PERIOPERATIVE FLUID MANAGEMENT IN CHILDREN
1. INTRODUCTION
Perioperative fluid management in children requires an understanding of age-dependent physiology, indications for fluid administration, the composition of available solutions, and the effects of anaesthesia and surgery on fluid distribution. Neonates and infants are particularly vulnerable because of their higher total body water fraction, greater extracellular fluid proportion, higher fluid turnover and limited physiological reserve.
• The goals are to maintain circulating volume, tissue perfusion, electrolyte balance and normoglycaemia while avoiding fluid overload.
• Fluid therapy should be individualised according to age, weight, comorbidities, surgical stress, measured losses and response to treatment.
• Avoid automatically adding maintenance, fasting deficit and presumed “third-space” losses without clinical evidence.
2. PHYSIOLOGY OF BODY FLUIDS
2.1 Total body water and compartments
Total body water (TBW) is distributed between intracellular fluid (ICF) and extracellular fluid (ECF). ECF includes interstitial and intravascular compartments. The proportion of TBW is highest in premature neonates and decreases with age.
|
Age group |
Approximate TBW |
Estimated blood volume |
|
Preterm neonate |
80–90% |
90–100 mL/kg |
|
Term neonate |
70–75% |
80–90 mL/kg |
|
Infant |
65–70% |
75–80 mL/kg |
|
Older child |
60–65% |
70–75 mL/kg |
|
Adolescent |
Approaches adult values |
65–75 mL/kg |
• Neonates have a larger ECF fraction and immature renal concentrating ability and sodium handling.
• Infants have a larger surface-area-to-body-weight ratio and are more vulnerable to evaporative and insensible losses.
• A relatively small absolute fluid loss can represent a clinically important proportion of circulating blood volume in an infant.
2.2 Perioperative changes
• Anaesthesia may reduce sympathetic tone and systemic vascular resistance, altering circulating volume distribution.
• Positive-pressure ventilation can reduce venous return, particularly in hypovolaemic children.
• Surgical exposure, blood loss, evaporation, irrigation and fluid shifts contribute to perioperative changes.
• Pain, nausea, stress, opioids and surgery stimulate antidiuretic hormone (ADH), increasing water retention and the risk of dilutional hyponatraemia.
3. OBJECTIVES OF PERIOPERATIVE FLUID THERAPY
• Maintain effective circulating blood volume and organ perfusion.
• Replace pre-existing deficits and ongoing measured losses.
• Maintain appropriate glucose and electrolyte concentrations.
• Avoid both hypovolaemia and fluid overload.
• Support renal, cerebral, cardiovascular and metabolic function.
• Facilitate early enteral intake and timely discontinuation of IV fluids.
4. CLASSIFICATION OF FLUID REQUIREMENTS
4.1 Maintenance
Replaces normal physiological water and electrolyte losses in a child who is adequately hydrated and has no significant abnormal losses.
4.2 Deficit replacement
Corrects pre-existing fluid loss due to reduced intake, vomiting, diarrhoea, fever or dehydration. Estimate clinically and correct according to severity, duration and biochemical abnormalities.
4.3 Resuscitation
Restores effective circulating volume and tissue perfusion in hypovolaemia or shock. Reassess after each bolus.
4.4 Replacement of ongoing losses
Measured losses such as blood, gastrointestinal drainage, stoma output, urine losses or surgical losses should be replaced according to volume, composition and clinical effect.
5. PREOPERATIVE ASSESSMENT
5.1 History
• Recent oral intake and fasting duration; quantify vomiting, diarrhoea, fever or reduced urine output.
• Prematurity, congenital heart disease, renal disease, endocrine/metabolic disorders or previous electrolyte abnormalities.
• Current medications, including diuretics and drugs affecting renal function or glucose homeostasis.
• Recent weight change and previous fluid therapy, where available.
5.2 Examination
• General appearance, mental status, mucous membranes, tears and skin turgor.
• Heart rate, blood pressure, pulse volume, capillary refill time and peripheral temperature.
• Respiratory pattern, work of breathing, lung auscultation and signs of pulmonary oedema.
