# Situation: A 61-year-old woman with type 2 diabetes and hypertension takes losartan 100 mg and spironolactone 25 mg daily and recently began using a salt substitute. She comes to the emergency room with generalized weakness and tingling in her legs. Her serum potassium is 7.0 mEq/L (3.5–5.0 mEq/L) on a non-hemolyzed sample, serum creatinine 1.0 mg/dL (88 µmol/L), capillary blood glucose 142 mg/dL (7.9 mmol/L), and her 12-lead electrocardiogram (ECG) shows tall, peaked T waves. She is on a cardiac monitor. While the first medication is being prepared, the nurse watches the monitor. Which change would show that her hyperkalemia is progressing?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=629802  
> language: ko  
> subject: Nursing Practice III — Care of Clients with Problems in Surgery, Oxygenation, Fluid and Electrolytes, Infectious, Inflammatory and Immunologic Response, Cellular Aberrations

## 문제

Situation: A 61-year-old woman with type 2 diabetes and hypertension takes losartan 100 mg and spironolactone 25 mg daily and recently began using a salt substitute. She comes to the emergency room with generalized weakness and tingling in her legs. Her serum potassium is 7.0 mEq/L (3.5–5.0 mEq/L) on a non-hemolyzed sample, serum creatinine 1.0 mg/dL (88 µmol/L), capillary blood glucose 142 mg/dL (7.9 mmol/L), and her 12-lead electrocardiogram (ECG) shows tall, peaked T waves. She is on a cardiac monitor.

While the first medication is being prepared, the nurse watches the monitor. Which change would show that her hyperkalemia is progressing?

## 보기

1. Flattened T waves followed by new U waves
2. ST-segment depression with a shorter QT
3. Progressive lengthening of the QT interval
4. Widening QRS complexes as P waves flatten **✔ 정답**

**정답: 4**

## 해설

Hyperkalemia changes the ECG in a typical sequence: peaked T waves, then a prolonged PR interval with flattened or absent P waves, then a wide QRS, a sine-wave pattern, and ventricular fibrillation or asystole. Widening QRS with disappearing P waves means she is moving toward cardiac arrest.

## 심화 해설

Why this patient is at risk

This patient has three simultaneous triggers for hyperkalemia: losartan, spironolactone, and a salt substitute. Losartan blocks the renin–angiotensin–aldosterone system, which reduces renal potassium excretion. Spironolactone is a potassium-sparing diuretic that directly antagonizes aldosterone in the collecting duct. Many salt substitutes replace sodium chloride with potassium chloride, adding a large exogenous potassium load. The result is a serum potassium of 7.0 mEq/L on a non-hemolyzed sample, with classic ECG findings of tall, peaked T waves.

Hyperkalemia does not depolarize all cardiac cells uniformly; it initially speeds repolarization, producing peaked T waves, then progressively slows conduction through the atria, AV node, and ventricles. The ECG changes follow a predictable sequence that mirrors worsening membrane excitability.

ECG progression in hyperkalemia

The earliest and most recognized change is tall, peaked T waves, especially in the precordial leads [1]. As potassium rises further, atrial conduction slows first. The P wave becomes flattened, then disappears entirely, while the PR interval lengthens. This reflects the atria becoming electrically silenced before the ventricles.

After P wave loss, the QRS complex begins to widen. A widening QRS with flattening or absent P waves indicates that the hyperkalemia is now impairing ventricular conduction and is progressing toward a sine-wave pattern, ventricular fibrillation, or asystole. This is the point at which the patient is moving toward cardiac arrest [4].

| ECG finding | Potassium level context | Clinical meaning |
| --- | --- | --- |
| Tall, peaked T waves | Early hyperkalemia, often 5.5–6.5 mEq/L | Accelerated repolarization; earliest warning sign |
| P wave flattening or loss, prolonged PR | Moderate hyperkalemia, often 6.5–7.5 mEq/L | Atrial conduction suppressed; AV conduction slowing |
| Widening QRS complex | Severe hyperkalemia, often >7.0 mEq/L | Ventricular conduction impaired; pre-arrest rhythm |
| Sine-wave pattern | Critical hyperkalemia | Imminent ventricular fibrillation or asystole |

Watch out! A widened QRS in hyperkalemia can be mistaken for a bundle branch block or ventricular tachycardia. The key discriminator is the accompanying loss of P waves and the clinical context of known hyperkalemia.

