Pediatric Fluid Calculator

The 4-2-1 rule calculates hourly maintenance: 4 mL/kg/hr for first 10 kg, 2 mL/kg/hr for next 10 kg (10–20 kg), and 1 mL/kg/hr for each kg above 20 kg. For a 15 kg child: 4×10=40 + 2×5=10 = 50 mL/hr. Daily = 50×24 = 1200 mL.

Use the Holliday-Segar (4-2-1) method: hourly rate based on weight, multiply by 24 for daily total. For neonates < 1 month, start at 60–80 mL/kg/day and advance by 10–20 mL/kg/day. Use isotonic fluids (D5 1/2NS or NS) per AAP 2018 guidelines.

Deficit is the fluid volume lost, calculated as: % dehydration × weight (kg) × 10. For moderate dehydration (8%) in a 10 kg child: 0.08 × 10 × 1000 = 800 mL deficit. Replace half over first 8 hours, remaining half over next 16 hours.

Mild (3–5%): dry mucus membranes, normal skin turgor. Moderate (6–9%): decreased turgor, prolonged capillary refill, sunken eyes, oliguria. Severe (≥10%): tenting skin, anuria, lethargy, hypotension. Use the WHO dehydration scale for rapid assessment.

Isotonic (Na 130–150): equal water and salt loss (most common). Hypotonic (Na < 130): more salt loss than water. Hypertonic (Na > 150): more water loss than salt. Treatment differs: isotonic uses NS bolus, hypertonic requires slow correction.

Give half of the total deficit over the first 8 hours, the remaining half over the next 16 hours, in addition to maintenance fluids. Use NS or LR for boluses (20 mL/kg). Reassess after each bolus. Add dextrose if glucose is low.

Mild dehydration (3–5%): slightly dry mucous membranes, normal or slightly decreased skin turgor, normal capillary refill (< 2 sec), slightly decreased urine output, thirsty, normal heart rate and blood pressure.

Moderate dehydration (6–9%): dry mucous membranes, decreased skin turgor, capillary refill 2–4 sec, sunken eyes, oliguria (< 1 mL/kg/hr), irritability, tachycardia, normal to low blood pressure.

Severe dehydration (≥10%): parched mucous membranes, skin tenting, capillary refill > 4 sec, deeply sunken eyes, anuria, lethargy or unconscious, significant tachycardia, hypotension, weak pulses, mottled skin.

Total = Maintenance + Deficit + Ongoing losses. Maintenance from 4-2-1. Deficit = % dehydration × weight (kg) × 10. Ongoing losses replace vomiting/diarrhea volume (10 mL/kg per episode). IV fluids are typically used for moderate-severe dehydration.

Isotonic crystalloids: NS (0.9% saline) or LR (Lactated Ringer’s). Give 20 mL/kg IV bolus over 20–30 minutes. Reassess after each bolus. For shock, give up to 40–60 mL/kg in the first hour. Avoid hypotonic fluids for resuscitation.

Per AAP 2018 guidelines: use isotonic fluids (NS, D5 1/2NS + KCl, or LR) rather than hypotonic fluids (D5 1/4NS) to reduce risk of iatrogenic hyponatremia. D5 1/2NS + 20 mEq KCl/L is the most commonly used maintenance fluid for children > 1 month.

Hypotonic fluids (D5 1/4NS) increase the risk of iatrogenic hyponatremia because hospitalized children have elevated ADH levels from stress, surgery, or nausea, leading to water retention and dilutional hyponatremia, which can cause cerebral edema.

NS is preferred for initial resuscitation (20 mL/kg boluses). LR is preferred for ongoing resuscitation in surgical patients, burns, and diabetic ketoacidosis. Both are isotonic. LR avoids hyperchloremic acidosis seen with large volumes of NS.

Neonates: D10W on day 1, then D10 1/4NS on day 2–3, advancing to D10 1/2NS. Start at 60–80 mL/kg/day. Increase by 10–20 mL/kg/day to max 150 mL/kg/day by day 5. Add calcium gluconate and TPN if prolonged IV therapy.