• Urine output and weight compared with baseline, if available.
5.3 Investigations
• Electrolytes, glucose, urea and creatinine when clinically indicated, especially in infants, prolonged fasting, dehydration, major surgery or relevant comorbidity.
• Blood gas, lactate, haemoglobin and coagulation studies according to clinical situation and expected blood loss.
• Routine laboratory testing is not required in every healthy child undergoing minor surgery.
6. PREOPERATIVE FASTING AND FASTING DEFICIT
Avoid unnecessarily prolonged fasting. Follow the current institutional paediatric fasting policy and consider age, clinical condition, procedure and aspiration risk.
|
Intake |
Common minimum fasting interval* |
|
Clear fluids |
1–2 hours, depending on guidelines |
|
Breast milk |
4 hours |
|
Infant formula |
6 hours |
|
Non-human milk / light meal |
6 hours |
|
Fatty meal or heavy food |
8 hours or longer |
*Intervals vary between professional guidelines and institutional policies. Use the applicable local protocol.
Traditional estimate: fasting deficit (mL) = hourly maintenance rate × fasting duration (hours).
• This is an estimate, not an instruction to automatically administer the entire calculated deficit.
• A well-hydrated child after a short fast may not have a clinically significant intravascular deficit.
• Correct documented dehydration or hypovolaemia according to clinical findings, not fasting duration alone.
7. MAINTENANCE FLUID REQUIREMENTS
7.1 Holliday–Segar method
The Holliday–Segar method estimates daily maintenance water requirements based on energy expenditure.
|
Body weight |
Daily maintenance requirement |
|
First 10 kg |
100 mL/kg/day |
|
Next 10 kg |
50 mL/kg/day |
|
Each kg above 20 kg |
20 mL/kg/day |
Hourly approximation: 4–2–1 rule
• First 10 kg: 4 mL/kg/hour.
• Next 10 kg: 2 mL/kg/hour.
• Each kg above 20 kg: 1 mL/kg/hour.
7.2 Limitations
• These are estimates for maintenance in otherwise stable children, not resuscitation rates.
• Requirements vary with age, fever, ambient temperature, renal/cardiac function, nutrition and surgical stress.
• Neonates, premature infants and children with cardiac or renal disease need age- and condition-specific prescriptions.
• Perioperative ADH secretion may reduce free-water excretion; full calculated maintenance may not always be appropriate after major surgery.
8. CHOICE OF INTRAVENOUS FLUID
8.1 Isotonic crystalloids
Isotonic crystalloids are commonly used for intravascular volume replacement. Balanced isotonic solutions are often preferred for larger-volume replacement because they produce less chloride loading than 0.9% saline.
|
Fluid |
Key features / considerations |
|
Ringer lactate / Hartmann’s |
Balanced crystalloid; contains sodium, chloride, potassium, calcium and lactate buffer. |
|
Plasma-Lyte |
Balanced crystalloid with electrolyte composition and buffer system designed to be closer to plasma. |
|
0.9% sodium chloride |
Isotonic; useful in selected situations. Large volumes may cause hyperchloraemia and metabolic acidosis. |
8.2 Dextrose-containing fluids
• Dextrose may be required in neonates, infants at risk of hypoglycaemia, children with metabolic/endocrine disorders, prolonged procedures or restricted intake.
• Dextrose-containing hypotonic solutions should not be used routinely for perioperative volume replacement.
• Tailor glucose concentration and infusion rate to age, fasting duration, clinical condition and measured blood glucose.
8.3 Colloids and blood products
• Albumin may be considered in selected clinical circumstances according to institutional practice and indication.
• Hydroxyethyl starch (HES) is generally avoided in children unless there is a compelling, protocol-supported indication.
• Use packed red cells and other blood components when indicated by haemorrhage, haemoglobin, physiology, coagulation status and clinical context.
• In major haemorrhage, prioritise haemorrhage control and early activation of the institutional paediatric massive transfusion protocol when appropriate.
9. INTRAOPERATIVE FLUID MANAGEMENT
9.1 General principles
• Assess intravascular volume, hydration, expected surgical losses and cardiac/renal reserve.
