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Define Fluid & Electrolyte Therapy in Children. Describe its types and management.

Pediatrics · Final Professional

Introduction

Fluid therapy in a sick child aims to provide the maintenance requirement, replace any existing deficit (dehydration), and cover ongoing (continuing) losses.
Children are more vulnerable to fluid imbalance than adults because of a higher body-water content, larger surface area and higher metabolic/turnover rate.

Body Water Compartments

Total body water is higher in children (~75% in a newborn, ~60% in an adult).
Distributed as intracellular fluid (ICF) and extracellular fluid (ECF = interstitial + plasma).
Infants have a proportionately larger ECF, making them more prone to rapid dehydration.

Maintenance Fluid — Holliday-segar Method

Maintenance replaces normal daily insensible and urinary losses. The Holliday-Segar formula (per 24 hours):

Body weight	Fluid per day
First 10 kg	100 mL/kg
Next 10 kg (10–20 kg)	+ 50 mL/kg
Each kg above 20 kg	+ 20 mL/kg

Hourly ('4-2-1') rule: 4 mL/kg/hr for the first 10 kg + 2 mL/kg/hr for the next 10 kg + 1 mL/kg/hr for each kg above 20 kg. Example: a 25 kg child = 1000 + 500 + 100 = 1600 mL/day.

Ongoing Losses

Replace continuing losses (diarrhoea, vomiting, drains, ileostomy) volume-for-volume with an appropriate fluid (e.g. ORS or Ringer lactate for stool losses).

Types of IV Fluids

Fluid	Use
Ringer lactate	Fluid of choice for resuscitation & dehydration (balanced, has lactate → bicarbonate)
Normal saline (0.9%)	Resuscitation; shock; hyp;natraemia
Isotonic saline + dextrose	Maintenance (reduces hyponatraemia risk)
10% dextrose	Hypoglycaemia (2 mL/kg bolus)

Management of Shock (hypovolaemic)

Rapid bolus of 20 mL/kg of Ringer lactate / normal saline over 15–20 min; repeat up to 40–60 mL/kg while reassessing.
In severe malnutrition, fluids are given more cautiously (risk of heart failure) — smaller volumes with close monitoring.
Add inotropes for fluid-refractory shock; treat the underlying cause (sepsis).

Monitoring

Vitals, capillary refill, urine output (aim > 1 mL/kg/hr), daily weight, and level of consciousness.
Serial electrolytes, blood glucose and acid-base status.
Watch for over-hydration (puffiness, raised JVP, crepitations) and correct sodium disturbances at a safe rate.

Worked Examples

Maintenance — a 16 kg child: (10 × 100) + (6 × 50) = 1300 mL/day (≈ 54 mL/hr).
Deficit — an 8 kg infant with 10% (severe) dehydration: deficit = 10% × 8 kg = 800 mL, replaced with WHO Plan C (Ringer lactate 100 mL/kg = 800 mL as 30 + 70 mL/kg).
Total = maintenance + deficit + ongoing stool losses, reassessed frequently.

Estimating the Deficit

Degree of dehydration	Approx. Fluid deficit
Some dehydration	~5% body weight (50 mL/kg)
Severe dehydration	~10% body weight (100 mL/kg)
(1% dehydration	= 10 mL/kg)

Special Situations

Severe malnutrition — give fluids cautiously (use ReSoMal orally; IV only for shock) because of the risk of heart failure.
Diabetic ketoacidosis — slow, careful rehydration over 48 h to avoid cerebral oedema.
Shock — rapid isotonic boluses (20 mL/kg) take priority over deficit calculations.

Common Errors to Avoid

Using hypotonic maintenance fluids in sick children → hospital-acquired hyponatraemia.
Rapid correction of chronic dysnatraemias; and adding potassium before urine output is established.

Daily Electrolyte & Glucose Requirements

Requirement	Amount
Sodium	2–3 mmol/kg/day
Potassium	1–2 mmol/kg/day (only after urine flows)
Glucose	Enough to prevent ketosis (5% dextrose in maintenance fluid)

Practical Point

In practice, maintenance is written as a specific fluid at a calculated hourly rate — e.g. Isotonic saline with 5% dextrose and added KCl — reassessing the child clinically at least every few hours and adjusting for ongoing losses.

Maintenance: 100/50/20 mL/kg for successive 10 kg bands.

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