# 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**](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html#introduction) [**2. The ABC's of Analysis**](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html#abcs) [Full article: Comprehensive Acid-Base Review](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html) [**4. Step-by-Step Approach**](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html#abcs) [**5. Compensation Rules**](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html#compensation) [**6. Anion Gap Analysis**](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html#anion-gap) [**7. Non-Anion Gap Acidosis**](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html#non-anion-gap) [**8. Mixed Disorders**](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html#mixed) [Full article: Comprehensive Acid-Base Review](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html) [Full article: Comprehensive Acid-Base Review](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/acid-base-comprehensive/index.html)

## 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

1.  **Identify acidemia or alkalemia**
    - pH \< 7.40 = Acidemia
    - pH \> 7.40 = Alkalemia
2.  **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

📚 For Educational Purposes Only

© 2025 Andrew Bland MD - All Rights Reserved


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