Dehydration and paediatric fluid therapy

• Dehydration is the lack of enough water in the body; in children it is usually caused by diarrhoea and vomiting, and it is a leading cause of death in young children worldwide.
• Most children with mild to moderate dehydration can be rehydrated with oral rehydration salt (ORS) solution given a little at a time; WHO and the American Academy of Pediatrics recommend oral rehydration therapy for mild to moderate dehydration.
• Shock from dehydration is treated with rapid intravenous (IV) boluses of an isotonic crystalloid; the exact bolus size differs between guideline sets, so follow your local protocol.
• IV fluid needs are calculated from body weight (Holliday-Segar for maintenance; sodium in the isotonic range, never as a rapid hypotonic bolus).
• Hypernatraemic dehydration must be corrected slowly over about 48 hours; hyponatraemic dehydration and acute symptomatic hyponatraemia have their own, faster saline strategies.
• Every child with dehydration must be checked for the red flags that signal shock, and re-checked repeatedly during treatment.

By the end of this page you should be able to:

1. Recognise dehydration clinically and distinguish mild, moderate and severe disease, including the red flags of shock.
2. Assess the child's risk of dehydration and classify the sodium type (isotonic, hyponatraemic, hypernatraemic).
3. Plan oral rehydration therapy (ORS composition, volume and frequency) and know when it must be replaced by IV therapy.
4. Calculate a fluid resuscitation bolus, a fluid deficit replacement and routine IV maintenance rates for children and neonates.
5. Describe how to correct hyponatraemic and hypernatraemic dehydration safely, including speed limits for plasma sodium.
6. Recognise and manage the complications of fluid therapy (hyponatraemia, hypernatraemia, fluid overload, osmotic demyelination).

A child becomes dehydrated when the body loses more water (and usually salt) than it takes in. Water makes up a larger share of body weight in infants (about 65 to 80 per cent) than in adults, and infants cannot ask for a drink or fetch one themselves.^[3] That is why diarrhoea and vomiting drain a child quickly, and why dehydration remains one of the leading causes of death in children under 5 years worldwide.^[3][4] In infants and toddlers, diarrhoea and dehydration together account for between 14 and 30 per cent of deaths.^[3]

Dehydration is not the same as hypovolaemia. Dehydration is a loss of total body water, which mainly affects the water compartments inside and around cells; hypovolaemia is a reduction in the circulating blood volume.^[4] The two usually happen together, and standard clinical practice treats the terms as overlapping, because most children with dehydration from diarrhoea have both salt and water losses.

Almost every child with dehydration can be rehydrated safely and cheaply if the condition is recognised early and treated with the right fluid in the right amount at the right speed.^[5] The substance of this topic therefore is judgement: how to recognise severity, how to choose the route (mouth, nasogastric tube or vein) and how to set the rate without causing the brain and salt problems that rapid or careless treatment can create.

Before managing the deficit it helps to know the normal state, because the fluid deficit is calculated as a percentage of that normal.

• Total body water is higher in infants (about 65 to 80 per cent of body weight) and falls towards the adult value (about 60 per cent) through childhood.^[3]
• Insensible losses are higher in infants, because the ratio of body surface area to weight is larger, so a child can become dehydrated faster than an adult with the same diarrhoea severity.^[3]
• Fluid needs scale with weight, not with age alone; this is why every calculation in this page starts with the child's weight in kilograms.
• Renal concentrating ability in infants is immature, so young children handle sodium and water loads less efficiently than older children and adults.
• Magnesium and calcium are not routinely added to maintenance fluids; the principle is to monitor plasma electrolytes and base the next prescription on them.

The serum (plasma) sodium concentration tells you which body compartment has lost the most water, and it guides the fluid chosen for correction.

• Isotonic (isonatraemic) dehydration: salt and water have been lost in roughly equal amounts. Plasma sodium is between 130 and 150 mEq/L.^[3] This is the commonest type in gastroenteritis.
• Hyponatraemic dehydration: more salt than water has been lost. Plasma sodium is below 130 mEq/L. It can cause seizures and is commonly due to over-secretion of the hormone that prevents urination (antidiuretic hormone).^[3]
• Hypernatraemic dehydration: more water than salt has been lost. Plasma sodium is above 150 mEq/L. It can occur with severe viral gastroenteritis, some metabolic or renal conditions, or when rehydration solutions have been mixed too concentrated.^[3] Hypernatraemic dehydration shrinks brain cells less visibly and is harder to judge clinically. ^[4]

Severity is usually expressed as the percentage of body weight lost. Clinical dehydration can therefore be grouped as follows: mild (3 to 5 per cent of body weight), moderate (6 to 10 per cent), and severe (more than 10 per cent).^[3] These are estimates, because a child needs a reliable recent pre-illness weight, and clinical assessment without one is always approximate.

