Infants and young children lose fluid balance faster and with less warning than adults. Understanding why explains most nursing priorities.

Dehydration types (by serum sodium)

Acid–base: diarrhea loses bicarbonate → metabolic acidosis (the child breathes faster to blow off CO₂). Prolonged vomiting loses acid and chloride → metabolic alkalosis with hypokalemia.

Maintenance fluid (Holliday–Segar method)

Examples: 10 kg = 1,000 mL/day (40 mL/h); 15 kg = 1,250 mL/day; 25 kg = 1,600 mL/day. Deficit replacement is added on top of maintenance. Children with heart failure, kidney disease, SIADH, or brain injury often need less.

Degree of dehydration

• Acute weight loss is the most accurate measure: (pre-illness weight − current weight) ÷ pre-illness weight × 100. For older children, thresholds of about 3%, 6%, and 9% are used for mild, moderate, and severe
• Most reliable single bedside signs: prolonged capillary refill, abnormal skin turgor, and abnormal (deep) respiratory pattern
• Infants: sunken anterior fontanel, fewer wet diapers
• Children keep their blood pressure until late; tachycardia and poor perfusion come first. Weak, rapid pulses signal circulatory compromise; absent peripheral pulses signal shock

Electrolyte disturbances

ABG example: pH 7.20, PaCO₂ 24 mmHg, HCO₃⁻ 10 mEq/L. pH is acidotic and HCO₃⁻ is low → metabolic acidosis. PaCO₂ is low (the lungs are compensating) but pH is still abnormal → partially compensated metabolic acidosis (seen in DKA and severe diarrhea).

Oral rehydration therapy (ORT) — first choice for mild and moderate dehydration (WHO plans)

• Low-osmolarity oral rehydration solution (ORS) (sodium 75 mEq/L, glucose 75 mmol/L, total osmolarity 245 mOsm/L). Glucose drives sodium and water absorption in the gut, which works even during diarrhea
• Plan A (no dehydration, home): extra fluid after each loose stool — about 50–100 mL for children under 2 years, 100–200 mL for ages 2–10; continue feeding
• Plan B (some dehydration): about 75 mL/kg of ORS over 4 hours in the clinic, then reassess (e.g., 10 kg child → about 750 mL)
• Plan C (severe dehydration): IV Ringer's lactate or normal saline, 100 mL/kg — infants under 12 months: 30 mL/kg in 1 hour, then 70 mL/kg over 5 hours; older children: 30 mL/kg in 30 minutes, then 70 mL/kg over 2.5 hours; start ORS as soon as the child can drink
• Plans B and C are not for children with severe acute malnutrition: rehydrate slowly with low-sodium ORS (ReSoMal) orally or by NG tube; IV fluids only for shock (see "Nutritional and Metabolic Disorders")
• Zinc for 10–14 days (shortens diarrhea and reduces recurrence). WHO (2024) now suggests a lower dose, 5 mg daily for up to 14 days, which causes less vomiting; many national programs, including the DOH, still use 10 mg (under 6 months) or 20 mg (6 months and older) — follow the local protocol
• Continue breastfeeding and age-appropriate feeding; no fasting ("bowel rest") and no routine lactose-free formula
• Sugary drinks, sodas, juices, and sports drinks are not substitutes for ORS — their high sugar and low sodium can worsen diarrhea and cause hyponatremia

IV therapy

• Shock: isotonic crystalloid bolus 10–20 mL/kg, reassess after each bolus (smaller volumes, 5–10 mL/kg, with heart disease)
• Maintenance IV fluids: isotonic solution (such as 0.9% sodium chloride or a balanced solution) with dextrose and potassium as needed — hypotonic maintenance fluids are avoided because of the risk of hospital-acquired hyponatremia
• Potassium is added only after urine output is confirmed; never given as IV push
• Hypernatremia: correct slowly over 48 hours or more (serum sodium lowered by no more than about 10–12 mEq/L in 24 hours) to prevent cerebral edema
• Symptomatic hyponatremia with seizures: small bolus of 3% saline under close monitoring; chronic hyponatremia is corrected slowly to avoid osmotic demyelination
• Hyperkalemia: stop potassium sources; calcium gluconate to protect the heart; insulin with glucose and inhaled albuterol to move potassium into cells; potassium binders or dialysis to remove it
• Hypocalcemia: IV calcium gluconate slowly with cardiac monitoring
• Refeeding: start nutrition slowly and replace phosphate, potassium, and magnesium

Pediatric DKA fluid principles (details in "Endocrine Disorders"): gradual fluid replacement, IV insulin infusion started after initial fluids, no insulin bolus, and close potassium monitoring — insulin and fluids drive potassium into cells and serum potassium can fall sharply. Watch for cerebral edema (headache, slowing heart rate, rising BP, falling consciousness).