• Use an isotonic crystalloid for routine intravascular replacement unless a specific indication requires another fluid.
• Avoid automatically adding maintenance, full fasting deficit and presumed third-space losses without clinical evidence.
• Use measured losses and repeated physiological assessment to guide ongoing administration.
9.2 Assessment of perfusion
• Heart rate and age-appropriate blood pressure trends.
• Capillary refill time, pulse volume, peripheral temperature and mental status.
• Urine output trends, interpreted in the context of age, procedure and renal function.
• Lactate, base deficit, haemoglobin and blood gas trends when clinically indicated.
• Surgical field, blood loss estimation, suction volume, swab count and irrigation fluid accounting.
• POCUS may provide useful adjunctive information but should not be the sole determinant of fluid responsiveness.
9.3 Fluid boluses
• A commonly used initial crystalloid bolus is 10 mL/kg, followed by reassessment.
• Some protocols use 10–20 mL/kg depending on cause and severity; follow local guidance.
• Stop and reassess if there is no meaningful improvement or signs of fluid overload develop.
• Use caution in cardiogenic shock, renal impairment and children with limited cardiac reserve.
• In haemorrhagic shock, crystalloid is not a substitute for blood products and definitive haemorrhage control.
10. BLOOD LOSS AND TRANSFUSION
Estimated blood volume (EBV) can be approximated using age-specific mL/kg values. It is useful for planning but should not replace clinical assessment.
Allowable blood loss (ABL) planning formula:
ABL = EBV × (Initial Hb − Target Hb) / Initial Hb
• ABL is a planning estimate, not a transfusion threshold.
• Transfusion decisions should consider haemodynamic status, ongoing bleeding, oxygen delivery, comorbidities, age and clinical context.
• In active major haemorrhage, do not delay necessary transfusion while waiting for a laboratory haemoglobin result.
11. GLUCOSE MANAGEMENT
• Neonates and young infants have limited glycogen stores and are particularly vulnerable to hypoglycaemia.
• Healthy older infants and children undergoing short procedures may not require routine dextrose supplementation, but risk assessment is essential.
• Check glucose in neonates, premature infants, prolonged procedures, prolonged fasting, metabolic/endocrine disease or when clinically indicated.
• Treat hypoglycaemia promptly using an age-appropriate institutional protocol and recheck glucose after treatment.
Glucose infusion rate (GIR):
GIR (mg/kg/min) = [Dextrose (%) × fluid rate (mL/hour)] / [6 × weight (kg)]
Example: D10 at 4 mL/hour in a 2 kg infant: GIR = (10 × 4) / (6 × 2) = 3.33 mg/kg/min.
12. ELECTROLYTE MANAGEMENT
12.1 Sodium
• Hyponatraemia may result from excess free water, hypotonic fluids and perioperative ADH secretion; acute severe hyponatraemia can cause cerebral oedema and seizures.
• Use isotonic fluids for routine perioperative maintenance in most children unless a specific indication dictates otherwise.
• Hypernatraemia requires controlled correction. Avoid rapid reduction in serum sodium because of cerebral oedema risk.
• Individualise correction rate and target, with serial sodium monitoring and specialist input for significant abnormalities.
12.2 Potassium
• Do not add potassium automatically to every IV fluid prescription.
• Consider potassium only after assessing serum potassium, renal function and urine output.
• Never administer potassium as an undiluted IV bolus.
• Monitor ECG and repeat electrolytes when clinically indicated.
12.3 Chloride and acid–base balance
• Large volumes of 0.9% saline can increase serum chloride and contribute to hyperchloraemic metabolic acidosis.
• Balanced crystalloids may reduce chloride loading during larger-volume replacement.
• Interpret acid–base changes in the context of perfusion, ventilation, lactate, renal function and administered fluids.
13. POSTOPERATIVE FLUID MANAGEMENT
• Reassess hydration, perfusion, oral intake, urine output and ongoing losses at the end of surgery.
• Encourage early oral or enteral fluids when safe and appropriate.
• Reduce or discontinue IV fluids as enteral intake becomes adequate.
