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 |
|
- 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
- **Osmolality = 2[sodium] + [glucose]/18 + [BUN]/2.8
Calcualtion of Basic Acid-Base abnormality
Step 1 - Find the primary abnormality
See pH
- if pH < 7.4 - Acidosis
- if Ph > 7.4 Alkalosis
Step 2 - Look for compensation
| Primary abnormality |
Compensation |
| Metablic acidosis |
Respiraory alkalosis |
| Metabloic alkalosis |
Respiratory acidosis |
| Respiratory acidosis |
Metabolic alkalosis |
| Respiratory alkalosis |
Metabolic acidosis |
For each 1 mEq/L decrease in HCO3, pCO2 will reduce by 1.2 mEq/L
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 ± 2