The nurse is reviewing a patient's ABG report. The pH is 7.30, PaCO2 is 50 mmHg, and HCO3 is 24 mEq/L. Based on this, the nurse interprets the results as:

1. A

   Metabolic acidosis

2. B

   Respiratory acidosis

3. C

   Respiratory alkalosis

4. D

   Metabolic alkalosis

Appeared in: NORCET 7 Prelims -2024

Explanation

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• The patient's pH of 7.30 is below the normal range of 7.35-7.45, indicating acidosis.
• The PaCO2 of 50 mmHg is above the normal range of 35-45 mmHg. Elevated PaCO2 (an acid) is the cause of the acidosis, pointing to a respiratory origin.
• The HCO3 level of 24 mEq/L is within the normal range (22-26 mEq/L), indicating the metabolic system has not yet compensated for the imbalance.
• This combination of low pH and high PaCO2 is characteristic of respiratory acidosis.

Why Other Options Were Wrong

• Option A: Metabolic acidosis would present with a low pH (acidosis) but also a low HCO3 level (below 22 mEq/L), as the primary problem is a deficit of base or an excess of metabolic acid. This patient's HCO3 is normal.
• Option C: Respiratory alkalosis is characterized by a high pH (above 7.45) and a low PaCO2 (below 35 mmHg), caused by hyperventilation. This patient's values are the opposite (low pH, high PaCO2).
• Option D: Metabolic alkalosis involves a high pH (above 7.45) and a high HCO3 (above 26 mEq/L), due to an excess of base or loss of acid. This patient has a low pH and a normal HCO3.

Related Visual

• Visual 1: Flowchart: A visual guide for systematic ABG interpretation, such as the ROME (Respiratory Opposite, Metabolic Equal) mnemonic, to quickly identify the primary disorder.
• Visual 2: Diagram: An illustration showing the chemical balance between CO2, carbonic acid (H2CO3), and bicarbonate (HCO3) in the blood, explaining how changes in PaCO2 affect pH.

Clinical Relevance

• Nursing practice connection: Knowing Interpretation of Arterial Blood Gas (ABG) results to identify primary acid-base imbalances helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• Respiratory acidosis is a critical condition often caused by hypoventilation from conditions like COPD, pneumonia, drug overdose (respiratory depressants), or airway obstruction.
• Nurses must promptly recognize signs of respiratory acidosis (e.g., confusion, lethargy, headache, dyspnea) and intervene by improving ventilation, which may involve positioning, encouraging deep breathing, or preparing for mechanical ventilation.
• Monitoring ABGs is crucial for assessing the severity of the imbalance and the effectiveness of treatment.

How to Approach the Question

• This is a lab data interpretation question. The key is a systematic, step-by-step analysis of the provided values.
• Step 1: Analyze the pH. Is it low (acidosis, below 7.35), high (alkalosis, above 7.45), or normal?
• Step 2: Analyze the PaCO2 (the respiratory parameter). Is it high (acidic) or low (alkalotic)?
• Step 3: Analyze the HCO3 (the metabolic parameter). Is it low (acidic) or high (alkalotic)?
• Step 4: Match the parameter (PaCO2 or HCO3) that corresponds with the pH change. Use the ROME mnemonic: Respiratory Opposite (pH and PaCO2 move in opposite directions), Metabolic Equal (pH and HCO3 move in the same/equal direction). In this case, pH is low and PaCO2 is high (opposite), indicating a respiratory problem.
• Step 5: Check for compensation. If the non-causative parameter is still normal, the condition is uncompensated. If it is moving in the opposite direction to correct the pH, it is compensated.

Concept Tested & Keywords

• Concept Tested: Interpretation of Arterial Blood Gas (ABG) results to identify primary acid-base imbalances.
• Stem keywords: ABG report, pH 7.30, PaCO2 50 mmHg, HCO3 24 mEq/L
• Lead-in keywords: interprets the results as
• Clinical cues: pH below 7.35 indicates acidosis.
• Clinical cues: PaCO2 above 45 mmHg indicates a respiratory cause.

Question ID

Q5XWdFO1i-tlaR7cV3tfJg

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