# Fluid and Electrolyte Therapy in Children

> Fluid and electrolyte therapy in children for NEET-PG Paediatrics, covering Holliday-Segar maintenance, deficit replacement and the choice of isotonic fluids.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/fluid-and-electrolyte-therapy-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; WHO guidelines on the clinical management of diarrhoea
- How to cite: "Fluid and Electrolyte Therapy in Children", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/fluid-and-electrolyte-therapy-in-children

## Direct answer

Fluid and electrolyte therapy in children replaces losses and meets daily needs with the right volume, composition and rate. The Holliday-Segar method sets maintenance at 100 mL/kg per day for the first 10 kg, 50 mL/kg for the next 10 kg and 20 mL/kg beyond 20 kg. Current practice favours isotonic solutions over hypotonic ones, and the deficit is replaced over a defined period.

## What you must remember

- **Holliday-Segar maintenance:** 100 mL/kg per day for the first 10 kg, 50 mL/kg for the next 10 kg and 20 mL/kg for each kilogram above 20.
- **The 4-2-1 rule:** hourly maintenance of 4, 2 and 1 mL/kg for the same three weight bands.
- **Dehydration grades:** mild below 5 percent, moderate at 5 to 10 percent and severe above 10 percent of body weight.
- **Deficit:** percentage dehydration multiplied by body weight, usually replaced over about 24 hours in gastroenteritis.
- **Shock bolus:** 10 to 20 mL/kg of isotonic crystalloid, reassessed after each bolus.
- **Oral rehydration:** WHO low-osmolarity solution contains 75 mmol/L of sodium, the first-line treatment for mild to moderate dehydration.
- **Potassium:** added to intravenous fluid only once the child has passed urine and renal function is adequate.

## A stepwise plan for a dehydrated child

A fluid plan is built from the bottom up, starting with the clinical state and ending with the rate. The steps below follow the order a paediatric team uses so that shock is treated first and the deficit and maintenance are then planned together.

1. **Assess the deficit:** use sunken eyes, skin turgor, mucous membranes, capillary refill and urine output to grade dehydration as mild, moderate or severe.
2. **Treat shock first:** give an isotonic bolus of 10 to 20 mL/kg to a child in shock, and reassess perfusion, heart rate and blood pressure after each bolus.
3. **Calculate the deficit:** multiply the estimated percentage dehydration by body weight, so a 10 kg child with 5 percent dehydration has a deficit of 500 mL.
4. **Add maintenance:** calculate daily maintenance by the Holliday-Segar rule, so that a 10 kg child needs about 1000 mL per day.
5. **Choose the fluid:** use an isotonic solution such as Ringer lactate or normal saline with dextrose, and avoid hypotonic solutions in sick children.
6. **Reassess and adjust:** check weight, urine output, electrolytes and clinical state at intervals, and change the rate accordingly.

Matching the rate to the child's response is the step most often forgotten in a fluid plan.

## Where the exam tries to catch you

Fluid questions usually hinge on the composition of the fluid or the timing of potassium. Each trap below mixes a correct principle with the wrong clinical moment.

- **Trap:** replacing the full deficit in one rapid bolus for a child with mild dehydration. — **Correct:** mild dehydration is usually treated with oral rehydration, and deficits in intravenous therapy are replaced over about 24 hours to avoid fluid overload.
- **Trap:** choosing half-normal saline as maintenance in a febrile child with diarrhoea. — **Correct:** sick children may retain water through raised antidiuretic hormone, so hypotonic fluids raise the risk of hyponatraemia and isotonic fluids are preferred.
- **Trap:** adding potassium before urine output is confirmed. — **Correct:** potassium is withheld until the child passes urine, to avoid hyperkalaemia in a child whose kidneys may be impaired.

## Frequently asked questions

### How is maintenance fluid calculated by the Holliday-Segar method?

The Holliday-Segar method gives daily maintenance of 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg and 20 mL/kg for each kilogram above 20. Hourly rates follow the 4-2-1 rule, using 4, 2 and 1 mL/kg per hour for the same weight bands. The method is applied to weight, not age.

### Why are isotonic fluids preferred over hypotonic fluids in sick children?

Sick children have raised antidiuretic hormone levels, so they retain water when given hypotonic fluids. This causes hyponatraemia and can lead to cerebral oedema. Isotonic fluids such as normal saline or Ringer lactate avoid this risk.

### How is the fluid deficit calculated in a dehydrated child?

The fluid deficit equals the estimated percentage of dehydration multiplied by body weight in kilograms. A 10 kg child with 5 percent dehydration has a deficit of 500 mL. In most gastroenteritis the deficit is replaced over about 24 hours, with maintenance added on top.

### When is potassium added to maintenance intravenous fluid in children?

Potassium is added to maintenance fluid only after the child has passed urine and renal function is adequate. A common concentration in maintenance fluid is 20 mEq/L. Adding potassium too early risks hyperkalaemia, particularly in children with acute kidney injury.

### What is the composition of WHO low-osmolarity oral rehydration solution?

WHO low-osmolarity oral rehydration solution contains 75 mmol/L of sodium and has an osmolarity of about 245 mOsm/L. It is used for mild to moderate dehydration from diarrhoea. Its lower osmolarity reduces stool output compared with older formulations.