What is the recommended approach to evaluating and managing a pediatric patient with vomiting, including assessment for red‑flag signs, rehydration, antiemetics, and investigations?

Approach to Pediatric Patient with Vomiting

Begin with immediate assessment for red-flag signs that indicate life-threatening conditions requiring urgent intervention, then proceed with hydration assessment and oral rehydration therapy as first-line treatment. 1, 2, 3

Immediate Red-Flag Assessment

Bilious vomiting at any age indicates intestinal obstruction until proven otherwise and requires immediate surgical evaluation. 1, 4, 5

Critical warning signs requiring urgent intervention include: 1, 2, 3, 4

• Bilious (green) vomiting - suggests malrotation with volvulus, intestinal obstruction
• Bloody vomiting (hematemesis) or bloody stools (hematochezia)
• Altered mental status - lethargy, severe irritability, decreased consciousness
• Signs of severe dehydration (≥10% fluid deficit): prolonged skin tenting >2 seconds, cool extremities with poor capillary refill, rapid deep breathing indicating acidosis
• Abdominal distension or tenderness - suggests surgical abdomen
• Bulging fontanelle, macro/microcephaly, seizures - indicates increased intracranial pressure
• Fever with toxic appearance - suggests sepsis, meningitis
• Projectile vomiting in infant <3 months - consider pyloric stenosis
• Bent-over posture - suggests pancreatitis or other serious abdominal pathology

Age-Specific Considerations

Neonates and Infants <3 months 2, 3, 6

This age group requires lower threshold for concern and hospitalization due to:

• Higher body surface-to-weight ratio and metabolic rate
• Complete dependence on caregivers for fluid intake
• Higher risk of severe dehydration and complications
• Life-threatening causes include: congenital intestinal obstruction, malrotation with volvulus, pyloric stenosis, necrotizing enterocolitis, sepsis, meningitis, inborn errors of metabolism, congenital adrenal hypoplasia 4

Infants 4-12 months 1, 3

Common presentation includes gastroesophageal reflux (peaks at 4 months, resolves by 12 months in 90-95% of cases), but must exclude:

• Intussusception (peak age 6-18 months)
• Gastroenteritis (most common cause)
• Urinary tract infection/pyelonephritis 2

Children >1 year and Adolescents 1, 4

Consider: appendicitis, diabetic ketoacidosis, intracranial mass lesions, toxic ingestions, cyclic vomiting syndrome, uremia

Hydration Status Assessment

Use specific clinical signs to categorize dehydration severity, as this determines treatment approach. 1, 2, 7, 3

Mild Dehydration (3-5% fluid deficit) 1, 2, 3

• Slightly dry mucous membranes
• Normal mental status
• Normal capillary refill
• Adequate urine output

Moderate Dehydration (6-9% fluid deficit) 1, 2, 3

• Dry mucous membranes
• Loss of skin turgor with tenting when pinched
• Decreased urine output
• Mild tachycardia

Severe Dehydration (≥10% fluid deficit) - MEDICAL EMERGENCY 1, 2, 3

• Severe lethargy or altered consciousness
• Prolonged skin tenting >2 seconds
• Cool, poorly perfused extremities
• Decreased capillary refill
• Rapid, deep breathing (metabolic acidosis)
• Minimal or absent urine output

Most reliable clinical predictors: prolonged skin retraction time, abnormal capillary refill, and rapid deep breathing. Acute weight change is most accurate if premorbid weight is known. 2, 3, 8

Rehydration Strategy

For Mild to Moderate Dehydration (First-Line Treatment) 1, 2, 7, 3

Oral rehydration solution (ORS) is the first-line treatment and successfully rehydrates >90% of children with vomiting and diarrhea without antiemetic medication. 2

Critical technique for vomiting patients: 1, 2, 3

• Start with 5 mL every 1-2 minutes using spoon or syringe
• Gradually increase volume as tolerated
• Small, frequent volumes prevent triggering more vomiting
• Close supervision is essential

Dosing: 1, 2, 7, 3

• Mild dehydration (3-5%): 50 mL/kg ORS over 2-4 hours
• Moderate dehydration (6-9%): 100 mL/kg ORS over 2-4 hours
• Replace ongoing losses: 10 mL/kg for each watery stool, 2 mL/kg for each vomiting episode
• Reassess hydration status after 2-4 hours; if still dehydrated, reestimate deficit and restart

Use low-osmolarity ORS formulations - avoid sports drinks, juices, or caffeinated beverages as primary rehydration fluids. 2, 7, 3

