Acid-Base Balance Overview

Acid-base Balance

• Definition: The system that maintains the pH of body fluids within a narrow range (7.35 - 7.45).

• Key Components:

  • Buffers: Bicarbonate, phosphate, proteins help resist changes in pH.
  • Respiratory Regulation: CO2 exhalation by lungs; affects carbonic acid formation.
  • Renal Regulation: Kidneys regulate bicarbonate and hydrogen ion concentration.

• pH Levels:

  • Acidemia: pH < 7.35; indicates acid-base imbalance.
  • Alkalemia: pH > 7.45; signifies excess base or loss of acid.

• Common Imbalances:

  • Respiratory Acidosis:

    • Caused by CO2 retention (e.g., COPD).
    • pH decreases, pCO2 increases.

  • Respiratory Alkalosis:

    • Caused by excessive CO2 loss (e.g., hyperventilation).
    • pH increases, pCO2 decreases.

  • Metabolic Acidosis:

    • Caused by loss of bicarbonate (e.g., diarrhea) or excess acid (e.g., diabetic ketoacidosis).
    • pH decreases, HCO3- decreases.

  • Metabolic Alkalosis:

    • Caused by excess bicarbonate (e.g., vomiting) or loss of acid (e.g., diuretics).
    • pH increases, HCO3- increases.

• Compensation Mechanisms:

  • Respiratory Compensation: Rapid change in breathing rate to adjust CO2 levels.
  • Metabolic Compensation: Kidney adjustments in bicarbonate and hydrogen ion excretion, slower process.

• Clinical Measurement:

  • Arterial Blood Gas (ABG) Analysis: Determines pH, pCO2, HCO3-, and oxygen levels.
  • Values:
    • Normal pH: 7.35 - 7.45
    • Normal pCO2: 35 - 45 mmHg
    • Normal HCO3-: 22 - 26 mEq/L

• Assessment Steps:

  1. Evaluate pH for acidosis/alkalosis.
  2. Assess pCO2 for respiratory status.
  3. Assess HCO3- for metabolic status.
  4. Identify primary disorder and compensatory response.

Acid-Base Balance

• The body maintains a stable pH range of 7.35 to 7.45 through a complex system.

Key Components

• Buffers like bicarbonate, phosphate, and proteins help resist changes in pH, acting as a first line of defense against acid or base imbalance.
• Respiratory System plays a crucial role in regulating pH through the exhalation of carbon dioxide (CO2) by the lungs. CO2 combines with water to form carbonic acid, so increased CO2 leads to increased acidity.
• Kidneys have a slower but more significant effect on pH by regulating the concentration of bicarbonate and hydrogen ions in the blood.

pH Levels

• Acidemia indicates an acidic state where pH is less than 7.35, signifying an imbalance in the body's acid-base balance.
• Alkalemia describes an alkaline state where pH exceeds 7.45, indicating an excess of base or loss of acid.

Common Imbalances

• Respiratory Acidosis occurs when CO2 retention takes place, commonly seen in conditions like chronic obstructive pulmonary disease (COPD). This leads to a decrease in pH and an increase in pCO2.
• Respiratory Alkalosis is characterized by excessive CO2 loss, often due to hyperventilation. The pH increases, and pCO2 decreases in this condition.
• Metabolic Acidosis arises from either a loss of bicarbonate, such as in diarrhea, or an excess of acid, as seen in diabetic ketoacidosis. It results in a decrease in pH and a decrease in HCO3-.
• Metabolic Alkalosis can occur due to excessive bicarbonate intake or loss of acid, for example through vomiting or diuretic use. This leads to an increase in pH and an increase in HCO3-.

Compensation Mechanisms

• Respiratory Compensation involves rapid changes in breathing rate to adjust CO2 levels in the blood.
• Metabolic Compensation involves the kidneys adjusting bicarbonate and hydrogen ion excretion to restore pH balance, a slower process compared to respiratory compensation.

Clinical Measurement

• Arterial Blood Gas (ABG) Analysis is a crucial diagnostic tool for evaluating acid-base balance. It measures pH, pCO2, HCO3-, and oxygen levels in the blood.

Normal Values

• pH: 7.35 - 7.45
• Partial Pressure of Carbon Dioxide (pCO2): 35 - 45 mmHg
• Bicarbonate (HCO3-): 22 - 26 mEq/L

Assessment Steps

• When assessing acid-base balance, it is essential to evaluate the pH level to determine if acidosis or alkalosis is present.
• Next, assess the pCO2 to determine the respiratory status.
• Subsequently, assess the HCO3- level to determine the metabolic status.
• Finally, identify the primary disorder, whether it's respiratory or metabolic, and the compensatory response the body is employing to maintain balance.

Test your knowledge of acid-base balance, including key components like buffers, respiratory and renal regulation, and common imbalances. Understand the implications of pH levels and learn about conditions such as respiratory acidosis and metabolic acidosis. Perfect for students studying physiology or nursing.