, nausea, rapid pulse, tremors.
  • Monitor for signs of hyperglycemia (high blood sugar). Signs include: drowsiness, flushed skin, acetone breath (fruity odor), polyuria (frequent urination), polydipsia (increased thirst), anorexia (loss of appetite).
  • Storage: Once opened, insulin can be kept at room temperature for 1 month or in the refrigerator for 3 months. Do not place it in the freezer, expose it to direct sunlight, or extremes of temperature.
  • Prefilled syringes can be stored in the refrigerator and used for 1-2 weeks.