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 for buffering.
• To maintain electrical balance, potassium (K+) ions move out of the cells into the blood, causing serum potassium levels to rise (hyperkalemia).
• Hyperkalemia is a primary concern due to its cardiotoxic effects, which can lead to dangerous heart rhythms and cardiac arrest.
• Patients with diabetes are at high risk for metabolic acidosis (DKA), a condition known for causing significant and complex potassium shifts.

Why Other Options Were Wrong

• Option B: Sodium (Na+) levels are primarily related to fluid balance, not the direct acid-base exchange. While hyponatremia can occur in conditions like DKA due to osmotic diuresis, it is not the most immediate life-threatening electrolyte imbalance caused by the acidosis itself.
• Option C: While acidosis can affect the level of ionized (active) calcium, the changes are typically less acute and less life-threatening than the rapid shift in potassium. In fact, rapid correction of acidosis with bicarbonate can cause a sharp drop in ionized calcium, leading to tetany.
• Option D: Magnesium (Mg2+) is not the primary electrolyte affected by the H+/K+ shift in acidosis. While severe magnesium depletion can contribute to potassium imbalances, it is not the main concern in the acute phase of metabolic acidosis.

Related Visual

• Visual 1: Diagram - An illustration showing the exchange of hydrogen (H+) ions entering a cell and potassium (K+) ions exiting the cell during acidosis. This visualizes the core mechanism of hyperkalemia.
• Visual 2: ECG Strip - A comparison of a normal ECG with one showing the characteristic changes of hyperkalemia: peaked T waves, widened QRS complex, and eventually a sine wave pattern. This highlights the cardiac danger.

Clinical Relevance

• Nursing practice connection: Knowing Electrolyte management in acid-base imbalances helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• A nurse's priority for a patient in metabolic acidosis is to initiate continuous cardiac monitoring (ECG) to detect arrhythmias caused by hyperkalemia.
• The nurse must anticipate that treatment for acidosis (e.g., with insulin in DKA) will cause potassium to shift back into the cells, potentially leading to a rapid drop in serum levels (hypokalemia). Therefore, frequent monitoring is essential throughout treatment.
• What if the patient begins treatment with an insulin infusion? The nurse must be prepared for a rapid shift from hyperkalemia to hypokalemia. Insulin drives potassium into the cells along with glucose, so the priority will shift to preventing and managing hypokalemia by adding potassium to IV fluids once levels start to fall.

How to Approach the Question

• First, identify the key clinical condition in the stem: 'metabolic acidosis'.
• Next, recall the primary physiological response to acidosis at the cellular level. The body buffers acid (H+) by moving it into cells.
• Remember the principle of electroneutrality: when a positive ion (H+) enters a cell, another positive ion must leave. In this case, it's potassium (K+).
• Connect the resulting electrolyte imbalance (hyperkalemia) to its most severe clinical consequence: cardiac arrhythmias.
• Evaluate the options based on this primary mechanism. Potassium is directly and acutely affected, making it the highest priority for monitoring.

Concept Tested & Keywords

• Concept Tested: Electrolyte management in acid-base imbalances.
• Stem keywords: hypertension, diabetes mellitus, metabolic acidosis, normal pH
• Lead-in keywords: monitor and manage carefully
• Clinical cues: The combination of diabetes and metabolic acidosis strongly suggests a risk for significant potassium shifts, as seen in Diabetic Ketoacidosis (DKA).
• Clinical cues: A normal pH indicates compensated acidosis, but it does not eliminate the underlying metabolic problem or the associated risk of hyperkalemia.

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