Select a result to preview

ABG

Normal Values

Component Value (range) Value (for calculation)
pH 7.35 - 7.45 7.4
HCO3 22-26 mEq/L 24 mEq/L
pCO2 36-44 mEq/L 40 mEq/L
sodium 135-145 mEq/L 140 mEq/L
Potassium 3.5-5.0 mEq/L
Chloride 90-110 mEq/L
Osmolality 280-295 mEq/L 295 mOsm/L
Osmolal Gap <10 mEq/L
Anion gap 9-16 mEq/l
BUN 10-20 mg/dl

Formulas

  1. Total body water = F x Body weight in Kg; where F is 0.5 for females, 0.6 for males, 0.7 for children, and 0.75 for neonates
  2. **Osmolality = 2[sodium] + [glucose]/18 + [BUN]/2.8

Calcualtion of Basic Acid-Base abnormality

Step 1 - Find the primary abnormality

See pH

Step 2 - Look for compensation

Primary abnormality Compensation
Metablic acidosis Respiraory alkalosis
Metabloic alkalosis Respiratory acidosis
Respiratory acidosis Metabolic alkalosis
Respiratory alkalosis Metabolic acidosis

Metabolic Acidosis

For each 1 mEq/L decrease in HCO3, pCO2 will reduce by 1.2 mEq/L

Metabolic Alkalosis

For each 1 mEq/L increase in HCO3, pCO2 will rise by 0.7 mEq/L

Respiratory Acidosis

For each 10 mEq/L decrease in pCO2, HCO3 will reduce by 2 mEq/L (in case of acute pathology) or 4 mEq/L (in case of chronic pathology)

Respiratory Alkalosis

For each 10 mEq/L increase in pCO2, HCO3 will rise by 1 mEq/L (in case of acute pathology) or 4 mEq/L (in case of chronic pathology)

Expected pCO2 can be calculated by winter's formula
expected pCO2 = 1.5 x HCO32- + 8 Β± 2