Drug safety (doses weight-based and verified against a pediatric reference)

Listed in priority order.

1. Circulation and perfusion
   • Recognize shock: tachycardia, weak pulses, capillary refill over 3 seconds, cool mottled skin, lethargy; hypotension is a late sign — call for help and prepare fluid boluses
   • Establish IV or intraosseous access as ordered in severe dehydration
2. Assess the degree of dehydration
   • Weigh the child (compare with the most recent known weight), then assess skin turgor, capillary refill, mucous membranes, tears, fontanel, heart rate, and mental status
3. Rehydrate
   • ORS in small, frequent amounts: 5 mL (1 teaspoon) every 1–2 minutes by spoon, syringe, or cup; if the child vomits, wait 10 minutes and restart more slowly
   • Criteria for oral rehydration: alert, able to swallow, not in shock, and without persistent vomiting; severe dehydration, altered consciousness, or failed ORT needs IV fluids
   • Use an infusion pump for every pediatric IV infusion (syringe pumps for small volumes) and check the rate and site hourly
4. Monitor
   • Daily weight, strict intake and output, diaper weights, urine specific gravity, and electrolytes as ordered
   • Monitor potassium closely with diuretics, DKA treatment, and ongoing losses; check ECG changes
   • Monitor neurologic status (irritability, lethargy, seizures) with sodium disorders; seizure precautions
   • Hypocalcemia: check Chvostek and Trousseau signs; keep suction and calcium gluconate available
5. Skin care and comfort — frequent diaper changes, barrier cream for diaper dermatitis; mouth care
6. Diet: hyperkalemia — limit high-potassium foods (bananas, oranges and orange juice, potatoes, tomatoes, dried fruit, leafy greens); hypokalemia — encourage those same foods

• Keep ORS at home; mix packets with the exact amount of clean water stated — never stronger or weaker
• Give ORS slowly and often; continue breastfeeding and regular meals; give zinc for the full 10–14 days
• Prepare formula exactly as directed — over-diluted formula causes hyponatremia and seizures; over-concentrated formula causes hypernatremia
• Do not use sodas, juice, sports drinks, or plain water alone to rehydrate an infant with diarrhea
• Return immediately for: no urine for 6–8 hours (infants), sunken eyes or fontanel, no tears, lethargy, unable to drink, repeated vomiting, blood in stool, or fever in a young infant
• Hand washing, safe water, breastfeeding, and rotavirus vaccine prevent diarrhea
• Children on diuretics: know signs of low potassium (weakness, leg cramps, irregular heartbeat); keep lab appointments

• Infants dehydrate faster: more body water, larger surface area, immature kidneys
• Acute weight loss is the most accurate measure of dehydration; weigh first
• Hypotension is a late sign in children — tachycardia and delayed capillary refill come first; weak, rapid pulse = circulatory compromise
• ORS: small amounts often (5 mL every 1–2 minutes); Plan B 75 mL/kg over 4 hours; continue feeding; zinc 10–14 days
• ORT candidates: alert, can swallow, not in shock, no persistent vomiting
• Maintenance: 100/50/20 mL/kg/day — a 10 kg child needs 1,000 mL/day
• Isotonic maintenance IV fluids; potassium only after urine output, never IV push; always use an infusion pump
• Hyponatremia → cerebral edema, seizures; hypernatremia → thirst, irritability, high-pitched cry; correct hypernatremia slowly
• Furosemide → hypokalemia; hyperkalemia diet limits bananas, oranges, potatoes, tomatoes
• Hypocalcemia → perioral tingling, tetany, Chvostek/Trousseau; hypophosphatemia → respiratory muscle weakness (refeeding)
• pH 7.20, HCO₃⁻ 10, PaCO₂ 24 = partially compensated metabolic acidosis