An infant is more seriously affected than a larger child at the same percentage, because the infant carries more body water and loses it faster.

Children in the following situations are most likely to become dehydrated, and risk should be checked before every decision.^[1]

• Children younger than 1 year, particularly those younger than 6 months. ^[1]
• Infants who were of low birth weight. ^[1]
• Children who have passed more than five diarrhoeal stools in the previous 24 hours. ^[1]
• Children who have vomited more than twice in the previous 24 hours.
• Children who have not been offered, or have not been able to tolerate, supplementary fluids before presentation.
• Infants who have stopped breastfeeding during the illness.
• Children with signs of malnutrition.
• Term neonates and young infants, who handle sodium and water less well.
• Children with metabolic or renal conditions that prevent normal concentration or dilution of urine.

Assessment is clinical first; blood tests refine rather than make the diagnosis. NICE warns not to perform blood biochemical testing routinely in children with gastroenteritis.^[1] Blood sodium and potassium, together with urea, creatinine and glucose, should be measured when IV therapy is required, when there are symptoms or signs that suggest hypernatraemia, or when shock is suspected.^[1][2] Venous blood acid-base status and chloride should be measured when shock is suspected or confirmed, because metabolic acidosis is common and guides both the speed and the composition of correction.^[1]

Ask directly about fluid losses and intake, not just whether a child looks unwell. Establish the number and character of diarrhoeal stools and vomits in the last 24 hours, the volume of fluid taken, whether breastfeeding or normal feeds have continued, and how much urine has been produced.^[1] Ask about recent contact with someone with acute diarrhoea or vomiting, exposure to contaminated water or food, and recent travel abroad.^[1] The duration of symptoms matters: diarrhoea usually lasts 5 to 7 days and stops within 2 weeks, and vomiting usually lasts 1 to 2 days and stops within 3 days; symptoms that run longer should prompt a look for another diagnosis.^[1]

Ask about the symptoms that suggest dehydration to a carer: appearing more unwell, becoming irritable or lethargic, passing less urine, pallor or a mottled colour, and cold hands or feet.^[1] These are also the symptoms of deterioration.

Examine circulation first. Heart rate, peripheral pulse volume and warmth, capillary refill time, skin colour and blood pressure together tell you whether the child is in shock. Then examine for dehydration itself: eyes, fontanelle, mucous membranes, skin turgor, urine output, mental state and weight if available. The suckling and crying child gives you clues: tearing, wet diapers, interest in playing. Weigh the child and record the same scale each day, because a 24-hour change in weight is one of the more objective measures of fluid balance.

The distinction that matters most is clinical dehydration (compensated) versus hypovolaemic shock (decompensated). Shock means altered consciousness, tachycardia, prolonged capillary refill, weak peripheral pulses, cold or mottled peripheries, and hypotension. Hypotension is a late sign in children; do not wait for it before treating. A child can be critically volume-depleted while still maintaining blood pressure.

Suspect hypernatraemic dehydration if you see any of jittery movements, increased muscle tone, hyperreflexia (over-active reflexes), convulsions, drowsiness or coma.^[1] These are particularly dangerous in children under 6 months, because body sodium is harder to judge from skin signs alone.

• Bicarbonate below 17 mEq/L suggests moderate to severe dehydration.^[3]
• Blood urea nitrogen (BUN) raised relative to creatinine suggests more severe dehydration, though it is also affected by diet and gastrointestinal bleeding.^[3]
• Specific urine gravity above 1.015 and urinary ketones may support dehydration.^[3]
• Serum sodium below 130 mEq/L is hyponatraemic dehydration; between 130 and 150 mEq/L is isotonic; above 150 mEq/L is hypernatraemic.^[3]
• Serum potassium is commonly low from diarrhoea losses; persistent metabolic acidosis can mask potassium changes and produce a falsely normal or high value. Correction of acidosis and rehydration can then reveal hypokalaemia.
• Infection testing is not routine; stool microbiology is considered with recent travel, failure to improve by day 7, diagnostic uncertainty, blood or mucus in stool, immunocompromise, or suspected septicaemia.^[1]

No proven tool yet determines the degree of dehydration in paediatric patients beyond clinical assessment plus these basic laboratories.^[3]

