Paeds · nephrology-urology-fluids-and-electrolytes
Dehydration and oral or intravenous rehydration
Also known as Paediatric dehydration · Acute gastroenteritis dehydration · Oral rehydration therapy · Intravenous rehydration in children · Clinical dehydration scale
Fellowship guide to paediatric dehydration and rehydration: the clinical dehydration scale and the WHO and percentage-weight-loss severity bands, the assessment of volume status at the bedside, oral rehydration therapy with reduced-osmolarity oral rehydration solution as the first-line treatment for mild to moderate dehydration, the staged intravenous rehydration protocol with isotonic crystalloid and the slow correction of dysnatraemia, and the prevention of cerebral oedema that dominates the safe management of the severely dehydrated child.
Checked against its sources on 2 Sept 2026
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Target exams
Red flags
- Shock with cold mottled peripheries, a rapid thready pulse, prolonged capillary refill, and altered consciousness requiring immediate 10 to 20 mL per kg isotonic crystalloid boluses
- Hypernatraemic dehydration with a serum sodium above 150 mmol per litre at risk of cerebral oedema if corrected faster than 0.5 mmol per litre per hour
- Hyponatraemic dehydration with a serum sodium below 135 mmol per litre causing seizures that need controlled correction to avoid osmotic demyelination
- Altered consciousness, deep acidotic breathing, or a reducing-substance positive stool suggesting diabetic ketoacidosis, sepsis, or an inborn error of metabolism rather than simple gastroenteritis
- A breastfed neonate in the first week of life with weight loss above 10 percent, fever, or lethargy from hypernatraemic dehydration from inadequate intake
- Bilious vomiting, severe localized abdominal pain, or a high-pitched cry raising the possibility of malrotation with volvulus, intussusception, or surgical pathology
- Persistent tachycardia, poor urine output, or a rising serum sodium after the first rehydration phase signalling ongoing losses or an inadequate regimen
- Reduced oral intake with profuse diarrhoea or vomiting unresponsive to ondansetron in a child at risk of progression to severe dehydration
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- Assesses the degree of dehydration using the clinical dehydration scale and the percentage weight loss bands and recognises the child in shock
- Initiates oral rehydration therapy with reduced-osmolarity oral rehydration solution for mild to moderate dehydration and escalates to intravenous fluids for the severe case
- Calculates maintenance and deficit replacement using the Holliday and Segar formula and uses isotonic crystalloid for resuscitation
- Applies the staged intravenous rehydration protocol with 100 mL per kg of 0.9 percent sodium chloride over 10 hours and the controlled addition of potassium
- Manages hypernatraemic and hyponatraemic dehydration with correction no faster than 0.5 mmol per litre per hour to avoid cerebral oedema
- Distinguishes simple dehydration from diabetic ketoacidosis, sepsis, and surgical pathology and arranges safe disposition
- Clinical dehydration scale and the WHO and percentage-weight-loss severity bands
- Oral rehydration therapy with reduced-osmolarity oral rehydration solution and the role of ondansetron
- Staged intravenous rehydration and the slow correction of dysnatraemia
- Recognises the deteriorating dehydrated child and escalates from oral to intravenous therapy and to intensive care for shock
- Communicates the rehydration plan, feeding, and fluid safety messages to a family in plain language
- Counsels on the warning signs that should bring the child back and the prevention of dehydration in gastroenteritis
- Level 1: Recognition of the degree of dehydration by clinical signs and the clinical dehydration scale
- Level 2: Initiation of oral or intravenous rehydration and the correction of electrolyte disturbance
- Level 3: Management of severe and dysnatraemic dehydration and safe fluid prescribing on the ward
- Clinical dehydration scale scoring and interpretation and the percentage weight loss severity bands
- Composition of reduced-osmolarity oral rehydration solution and the principles of oral rehydration therapy
- Staged intravenous rehydration and the safe correction of hypernatraemic and hyponatraemic dehydration
- Assessment of volume status and the clinical signs of moderate and severe dehydration
- Interpretation of serum sodium and the calculation of fluid and electrolyte deficits
- Structured explanation of the oral to intravenous rehydration pathway and fluid safety counselling
