A patient with hypertension and diabetes mellitus presents with metabolic acidosis. Arterial blood gas shows a normal pH. Which electrolyte should the nurse monitor and manage carefully?

1. A

   Potassium (K+)

2. B

   Sodium (Na+)

3. C

   Calcium (Ca2+)

4. D

   Magnesium (Mg2+)

Appeared in: NORCET 9 Prelims-2025

Explanation

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• In metabolic acidosis, excess hydrogen ions (H+) move into cells to be buffered.
• To maintain electrical neutrality, potassium ions (K+) shift out of the cells and into the bloodstream.
• This cellular exchange results in hyperkalemia (elevated serum potassium), which poses a significant risk of cardiac arrhythmias.
• Even though the pH is normal (compensated), the underlying potassium shift continues, making it the most critical electrolyte to monitor.

Why Other Options Were Wrong

• Option B: Sodium levels are more related to the patient's fluid volume status rather than being directly affected by the acid-base shift mechanism. While it should be monitored, it is not the primary electrolyte of concern in this specific context.
• Option C: While acidosis can increase the level of ionized (active) calcium, the risk of life-threatening complications from this is less immediate and severe than the cardiac effects of hyperkalemia.
• Option D: Significant shifts in magnesium are less common in acute metabolic acidosis compared to potassium. While it is an important electrolyte for cardiac and neuromuscular function, it is not the one that shifts most predictably and dangerously in this situation.

Related Visual

Clinical Relevance

• Nursing practice connection: Knowing Electrolyte management in compensated metabolic acidosis helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• A nurse's primary responsibility in this scenario is to place the patient on a cardiac monitor immediately to watch for ECG changes indicative of hyperkalemia, such as tall, peaked T-waves.
• Anticipate orders for interventions to lower potassium, which may include intravenous insulin and dextrose, sodium bicarbonate, or sodium polystyrene sulfonate (Kayexalate).
• What if the patient's acidosis was being aggressively treated with insulin? The nurse's priority would shift to monitoring for hypokalemia. As insulin drives glucose into the cells, it also drives potassium back in, which can cause a rapid and dangerous drop in serum potassium levels.

How to Approach the Question

• First, identify the patient's primary problem: metabolic acidosis.
• Note the key detail that the pH is normal. This signifies a 'compensated' state, but it does not mean the underlying problem is resolved.
• Recall the fundamental pathophysiology of acidosis at the cellular level. The body attempts to buffer excess acid (H+) by pushing it into cells.
• Remember the principle of electroneutrality: to balance the positive charge of H+ entering the cell, another positive ion must leave. That ion is potassium (K+).
• Conclude that metabolic acidosis causes a shift of K+ into the blood, leading to hyperkalemia.
• Evaluate the options based on this knowledge. Potassium is the electrolyte most directly and dangerously affected. Therefore, it is the priority for monitoring.

Concept Tested & Keywords

• Concept Tested: Electrolyte management in compensated metabolic acidosis
• Stem keywords: metabolic acidosis, normal pH, hypertension, diabetes mellitus
• Lead-in keywords: monitor, manage carefully
• Clinical cues: Patient has diabetes, a major risk factor for metabolic acidosis (e.g., DKA).
• Clinical cues: Normal pH indicates a compensated state, but the underlying electrolyte shift persists.

Question ID

Qoh3OXd1_Ggps9SD1u6YSC

Copy ID

Reference Book

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 546-548

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1048-1050

E6 Pharmacology Nursing Lilley 11e Part 2 p. 164-166