2. Normal ABG values
pH 7.35 – 7.45
pCO2 35 – 45 mmHg
pO2 70 – 100 mmHg
HCO3 20 – 24 mmHg
BE +/- 2 (+ more base, - Deficit of
base(HCO3)
Lactate 0.5 – 1mm0l/ L
3. 6 Steps Approach
I. paO2 and the O2 saturation normal?
II. pH normal ? – Acidemia / Alkalemia
III. Respiratory paCO2 / Metabolic HCO3
IV. Match the paCO2 & HCO3 with the pH
V. If respiratory --- Acute / chronic, Is there any metabolic
compensation?
VI. If Met. Acidosis – Is there an anion gap?
4. • If AG metabolic acidosis, calculate Delta-Delta
to determine concurrent processes?
6. Prediction of Metabolic compensation
Respiratory
acidosis
Respiratory
alkalosis
Acute ↑ By 0.1 mmol ↓By 0.2 mmol
Chronic ↑ By 0.4 mmol ↓By 0.4 mmol
Harrison’s Text book of Medicine – Volume I , 21St Edition
7. Prediction of Respiratory compensation
Metabolic acidosis Metabolic alkalosis
paCO2
= (1.5 x HCO3) + 8 +/- 2
Winter’s equation
paCO2
= (HCO3) + 15
Harrison’s Text book of Medicine – Volume I , 21St Edition
8. Anion Gap
• The anion gap measures the difference—or gap—between the
negatively charged and positively charged electrolytes in your
blood. If the anion gap is too high, your blood is more acidic
than normal. If the anion gap is too low, your blood isn't acidic
enough,
• Normal results are 4 to 12 mEq/L
• AG = (Na+ + K+) – (Cl- + HCO3-)
