# A patient with acute kidney injury has serum potassium of 7.2 mEq/L. The ECG shows peaked T waves and a widening QRS. Which intervention does the nurse expect first?

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> url: https://mymerci.kr/pages/nclex_q.php?qn_id=372751&lang=en  
> language: en  
> subject: Diagnostic Tests  
> category: PA

## Question

A patient with acute kidney injury has serum potassium of 7.2 mEq/L. The ECG shows peaked T waves and a widening QRS. Which intervention does the nurse expect first?

## Option

1. IV regular insulin 10 units with 50% dextrose 25 g.
2. IV calcium gluconate 1 g over 2–3 minutes for cardiac membrane stabilization. **✔ Correct answer**
3. Sodium polystyrene sulfonate 30 g orally to remove potassium.
4. Hemodialysis after the nephrology consult arrives.

**Correct answer: 2**

## Explanation

A potassium of 7.2 with ECG changes (peaked T waves, widening QRS) is critical hyperkalemia. The first priority is IV calcium gluconate (or chloride) — it does NOT lower potassium but stabilizes the cardiac membrane and prevents lethal dysrhythmia within minutes. After cardiac stabilization the team adds insulin with dextrose (drives K into cells, onset 15 minutes), beta-2 agonist (albuterol nebulized), and sodium bicarbonate if acidotic. These shift potassium intracellularly. Subsequently, a removal therapy is needed because shift only buys time: sodium polystyrene sulfonate or patiromer/sodium zirconium cyclosilicate (gut), loop diuretic (kidney if functional), or hemodialysis (definitive in oliguric AKI). Choice 1 is correct second-step but not first. Choice 3 acts slowly. Choice 4 is definitive but takes time to arrange.

## In-depth explanation

Critical hyperkalemia is serum K greater than 6.0 to 6.5 with ECG changes — a medical emergency. ECG progression: peaked T waves, then flattened P waves and prolonged PR, then widened QRS, then sine wave, then ventricular fibrillation or asystole. ECG severity, not the absolute potassium, drives the urgency of intervention. Treatment has three pillars. Stabilize: IV calcium gluconate or chloride (does not lower K but protects the heart) — first action when ECG changes are present. Shift: insulin plus dextrose (onset about 15 minutes), beta-2 agonist (albuterol nebulized), sodium bicarbonate if acidotic. Remove: sodium polystyrene sulfonate or patiromer or sodium zirconium cyclosilicate (slow), loop diuretic (kidney if functional), hemodialysis (definitive for oliguric AKI). Calcium acts within minutes and lasts 30 to 60 minutes; repeat dosing is appropriate while shift and removal therapies take effect.

## Clinical scenario

A patient with **acute kidney injury** has **serum potassium 7.2 mEq/L**. ECG shows **peaked T waves** and a **widening QRS**.

## Key concepts

- **Critical Hyperkalemia** — Serum K >6.0–6.5 with ECG changes is a medical emergency. ECG progression: peaked T waves → flattened P waves and prolonged PR → widened QRS → sine wave → ventricular fibrillation/asystole. ECG severity, not absolute K alone, drives the urgency of intervention.
- **Three Pillars of Treatment** — Stabilize: IV calcium gluconate or chloride (does not lower K but protects the heart). Shift: insulin + dextrose, beta-2 agonist (albuterol), sodium bicarbonate if acidotic. Remove: sodium polystyrene sulfonate or patiromer/sodium zirconium cyclosilicate (slow), loop diuretic (kidney), hemodialysis (definitive).
- **Calcium First in Cardiac Toxicity** — Calcium does NOT lower potassium; it raises the cardiac action-potential threshold and protects the myocardium from the depolarizing effects of hyperkalemia. Onset within minutes, duration 30–60 minutes. Repeat doses are appropriate while shift and removal therapies take effect.

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