• Postoperative ADH secretion may increase water retention; avoid unnecessary hypotonic fluid and excessive maintenance volumes.
• Some protocols reduce postoperative maintenance rates (for example, to approximately 30–50% in selected settings), but this is not universal and must not replace individual assessment.
• Monitor weight, cumulative fluid balance, urine output, electrolytes and glucose according to risk and clinical course.
14. SPECIAL CLINICAL SITUATIONS
14.1 Neonates and premature infants
• Require careful attention to glucose, sodium, fluid balance, temperature and renal maturity.
• Use neonatal-specific prescriptions and monitor weight, urine output, glucose and electrolytes closely.
• Insensible water losses may be substantial, particularly in very premature infants and those under radiant warmers or phototherapy.
14.2 Major haemorrhage
• Prioritise early recognition, haemorrhage control, warming and appropriate blood component therapy.
• Use institutional paediatric massive transfusion protocols and monitor calcium, temperature, coagulation and acid–base status.
14.3 Congenital heart disease / cardiac dysfunction
• Individualise fluid administration because excessive volume may precipitate pulmonary oedema or worsen cardiac function.
• Use small, carefully reassessed interventions and integrate clinical examination, haemodynamic monitoring and echocardiographic information when available.
14.4 Renal impairment
• Maintenance requirements and electrolyte prescriptions must be individualised.
• Avoid potassium supplementation without confirming renal excretion and serum potassium.
• Monitor cumulative balance, weight, renal function and signs of overload.
14.5 Burns and laparoscopy
• Burn resuscitation requires a dedicated paediatric burn protocol based on burn size and weight with frequent reassessment.
• Do not use routine maintenance calculations as a substitute for burn resuscitation.
• Pneumoperitoneum and positioning can alter venous return, renal perfusion and urine output; avoid reflex fluid loading for reduced urine output without assessing the context.
15. COMPLICATIONS OF INAPPROPRIATE FLUID THERAPY
|
Complication |
Possible consequences / clues |
|
Hypovolaemia |
Tachycardia, poor perfusion, hypotension (often late in children), oliguria, rising lactate. |
|
Fluid overload |
Oedema, pulmonary congestion, impaired oxygenation, weight gain and delayed recovery. |
|
Hyponatraemia |
Altered sensorium, seizures and cerebral oedema in severe/acute cases. |
|
Hypernatraemia |
Neurological dysfunction, irritability, seizures and cellular dehydration. |
|
Hyperchloraemic acidosis |
Reduced bicarbonate and increased chloride after substantial saline exposure. |
|
Glucose abnormalities |
Neurological and metabolic consequences of hypo- or hyperglycaemia. |
|
Potassium abnormalities |
Muscle weakness and potentially dangerous cardiac dysrhythmias. |
|
Dilutional anaemia/coagulopathy |
Dilution of haemoglobin and coagulation factors with excessive fluid administration. |
|
Tissue / airway oedema |
Can impair ventilation, airway patency and postoperative recovery. |
16. PRACTICAL APPROACH: SIX-STEP ALGORITHM
• Assess the child: age, weight, hydration, perfusion, comorbidities, fasting, glucose and electrolytes where indicated.
• Define the indication: maintenance, deficit, resuscitation, measured-loss replacement or blood component therapy.
• Choose the fluid: usually an isotonic crystalloid for intravascular replacement; tailor glucose and electrolytes to age and risk.
• Estimate requirements: use maintenance formulas as a starting estimate, not an automatic perioperative prescription.
• Administer and reassess: monitor haemodynamics, perfusion, blood loss, urine output and relevant laboratory trends.
• Plan postoperative care: early enteral intake, adjust or stop IV fluids, and monitor for fluid-balance complications.
17. RECENT DEVELOPMENTS AND CURRENT CONCEPTS
• Shift from rigid formula-based administration towards physiology-guided, goal-directed fluid therapy.
• Greater preference for balanced isotonic crystalloids for many perioperative replacement indications.
• More individualised glucose and electrolyte management, particularly in neonates and high-risk children.
