Pediatric Dehydration and Fluid Management

Dehydration means losing water and electrolytes, usually through vomiting, diarrhea, fever or poor intake. Kids lose fluid faster than adults, with less in reserve. A modest deficit can change perfusion and mental status fast. Your job has three parts: estimate the deficit, restore perfusion with the right fluid, and avoid changing sodium too fast.

Why Kids Are Different

• Small reserve: in an infant, a few hundred milliliters is a large share of circulating volume.
• Heart rate is the early response: stroke volume is capped by heart size. Tachycardia comes before hypotension.
• Weight change is the reference: validation studies estimate the deficit from weight loss against a known baseline. Most field weights, though, are estimates.
• Isotonic fluid is the default: AAP 2018 recommends isotonic solutions for children aged 28 days to 18 years who need maintenance fluid. Hypotonic fluid raises the risk of hyponatremia.

Grade dehydration from the bedside signs. If a baseline weight exists, use the weight change too. The validation studies use different cut points. Falszewska 2018 puts some dehydration at 3–6% weight loss and moderate to severe at 6% or more. Gorelick 1997 used 5% or more. Treat the table as a bedside guide, not a precise percentage. The grade picks the route. A child with adequate perfusion starts with oral or NG rehydration. Poor perfusion, shock or failed enteral therapy needs IV or IO (see Management by Severity).

Gorelick 1997 derived the any-two-of-four rule: capillary refill over 2 s, absent tears, dry mucous membranes and ill general appearance. The derivation used 186 children aged 1 month to 5 years. Two or more of these signs predicted a deficit of at least 5%. Individual signs have low sensitivity. The diagnosis rests on several findings together. A later systematic review did not confirm the Gorelick scale in most validation studies. It also found little value in the WHO scale. Use these rules as a rough guide per Falszewska 2018.

Usually it's vomiting and diarrhea. The trap is the look-alikes: several must-not-miss conditions present the same way.

Some or Moderate Dehydration With Adequate Perfusion: Oral or NG Rehydration

1. Start oral rehydration solution: 75 mL/kg over 4 hours (WHO plan B), in small frequent amounts, per local protocol. Guidelines differ on volume, so follow local protocol. ESPGHAN/ESPID 2014 calls enteral rehydration superior to IV rehydration. Rapid rehydration over 4 hours is effective (2013 Pieścik-Lech review). Replace ongoing stool and vomit losses per protocol. Keep breastfeeding or a normal diet going as tolerated. Refuses, or cannot keep up with oral intake? A nasogastric tube is an accepted route, per local protocol. Avoid loperamide and other antimotility agents in children with gastroenteritis.
2. Treat vomiting that stops intake: ondansetron as in Medications & Dosing. It reduces vomiting, but it's off-label for gastroenteritis in the US.
3. Reassess at 4 hours: weight, perfusion, urine output and mental status. Choose discharge, or move to IV rehydration if oral or NG therapy has failed or perfusion is poor.
4. Do not give antibiotics for uncomplicated gastroenteritis: empirical antibiotics are reserved for these cases: infants under 3–6 months with suspected bacterial illness, underlying disease, sepsis, or institutional settings, per the 2025 Spanish consensus.

Shock, Poor Perfusion or Severe Dehydration: IV or IO Rehydration

1. Give an isotonic bolus: 10–20 mL/kg IV or IO, reassess after each (Paramedic/RN/CCT, per local protocol). Use IV or IO for shock or poor perfusion, severe dehydration, ileus or vomiting that prevents enteral intake, or failed oral or NG rehydration. Don't start IV access for a moderately dehydrated child who has adequate perfusion and can take ORS. The Pieścik-Lech 2013 review judged 20 mL/kg an appropriate IV volume in gastroenteritis, until more data are in. The Pediatric Shock page and local protocol set the bolus volume and reassessment.
2. Reassess after each bolus: mental status, capillary refill, heart rate, blood pressure, urine output, lung exam and work of breathing.
3. Repeat until perfusion recovers: stop for crackles, hepatomegaly or rising oxygen need. Above 20 mL/kg in the first hour, you're making a shock decision. See the Pediatric Shock page.
4. Check glucose and replace ongoing losses: treat hypoglycemia per the Dextrose page, then start maintenance fluid once perfusion is restored.

Doses vary by protocol; follow local protocols and medical direction.

Sodium Correction Limits

• Hyponatremia: These limits come from an adult nephrology standard (Spasovski 2024, reported in mmol/L). They are not pediatric guidance. In children, a pediatric nephrologist or intensivist should direct correction. For acute or severe symptomatic cases, the goal is a rise of 4–6 mEq/L in the first 6 hr. The rise should not exceed 8 mEq/L in any later 24-hr period. Here's the trap: a rise of more than 10 mEq/L in the first 24 hr is the level most often linked to osmotic demyelination. In vaptan-treated patients, the same standard caps high-risk patients at 8 mEq/L. Examples: hypokalemia, alcoholism, malnutrition or liver disease.
• Hypernatremia of chronic or unknown duration: Restore perfusion with isotonic fluid first. Then lower Na⁺ by no more than 0.5 mEq/L per hour and 10 mEq/L per 24 hr. These are commonly used targets, not pediatric guideline values (see the 0.45% Sodium Chloride page).

Disposition

• Discharge: perfusion normal and keeping fluids down after the oral plan, per local protocol.
• Admit or transfer: failed oral or IV rehydration, persistent shock, altered mental status, or sodium that needs controlled correction.

Infants

• Small reserve: a short illness can mean a large deficit. Weigh the infant whenever possible.
• Antibiotics are kept for infants under 3–6 months with suspected bacterial illness, per the 2025 Spanish consensus.

Children With Heart or Kidney Disease

• Give smaller boluses and reassess more often. The Lactated Ringer's page makes the same point for heart failure and end-stage kidney disease.
• Stop fluid for crackles, hepatomegaly or rising oxygen need.

Adolescents

• Use adult fluid volumes once the weight rule on the Weight-Based Dosing page is met.

Children With Diabetes

• Vomiting with high glucose: treat as possible DKA and follow the DKA protocol.
• Hypoglycemia can look like dehydration. Check glucose first.

Commonly, these roles are set by state or agency protocol. Know your local scope before you act.

• Equipment: pediatric weight tape or length-based tool, pre-measured bolus volumes, and a pump that delivers mL/hr.
• Destination: pediatric-ready ED for dehydration with shock or failed oral therapy; PICU for shock or sodium needing controlled correction.
• Handoff: use IMIST-AMBO or MIST, with the weight, the total volume given, the sodium and glucose, and the urine output.