Acid-Base Balance

Acid-Base Balance

  • Definition of Acid-Base Balance:   - Refers to the body's hydrogen ion concentration.   - Measured by pH, representing hydrogen concentration in the patient's body.   - Essential for normal body function, with hydrogen levels needing regulation within a narrow range.

  • Key Terms:
      - Acid: A chemical substance that dissociates and releases hydrogen ions in solution.
      - Base: A chemical substance that combines with hydrogen ions in a solution.

  • pH Scale:
      - Neutral is pH 7.
      - Less than 7 is acidic and greater than 7 is alkaline (basic).
      - Inverse relationship between hydrogen concentration and pH levels.
        - More hydrogen = lower pH (more acidic).
        - Less hydrogen = higher pH (more alkaline).

  • Normal Blood pH Range:
      - Between 7.35 and 7.45.
        - Below 7.35: Acidosis (caused by increased hydrogen or decreased bicarbonate).
        - Above 7.45: Alkalosis (caused by decreased hydrogen or increased bicarbonate).

  • Homeostasis:
      - Key components:     - Common Acid: Carbonic Acid.
        - Common Base: Bicarbonate (HCO3).   - Required ratio: 1 molecule of carbonic acid to 20 molecules of bicarbonate maintained via carbon dioxide and hydrogen ion elimination.

  • pH Ranges and Effects:
      - pH < 6.8 or pH > 7.8 can result in death.
      - Gastric juices: pH between 1 and 3.   - Urine: pH around 6.   - Arterial blood: pH 7.35-7.45, venous blood slightly lower (~7.37).
      - Cerebrospinal fluid: pH 7.32.
      - Pancreatic fluid: pH 7.8 to 8.

Regulation of Acid-Base Balance

  • Three Regulation Systems:
      1. Blood Buffers (Chemical Buffers):
         - Substances in blood with both acidic and basic properties.
         - Fastest response (seconds).
         - Types of buffers: Bicarbonate, Carbonic Acid, Phosphate, Protein, Hemoglobin.
          - Bicarbonate and Phosphate are the primary buffers.
          - Hemoglobin assists in binding excess hydrogen, affecting red blood cells.

  2. Respiratory System:
     - Regulates CO2 in blood through respiratory rate adjustments.
     - Fast response (minutes) compared to the buffer system.
     - Increased acidity (more hydrogen) triggers faster breathing to expel CO2.
     - Decreased acidity (higher pH) may lead to slower, shallower breathing to retain CO2.

  3. Kidneys:
     - Slowest response (hours to days).
     - Regulate pH by excreting or absorbing acid or base.
     - Increased acidity leads kidneys to eliminate more acid or retain bicarbonate.      - Decreased acidity means eliminating more bases.

Acid-Base Imbalances

  • Types of Imbalances:   - Acidosis and Alkalosis can be respiratory or metabolic.   - Imbalances can be acute (sudden) or chronic (long-term).   - Can impair organ function and be life-threatening.

Acidosis

  • Definition: Condition caused by excess hydrogen ions (low pH).

  • Causes:
      - Actual Acidosis: Excess acid production or insufficient acid elimination (e.g., diabetic ketoacidosis).
      - Relative Acidosis: Insufficient base (bicarbonate) production (e.g., pancreatitis, dehydration, diarrhea).

  • Metabolic Acidosis: Caused by decreased bicarbonate or increased acid levels.   - Events leading to metabolic acidosis:
        - Malnutrition, starvation, anorexia (ketone production).
        - Diabetic ketoacidosis (breakdown of fats).
        - Renal failure (retaining phosphate/sulfate).
        - Severe diarrhea (loss of bicarbonate).

  • Signs and Symptoms:
      - CNS depression: Weakness, drowsiness, disorientation, potential coma.
      - Kussmaul’s respirations: Deep, rapid breaths trying to expel CO2.
      - Hyperkalemia: Potassium shifts to the blood.
      - Lab values:
        - pH < 7.35.
        - Increased potassium, decreased bicarbonate.

Respiratory Acidosis

  • Occurs when CO2 production exceeds removal.

  • Causes:
      - Any condition leading to hypoventilation or inability to exhale CO2.
      - Examples include respiratory depression, COPD, pneumonia, airway obstruction.

  • Signs and Symptoms:
      - Lethargy, confusion, shallow breathing.
      - Increased CO2 levels (> 45 mmHg); pH < 7.35.   - Hyperkalemia due to H+ entering cells and K+ exiting.

  • Nursing Diagnosis: Decreased cardiac output, risk for fluid volume excess, risk for injury, ineffective gas exchange.

Alkalosis

  • Definition: Condition characterized by excessive base or deficiency of acid (high pH).

  • Causes:
      - Actual Alkalosis: Excess bicarbonate intake or inadequate acid elimination.
      - Relative Alkalosis: Insufficient acid production (e.g., vomiting, certain diuretics).

  • Metabolic Alkalosis: Caused by increased bicarbonate or decreased acid levels.   - Common causes:
        - Vomiting, gastric suctioning, excessive sodium bicarbonate intake.

  • Signs and Symptoms:
      - CNS irritability: Disorientation, confusion, seizures.
      - Hypertonic muscles, dysrhythmias, shallow slow respirations.
      - Lab values: pH > 7.45, decreased potassium.

Respiratory Alkalosis

  • Occurs when CO2 is excessively excreted.

  • Causes:
      - Hyperventilation due to anxiety, pain, or fever.
      - Overventilation on a ventilator.

  • Signs and Symptoms:
      - Rapid respirations, dizziness, hyperactive CNS, potential seizures.
      - Lab values: Decreased CO2, labile potassium levels.

  • Nursing Diagnosis for Alkalosis:   - Ineffective breathing pattern, risk for impaired gas exchange, potential fluid volume deficiency.

  • Conclusion: Understanding the mechanisms of acid-base balance is critical for maintaining physiological homeostasis and addressing potential health complications caused by imbalances.