For Severe Dehydration (≥10% fluid deficit) 1, 2, 7, 3

Immediate intravenous rehydration is required:

• Administer 20 mL/kg boluses of lactated Ringer's or normal saline
• Repeat until pulse, perfusion, and mental status normalize
• May require two IV lines or alternate access (venous cutdown, femoral vein, intraosseous)
• Once consciousness returns, transition to ORS for remaining deficit

Antiemetic Use

Ondansetron (0.15-0.2 mg/kg, maximum 4 mg) may be given to children >4 years with significant vomiting to facilitate oral rehydration. 2, 7, 4, 8, 9

Benefits: 8, 9

• Decreases vomiting rate
• Improves oral intake success
• Reduces need for IV hydration
• Decreases ED length of stay
• Very few serious side effects reported

Indications: 4

• Persistent vomiting preventing oral intake
• Post-operative vomiting
• Chemotherapy-induced vomiting
• Cyclic vomiting syndrome

Do NOT use metoclopramide - it is ineffective and potentially harmful in gastroenteritis, as it accelerates GI transit which is counterproductive. 2

Nutritional Management

Resume age-appropriate diet during or immediately after rehydration - do NOT fast or restrict diet. 1, 2, 7, 3

• Breastfed infants: Continue nursing on demand throughout illness 1, 7, 3
• Bottle-fed infants: Full-strength formula immediately upon rehydration 1
• Older children: Resume usual diet including starches, cereals, yogurt, fruits, vegetables 1, 2
• Avoid: Foods high in simple sugars (soft drinks, undiluted apple juice), high-fat foods, caffeinated beverages 1, 2

Investigations

For most pediatric patients with vomiting, history and physical examination are sufficient - diagnostic testing is NOT routinely necessary. 1, 3, 9

When to Obtain Laboratory Studies 2, 4

Order investigations if:

• Any red-flag signs present
• Moderate to severe dehydration
• Diagnostic uncertainty
• Concern for surgical causes

Specific tests: 2, 4

• Urinalysis with culture (if urinary symptoms, fever, abdominal pain - to exclude UTI/pyelonephritis)
• Serum electrolytes and blood gases (if moderate-severe dehydration)
• Blood cultures (if febrile or toxic-appearing)
• Renal and liver function tests (if severe dehydration or concern for metabolic disorder)

When to Obtain Imaging 1, 6

Upper GI series is NOT routinely indicated for diagnosing gastroesophageal reflux or gastroenteritis. 1

Obtain imaging when: 1, 4, 6

• Bilious vomiting (urgent upper GI series or abdominal ultrasound to exclude malrotation)
• Abdominal distension or tenderness (plain abdominal radiography)
• Suspected intussusception (abdominal ultrasound)
• Suspected pyloric stenosis (abdominal ultrasound)

Hospitalization Criteria

Admit patients with: 2, 7, 3

• Severe dehydration (≥10% fluid deficit)
• Signs of shock or hemodynamic instability
• Altered mental status
• Failure of oral rehydration therapy despite ondansetron
• Intractable vomiting
• Absent bowel sounds (ileus)
• Infants <3 months with moderate-severe dehydration
• Immunocompromised patients
• Significant comorbidities increasing complication risk

Common Pitfalls to Avoid

• Never delay rehydration while awaiting diagnostic testing - begin ORS immediately 2
• Never use antimotility agents (loperamide) in children <18 years - serious adverse events including ileus and deaths have been reported 2, 7
• Never use sports drinks or juices as primary rehydration fluids for moderate-severe dehydration 2, 3
• Never give oral fluids if bowel sounds are absent - this is an absolute contraindication to oral rehydration 2
• Never underestimate dehydration in young infants - they have higher risk and may not manifest classic signs 2, 3
• Never assume vomiting is always GI-related - look for extra-GI causes (meningitis, UTI, metabolic disorders) if no GI disease identified 4, 5

Monitoring and Follow-Up

Monitor vital signs every 2-4 hours including capillary refill, skin turgor, mental status, mucous membrane moisture. 2, 3

Discharge criteria: 2

• Tolerating oral intake
• Producing adequate urine
• Clinically rehydrated
• No red-flag signs

Parent education: 1, 2, 3

• Provide 24-hour supply of ORS
• Teach small-volume, frequent administration technique (5 mL every 1-2 minutes)
• Instruct to return if: decreased urine output, lethargy/irritability, intractable vomiting, persistent diarrhea, bloody stools, high fever