An ABG analysis report shows: pH - 7.20; PCO2 - 35 mm Hg; HCO3 - 20 mEq/L. These findings are suggestive of? - OSSSC Nursing Officer-2023

OSSSC Nursing Officer-2023

Medical & Surgical Nursing

Medium

Appeared in: OSSSC Nursing Officer-2023

Explanation

The pH of 7.20 is below the normal range of 7.35-7.45, indicating a state of acidemia.
The bicarbonate (HCO₃⁻) level of 20 mEq/L is below the normal range of 22-26 mEq/L. A primary decrease in HCO₃⁻ is the defining characteristic of metabolic acidosis.
The partial pressure of carbon dioxide (PCO₂) is 35 mm Hg, which falls within the normal range (35-45 mm Hg). This confirms the problem is not respiratory in origin.
The combination of a low pH and a low HCO₃⁻ level, with a normal PCO₂, points directly to uncompensated metabolic acidosis.

Option B: Metabolic alkalosis is incorrect because the patient's pH is low (acidic), not high (alkalotic).
Option C: Respiratory alkalosis is incorrect as the pH is acidic, not alkalotic, and the PCO₂ is normal, not low.
Option D: Respiratory acidosis is incorrect because the PCO₂, which is the respiratory component, is within the normal range and not elevated.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Interpretation of Arterial Blood Gas (ABG) results to identify acid-base imbalances as background academic context rather than a clinical decision trigger.
Nurses must be able to interpret ABG results promptly to identify life-threatening conditions like metabolic acidosis. This allows for timely notification of the physician and initiation of critical interventions.
Common causes of metabolic acidosis that nurses should be aware of include diabetic ketoacidosis (DKA), lactic acidosis (from shock or sepsis), severe diarrhea (due to bicarbonate loss), and renal failure.
Nursing interventions for metabolic acidosis focus on treating the underlying cause, monitoring vital signs and level of consciousness, administering prescribed fluids and electrolytes (like sodium bicarbonate), and ensuring patient safety.

How to Approach the Question

First, evaluate the pH. A value below 7.35 indicates acidosis. A value above 7.45 indicates alkalosis.
Second, determine if the primary cause is respiratory or metabolic. Use the ROME mnemonic: Respiratory Opposite, Metabolic Equal.
Check the PCO₂ (respiratory parameter). If it moves in the opposite direction of the pH (e.g., pH is low, PCO₂ is high), the cause is respiratory.
Check the HCO₃⁻ (metabolic parameter). If it moves in the same (equal) direction as the pH (e.g., pH is low, HCO₃⁻ is low), the cause is metabolic.
In this question, the pH (7.20) is low and the HCO₃⁻ (20) is also low. They are moving in the same direction, indicating a metabolic problem.
Finally, check for compensation. Since the PCO₂ (35) is normal, there is no respiratory compensation yet.

Concept Tested & Keywords

Concept Tested: Interpretation of Arterial Blood Gas (ABG) results to identify acid-base imbalances.
Stem keywords: ABG analysis, pH, PCO2, HCO3
Lead-in keywords: suggestive of
Clinical cues: pH: 7.20 (low)
Clinical cues: PCO2: 35 mm Hg (normal)

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