- Clinical dehydration scale and the WHO classification of dehydration severity in children
- Oral rehydration therapy as first-line therapy and the indications for intravenous rehydration
- Fluid and electrolyte management including the avoidance of hypotonic fluids and the prevention of hyponatraemia
- Recognition of dehydration and shock as a time-critical emergency requiring prompt fluid resuscitation
- Initiation of oral or intravenous rehydration and the safe prescribing of maintenance fluids
- Family communication around feeding, oral rehydration solution, and the warning signs of deterioration
- Canadian approach to paediatric dehydration and oral and intravenous rehydration in regional and rural settings
- Use of the clinical dehydration scale and isotonic maintenance fluids to reduce hospital-acquired hyponatraemia
- Safe correction of dysnatraemia and the prevention of cerebral oedema in severe dehydration
Overview & Definition
A child who has been vomiting and passing watery stools for two days, who is now listless with sunken eyes and a dry mouth, is the everyday face of dehydration and the most common paediatric fluid emergency. The defining problem is a net loss of body water and electrolytes that outruns intake, so the extracellular volume contracts and the circulating volume falls until the tissues are underperfused. Most episodes follow acute gastroenteritis, and most are mild, but the small proportion that progress to severe dehydration carry a real risk of shock, electrolyte crisis, and cerebral oedema. [11]
The degree of dehydration is expressed most usefully as a percentage of body weight lost, because a recent weight is the single most reliable measure of the water deficit. A loss below 5 percent of body weight is mild and usually clinically inapparent, a loss of 5 to 10 percent produces the recognisable signs of moderate dehydration, and a loss above 10 percent is severe and accompanied by shock and a threatened circulation. The clinical dehydration scale converts these weight bands into a reproducible bedside score, so the clinician can grade severity without waiting for a weight or a blood test. [4]
The treatment is simple in concept and exact in execution, which is the whole point of the topic for an examiner. Mild and moderate dehydration are managed with oral rehydration therapy using reduced-osmolarity oral rehydration solution, which works as well as intravenous fluid and avoids the cannula and the admission. Severe dehydration and shock need intravenous isotonic crystalloid in a staged protocol, and the dysnatraemic child needs that fluid given slowly, because the brain defends its volume and a rapid correction causes cerebral oedema. [7]
References12ShowHide
- [1]Holliday MA, Segar WE The maintenance need for water in parenteral fluid therapy. Pediatrics, 1957.PMID 13431307
- [2]Steiner MJ, DeWalt DA, Byerley JS Is this child dehydrated? JAMA, 2004.PMID 15187057
- [3]Gorelick MH, Shaw KN, Murphy KO Validity and reliability of clinical signs in the diagnosis of dehydration in children. Pediatrics, 1997.PMID 9113963
- [4]Friedman JN, Goldman RD, Srivastava R, Parkin PC Development of a clinical dehydration scale for use in children between 1 and 36 months of age. J Pediatr, 2004.PMID 15289767
- [5]Goldman RD, Friedman JN, Parkin PC Validation of the clinical dehydration scale for children with acute gastroenteritis. Pediatrics, 2008.PMID 18762524
- [6]Freedman SB, Willan AR, Boutis K, Schuh S Effect of Dilute Apple Juice and Preferred Fluids vs Electrolyte Maintenance Solution on Treatment Failure Among Children With Mild Gastroenteritis: A Randomized Clinical Trial. JAMA, 2016.PMID 27131100
- [7]Hartling L, Bellemare S, Wiebe N, Russell K, et al Oral versus intravenous rehydration for treating dehydration due to gastroenteritis in children. Cochrane Database Syst Rev, 2006.PMID 16856044
- [8]Freedman SB, Adler M, Seshadri R, Powell EC Oral ondansetron for gastroenteritis in a pediatric emergency department. N Engl J Med, 2006.PMID 16625009
- [9]Duggan C, Fontaine O, Pierce NF, Glass RI, et al Scientific rationale for a change in the composition of oral rehydration solution. JAMA, 2004.PMID 15173155
- [10]Neilson J, O'Neill F, Dawoud D, Crean P, et al Intravenous fluids in children and young people: summary of NICE guidance. BMJ, 2015.PMID 26662119
- [11]Khanna R, Lakhanpaul M, Burman-Roy S, Murphy MS, et al Diarrhoea and vomiting caused by gastroenteritis in children under 5 years: summary of NICE guidance. BMJ, 2009.PMID 19386673
- [12]Ozdogan T, Iscan M, Ellikcioglu C, Yildiz E Hypernatraemic dehydration in breast-fed neonates. Arch Dis Child, 2006.PMID 17119086