Sip Sheet — Pediatric Oral Rehydration & Anti-Emetic Dosing

Evidence-based oral rehydration therapy and weight-based ondansetron dosing for vomiting and dehydration in children, based on SickKids AboutKidsHealth, CHEO, and CPS guidelines.

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What is Dehydration?

Clinical Definition

Mild <5%
Moderate 5–10%
Severe >10%
Dehydration is the loss of body fluids exceeding intake, most commonly from vomiting and diarrhea in children. Severity is classified by estimated percent body weight loss. Most mild-to-moderate dehydration in children can be managed safely at home with oral rehydration therapy.

Red Flag Symptoms — Seek Medical Attention

  • Sunken fontanelle (infants)
  • No urine output for >8 hours
  • No tears when crying
  • Dry mouth and tongue
  • Lethargic or difficult to rouse
  • Rapid or weak pulse
  • Sunken eyes
  • Poor skin turgor (skin does not spring back when pinched)
ORT Dosing Calculator

About ORT

Oral rehydration therapy (ORT) is appropriate for mild-to-moderate dehydration in children ≥ 1 month. Use WHO/UNICEF standard oral rehydration solution (ORS) such as Pedialyte or Hydralyte. Avoid plain water, juice, or sports drinks.
Rehydration — Oral Deficit Replacement

Mild Dehydration (<5%)

Total ORS
—
mL over 4 hours
Approx. Cups
—
cups (250 mL each)
Rate
—
mL/hour
Syringe Rate
—
mL every 5 min
50 mL/kg of ORS over 4 hours. If vomiting, offer by syringe — 5 mL every 1–2 minutes.

Moderate Dehydration (5–10%)

Total ORS
—
mL over 4 hours
Approx. Cups
—
cups (250 mL each)
Rate
—
mL/hour
Syringe Rate
—
mL every 5 min
100 mL/kg of ORS over 4 hours. If vomiting, offer by syringe — 5 mL every 1–2 minutes.
Maintenance Fluids (Holliday-Segar)

Daily Maintenance — Calculated

Daily Volume
—
mL/day
Daily Volume (L)
—
L/day
Hourly Rate
—
mL/hour
Baseline fluid needs only. Additional ORS should be given for each episode of ongoing diarrhea or vomiting.

What to Use for ORS

Use WHO/UNICEF standard ORS (e.g. Pedialyte, Hydralyte, or homemade: 1L water + 6 tsp sugar + ½ tsp salt). Serve chilled or with a straw to improve palatability. Avoid Gatorade/sports drinks — too much sugar, too little sodium.

Ondansetron (Zofran) Dosing Calculator

About Ondansetron (Zofran)

Ondansetron ODT is appropriate for children ≥ 6 months with vomiting due to gastroenteritis. It is not routinely recommended for vomiting from other causes without physician assessment. Prescription required in Canada.

Ondansetron Dose — Calculated

Single Dose
—
mg
Formulation
—
ODT tablet
Max Doses
2 in 24 hours
repeat once after 8 h
Available as 4 mg and 8 mg ODT. 2 mg dose = ½ of a 4 mg ODT. Prescription required in Canada — discuss with your physician or emergency provider.
⚠️ Caution: Do not use in children with known prolonged QTc, electrolyte abnormalities (hypokalemia, hypomagnesemia), or those taking other QT-prolonging medications. Use with caution in hepatic impairment.

When NOT to Use Ondansetron

Bilious (green) vomiting, suspected surgical abdomen, head injury, ingestion or poisoning, or child appears toxic or seriously unwell — these require physician assessment first.

Other Evidence-Based Strategies

Continue Feeding

  • Do not withhold feeds — resume age-appropriate diet as soon as tolerated
  • Breastfed infants: continue breastfeeding throughout rehydration
  • Avoid the BRAT diet (bananas, rice, applesauce, toast) — no evidence it speeds recovery
  • Complex carbohydrates, lean meats, fruits, and vegetables are appropriate
  • Avoid high-fat and high-sugar foods during acute illness

Probiotics

  • Lactobacillus rhamnosus GG (e.g., Culturelle) and Saccharomyces boulardii have the best evidence for reducing duration of diarrhea in children
  • May reduce duration of diarrhea by approximately 1 day
  • Safe for healthy children; use standard pediatric dosing on package
  • Not routinely recommended but reasonable to try

Hand Hygiene & Infection Control

  • Most pediatric gastroenteritis is viral (rotavirus, norovirus, adenovirus)
  • Rigorous handwashing with soap and water for ≥20 seconds — alcohol-based sanitizers are less effective against norovirus and rotavirus
  • Keep child home from daycare/school until 48 hours after last episode of vomiting or diarrhea
  • Disinfect surfaces with a dilute bleach solution (1:10)

Monitoring at Home

  • Track wet diapers / urine output: expect at least 1 wet diaper every 6–8 hours
  • Weigh child if possible — weight returning toward baseline indicates successful rehydration
  • Signs of improvement: improved activity, moist mouth, tears when crying, resumed urination
  • Keep a simple log of fluid intake and output
When to Seek Medical Attention

When to Seek Medical Attention

Go to the Emergency Department if:
  • Bloody diarrhea or bloody vomit
  • Bilious (green or yellow) vomiting
  • Signs of severe dehydration (see Section 1 red flags)
  • Child is lethargic, unresponsive, or very difficult to rouse
  • Vomiting persists >24 hours in an infant under 6 months
  • High fever in an infant under 3 months
  • Suspected ingestion or poisoning
  • Child appears to be in significant pain
See your doctor or nurse practitioner if:
  • Child is not improving after 8–12 hours of home ORT
  • Diarrhea persists >7 days or worsens
  • Child is not tolerating any oral fluids despite ondansetron
  • Frequent vomiting in an infant under 2 months (rule out pyloric stenosis)
  • You are unsure or concerned for any reason