Acid-Base Buddy 🧪

Your quick reference guide for acid-base disorders

Respiratory Acidosis

pH < 7.35

CO2 > 45

HCO3 = 22-26

→ Retain CO2 → ↓ pH

Possible Causes:

  • COPD
  • DKA
  • Pneumonia
  • Anesthesia
  • Hypoventilation (↓ RR)

Treatment (DOC):

  • Airway
  • Reverse anesthesia
  • O2

Respiratory Alkalosis

pH > 7.45

CO2 < 35

HCO3 = 22-26

→ Expelling CO2 → ↑ pH

Possible Causes:

  • Anxiety
  • Pain
  • Fever
  • Pulmonary emboli
  • Hyperventilation

Treatment (DOC):

  • Slow down RR
  • Paper bag
  • Rebreather mask

Metabolic Acidosis

pH < 7.35

CO2 = 35-45

HCO3 < 22

→ ↓ pH → ↓ HCO3

Possible Causes:

  • AKI/CKD
  • DKA
  • Diarrhea
  • Sepsis
  • Shock

Treatment (DOC):

  • Hydration
  • Bicarb
  • Dialysis

Metabolic Alkalosis

pH > 7.45

CO2 = 35-45

HCO3 > 26

→ ↑ pH → ↑ HCO3

Possible Causes:

  • NG suction
  • Vomiting
  • Diuretics
  • Antacids
  • Steroids

Treatment (DOC):

  • Anti-emetic
  • Stop diuretics
  • Replace electrolytes

ABG Interpretation Guide

Compensation Rules:

  • pH abnormal: <7.35 OR >7.45 → uncompensated
  • pH 7.35-7.45 (compensated)
  • pH closer to 7.35 = compensated acidosis
  • pH closer to 7.45 = compensated alkalosis

Diagnosis Rules:

  • If CO2 value matches pH (acid or alk), then it's respiratory
  • If HCO3 matches pH (acid or alk), then it's metabolic

Examples

Example 1:

pH: 7.28 (acidic)

CO2: 45 (acidic)

HCO3: 24 (normal)

→ Uncompensated Respiratory Acidosis

Example 2:

pH: 7.48

HCO3: 32 (matches pH)

CO2: 40 (normal)

→ Uncompensated Metabolic Alkalosis

Color Key:

Diagnostic Category
Key Values
Key Terms
Mechanisms
Examples