Dehydration is usually a sign of an acute diarrhoeal illness, but it is not a diagnosis on its own. The same clinical picture of dry mucous membranes, tachycardia and poor intake can arise from diabetic ketoacidosis, adrenal insufficiency, nephrogenic diabetes insipidus, sepsis, meningitis, intestinal obstruction and severe respiratory distress, among others. Red-flag features that should make you think of an alternative diagnosis rather than straightforward gastroenteritis include fever of 39 degrees C or higher in a child aged 3 months or older (or 38 degrees C or higher under 3 months), shortness of breath, altered consciousness, neck stiffness, a bulging fontanelle, non-blanching rash, blood or mucus in stool, bilious (green) vomit, severe or localised abdominal pain, and abdominal distension with rebound tenderness.^[1] Bilious vomiting or abdominal peritonism must be treated as a surgical emergency, not as gastroenteritis.

The plan for any dehydrated child is the same seven steps: assess, resuscitate if shocked, rehydrate, monitor, correct losses, restore feeding, and reassure and hand back with safety netting.

Oral rehydration therapy (ORT) is the administration of a structured glucose-electrolyte solution to replace water and electrolytes lost in stool and vomit. It was introduced in the 1960s and is still the gold standard for fluid loss from acute diarrhoea in children with mild to moderate dehydration.^[4] ORT reduces deaths, hospitalisation and complications, and it is cheap, safe and easy to give at home.^[5]

Glucose and sodium are absorbed together in the small intestine, even when diarrhoea is copious, and water follows them. That single mechanism is why a drink that contains both works when plain water and salt water do not.

WHO and UNICEF now recommend a single low-osmolarity ORS formulation with an osmolarity of 245 mOsm/L rather than the older standard WHO ORS of about 310 mOsm/L; the lower osmolarity was shown to reduce stool output by about 20 per cent, vomiting by about 30 per cent, and the need for unscheduled IV therapy by about 33 per cent.^[4][5] The composition per litre is 75 mmol/L sodium, 65 mmol/L chloride, 20 mmol/L potassium, 10 mmol/L citrate and 75 mmol/L glucose (13.5 g/L), made up from sodium chloride 2.6 g, glucose (anhydrous) 13.5 g, potassium chloride 1.5 g and trisodium citrate dihydrate 2.9 g.^[4]

NICE CG84 specifies a low-osmolarity ORS in the range 240 to 250 mOsm/L for oral rehydration therapy.^[1]

• Gastroenteritis with no clinical dehydration: continue breastfeeding and milk feeds, encourage fluids, discourage fruit juices and carbonated drinks, and offer ORS as a supplemental fluid to children at increased risk of dehydration.^[1]
• Mild to moderate dehydration (clinical dehydration without shock): rehydrate with ORS, 50 ml/kg for fluid deficit replacement over 4 hours as well as maintenance, given frequently in small amounts (NICE).^[1][4]
• Children who refuse sufficient ORS and have no red-flag symptoms or signs: consider supplementation with their usual fluids, including milk feeds or water, but not fruit juices or carbonated drinks.^[1]
• Children unable to drink or who vomit persistently: give ORS via a nasogastric tube.^[1]
• Rehydration for hypernatraemic dehydration as well, unless IV therapy is specifically indicated.^[1] ORS rehydrates children including those with hypernatraemia.

After rehydration, restart usual solid food (full-strength milk from the start) and avoid fruit juices and carbonated drinks until the diarrhoea stops.^[1] In children at increased risk of dehydration recurring, consider giving 5 ml/kg ORS after each large watery stool.^[1]

• Altered mental state, abdominal ileus, malabsorption, persistent vomiting that prevents retention, or severe dehydration or shock.^[3][4]
• Clinical shock at any point: children with shock need rapid IV fluid, not oral fluid.
• Suspected or confirmed shock, deterioration despite ORT, or persistent vomiting of ORS given orally or by nasogastric tube all move the child to IV fluid therapy.^[1]

Most children with gastroenteritis can be managed at home with advice.^[1] Parents and carers should be told how to recognise developing dehydration (becoming more unwell, changing responsiveness, decreased urine output, pale or mottled skin, cold extremities), how to give 50 ml/kg ORS over a 4-hour period in small frequent amounts together with continued breastfeeding, not to give solid foods during rehydration, and when to seek help if the child refuses ORS or vomits persistently.^[1] After rehydration, children should drink their usual fluids and reintroduce their usual diet, with 5 ml/kg ORS after each large watery stool if they are at increased risk of dehydration recurring.^[1]

