Maintenance fluids and dehydration assessment

Fluid prescribing begins with the clinical question. A shocked child needs resuscitation; a stable dehydrated child needs deficit replacement; a nil-by-mouth child needs maintenance; a child with a stoma or drain needs additional replacement. Combining these into one unlabelled rate causes under-resuscitation, overload and electrolyte error. Record current weight, clinical fluid status, input, output, losses, medicines, renal and cardiac function and the calculation for each component.

Dehydration is a syndrome, not a skin-turgor percentage. Ask about usual and current feeds, vomiting and diarrhoea frequency, urine or wet nappies, tears, thirst, fever and weight. Observe interaction, respiratory pattern and eyes; inspect mouth; assess pulses, capillary refill, skin temperature and consciousness. A recent accurate pre-illness weight gives the best deficit estimate: percentage loss equals weight lost divided by pre-illness weight × 100. Without it, use a cluster of signs and reassess response.

NICE gastroenteritis guidance groups children as no dehydration, clinical dehydration or shock. Red flags for progression include altered responsiveness, sunken eyes, tachycardia, tachypnoea, reduced skin turgor and reduced urine. Shock includes reduced consciousness, pale or mottled skin, cold extremities, weak pulses, prolonged refill and hypotension. The shock phenotype triggers ABCDE and rapid intravenous or intraosseous access; do not attempt to prove a numerical dehydration percentage first.

Oral rehydration solution exploits sodium-glucose cotransport and replaces water plus electrolytes more safely than juice, fizzy drink or plain water. For clinical dehydration, give low-osmolarity ORS 50 mL/kg over four hours in addition to maintenance, using small frequent volumes. Continue breastfeeding. If drinking is insufficient, use nasogastric administration before defaulting to IV when clinically safe. Persistent vomiting of oral and NG ORS, deterioration or shock are IV indications.

After rehydration, restart full-strength milk and normal food and encourage usual fluids. For children at increased recurrence risk, NICE suggests 5 mL/kg ORS after each large watery stool. Give parents a practical volume and syringe or cup plan and explain red flags. Antidiarrhoeal medicines are not routine treatment in young children, and fruit juice or carbonated drinks can worsen osmotic diarrhoea.

For IV resuscitation, NICE NG29 recommends a glucose-free crystalloid containing 131–154 mmol/L sodium, 10 mL/kg over less than ten minutes. Term neonates may receive 10–20 mL/kg under the neonatal recommendation. Reassess heart rate, pulses, refill, blood pressure, consciousness, urine, breathing, crackles and liver size after each aliquot. A child with persistent shock after fluid needs review of sepsis, haemorrhage, cardiogenic obstruction, adrenal crisis and critical-care support rather than automatic unlimited boluses.

Routine maintenance uses the Holliday–Segar method. A 24 kg child receives 1,000 mL for the first 10 kg, 500 mL for the next 10 and 80 mL for the remaining 4: 1,580 mL/day, about 66 mL/hour. This is an upper starting calculation for a normally hydrated stable child, not a mandatory volume. Fever, ventilation, renal impairment, oedema and high ADH states alter need, while ongoing losses are added separately.

NICE recommends initial routine maintenance with isotonic crystalloid containing 131–154 mmol/L sodium to reduce hospital-acquired hyponatraemia. Glucose need depends on age and intake. Term neonates at least 8 days old generally need isotonic fluid with 5–10% glucose; in the first seven days, sodium and glucose requirements follow postnatal adaptation and specialist judgement. Preterm neonates use neonatal protocols. Potassium is added only after checking concentration, renal function and urine output and following local standard bags.

Non-osmotic ADH secretion occurs with pain, nausea, surgery, lung or brain disease and many acute illnesses. NICE advises considering 50–80% of routine maintenance or insensible losses plus urine output when water retention risk is present. Restriction is a monitored prescription, not neglect: reassess hydration, weight, sodium, glucose, urine and losses. A child with simultaneous deficit or high-output loss needs those components replaced despite restricted baseline maintenance.

Hyponatraemia during IV therapy requires immediate volume and fluid review. Change hypotonic maintenance to isotonic and restrict when hypervolaemic or ADH-driven. Acute neurological symptoms require critical-care advice and NICE hypertonic therapy: 2 mL/kg of 2.7% sodium chloride, maximum 100 mL, over 10–15 minutes, repeat while symptoms persist under the algorithm and monitor sodium at least hourly. Fluid restriction alone is not treatment for hyponatraemic encephalopathy.

Hypernatraemic dehydration is corrected slowly to avoid cerebral oedema. NICE gastroenteritis guidance advises urgent expert input, an isotonic solution for deficit and maintenance, replacement typically over 48 hours and a sodium fall below 0.5 mmol/L/hour. Monitor neurological status, glucose, electrolytes, weight and fluid balance frequently. Do not subtract every hypernatraemic child into the standard four-hour ORS pathway without assessing severity, although ORS remains appropriate in stable clinical dehydration.

Monitor all IV therapy as a medicine. Record fluid type, additives, rate and indication, hourly input and urine or other output, 12-hour balance subtotal and at least 12-hour prescription review under NICE. Weigh when feasible. Check electrolytes and glucose before routine IV therapy except selected elective surgery and at least daily, more often during correction or high losses. Stop IV fluid as soon as adequate enteral intake is established.