Pharmacology and Acid-Base Balance Review

Acid-Base Balance and pH

  • Normal pH Range: 7.35 - 7.45
      - The pH value indicates how acidic or basic blood is.
      - Low pH: < 7.35 (More acidic conditions).   - High pH: > 7.45 (More basic conditions, alkalotic).

  • CO2 vs. HCO3 (Bicarbonate): Vital for balancing acid (CO2) and base (HCO3).
      - CO2:
        - Originates from the lungs.
        - Acts as an acid in the body.
      - HCO3 (Bicarbonate):
        - Derived from the kidneys and controls base.
        - Acts as a base.

  • Breathing and pH Regulation:
      - If there's a low pH (acidosis), the breathing process is usually stimulated to expel CO2.
      - Conversely, for a high pH (alkalosis), the breathing rate may slow down to retain CO2.

  • Potassium (K+) Relationship:
      - Swap Mechanism: H+ and K+ switch places in the bloodstream based on pH levels.
        - In Acidic Conditions (Low pH):
          - Excess H+ ions lead to H+ entering cells and K+ exiting.
          - This results in hyperkalemia (high potassium levels).
        - In Basic Conditions (High pH):
          - A deficiency of H+ leads to H+ leaving cells and K+ entering.
          - This results in hypokalemia (low potassium levels).

  • Homeostasis: The body continually strives to maintain a balanced state, where:
      - Respiratory System: Quick response to pH changes.
      - Renal System: Slower, long-term adjustment to pH changes.

Diagnostic Tests in Pathophysiology

  • Purpose of Diagnostic Tests:
      - Reflect the underlying pathophysiology of diseases.
      - Identify abnormalities indicating alterations in bodily functions.

  • Screening:
      - Aimed at detecting diseases before symptoms appear (e.g., Type 2 Diabetes Mellitus).

  • Diagnosing:
      - Involves confirming a disease presence after symptoms manifest.

  • Lab Results Interpretation:
      - Always compare results to the patient's previous data to ensure accuracy.
      - Abnormal lab results typically indicate health issues.
      - Hemolysis of RBCs can lead to elevated potassium levels due to cell breakdown during sample collection.

Pharmacological Principles

  • Pharmacokinetics (PK):
      - Focuses on what the body does to a drug, encompassing the movement of the drug through the body (ADME).
  • Pharmacodynamics (PD):
      - Concerns what the drug does to the body, detailing how the drug interacts with its target.

ADME Components

  • A (Absorption):
      - Refers to how the drug enters the bloodstream.
      - IV Administration: Provides immediate effect.
      - PO Administration: Slower absorption due to the necessity of passage through the stomach and intestines before entering hepatic circulation (first-pass effect).

  • D (Distribution):
      - The dispersal of the drug within the body's tissues.
      - Factors affecting distribution include blood flow to various organs and protein binding with albumin (which can affect the drug's activity).

  • M (Metabolism):
      - Mainly occurs in the liver, where drugs are broken down.

  • Bioavailability:
      - % of drug that reaches systemic circulation; for IV = 100%, for PO = <100% (due to the first-pass effect).

  • E (Excretion):
      - Kidneys remove drugs from the body.

  • Onset, Peak, and Duration:
      - Onset: The time it takes for the drug to start working.
      - Peak: The time at which the drug's effects are strongest.
      - Duration: How long the drug effects last.

  • Therapeutic Range:
      - Defined as the safe zone for drug concentrations; too low means no effect, too high may cause toxicity, and an appropriate range achieves the desired therapeutic effect.
      - A narrow therapeutic range indicates high risk due to a small margin for safety.

  • Protein Binding:
      - Drugs can either bind to proteins (inactive) or remain unbound (active/free).
      - Drug interactions may occur depending on protein binding levels (e.g., synergistic effects = enhanced effect vs. antagonistic effects = blocked effect).

