Interpreting an ABG with pH 7.35, PCO2 30 mmHg, and HCO3- 18 mEq/L indicates which acid-base disorder?

Interpreting an ABG with pH 7.35, PCO2 30 mmHg, and HCO3- 18 mEq/L indicates which acid-base disorder?

• A. Respiratory alkalosis
• B. Metabolic acidosis (compensated)
• C. Normal
• D. Metabolic alkalosis

Answer: (B)

The main idea here is identifying a metabolic problem with the body's compensatory response. The bicarbonate is low (18 mEq/L), which signals metabolic acidosis as the primary disturbance. The pH is at the low end of normal (7.35), meaning the body is partially compensating rather than presenting a pure disorder. The CO2 is also reduced (30 mmHg), showing the lungs are blowing off CO2 to raise pH. When you have a low bicarbonate with a low CO2 and a pH that’s near normal, the pattern fits metabolic acidosis with respiratory compensation.

The main idea here is identifying a metabolic problem with the body's compensatory response. The bicarbonate is low (18 mEq/L), which signals metabolic acidosis as the primary disturbance. The pH is at the low end of normal (7.35), meaning the body is partially compensating rather than presenting a pure disorder. The CO2 is also reduced (30 mmHg), showing the lungs are blowing off CO2 to raise pH. When you have a low bicarbonate with a low CO2 and a pH that’s near normal, the pattern fits metabolic acidosis with respiratory compensation.