Synopsis
Distinguish maintenance, deficit, replacement and resuscitation needs, prioritise oral rehydration, prescribe age-appropriate intravenous fluid and monitor electrolytes and clinical response safely.
- Separate four prescriptions: resuscitation restores circulation, deficit replaces prior loss, maintenance covers normal needs and replacement matches continuing abnormal loss.
- Assess dehydration from appearance, interaction, thirst, mucosa, tears, eyes, pulses, refill, breathing, urine and weight change; no single sign gives a reliable percentage.
- First-line for clinical dehydration from gastroenteritis without shock is low-osmolarity oral rehydration solution, 50 mL/kg deficit over 4 hours plus maintenance, given frequently in small amounts.
- Continue breastfeeding during oral rehydration and consider nasogastric ORS when the child cannot drink enough or vomits persistently.
- Use IV fluid for shock, deterioration despite oral or nasogastric ORS or persistent vomiting of ORS.
- NICE IV resuscitation uses 10 mL/kg glucose-free crystalloid with sodium 131–154 mmol/L over less than 10 minutes, then immediate reassessment.
- Calculate routine daily maintenance by Holliday–Segar: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg and 20 mL/kg for each kg above 20.
- For hourly maintenance, the corresponding 4-2-1 rule gives 4 mL/kg/hour for the first 10 kg, 2 for the next 10 and 1 for each kg above 20.
- Initial routine IV maintenance for children uses isotonic crystalloid with sodium 131–154 mmol/L; add glucose and potassium according to age, results and clinical need.
- Restrict to about 50–80% of calculated maintenance when non-osmotic ADH and water retention are likely, then review clinically and biochemically.
- Check electrolytes and glucose at initiation and at least every 24 hours during routine IV maintenance, more often with instability, abnormal results or high losses.
- Replace ongoing gastric, diarrhoeal, stoma, drain or urinary losses separately with measured or estimated volume and appropriate electrolyte composition.
Key red flags
Reduced consciousness, weak pulses, cold mottled skin, markedly prolonged refill or hypotension indicates shock and invalidates routine oral rehydration alone.
Bilious vomiting, severe abdominal pain or distension, bloody stool, meningism, non-blanching rash or testicular pain suggests a cause other than uncomplicated gastroenteritis.
Hypernatraemia can present with doughy skin, irritability, hypertonia or seizures and requires slow correction with expert advice.
Headache, vomiting, confusion, reduced consciousness, seizure or apnoea during IV fluids may indicate acute hyponatraemic encephalopathy.
Heart disease, renal failure, severe malnutrition, DKA, burns and neonates require condition-specific fluid pathways rather than an unmodified maintenance formula.
Investigation priorities
Distinguish stable dehydration from shock and detect alternative emergencies.
Management branches
A child has dehydration without shock or another IV indication.
- Give low-osmolarity ORS 50 mL/kg over four hours plus maintenance in small frequent amounts and continue breastfeeding.
- Use nasogastric ORS if oral intake is insufficient or vomiting persists but the child remains suitable for enteral therapy.
- Reassess regularly and switch to IV only for shock, deterioration or persistent failure of oral and NG treatment.
A stable child cannot meet normal fluid needs enterally.
- Calculate 100-50-20 mL/kg/day or 4-2-1 mL/kg/hour and separate deficit and ongoing replacement.
- Start an isotonic crystalloid with glucose and potassium selected from age, results and urine; use neonatal guidance where applicable.
- Consider 50–80% maintenance in high-ADH states and review balance, weight, electrolytes, glucose and enteral readiness at least 12-hourly.