Key point! The progression from peaked T waves to P wave loss to QRS widening is not a laboratory diagnosis; it is a bedside monitor finding that tells the nurse the patient is deteriorating before repeat labs return.

Why the other options are incorrect

Flattened T waves with new U waves describe hypokalemia, not hyperkalemia. ST-segment depression with a shorter QT interval is not part of the hyperkalemia sequence; hyperkalemia typically shortens the QT interval early, but ST depression is not a defining feature. Progressive lengthening of the QT interval is more characteristic of hypocalcemia or certain drug toxicities, not hyperkalemia. The correct answer is the widening QRS with flattening P waves, because it represents the transition from atrial silencing to ventricular conduction failure [1][4].

Nursing implications at the bedside

While the first medication is being prepared, the nurse must continuously observe the monitor for QRS widening. This is the moment to notify the provider immediately and prepare for more aggressive interventions, because the ECG can reveal dangerous progression long before a repeat serum potassium is available . A patient with a potassium of 7.0 mEq/L and widening QRS complexes is in a peri-arrest state and requires rapid treatment with calcium to stabilize the myocardium, followed by potassium-shifting and potassium-removing therapies.References (research sources)

- [1]Electrocardiographic manifestations of hyperkalemia.Research articleMattu A, Brady WJ, Robinson DA (2000) · DOI: 10.1053/ajem.2000.7344

- [4]Treatment of Hyperkalemia-Induced-Cardiac-Arrest by Dynamic Electrocardiogram and Point-of-Care-testing Potassium: A Case Report.Case reportChen J, Chen J, Dang X, Chen J, Chen Y, Lei Y. (2026) · DOI: 10.1177/11795476261457670

## 임상 시나리오

Hyperkalemia ECG ProgressionMonitor for P-wave loss and QRS widening
The ECG changes of hyperkalemia follow a predictable sequence: peaked T waves first, then PR prolongation with flattened or absent P waves, followed by QRS widening. A potassium of 7.0 mEq/L with widening QRS and disappearing P waves indicates progression toward ventricular fibrillation or asystole.

This patient has three simultaneous potassium-raising factors: losartan, spironolactone, and a salt substitute containing potassium chloride. Renal excretion is blocked while exogenous potassium intake is increased.

CautionDo not wait for all ECG stages to appear. Any progression beyond peaked T waves, especially P-wave flattening or QRS widening, requires immediate treatment while calcium is prepared.

## 핵심 개념

- **Hyperkalemia** — Serum potassium above 5.0 mEq/L; causes progressive cardiac conduction slowing and characteristic ECG changes.
- **Peaked T waves** — Earliest ECG sign of hyperkalemia, best seen in precordial leads.
- **Sine-wave pattern** — Late, pre-arrest ECG morphology in severe hyperkalemia as QRS merges with T wave.
- **Spironolactone** — Potassium-sparing diuretic that antagonizes aldosterone, reducing renal potassium excretion.
- **Salt substitute** — Often contains potassium chloride instead of sodium chloride, adding exogenous potassium load.

## 같은 주제 문제

- [Situation: A 46-year-old man is admitted to the medical ward after 3 days of profuse water…](https://mymerci.kr/pages/nclex_q.php?qn_id=629696)
- [Situation: A 46-year-old man is admitted to the medical ward after 3 days of profuse water…](https://mymerci.kr/pages/nclex_q.php?qn_id=629697)
- [Situation: A 46-year-old man is admitted to the medical ward after 3 days of profuse water…](https://mymerci.kr/pages/nclex_q.php?qn_id=629698)
- [Situation: A 64-year-old man with chronic atrial fibrillation and hypertension takes digox…](https://mymerci.kr/pages/nclex_q.php?qn_id=629699)
- [Situation: A 64-year-old man with chronic atrial fibrillation and hypertension takes digox…](https://mymerci.kr/pages/nclex_q.php?qn_id=629700)
- [Situation: A 64-year-old man with chronic atrial fibrillation and hypertension takes digox…](https://mymerci.kr/pages/nclex_q.php?qn_id=629701)
- [Situation: A 64-year-old man with chronic atrial fibrillation and hypertension takes digox…](https://mymerci.kr/pages/nclex_q.php?qn_id=629702)
- [Situation: A 49-year-old woman who had most of her small bowel removed 6 months ago is adm…](https://mymerci.kr/pages/nclex_q.php?qn_id=629703)

---

More free questions: [기출문제](https://mymerci.kr/)

_학습 참고용입니다. 실제 임상은 최신 지침과 소속 기관 프로토콜을 따르세요._