Shock in a dehydrated child is recognised clinically (see the table above): decreased level of consciousness, tachycardia, tachypnoea, weak peripheral pulses, prolonged capillary refill, cold or mottled extremities and, in the late stage, low blood pressure. Emergency transfer to secondary care is arranged for any child with features of shock during remote or face-to-face assessment.^[1]

IV crystalloid is the treatment. NICE CG84 recommends a rapid IV infusion of 10 ml/kg of 0.9% sodium chloride solution for suspected or confirmed shock, repeated once if the child is still shocked after the first infusion; children who remain shocked after two boluses should be referred to a paediatric intensive care specialist and have other causes of shock considered.^[1]

NICE NG29 sets the wider age-based bolus dose: glucose-free crystalloids containing sodium in the range 131 to 154 mmol/L, with a bolus of 10 ml/kg over less than 10 minutes for children and young people, and 10 to 20 ml/kg over less than 10 minutes for term neonates.^[2] The same guideline advises expert (paediatric intensive care) advice if 40 to 60 ml/kg or more is needed as part of the initial resuscitation.^[2]

A review of paediatric fluid management in the literature also uses 20 ml/kg isotonic saline for severe dehydration in its algorithms.^[4] The difference between 10 and 20 ml/kg is an honest place where guidelines disagree; local protocol and the child's condition decide, and every further bolus must be followed by reassessment of consciousness, pulse volume, skin perfusion and blood pressure.

Term neonates need individual judgement, and neonates in the first days of life need sodium and glucose tailored carefully (lower sodium tolerance, higher glucose requirements in the first week).

Once shock has resolved, start rehydration with IV fluid therapy.^[1] Correct the metabolic acidosis that usually accompanies dehydration by restoring perfusion and giving the fluid that follows the algorithm, rather than by blind bicarbonate boluses. Cardiac failure can mimic or follow volume depletion, so reassess mentation, perfusion and breathing after every intervention.

When IV therapy is needed for rehydration and the child was not hypernatraemic at presentation:

• Use an isotonic solution such as 0.9% sodium chloride, or 0.9% sodium chloride with 5% glucose, for both fluid deficit replacement and maintenance.^[1]
• For children who required initial rapid IV boluses for shock, add 100 ml/kg for fluid deficit replacement to maintenance fluid requirements, and monitor the clinical response.^[1]
• For children who were not shocked at presentation, add 50 ml/kg for fluid deficit replacement to maintenance fluid requirements, and monitor the clinical response.^[1]
• Measure plasma sodium, potassium, urea, creatinine and glucose at the outset, monitor regularly, and alter fluid composition or rate if necessary.^[1]
• Consider IV potassium supplementation once the plasma potassium level is known; do not give potassium before it has been measured.

When IV therapy is needed in a child presenting with hypernatraemic dehydration, obtain urgent expert advice, use an isotonic solution for deficit replacement and maintenance, replace the deficit slowly (typically over 48 hours) and monitor plasma sodium frequently, aiming to reduce it at less than 0.5 mmol/L per hour.^[1]

For routine IV maintenance in children, NICE NG29 uses the Holliday-Segar formula: 100 ml/kg/day for the first 10 kg of weight, 50 ml/kg/day for the next 10 kg, and 20 ml/kg/day for weight over 20 kg; males rarely need more than 2,500 ml and females rarely more than 2,000 ml over 24 hours.^[2]

Term neonates need age-based maintenance in the first month:

• From birth to day 1: 50 to 60 ml/kg/day. ^[2]
• Day 2: 70 to 80 ml/kg/day. ^[2]
• Day 3: 80 to 100 ml/kg/day. ^[2]
• Day 4: 100 to 120 ml/kg/day. ^[2]
• Days 5 to 28: 120 to 150 ml/kg/day.^[2]

Mistaken use of hypotonic fluids for maintenance (for example 0.45% sodium chloride or 5% glucose as the sole maintenance fluid) is a recognised cause of iatrogenic hyponatraemia. NICE therefore recommends that initial routine maintenance in children uses isotonic crystalloids containing sodium in the range 131 to 154 mmol/L.^[2] When fluid is for replacement or redistribution, use 0.9% sodium chloride containing potassium to replace ongoing losses.^[2]