• POCUS, including focused cardiac and lung assessment, is an adjunct to clinical evaluation; no single ultrasound measurement should independently dictate fluid administration.
• Enhanced recovery pathways emphasise avoidance of unnecessary fasting, early oral/enteral intake and prompt discontinuation of IV fluids.
• Greater awareness of perioperative ADH secretion and iatrogenic hyponatraemia from hypotonic fluids.
18. HIGH-YIELD VIVA QUESTIONS
What is the 4–2–1 rule?
Answer: 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 kg above 20 kg.
Why are children more vulnerable to dehydration?
Answer: Higher TBW and fluid turnover relative to body weight, larger surface-area-to-weight ratio and age-dependent renal concentrating limitations.
Why should hypotonic fluids generally be avoided perioperatively?
Answer: Surgical stress and anaesthesia increase ADH activity; hypotonic fluid can cause water retention and dilutional hyponatraemia.
Which fluid is commonly used for intraoperative volume replacement?
Answer: An isotonic crystalloid; a balanced isotonic crystalloid is often preferred for larger-volume replacement.
What is the concern with large-volume 0.9% saline?
Answer: Chloride loading and hyperchloraemic metabolic acidosis.
What is a commonly used initial paediatric crystalloid bolus?
Answer: 10 mL/kg followed by reassessment; some protocols use 10–20 mL/kg depending on the situation.
When should potassium be added to IV fluids?
Answer: Only when indicated after assessing serum potassium, renal function and urine output; never as an IV bolus.
Which children are at increased risk of perioperative hypoglycaemia?
Answer: Neonates, premature infants, small or malnourished children, metabolic/endocrine disorders, prolonged fasting or prolonged procedures.
What is the GIR formula?
Answer: Dextrose (%) × fluid rate (mL/hour) ÷ [6 × weight (kg)].
Why can postoperative fluid requirements be lower?
Answer: ADH-mediated water retention and reduced free-water excretion may occur after surgery; reassess ongoing need.
19. EXAM TAKE-HOME POINTS
• Use the 4–2–1 rule to estimate maintenance, but do not confuse maintenance with resuscitation.
• Do not automatically replace the entire fasting deficit in every child.
• Use isotonic fluids for most routine perioperative maintenance and intravascular replacement; individualise neonatal prescriptions.
• Balanced crystalloids reduce chloride exposure compared with large volumes of 0.9% saline.
• Avoid routine hypotonic perioperative fluids because of ADH-associated hyponatraemia risk.
• Glucose monitoring and supplementation are particularly important in neonates and high-risk children.
• Add potassium only when indicated and after assessment of renal function and urine output.
• Reassess after every bolus; in haemorrhagic shock, use blood products and haemorrhage control rather than repeated crystalloid alone.
• Review postoperative prescriptions frequently, encourage enteral intake and discontinue unnecessary IV fluids.
20. REFERENCES
• Eaddy N, Watene C. Perioperative management of fluids and electrolytes in children. BJA Education. 2023;23(7):273–278. https://pmc.ncbi.nlm.nih.gov/articles/PMC10718623/
• Lee H, Kim JT. Pediatric perioperative fluid management. Korean Journal of Anesthesiology. 2023;76:519–530.
• Beels M, Stevens S, Saldien V. Perioperative fluid management in children. Acta Anaesthesiologica Belgica. 2022;73:179–189.
• Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19:823–832.
• Sümpelmann R, et al. Perioperative intravenous fluid therapy in children. Current Opinion in Anaesthesiology. 2019;32:384–391.
• Jacob R, Naik V, editors. Understanding Paediatric Anaesthesia. 4th ed. Wolters Kluwer; 2023.
• Davis PJ, Cladis FP, editors. Smith’s Anesthesia for Infants and Children. 8th ed. Elsevier; 2011.
• NICE. Intravenous fluid therapy in children and young people in hospital. Guideline NG29. https://www.nice.org.uk/guidance/ng29
Note: These notes are intended for postgraduate education and revision. Prescriptions must be individualised and should follow current age-specific institutional protocols and specialist guidance, particularly for neonates, major haemorrhage, cardiac disease, renal impairment and significant electrolyte disorders.