Acid-Base Imbalances (3)

Acid-Base Imbalances Overview

Acid-Base Balance

  • Essential for optimal cellular function.

  • Represents homeostasis of hydrogen ion concentration in body fluids.

  • Hydrogen shifts between compartments to compensate for imbalances.

  • Minor changes in hydrogen concentration can have major effects on cellular function.

pH

  • Evaluated using arterial blood gases (ABGs).

  • pH indicates the balance between carbon dioxide (lungs) and bicarbonate (kidneys).

  • Higher hydrogen concentration = more acidic (lower pH).

  • Normal pH range: 7.35-7.45.

Maintenance of Acid-Base Balance

  • Three buffer systems maintain pH:

    1. Chemical and Protein Buffers: First line of defense; respond quickly to pH changes.

    2. Respiratory Buffers: Second line of defense; regulate hydrogen ions via CO2 levels.

    3. Kidney Buffers: Third line of defense; slow response but most effective; control bicarbonate levels.

Respiratory Acidosis

  • pH < 7.35; PaCO2 > 42 mm Hg.

  • Occurs due to inadequate ventilation (hypoventilation), causing CO2 retention.

Signs and Symptoms of Respiratory Acidosis

  • Sudden hypercapnia, tachypnea, increased pulse, mental cloudiness, confusion, anxiety.

Causes of Respiratory Acidosis

  • Includes pulmonary edema, pneumonia, asthma, CNS depression (e.g., sedatives).

Treatment of Respiratory Acidosis

  • Improve ventilation; use bronchodilators, antibiotics, mechanical ventilation, oxygen therapy.

Respiratory Alkalosis

  • pH > 7.45; PaCO2 < 38 mm Hg.

  • Caused by hyperventilation, resulting in excessive CO2 elimination.

Signs and Symptoms of Respiratory Alkalosis

  • Lightheadedness, numbness, tingling, tachycardia, potential for loss of consciousness.

Treatment of Respiratory Alkalosis

  • Treat underlying cause; breathe slowly or use paper bag to restore CO2 levels.

Metabolic Acidosis

  • Characterized by low pH and low bicarbonate concentration.

  • Two types: Normal or High Anion Gap acidosis.

Anion Gap

  • Calculated to identify the cause of metabolic acidosis (difference between cations and anions).

  • Formula: Anion gap = Na + K - (Cl + HCO3).

Signs and Symptoms of Metabolic Acidosis

  • Headache, confusion, respiratory changes, nausea, decreased BP.

Causes of Metabolic Acidosis

  • Includes diabetic ketoacidosis, kidney failure, lactic acidosis.

Treatment of Metabolic Acidosis

  • Based on cause; may include insulin for DKA, bicarbonate administration, dialysis.

Metabolic Alkalosis

  • Characterized by high pH and high bicarbonate concentration.

  • Often due to loss of acidic gastric fluids or hypokalemia.

Signs and Symptoms of Metabolic Alkalosis

  • Tingling, dizziness, depressed respiration, tachycardia.

Treatment of Metabolic Alkalosis

  • Varies by cause; may involve fluid replacement, electrolyte management.

Interpretation of ABGs

  1. Check pH: < 7.35 = acidosis; > 7.45 = alkalosis.

  2. Analyze PaCO2 and HCO3 while determining the source of imbalance.

  3. Combine findings from pH and PaCO2/HCO3 for the type of imbalance.

  4. Evaluate PaO2 and SaO2 for hypoxia.

  5. Assess compensation status: uncompensated, partially compensated, fully compensated.