Fluids should be glucose-free for resuscitation, but maintenance for term neonates aged 8 days or more may contain 5 to 10 per cent glucose alongside sodium in the range 131 to 154 mmol/L.^[2] In the first days of life, sodium may not be needed and the glucose concentration may need to be higher; this is a decision for a senior. Term neonates in critical postnatal adaptation (for example, respiratory distress syndrome, meconium aspiration, hypoxic ischaemic encephalopathy) should receive no or minimal sodium until postnatal diuresis with weight loss occurs.^[2]

If there is a risk of water retention from non-osmotic antidiuretic hormone secretion (as in sepsis, pneumonia, meningitis or major surgery), restrict maintenance to 50 to 80 per cent of routine needs, or calculate insensible losses of 300 to 400 ml/m2/24 hours plus urinary output.^[2]

Assess and record fluid input, output and balance at least 12 hourly, reassess the prescription, hydration status and whether oral fluids can start every 12 hours, and check plasma electrolytes every 24 hours or more often if deranged.^[2] Term neonates and children on IV fluids need blood glucose at least daily too.^[2]

Attempt early and gradual introduction of oral rehydration during IV therapy; once tolerated, stop IV fluids and complete rehydration by mouth.^[1]

A child presenting with clinical dehydration and a plasma sodium below 130 mEq/L has hyponatraemic dehydration. Common causes include diarrhoea with greater salt than water loss, excessive free water intake, or syndrome of inappropriate antidiuretic hormone secretion from underlying disease. Warning features include nausea, vomiting, lethargy and, at lower levels, seizures. Hyponatraemic dehydration can cause seizures more readily than isotonic dehydration.

General rehydration principles apply: restore volume first, correct sodium slowly. Because this page covers correction that develops during IV therapy in most detail (below), the chronic form is managed by ensuring perfusion, using an isotonic fluid containing sodium in the isotonic range for deficit and maintenance, and not allowing the plasma sodium to rise by more than 12 mmol/L in any 24-hour period.^[2] Recheck plasma sodium frequently and adjust the prescription to the result.

Acute symptomatic hyponatraemia during treatment (headache, nausea, confusion, irritability, lethargy, reduced consciousness, convulsions, coma, apnoea) is a medical emergency.^[2] NICE NG29 recommends, after reviewing fluid status and seeking immediate expert advice:

• A bolus of 2 ml/kg (maximum 100 ml) of 2.7% sodium chloride over 10 to 15 minutes. ^[2]
• A further bolus of 2 ml/kg (maximum 100 ml) over the next 10 to 15 minutes if symptoms persist.
• A third bolus of 2 ml/kg (maximum 100 ml) over 10 to 15 minutes if symptoms still remain, after checking the plasma sodium.
• Hourly (or more frequent) plasma sodium measurement, with decreasing frequency as symptoms resolve.
• Fluid restriction alone is not enough for acute symptomatic hyponatraemic encephalopathy.
• Once symptoms have resolved, the plasma sodium should not rise by more than 12 mmol/L in 24 hours.^[2]

The rapid 3% saline boluses are a bridge to stop seizures and cerebral oedema; they do not correct the total body deficit. They are given under senior supervision, usually in a high-dependency setting.

Avoid the problem by using isotonic maintenance fluids rather than hypotonic ones.^[2] For children who are hypervolaemic or at risk of increased ADH secretion, restrict maintenance to 50 to 80 per cent of routine needs or calculate insensible losses of 300 to 400 ml/m2/24 hours plus urinary output.^[2] Asymptomatic hyponatraemia is managed by switching to an isotonic fluid and reviewing fluid status rather than by ignoring it.^[2]

Hypernatraemic dehydration (plasma sodium above 150 mEq/L) reflects water loss greater than salt loss.^[3] It is harder to assess clinically, because skin signs are misleadingly preserved, and it carries a higher risk of brain injury (osmotic demyelination or cerebral oedema) if corrected too quickly.

Suspect it from the history of poor free water intake, hypertonic feeds, or gastroenteritis with disproportionate water loss, and confirm with a blood sodium above 150 mEq/L. Measure plasma sodium, potassium, urea, creatinine and glucose before starting IV therapy, and ask for urgent expert advice on fluid management.^[1]

• Use an isotonic solution such as 0.9% sodium chloride, or 0.9% sodium chloride with 5% glucose, for fluid deficit replacement and maintenance.^[1]
• Replace the fluid deficit (slowly) over 48 hours.^[1]
• Monitor plasma sodium frequently, aiming to reduce it at less than 0.5 mmol/L per hour.^[1]
• ORS (including for children with hypernatraemia) is appropriate once shock is excluded, provided the child can drink; it is rehydrating as effectively as IV therapy in most.^[1]

