Paeds · nephrology-urology-fluids-and-electrolytes
Fluid maintenance and deficit replacement
Also known as Holliday-Segar · Maintenance fluids · Deficit replacement · 4-2-1 rule · Isotonic maintenance · Intravenous fluid therapy · Fluid prescription
Fellowship guide to prescribing fluids in children: the Holliday-Segar 100/50/20 mL/kg/day rule (the 4/2/1 hourly form) for maintenance water, the 2 to 3 mmol/kg/day sodium and 1 to 2 mmol/kg/day potassium requirement, the switch to isotonic maintenance fluids with dextrose and potassium to prevent hospital-acquired hyponatraemia and hyponatraemic encephalopathy, the percentage method for calculating a dehydration deficit with half replaced over 8 hours and half over 16 hours, and the slow correction of hypernatraemic dehydration at no faster than 0.5 mmol per litre per hour.
Checked against its sources on 13 Sept 2026
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- Hypotonic maintenance fluids such as 0.45 percent, 0.225 percent or 0.18 percent saline cause hospital-acquired hyponatraemia in sick children whose ADH is raised by stress, pain, nausea and respiratory illness, and the result can be seizures, brainstem herniation and death — use isotonic fluid with dextrose and potassium instead
- A sick child is not a healthy child: non-osmotic ADH turns every hypotonic litre into free water, so a maintenance rate that is safe on paper can drop the sodium by several mmol per litre within hours in the acutely ill or postoperative child
- Correct hypernatraemic dehydration slowly — the sodium must not fall faster than 0.5 mmol per litre per hour and not more than 10 to 12 mmol per litre in 24 hours, because rapid correction causes cerebral oedema, seizures and death
- Never add potassium to an intravenous fluid until you have confirmed the serum potassium is normal and the child is passing urine, because potassium in an anuric or hyperkalaemic child is a cardiac arrest in a bag
- Maintenance fluid is a prescription, not a default bag: it must account for the daily water requirement, any dehydration deficit, ongoing abnormal losses, and the maximum daily cap for larger adolescents, or the child will drift toward over- or under-hydration
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- Holliday-Segar 100/50/20 mL/kg/day and the 4/2/1 hourly rule
- Maintenance sodium 2 to 3 mmol/kg/day and potassium 1 to 2 mmol/kg/day
- Isotonic maintenance fluids to prevent hospital-acquired hyponatraemia
- Non-osmotic ADH and why hypotonic fluids are unsafe in the acutely ill child
- Deficit by percentage dehydration: half over 8 hours, half over 16 hours
- Slow correction of hypernatraemic dehydration at no more than 0.5 mmol per litre per hour
- Prescribing isotonic maintenance fluid with dextrose and potassium
- Calculating and replacing a fluid deficit over 24 hours
- Fluid stewardship and the daily volume cap for larger adolescents
- Short case: a postoperative child with a falling sodium
- Long case: an infant with hypernatraemic dehydration
- Communication: explaining a maintenance fluid plan to a family
- Nephrology and fluids: maintenance and deficit prescription
- Hospital-acquired hyponatraemia and isotonic fluids
- Monitoring sodium and chloride on maintenance therapy
- Physiology of water homeostasis and ADH in the sick child
- Holliday-Segar derivation and the 4/2/1 rule
- Tonicity of crystalloid solutions and the hyponatraemia risk
- Writing and defending a paediatric fluid prescription
- Communication: explaining why a saline bag has changed
- Maintenance fluids: Holliday-Segar and isotonic solutions
- Hospital-acquired hyponatraemia and the move to isotonic fluids
- Deficit calculation and replacement over 24 hours
- Patient Care: prescribing safe maintenance and deficit fluids
- Medical Knowledge: ADH physiology and fluid tonicity
- Systems-Based Practice: fluid stewardship and protocolised prescribing
- Nephrology: maintenance and deficit fluid therapy
- Hospital-acquired hyponatraemia prevention
- Holliday-Segar and isotonic maintenance fluids