Hypernatremic dehydration (Na > 150) requires slow correction over 48–72 hours at a rate not exceeding 0.5 mEq/L/hr. Use D5 1/4NS or D5W. Replace deficit over 48 hours rather than 24 hours. Monitor for cerebral edema.

Hyponatremic dehydration (Na < 130) requires cautious correction with NS (0.9% saline) boluses. Rate should not exceed 8–12 mEq/L in 24 hours. Severe hyponatremia (< 120) with symptoms may require 3% saline (2–4 mL/kg IV). Risk of ODS.

Replace ongoing stool losses mL-for-mL or at 10 mL/kg per diarrheal stool. For a 10 kg child with 3 loose stools/day: 10×3 = 30 mL/kg = 300 mL extra per day. Add to maintenance + deficit. Use NS or LR for replacement of losses.

WHO Plan A (no dehydration): ORS at home. Plan B (some dehydration): ORS 50–100 mL/kg over 4 hours. Plan C (severe dehydration): IV fluids 100 mL/kg over 3–6 hours (30 mL/kg in first 30 min, then 70 mL/kg over 2.5–5.5 hours).

DKA fluids: NS 10–20 mL/kg bolus if hypotensive, then calculate deficit (5–10% of body weight). Replace over 24–48 hours. Use NS for the first 4–6 hours, then switch to D5 1/2NS when glucose < 250–300. Add KCl 20–40 mEq/L once K+ is known.

Add KCl 20 mEq/L to maintenance fluids once the child has voided and serum K+ is normal. Never give KCl IV push. For hypokalemia, may add 40 mEq/L. Maximum infusion rate: 0.5 mEq/kg/hr. Monitor cardiac rhythm if high rates.

Premature infants start at 80–100 mL/kg/day (higher due to increased insensible losses). Use D10W initially, advance to D5 1/2NS. Monitor glucose, Na, and urine output. Insensible losses are higher due to immature skin. Use humidified incubator to reduce losses.

Maintenance: 4×10=40 + 2×10=20 + 1×5=5 = 65 mL/hr (1560 mL/day). For moderate dehydration (8%): deficit = 0.08×25×1000 = 2000 mL. Total first 24h = 1560 + 2000 + ongoing losses. Replace deficit half in 8h (1000 mL) and half in 16h (1000 mL).

Yes. ORS (oral rehydration solution) is preferred for mild-moderate dehydration in children who can tolerate PO. Give 50–100 mL/kg over 4 hours (WHO Plan B). IV is indicated for severe dehydration, persistent vomiting, or failed ORS.

WHO ORS: 1 L clean water + 6 tsp sugar + 1/2 tsp salt. Commercial ORS (Pedialyte, Enfalyte) is preferred. Avoid sports drinks (high sugar) and plain water (no electrolytes). Give 5–10 mL every 5–10 minutes for mild dehydration.

The most common error is using hypotonic fluids for maintenance, leading to iatrogenic hyponatremia. Other errors: underestimating dehydration %, not accounting for ongoing losses, giving too-rapid correction in hypernatremia, and not reassessing after boluses.

Monitor hourly urine output (goal 1–2 mL/kg/hr), daily weights (most accurate), serum electrolytes (Na, K, Cl, HCO3, glucose), clinical signs (mucous membranes, skin turgor, capillary refill, heart rate, blood pressure), and I/O charting strictly.

Dextrose (D5, D10) prevents hypoglycemia and starvation ketosis. Children have limited glycogen stores and higher glucose utilization. D5 is standard for maintenance. D10 for neonates. D12.5–D25 for TPN. Check blood glucose regularly.

Surgery increases ADH and aldosterone, reducing the need for maintenance fluids (stress response causes water and salt retention). Use isotonic fluids at ⅔ maintenance postoperatively. Replace third-space losses with NS or LR boluses (10–20 mL/kg).

Consult PICU for: severe dehydration with shock, hypernatremia (Na > 160) or hyponatremia (Na < 120), DKA with altered mental status, burns > 15% TBSA, renal failure, cardiac disease requiring careful fluid restriction, or persistent electrolyte abnormalities.