If hypernatraemia develops while a child is on IV fluids:

• Review fluid status. If there is no dehydration and an isotonic fluid is in use, consider moving to a hypotonic fluid such as 0.45% sodium chloride with glucose.
• If dehydration is diagnosed, calculate the water deficit and replace it over 48 hours, initially with 0.9% sodium chloride.
• If fluid status is uncertain, measure urine sodium and osmolality.
• If hypernatraemia worsens or is unchanged, review fluid type and consider changing to a hypotonic solution.^[2]
• Measure plasma electrolytes every 4 to 6 hours for the first 24 hours and then as guided by response. ^[2]
• Correct at no more than 12 mmol/L fall in plasma sodium in 24 hours.^[2]

Speed of correction is the critical neurological safeguard. Correcting hypernatraemia too quickly can cause brain swelling and seizures. Osmotic demyelination (central pontine myelinolysis) is described with too-rapid correction of hyponatraemia and with other electrolyte shifts, not with hypernatraemic dehydration itself.^[3]

Dehydration causes the majority of diarrhoeal deaths, and most of these deaths are preventable with simple fluid administration.^[5] In settings where clean water, sodium and glucose are available, ORS is cheap and effective; where commercial ORS is too costly, teach the making of the salt-sugar solution only with accurate measuring spoons and clean water.

• Vaccinate against rotavirus, measles and cholera where available; encourage exclusive breastfeeding for the first 6 months and continued breastfeeding up to 2 years.^[3]
• Safe water, sanitation and hand-washing with soap are the fundamental preventions.

Electrolyte imbalances (hyponatraemia or hypernatraemia), neurological problems (confusion, seizures, coma), acute kidney injury, hypovolaemic shock, metabolic acidosis, heart rhythm problems, and death can all follow severe dehydration.^[3] Risks of treatment include electrolyte imbalance from a wrongly mixed ORS, brain swelling from too-rapid correction of hypernatraemia, osmotic demyelination, heart failure and pulmonary oedema from too-rapid IV infusion, and the usual risks of an IV cannula (vein inflammation, leakage, bruising and catheter-related infection).^[3] Hypernatraemic dehydration corrected too quickly is especially dangerous.

• Dehydration in children is loss of total body water, usually from diarrhoea and vomiting, and it is a leading cause of childhood death; infants carry more body water and lose it faster.
• Clinical severity maps roughly to weight loss: mild 3 to 5 per cent, moderate 6 to 10 per cent, severe more than 10 per cent body weight.
• Classification by plasma sodium: isotonic 130 to 150 mEq/L, hyponatraemic below 130 mEq/L, hypernatraemic above 150 mEq/L.
• Signs of shock are decreased consciousness, tachycardia, weak pulses, prolonged capillary refill, cold mottled skin and late hypotension; do not wait for hypotension.
• NICE shock treatment is 10 ml/kg of 0.9% sodium chloride, repeated once; some texts use 20 ml/kg isotonic saline for severe dehydration. Expert help if 40 to 60 ml/kg is needed.
• ORS (WHO low-osmolarity, 245 mOsm/L; NICE 240 to 250 mOsm/L) in 50 ml/kg over 4 hours plus maintenance treats mild to moderate dehydration.
• IV deficit replacement adds 50 ml/kg (or 100 ml/kg after shock) to maintenance requirements, with isotonic crystalloids (sodium 131 to 154 mmol/L).
• Maintenance rates follow Holliday-Segar, and neonatal rates are age-based for the first month.
• Hyponatraemic dehydration and acute symptomatic hyponatraemia are treated with 2.7% saline boluses of 2 ml/kg (max 100 ml) and careful rate limits; fluid restriction alone is not enough for symptomatic hyponatraemic encephalopathy. ^[2]
• Hypernatraemic dehydration is corrected slowly over 48 hours at no more than 0.5 mmol/L per hour, with an overall fall no more than 12 mmol/L in 24 hours.
• Always avoid hypotonic maintenance fluids; monitor plasma electrolytes, glucose, and fluid balance.
• Feeding (breastfeeding, usual diet) continues or restarts as soon as rehydration allows.

Plain references only: hyponatraemia (electrolyte topic), hypernatraemia, acute kidney injury, sepsis, diarrhoea and gastroenteritis, breastfeeding and neonatal care, and the drug topics on fluid management. These sibling slugs should be linked once they are published in the registry.