What is the best course of treatment for a child with persistent vomiting?

Management of Persistent Vomiting in a 4-Year-Old

For a 4-year-old with persistent vomiting, immediately assess for bilious (green) emesis and initiate oral rehydration therapy with small, frequent volumes (5 mL every 1-2 minutes) of oral rehydration solution (ORS), escalating as tolerated; if vomiting persists despite adequate hydration attempts, administer ondansetron 0.2 mg/kg orally (maximum 4 mg) to facilitate oral intake. 1, 2

Immediate Red Flag Assessment

Before initiating any treatment, you must rule out surgical emergencies:

• Bilious (green-colored) vomiting requires immediate emergency surgical consultation as this suggests intestinal obstruction or malrotation with volvulus 1, 2
• Projectile vomiting that persists may indicate pyloric stenosis or other obstructive conditions requiring urgent evaluation 1
• Abdominal distension or tenderness necessitates emergency care 1

Hydration Status Assessment

Determine the severity of dehydration to guide your rehydration strategy:

• Mild dehydration (3-5% deficit): Slightly dry mucous membranes, normal mental status, normal urine output 2
• Moderate dehydration (6-9% deficit): Sunken eyes, decreased skin turgor, reduced urine output, increased thirst 2
• Severe dehydration (≥10% deficit): Severe lethargy, prolonged skin tenting >2 seconds, cool extremities, minimal urine output, signs of shock 2

Rehydration Protocol

For Mild to Moderate Dehydration (Most Common Scenario)

Start with aggressive oral rehydration using this specific approach:

• Administer 5 mL of ORS every 1-2 minutes using a spoon or syringe under close supervision 1, 2
• Gradually increase volume as tolerated 1
• Target 50-100 mL/kg of ORS over 2-4 hours for moderate dehydration 2
• Replace each vomiting episode with an additional 2 mL/kg of ORS 2
• Over 90% of children with vomiting can be successfully rehydrated orally when small volumes are administered frequently 1

For Severe Dehydration

• Initiate immediate intravenous rehydration with 20 mL/kg boluses of Ringer's lactate or normal saline until vital signs normalize 3
• Once stabilized, transition to oral rehydration to complete fluid replacement 3

Ondansetron Administration

Ondansetron is specifically indicated for children ≥4 years with persistent vomiting that impedes oral rehydration:

• Dose: 0.2 mg/kg orally (maximum 4 mg) 1, 4
• Alternative parenteral dose: 0.15 mg/kg (maximum 4 mg) 4
• Only administer after attempting oral rehydration, not as first-line therapy 1, 5
• Ondansetron reduces vomiting episodes and facilitates ORS tolerance without significant adverse events 6
• For children 4-11 years receiving chemotherapy, the dose is 4 mg administered 30 minutes before chemotherapy 7

Critical caveat: The FDA label indicates ondansetron for chemotherapy-induced and postoperative vomiting 7, but guidelines support its use for gastroenteritis-related vomiting when persistent 1, 4

Nutritional Management During Vomiting

Do not withhold nutrition once rehydration begins:

• Continue breastfeeding on demand throughout the illness 1, 5
• Continue full-strength formula if tolerated; consider lactose-free formula only if intolerance is suspected 1, 5
• For solid foods, continue the usual diet with starches, cereals, yogurt, fruits, and vegetables 1, 5
• Avoid foods high in simple sugars and fats 1, 5

Medications to AVOID

Never administer antimotility drugs (loperamide) to children <18 years with vomiting and diarrhea as they can cause serious complications including ileus and toxic megacolon 2, 5

When to Return for Emergency Care

Instruct parents to return immediately if:

• Vomiting becomes bilious (green) or bloody 2
• Child becomes increasingly lethargic or difficult to arouse 2
• Urine output decreases significantly (no urine for >8 hours) 1
• Signs of severe dehydration develop despite oral rehydration attempts 1
• Persistent symptoms beyond 5 days, especially with high fever 1

Common Pitfalls to Avoid

• Do not give large volumes of ORS at once—this will trigger more vomiting. Small, frequent volumes are key 1, 2
• Do not use apple juice, Gatorade, or soft drinks for rehydration—these have inappropriate osmolarity and electrolyte composition 3
• Do not routinely use antiemetics before attempting oral rehydration—most children respond to proper ORS administration alone 1, 5
• Do not assume viral gastroenteritis without considering other causes—bilious vomiting, abdominal distension, or altered mental status require immediate evaluation 2, 4