Question

Renal tubular acidosis with ABG value \(pH = 7.24; P_{O_2}=80; Pa_{CO_2}= 36; Na = 131; HCO_3 = 14; Cl= 90; BE = -13; Glucose = 135\)
above ABG picture suggest :

• A. Respiratory acidosis
• B. Respiratory alkalosis
• C. Metabolic acidosis
• D. Metabolic alkalosis

Answer 1

The Correct Option is C

To determine the acid-base disorder present, we need to analyze the arterial blood gas (ABG) values provided:

• pH = 7.24
• Pa_O2= 80 mmHg
• Pa_CO2 = 36 mmHg
• Na⁺ = 131 mEq/L
• HCO_3^- = 14 mEq/L
• Cl^- = 90 mEq/L
• Base Excess (BE) = -13
• Glucose = 135 mg/dL

Step 1: Evaluate the pH

A normal pH range is approximately 7.35 to 7.45. A pH of 7.24 indicates an acidosis.

Step 2: Determine if it is Respiratory or Metabolic

Metabolic Acidosis is characterized by a low pH and low HCO_3^-. Here, pH is 7.24 and HCO_3^- is 14 mEq/L, which confirms metabolic acidosis since HCO_3^- is below the normal range (22-26 mEq/L). Although Pa_CO2 is slightly low (normal is 35-45 mmHg), indicating a potential respiratory compensation, it doesn’t match the primary disturbance.

Step 3: Rule out other Acid-Base Disorders

Respiratory Acidosis typically shows increased Pa_CO2 with decreased pH, but here, Pa_CO2 is not elevated. Respiratory Alkalosis usually results in increased pH with decreased Pa_CO2. Metabolic Alkalosis displays elevated pH and HCO_3^-, neither of which are seen here.

Based on the ABG values, the presence of a low pH with low HCO_3^- specifically supports the diagnosis of Metabolic Acidosis.