The Ultimate Acid-Base Imbalances Cheat Sheet.
The "No-Fluff" Guide for NCLEX & Med-Surg Success
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Pages: 4 (High-Yield)
Format: Instant Download (PDF)
Page 1: The Fundamentals & Normal Values
The "Why" Behind the Numbers
Acid-Base balance is the body's effort to maintain a stable pH for
enzymatic and cellular function. The Lungs (PaCO2)
and Kidneys (HCO3) are the regulatory organs.
✅ Normal Lab Values (Memorize These!)
Lab Test Normal Range Critical Value (NCLEX Alert)
pH 7.35 – 7.45 < 7.35 (Acidosis) / > 7.45 (Alkalosis)
PaCO2 35 – 45 mmHg Respiratory Indicator
HCO3- 22 – 26 mEq/L Metabolic (Renal) Indicator
, 2|Page
Lab Test Normal Range Critical Value (NCLEX Alert)
PaO2 80 – 100 mmHg Oxygenation Status (Not acid-base)
Base Excess -2 to +2 > +2 = Base Excess / < -2 = Base Deficit
Page 2: ABG Interpretation (The "How-To")
Method 1: The ROME Mnemonic (Respiratory Opposite,
Metabolic Equal)
• Respiratory = Opposite:
opH ⬆️ (Alk) + PaCO2 ⬇️ = Respiratory Alkalosis
o pH ⬇️ (Acid) + PaCO2 ⬆️ = Respiratory Acidosis
• Metabolic = Equal:
o pH ⬆️ (Alk) + HCO3 ⬆️ = Metabolic Alkalosis
o pH ⬇️ (Acid) + HCO3 ⬇️ = Metabolic Acidosis
Method 2: The Tic-Tac-Toe Grid
Acidosis Normal Alkalosis
pH < 7.35 7.35-7.45 > 7.45
PaCO2 > 45 35-45 < 35
HCO3 < 22 22-26 > 26
1. Plot the patient's values.