Question

A 50-year-old man presents with altered sensorium and deep labored breathing. ABG shows: pH \(7.20\), \(pCO_2 = 35\) mmHg, \(HCO_3^- = 16\) mEq/L, \(Na^+ = 130\) mEq/L, \(Cl^- = 84\) mEq/L, \(PaO_2 = 80\) mmHg. What is the most likely acid-base abnormality?

• A. Acute metabolic acidosis with AG 30
• B. Chronic metabolic acidosis with AG 30
• C. Acute respiratory acidosis
• D. Chronic respiratory acidosis

Hint:

Anion gap formula: \[ AG = Na^+ - (Cl^- + HCO_3^-) \] Low pH with low bicarbonate = metabolic acidosis.

Answer 1

The Correct Option is A

Concept: Low pH indicates acidemia. Low bicarbonate indicates metabolic acidosis. The anion gap helps classify metabolic acidosis.

Step 1: Identify acidemia.
\[ pH = 7.20 \] This is low, so the patient has acidemia.

Step 2: Identify primary disorder.
\[ HCO_3^- = 16\ \text{mEq/L} \] Low bicarbonate indicates: \[ \text{Metabolic acidosis} \]

Step 3: Calculate anion gap.
\[ AG = Na^+ - (Cl^- + HCO_3^-) \] \[ AG = 130-(84+16) \] \[ AG = 130-100=30 \] Therefore, the abnormality is: \[ \text{Acute metabolic acidosis with anion gap 30} \]