Fluid therapy is where physiology meets arithmetic, and both have to be right. A maintenance bag is not a generic drip. It is a calculated prescription of water, sodium, potassium and glucose, matched to a child's weight and to whatever the body is doing with ADH that day. The two classic errors are the opposite of each other: giving too little water, so the child slides into hypernatraemia, or giving too much free water, so the sodium falls and the brain swells. The Holliday-Segar rule solves the first problem, and the move to isotonic maintenance fluids solves the second. [1] [2]
This page treats prescription as a sequence of four questions. How much water does the child need each day? What tonicity should it be? How much deficit must be added back, and over how long? What ongoing losses must be matched? Answer all four and the fluid chart writes itself. The evidence base for the isotonic shift is now large and consistent, built on the Holliday and Segar observation, the McNab trial, the Cochrane and meta-analytic syntheses, and the American Academy of Pediatrics 2018 clinical practice guideline that made isotonic maintenance fluid the default for hospitalised children. [2] [3] [5]
Overview & Definition
Maintenance fluid is the daily intake of water and electrolytes needed to balance the obligatory losses a healthy child makes every day: urine, stool, sweat, and insensible loss from the skin and respiratory tract. Holliday and Segar derived it in 1957 from the metabolic observation that water need tracks energy expenditure, and their numbers have survived because they are simple and they work. [1]
The daily water requirement is 100 mL/kg for the first 10 kg of body weight, 50 mL/kg for the next 10 kg, and 20 mL/kg for every kilogram above 20. A 25 kg child therefore needs 1000 plus 500 plus 100, which is 1600 mL per day, or about 67 mL per hour. Expressed as the 4-2-1 hourly rule, the same child needs 4 mL/kg/hour for the first 10 kg, 2 mL/kg/hour for the next 10 kg, and 1 mL/kg/hour for each kilogram above 20 — giving 40 plus 20 plus 5, or 65 mL per hour. The two methods agree to within rounding. [1] [2]
Maintenance electrolytes ride along with the water. The daily sodium requirement is 2 to 3 mmol/kg/day, and the daily potassium requirement is 1 to 2 mmol/kg/day. Dissolved into the Holliday-Segar water volume, this lands the potassium at roughly 20 mmol per litre, which is why a standard maintenance bag adds 20 mmol/L of potassium chloride to its dextrose-saline base. [2]
Deficit is the fluid already lost before the child arrives, and it is separate from maintenance. It is estimated from the percentage dehydration: a clinically mild deficit is about 5 percent of body weight, a moderate deficit is 5 to 10 percent, and a severe deficit is at least 10 percent. Each 1 percent dehydration equals 10 mL/kg of lost fluid, so a 10 kg child at 10 percent dehydration has lost 1000 mL. [8]
References11ShowHide
- [1]Holliday MA; Segar WE The maintenance need for water in parenteral fluid therapy. Pediatrics, 1957.PMID 13431307
- [2]Feld LG; Neuspiel DR; Foster BA; et al Clinical Practice Guideline: Maintenance Intravenous Fluids in Children. Pediatrics, 2018.PMID 30478247
- [3]McNab S Isotonic vs Hypotonic Intravenous Fluids for Hospitalized Children. JAMA, 2015.PMID 26284724
- [4]McNab S; Ware RS; Neville KA; et al Isotonic versus hypotonic solutions for maintenance intravenous fluid administration in children. Cochrane Database Syst Rev, 2014.PMID 25519949
- [5]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. Pediatr Nephrol, 2024.PMID 37365423
- [6]Wang J; Xu E; Xiao Y Isotonic versus hypotonic maintenance IV fluids in hospitalized children: a meta-analysis. Pediatrics, 2014.PMID 24379232
- [7]Moritz ML; Ayus JC New aspects in the pathogenesis, prevention, and treatment of hyponatremic encephalopathy in children. Pediatr Nephrol, 2010.PMID 19894066
- [8]Moritz ML; Ayus JC Improving intravenous fluid therapy in children with gastroenteritis. Pediatr Nephrol, 2010.PMID 20309584
- [9]Karageorgos SA; Kratimenos P; Landicho A; et al Hospital-Acquired Hyponatremia in Children Following Hypotonic versus Isotonic Intravenous Fluids Infusion. Children (Basel), 2018.PMID 30279348
- [10]Sensing W; Wenker M; Whitney E Maintenance fluid management in pediatrics: Current practice and quality improvement achievements. Curr Probl Pediatr Adolesc Health Care, 2021.PMID 34092514
- [11]Roberts DN; Vallen P; Cronhjort M; et al Perioperative water and electrolyte balance and water homeostasis regulation in children with acute surgery. Pediatr Res, 2023.PMID 36759747