Comprehensive Acid-Base Review

A Systematic Approach to Diagnosing and Managing Acid-Base Disorders

⏱️ Core Module 🎯 Essential Knowledge 📚 Complete Reference

📚 Module Navigation

1. Introduction & Key Concepts 2. The ABC's of Analysis Full article: Comprehensive Acid-Base Review 4. Step-by-Step Approach 5. Compensation Rules 6. Anion Gap Analysis 7. Non-Anion Gap Acidosis 8. Mixed Disorders Full article: Comprehensive Acid-Base Review Full article: Comprehensive Acid-Base Review

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1. Introduction to Acid-Base Physiology

🎯 Core Definitions

Term	Definition	Clinical Significance
Acidemia	Blood pH < 7.40	Describes the blood pH state
Alkalemia	Blood pH > 7.40	Describes the blood pH state
Acidosis	The underlying pathologic process causing acidemia	Can exist without acidemia if compensated
Alkalosis	The underlying pathologic process causing alkalemia	Can exist without alkalemia if compensated

⚠️ Critical Concept

You can have acidosis without acidemia if another disorder is providing compensation. For example, a patient with chronic metabolic acidosis may have a normal pH due to respiratory compensation, but the underlying acidosis still exists.

2. The ABC's of Acid-Base Analysis

A. Initial Assessment

Identify acidemia or alkalemia
- pH < 7.40 = Acidemia
- pH > 7.40 = Alkalemia
Identify primary disorder
- Metabolic: Changes in HCO₃⁻
  - ↑ HCO₃⁻ (> 24 mEq/L) = Metabolic alkalosis
  - ↓ HCO₃⁻ (< 24 mEq/L) = Metabolic acidosis
- Respiratory: Changes in pCO₂
  - ↑ pCO₂ (> 40 mmHg) = Respiratory acidosis
  - ↓ pCO₂ (< 40 mmHg) = Respiratory alkalosis

B. Assess Compensation

⚠️ Golden Rules of Compensation

Compensation is ALWAYS incomplete
Overcompensation NEVER occurs
If it appears to overcompensate, look for a secondary disorder

C. Calculate Anion Gap

AG = Na⁺ - Cl⁻ - HCO₃⁻
Normal AG ≈ 10 mEq/L (range 8-12)

D. Evaluate for Multiple Disorders

Use Potential Bicarbonate or Delta/Delta ratio (covered in Mixed Disorders section)

E. For Non-Anion Gap Acidosis

Calculate Urinary Anion Gap (UAG)

🔑 Key Takeaways

Always approach acid-base systematically using the 5-step method
Compensation is never complete - if it appears so, look for a mixed disorder
Check for mixed disorders in complex cases using delta/delta ratio
UAG differentiates renal from GI causes of non-AG acidosis
Remember correction factors (especially albumin for AG)
Winter's formula is your best friend for metabolic acidosis
Mixed respiratory + metabolic acidosis = "closed system" = severe acidemia