3. Acid-base balance - Disorders of acid-base balance (Video)

Overview of Acid-Base Balance Disorders

This section summarizes the key points discussed with a focus on diagnosing acid-base disorders through the analysis of blood test results.

Understanding Acid-Base Balance

• Normal Ranges:

  • pH: Approximately 7.4

  • Carbon Dioxide (CO2): Weak acid; higher levels indicate acidotic conditions.

  • Bicarbonate (HCO3): Acts as a base; higher levels indicate alkalotic conditions.

Key Definitions

• Acidosis: A condition where the pH is lower than the normal range (acidic). Generally, pH < 7.35.

• Alkalosis: A condition where the pH is higher than the normal range (alkaline). Generally, pH > 7.45.

• Compensation: The body’s physiological response to counteract the primary acid-base disturbance, involving either the respiratory or renal systems.

Analytical Framework

• Case Study Approach: Focus on three key values - pH, CO2, and bicarbonate - to arrive at a diagnosis.

• Tic-Tac-Toe Chart: A tool used to categorize each value as acidic, normal, or alkaline to aid diagnosis.

Case Study Examples

Case 1: 70-Year-Old Male Diabetic

• Blood Test Results:

  • pH: 7.26 - Acidic

  • CO2: 42 - Normal

  • Bicarbonate: 17 - Acidic

• Diagnosis:

  • Imbalance: Acidosis (pH is acidic)

  • Cause: Metabolic issue (bicarbonate is acidic)

  • Compensation: No (CO2 is normal)

  • Final Conclusion: Metabolic Acidosis

Case 2: 24-Year-Old Female Post-MVC

• Blood Test Results:

  • pH: 7.49 - Alkaline

  • CO2: 30 - Acidic

  • Bicarbonate: 23 - Normal

• Diagnosis:

  • Imbalance: Alkalosis

  • Cause: Respiratory issue (low CO2 due to rapid breathing)

  • Compensation: None (bicarbonate is normal)

  • Final Conclusion: Respiratory Alkalosis

Case 3: 64-Year-Old Male with COPD

• Blood Test Results:

  • pH: 7.26 - Acidic

  • CO2: 52 - Acidic

  • Bicarbonate: 34 - Alkaline

• Diagnosis:

  • Imbalance: Acidosis

  • Cause: Respiratory issue (high CO2)

  • Compensation: Yes (bicarbonate is high)

  • Final Conclusion: Respiratory Acidosis with Partial Metabolic Compensation

Case 4: 48-Year-Old Female with Adrenal Tumor

• Blood Test Results:

  • pH: 7.48 - Alkaline

  • CO2: 51 - Acidic

  • Bicarbonate: 29 - Alkaline

• Diagnosis:

  • Imbalance: Alkalosis

  • Cause: Metabolic issue

  • Compensation: Yes (CO2 is high)

  • Final Conclusion: Metabolic Alkalosis with Partial Respiratory Compensation

Case 5: 45-Year-Old Female with Myasthenia Gravis

• Blood Test Results:

  • pH: 7.36 - Normal but closer to acidic

  • CO2: 50 - Acidic

  • Bicarbonate: 34 - Alkaline

• Diagnosis:

  • Imbalance: Acidosis

  • Cause: Respiratory issue (high CO2)

  • Compensation: Complete (since pH is normal)

  • Final Conclusion: Respiratory Acidosis with Complete Metabolic Compensation

Additional Notes

• Diagnoses can vary based on different combinations of pH, CO2, and bicarbonate values.

• Understanding relationships among these values is critical to establishing appropriate treatment and management plans.

• Be prepared for variations in how these parameters may present in real-world scenarios.

• Remember the importance of both the absolute and relative values of each component in diagnosing acid-base disorders.