The arterial blood gas (ABG) analysis report shows that a decreased bicarbonate level and pH value denote & x… - RRB Nsg. Superintendent-21 July 2019 (Shift-2nd)

RRB Nsg. Superintendent-21 July 2019 (Shift-2nd)

Medical & Surgical Nursing

Medium

Appeared in: RRB Nsg. Superintendent-21 July 2019 (Shift-2nd)

Explanation

A decreased blood pH (value below 7.35) signifies an acidic state in the body, known as acidosis.
A decreased bicarbonate (HCO₃⁻) level (value below 22 mEq/L) indicates that the cause of the acidosis is metabolic in origin, as bicarbonate is the primary metabolic buffer regulated by the kidneys.
The mnemonic ROME (Respiratory Opposite, Metabolic Equal) is a quick way to remember this relationship. In metabolic conditions, the pH and the bicarbonate level move in an 'Equal' direction. Here, both are decreased.
Therefore, the combination of a low pH and a low bicarbonate level is the classic sign of metabolic acidosis.

Option A: Respiratory acidosis is characterized by a decreased pH but an increased partial pressure of carbon dioxide (pCO₂), not a decreased bicarbonate level. The primary problem is respiratory, involving CO₂ retention.
Option C: Respiratory alkalosis involves an increased pH (alkalosis) and a decreased pCO₂. This is the opposite of the findings in the question.
Option D: Metabolic alkalosis involves an increased pH (alkalosis) and an increased bicarbonate level. This is the opposite of the findings in the question.

Visual 1: Diagram: A chart illustrating the ROME (Respiratory Opposite, Metabolic Equal) mnemonic for quick ABG interpretation.
Visual 2: Flowchart: A step-by-step decision tree for analyzing ABG results, starting with pH, then assessing pCO₂ and HCO₃⁻ to determine the primary disorder and any compensation.
Visual 3: Table: A comprehensive table of normal ABG values (pH, pCO₂, HCO₃⁻, PaO₂) for adults.

Clinical Relevance

Nursing practice connection: Knowing Interpretation of Arterial Blood Gas (ABG) results for acid-base balance helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses in critical care, emergency, and medical-surgical units frequently monitor ABG results to evaluate a patient's ventilation and metabolic status, which is essential for timely intervention.
Recognizing metabolic acidosis is vital as it can signal life-threatening conditions such as diabetic ketoacidosis (DKA), sepsis, acute kidney injury, or severe diarrhea. Prompt identification allows for treatment of the underlying cause.
What if? If the ABG report showed a decreased pH but an increased pCO₂ level, the diagnosis would be Respiratory Acidosis. The nursing priority would then shift to improving the patient's ventilation (e.g., through respiratory treatments, positioning, or mechanical ventilation) rather than addressing a metabolic issue.

How to Approach the Question

First, analyze the pH. A value below 7.35 indicates acidosis. A value above 7.45 indicates alkalosis. The question states the pH is decreased, so the condition is an 'acidosis'. This immediately eliminates the 'alkalosis' options (C and D).
Next, determine if the cause is respiratory or metabolic. Use the ROME mnemonic: Respiratory Opposite, Metabolic Equal.
Look at the bicarbonate (HCO₃⁻), which is the metabolic parameter. The question states it is decreased.
Compare the direction of change of the pH (decreased) and the HCO₃⁻ (decreased). They are moving in the same, or 'Equal', direction.
According to ROME, if the change is 'Metabolic', the pH and HCO₃⁻ will be 'Equal' (both go up or both go down).
Since both are decreased, the condition is confirmed as Metabolic Acidosis.

Concept Tested & Keywords

Concept Tested: Interpretation of Arterial Blood Gas (ABG) results for acid-base balance.
Stem keywords: arterial blood gas, ABG, decreased bicarbonate, decreased pH
Lead-in keywords: denote
Negative lead-in flag: false

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