The nurse reviews the arterial blood gas (ABG) results of a client and notes the following result: pH of 7.30, paCO2 of 50 mm of Hg, and bicarbonate (HCO3) of 22 mEq/L. Which is a?

Appeared in: JIPMER Pondicherry NO - 2022

Explanation

The client's pH of 7.30 is below the normal range of 7.35-7.45, indicating acidosis.
The PaCO₂ of 50 mm Hg is above the normal range of 35-45 mm Hg. Elevated PaCO₂ is caused by hypoventilation and leads to an accumulation of carbonic acid, causing respiratory acidosis.
The bicarbonate (HCO₃⁻) level of 22 mEq/L is within the normal range (22-26 mEq/L), indicating that the kidneys have not yet compensated for the imbalance.
Using the ROME mnemonic (Respiratory Opposite, Metabolic Equal), the pH is low and the PaCO₂ is high (opposite directions), which points directly to respiratory acidosis.

Option A: Metabolic acidosis is incorrect because it is characterized by a low pH and a low bicarbonate (HCO₃⁻) level (below 22 mEq/L). In this case, the HCO₃⁻ is normal.
Option B: Respiratory alkalosis is incorrect because it is characterized by a high pH (above 7.45) and a low PaCO₂ (below 35 mm Hg). The client's values are the opposite.
Option C: Metabolic alkalosis is incorrect because it is characterized by a high pH (above 7.45) and a high HCO₃⁻ (above 26 mEq/L). The client's pH is low, indicating acidosis.

Clinical Relevance

Nursing practice connection: Knowing Arterial Blood Gas (ABG) interpretation helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Respiratory acidosis is a critical condition caused by inadequate ventilation and CO₂ retention. Common causes include COPD, pneumonia, drug overdose (respiratory depressants), and airway obstruction.
Nurses must promptly recognize the 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 serial ABGs is crucial to evaluate the effectiveness of interventions and track the patient's progress.

How to Approach the Question

First, look at the pH. Classify it as acidosis (less than 7.35), normal (7.35-7.45), or alkalosis (greater than 7.45). In this case, 7.30 is acidosis.
Second, examine the PaCO₂. This value reflects the respiratory component. A value greater than 45 mm Hg is acidic; less than 35 mm Hg is alkalotic. Here, 50 mm Hg is acidic.
Third, examine the HCO₃⁻. This value reflects the metabolic component. A value less than 22 mEq/L is acidic; greater than 26 mEq/L is alkalotic. Here, 22 mEq/L is normal.
Finally, determine the cause. Does the PaCO₂ or the HCO₃⁻ match the pH's acid/base status? The PaCO₂ is acidic, matching the acidosis of the pH. Therefore, the primary problem is respiratory.
Check for compensation. Since the HCO₃⁻ is normal, there is no compensation from the metabolic system.

Concept Tested & Keywords

Concept Tested: Arterial Blood Gas (ABG) interpretation
Stem keywords: arterial blood gas, ABG, pH 7.30, paCO2 50 mm of Hg, bicarbonate 22 mEq/L
Lead-in keywords: Which is a
Clinical cues: pH of 7.30 indicates acidosis.
Clinical cues: PaCO2 of 50 mm Hg indicates a respiratory component.

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