Paeds · nephrology-urology-fluids-and-electrolytes
Hyponatraemia and hypernatraemia
Also known as Hyponatraemia · Hypernatraemia · Sodium disorders · Dysnatraemia · Low sodium · High sodium · Water balance disorders · SIAD
Fellowship guide to hyponatraemia and hypernatraemia in children: definitions, hyponatraemic encephalopathy and 3% NaCl boluses, correction limits, hospital-acquired hyponatraemia and isotonic maintenance fluids, and hypernatraemia correction evidence including breastfed neonates.
Checked against its sources on 23 Oct 2026
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- Headache, nausea and vomiting in a child with hyponatraemia can be hyponatraemic encephalopathy, which can progress rapidly to death from transtentorial herniation
- Treat hyponatraemic encephalopathy with a 2 mL/kg bolus of 3% NaCl, repeated 1 to 2 times if symptoms persist
- Hypotonic intravenous fluids should be avoided in hospital patients with possible non-osmotic stimuli for vasopressin
- Anticonvulsants alone may fail in hyponatraemic seizures and are associated with apnoea
- A lethargic, jaundiced, poorly feeding breastfed newborn may have hypernatraemic dehydration
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- Definition of hyponatraemia and hypernatraemia by serum sodium
- Volume-status classification of hyponatraemia and water-loss versus sodium-gain for hypernatraemia
- Hospital-acquired hyponatraemia and isotonic maintenance fluid
- Osmotic demyelination syndrome and the hyponatraemia correction limit
- Central versus nephrogenic diabetes insipidus
- SIAD versus cerebral salt wasting
- 3 percent hypertonic saline for severe symptomatic hyponatraemia
- The hypernatraemia correction rate to avoid cerebral oedema
- Sodium and free-water management in diabetic ketoacidosis
- Short case: a postoperative child with hyponatraemia and seizure
- Long case: an adolescent with diabetes insipidus
- Communication station explaining slow correction to a family
- Nephrology and fluids: disorders of sodium and water balance
- Maintenance fluid prescription and the isotonic default
- Investigation of hypotonic hyponatraemia
- Physiology of arginine vasopressin, thirst, and renal dilution and concentration
- Brain cell volume adaptation and idiogenic osmoles
- Pharmacology of hypertonic saline, desmopressin, and fluid restriction
- Clinical assessment and volume-status examination in the dysnatraemic child
- Communication: explaining slow correction and the safety-net to a family
- Hyponatraemia and hypernatraemia: definition, causes and emergency management
- Hypertonic saline for severe symptomatic hyponatraemia and the correction limit
- Diabetes insipidus and SIAD
- Patient Care: sodium and water disorders and maintenance fluid choice
- Medical Knowledge: vasopressin physiology and brain cell adaptation
- Systems-Based Practice: isotonic maintenance fluid protocols and error prevention
- Nephrology: sodium and water homeostasis and dysnatraemia
- Emergency management of severe symptomatic hyponatraemia in children
- Osmotic demyelination and the correction rate
A child on an intravenous drip who becomes drowsy and vomits may have a falling sodium. A breastfed newborn who is lethargic and jaundiced may have a high one. This page covers both ends of the sodium range in children: how they present, how they are prevented and how they are corrected. [2] [10]
Overview & Definition
The European clinical practice guideline defines hyponatraemia as a serum sodium below 135 mmol/L. It can cause symptoms from subtle to life-threatening. It is associated with increased mortality, morbidity and length of hospital stay. [1]
Hyponatraemic encephalopathy is a potentially life-threatening condition with high morbidity and mortality. It can be hard to diagnose because its symptoms are non-specific and do not always match the degree of hyponatraemia. [2]
In the Melbourne hypernatraemia study, the normal range of serum sodium was taken as 135 to 145 mmol/L. Children were included if they had at least one serum sodium of 150 mmol/L or more. [9]
References12ShowHide
- [1]Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association, 2014.PMID 24569496
- [2]Ayus JC, Moritz ML Misconceptions and Barriers to the Use of Hypertonic Saline to Treat Hyponatremic Encephalopathy. Frontiers in medicine, 2019.PMID 30931308
- [3]Sarnaik AP, Meert K, Hackbarth R, et al. Management of hyponatremic seizures in children with hypertonic saline: a safe and effective strategy. Critical care medicine, 1991.PMID 2055051
- [4]Rondon-Berrios H, Sterns RH Hypertonic Saline for Hyponatremia: Meeting Goals and Avoiding Harm. American journal of kidney diseases : the official journal of the National Kidney Foundation, 2022.PMID 34508830
- [5]Feld LG, Neuspiel DR, Foster BA, et al. Clinical Practice Guideline: Maintenance Intravenous Fluids in Children. Pediatrics, 2018.PMID 30478247
- [6]Amer BE, Abdelwahab OA, Abdelaziz A, et al. Efficacy and safety of isotonic versus hypotonic intravenous maintenance fluids in hospitalized children: an updated systematic review and meta-analysis of randomized controlled trials. Pediatric nephrology (Berlin, Germany), 2024.PMID 37365423
- [7]Lehtiranta S, Honkila M, Kallio M, et al. Severe hospital-acquired hyponatremia in acutely ill children receiving moderately hypotonic fluids. Pediatric nephrology (Berlin, Germany), 2022.PMID 34398305
- [8]Karageorgos SA, Kratimenos P, Landicho A, et al. Hospital-Acquired Hyponatremia in Children Following Hypotonic versus Isotonic Intravenous Fluids Infusion. Children (Basel, Switzerland), 2018.PMID 30279348
- [9]Didsbury M, See EJ, Cheng DR, et al. Correcting Hypernatremia in Children. Clinical journal of the American Society of Nephrology : CJASN, 2023.PMID 36888887
- [10]Bischoff AR, Dornelles AD, Carvalho CG Treatment of Hypernatremia in Breastfeeding Neonates: A Systematic Review. Biomedicine hub, 2017.PMID 31988896
- [11]Moritz ML Syndrome of Inappropriate Antidiuresis. Pediatric clinics of North America, 2019.PMID 30454744
- [12]Driano JE, Lteif AN, Creo AL Vasopressin-Dependent Disorders: What Is New in Children? Pediatrics, 2021.PMID 33795481