# Hypokalaemia and Hyperkalaemia in Children

> Hypokalaemia and hyperkalaemia in children for NEET-PG Paediatrics, covering ECG changes, causes and emergency treatment of potassium disorders.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/hypokalaemia-and-hyperkalaemia-in-children
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Nelson Textbook of Pediatrics; IAP Textbook of Pediatrics; Harriet Lane Handbook
- How to cite: "Hypokalaemia and Hyperkalaemia in Children", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/hypokalaemia-and-hyperkalaemia-in-children

## Direct answer

Hypokalaemia and hyperkalaemia are potassium disorders, defined as serum potassium below about 3.5 and above about 5.5 mmol/L, that act mainly by disturbing cardiac conduction. Hypokalaemia shows flattened T waves, prominent U waves and ST depression, while hyperkalaemia shows tall peaked T waves, a widened QRS and, at extremes, a sine-wave pattern before asystole. Hyperkalaemia with ECG changes is an emergency, treated first with intravenous calcium to stabilise the myocardium.

## What you must remember

- **Hypokalaemia ECG:** flattened T waves, prominent U waves, ST depression and a prolonged QT interval.
- **Hyperkalaemia ECG:** tall peaked T waves first, then PR prolongation, flattened P waves and a widened QRS, with a sine-wave pattern at extremes.
- **Hypokalaemia causes:** vomiting, diarrhoea, diuretics, renal tubular acidosis type 1, Bartter and Gitelman syndromes and hyperaldosteronism.
- **Hyperkalaemia causes:** acute and chronic kidney disease, renal tubular acidosis type 4, acidosis, adrenal insufficiency, tumour lysis and haemolysis.
- **Pseudohyperkalaemia:** falsely high values from a haemolysed sample, or from very high platelet or white cell counts releasing potassium in vitro.
- **Calcium gluconate:** first-line intravenous membrane stabiliser for hyperkalaemia with ECG changes, acting within minutes.
- **Insulin with glucose and salbutamol:** shift potassium into cells temporarily, without removing it from the body.

## A pathway for an abnormal potassium

Potassium disorders are managed by checking the sample, reading the ECG and then choosing between urgent stabilisation and slower correction. The steps below follow that order, so the most dangerous findings are treated first.

1. **Confirm the value:** repeat a sample that looks haemolysed or comes with very high cell counts, since both can falsely raise potassium.
2. **Read the ECG:** look for T wave, QRS and rhythm changes, because these set how urgent the treatment is.
3. **Stabilise the heart:** give intravenous calcium gluconate for hyperkalaemia with ECG changes, which protects the myocardium but does not lower potassium.
4. **Shift potassium into cells:** give insulin with glucose, with nebulised salbutamol as an adjunct, to lower serum potassium temporarily.
5. **Remove potassium:** treat the cause, stop potassium-raising drugs and use dialysis for renal failure or refractory cases.
6. **Replace in hypokalaemia:** give oral potassium where possible, and intravenous potassium slowly under cardiac monitoring when the deficit is severe.

The protective effect of calcium lasts only minutes, so the potassium-lowering measures must follow promptly.

## Where the exam tries to catch you

Potassium questions usually test ECG recognition and treatment order. Each trap below swaps a finding or a drug with its opposite.

- **Trap:** giving insulin before calcium for hyperkalaemia with ECG changes. — **Correct:** calcium is given first because it stabilises the myocardium immediately, while insulin and glucose act more slowly.
- **Trap:** reading ST depression and U waves as hyperkalaemia. — **Correct:** ST depression and prominent U waves belong to hypokalaemia, whereas hyperkalaemia gives tall peaked T waves and a widened QRS.
- **Trap:** treating a potassium of 6.8 mmol/L from a haemolysed sample without repeating it. — **Correct:** haemolysis causes pseudohyperkalaemia, so the sample should be repeated unless there are definite ECG changes.

## Frequently asked questions

### Which ECG changes suggest hypokalaemia?

Hypokalaemia produces flattened T waves, prominent U waves, ST depression and a prolonged QT interval. These changes reflect delayed repolarisation of the myocardium. Severe hypokalaemia can also cause arrhythmias, so the ECG should always be read alongside the serum value.

### Which ECG finding is the earliest sign of hyperkalaemia?

Tall, peaked, narrow-based T waves are the earliest ECG sign of hyperkalaemia. The PR interval then lengthens, the P wave flattens and the QRS widens. Very high levels produce a sine-wave pattern before asystole.

### What is the first-line treatment for hyperkalaemia with ECG changes?

Intravenous calcium gluconate is the first-line treatment, because it stabilises the myocardial membrane within minutes. Calcium does not lower serum potassium, so insulin with glucose and other measures follow. Doses should be guided by the paediatric protocol and the ECG.

### What causes hyperkalaemia in children with kidney disease?

Acute kidney injury and chronic kidney disease reduce potassium excretion, so serum potassium rises. Renal tubular acidosis type 4 and adrenal insufficiency also raise potassium. Potassium-sparing diuretics and ACE inhibitors add to the risk in children with impaired kidneys.

### How does pseudohyperkalaemia occur and how is it recognised?

Pseudohyperkalaemia occurs when potassium leaks out of cells in the sample, through haemolysis, or when very high platelet or white cell counts release potassium in vitro. It is suspected when the ECG is normal and the sample is haemolysed or the cell count is raised. Repeating the test on a fresh sample confirms the true value.