Determining Compensation in Arterial Blood Gas (ABG) Problems

Introduction

• Solving ABG problems can be confusing, especially when determining compensation.
• People often struggle with identifying if a condition is respiratory or metabolic in nature.
• This guide presents a simple method using "Tic Tac Toe" to figure out compensation.

Understanding the Problem

• Example problem: pH of 7.34, PaCO2 of 36, and Bicarb of 20.
• These values suggest a metabolic system problem.

Tic Tac Toe Method

• Step 1: Identify the pH level:
  • pH = 7.34 (Acidic)
• Step 2: Place pH under "Acid."
• Step 3: Evaluate PaCO2 and Bicarb:
  • PaCO2 = 36 (Normal, place under "Normal")
  • Bicarb = 20 (Acidic, place under "Acid")
• Outcome: Vertical three in a row under "Acid" indicates metabolic acidosis.

Determining Compensation

• Full Compensation: Achieved when pH is normal, but there's no vertical three in a row.
• Uncompensated vs. Partially Compensated:
  • Uncompensated: The non-causing system (respiratory) is within normal range (PaCO2 = 36).
  • Partially Compensated: Non-causing system deviates from normal range to try to compensate (e.g., PaCO2 = 29, below normal).

Changing Parameters

• Example 1: PaCO2 = 29
  • Still metabolic acidosis, but now partially compensated because respiratory system is attempting to correct pH.
• Example 2: pH changes to 7.37
  • pH is within normal range, indicating full compensation.
  • Check specific pH value to determine if it is acidic or alkaline normal.

Evaluating Full Compensation

• Blood pH:
  • Absolute normal blood pH is around 7.40.
  • pH 7.35-7.40: slightly acidic
  • pH 7.40-7.45: slightly alkaline
• Example: pH = 7.37
  • Normal but on acidic side, indicating metabolic acidosis fully compensated.

Conclusion

• Use Tic Tac Toe for quick evaluation of compensation in ABG problems.
• For deeper understanding, refer to comprehensive resources like the "Acid Base Balance" video available on the "Registered Nurse RN" YouTube channel.