Drug Reference - PD1 Test 1

Clopidogrel Bisulfate
  • Class: Antiplatelet
  • Indication: Acute Coronary Syndrome (ACS), post-stent placement.
  • Mechanism of Action (MoA): Prevents platelet aggregation, thus reducing clot formation.
  • Side Effects/Nursing Considerations: Monitoring for bleeding and bruising; it’s often given with aspirin.
Enoxaparin (Low Molecular Weight Heparin)
  • Indication: ACS, Deep Vein Thrombosis (DVT) prevention.
  • MoA: Prevents clot formation but does not dissolve existing clots.
  • Side Effects/Nursing Considerations: Monitor for bleeding and bruising; given subcutaneously with no required aPTT monitoring.
Evolocumab
  • Class: PCSK9 Inhibitor
  • Indication: High cholesterol.
  • MoA: Facilitates the removal of LDL from circulation.
  • Side Effects/Nursing Considerations: Injection site reactions; effective when statins are insufficient.
Glargine Insulin
  • Indication: Basal glucose control in diabetes management.
  • Class: Long-acting insulin
  • Onset: 1-2 hours
  • Peak: None
  • Duration: 24 hours
  • MoA: Provides a steady amount of insulin throughout the day.
  • Side Effects/Nursing Considerations: Risk of hypoglycemia; effective for day-long control, not suited for emergencies.
Gliclazide IR
  • Class: Sulfonylurea
  • Indication: Type 2 Diabetes.
  • MoA: Stimulates insulin release from the pancreas.
  • Side Effects/Nursing Considerations: Risk of hypoglycemia (safer than others), weight gain, should be taken with meals; monitor blood glucose.
Glyburide
  • Class: Sulfonylurea
  • Indication: Type 2 Diabetes.
  • MoA: Stimulates insulin secretion from the pancreas.
  • Side Effects/Nursing Considerations: High risk of hypoglycemia, especially in elderly patients; also causes weight gain; take with meals.
Abciximab (Glycoprotein IIB/IIIA Inhibitor)
  • Class: Antiplatelet
  • Indication: ACS, during Percutaneous Coronary Intervention (PCI).
  • MoA: Blocks platelet aggregation, thereby preventing clot formation.
  • Side Effects/Nursing Considerations: High bleeding risk; monitor closely; typically given post-PCI.
Hydrochlorothiazide
  • Class: Thiazide diuretic
  • Indication: Hypertension (HTN).
  • MoA: Promotes excretion of sodium and water, which reduces blood volume and blood pressure.
  • Side Effects/Nursing Considerations: Risk of hypokalemia, dehydration, dizziness; monitor electrolyte levels.
Aspart Insulin
  • Class: Rapid-acting insulin
  • Indication: Treatment of hyperglycemia (mealtime insulin).
  • Onset: 10-20 minutes
  • Peak: 1-3 hours
  • Duration: 3-5 hours
  • MoA: Facilitates cellular glucose uptake, lowering blood sugar levels.
  • Side Effects/Nursing Considerations: Highest risk of hypoglycemia; check blood glucose before administration and monitor for signs of hypoglycemia.
Aspirin (ASA)
  • Class: Antiplatelet
  • Indication: ACS and prevention of Myocardial Infarction (MI).
  • MoA: Prevents platelet adhesion and aggregation to stop formation of larger clots.
  • Side Effects/Nursing Considerations: Risk of bleeding and gastrointestinal (GI) upset; check for allergies; administer first in ACS situations (chewed).
Carvedilol
  • Class: Beta-Blocker
  • Indication: Hypertension and heart failure.
  • MoA: Reduces heart rate and contractility, thus decreasing the workload on the heart.
  • Side Effects/Nursing Considerations: May cause bradycardia and hypotension; check heart rate and blood pressure prior to administration.
Cholestyramine Resin
  • Class: Bile acid sequestrant
  • Indication: High cholesterol.
  • MoA: Binds bile acids, leading to increased use of cholesterol in the body, thus lowering LDL levels.
  • Side Effects/Nursing Considerations: May cause constipation and bloating; should be taken with fluids as it can interfere with the absorption of other medications.
Isosorbide Dinitrate
  • Class: Nitrate
  • Indication: Angina (chest pain).
  • MoA: Causes vasodilation, thereby reducing workload on the heart and improving blood flow.
  • Side Effects/Nursing Considerations: Monitor for hypotension, headache, and dizziness; same precautions apply as with nitroglycerin.
Levothyroxine
  • Class: Thyroid Hormone
  • Indication: Hypothyroidism.
  • MoA: Replaces deficient thyroid hormones to regulate metabolism.
  • Side Effects/Nursing Considerations: Ideally taken on an empty stomach, monitor thyroid-stimulating hormone (TSH) levels due to long-term use implications.
Losartan
  • Class: Angiotensin Receptor Blocker (ARB)
  • Indication: Hypertension.
  • MoA: Blocks the action of angiotensin II, leading to vasodilation and reduced blood pressure.
  • Side Effects/Nursing Considerations: Risk of hypotension and dizziness; regularly monitor blood pressure.
Metformin
  • Class: Biguanide
  • Indication: Type 2 Diabetes.
  • MoA: Decreases glucose production in the liver.
  • Side Effects/Nursing Considerations: May cause gastrointestinal upset and rare but serious lactic acidosis; should be withheld when contrast dye is used; monitor kidney function.