What is the treatment for a 5-month-old infant with a barking cough and vomiting, suspected of having croup?

Management of Barking Cough with Vomiting in a 5-Month-Old Infant

Immediate Clinical Assessment

This 5-month-old infant with barking cough and vomiting most likely has croup, and should receive a single dose of oral dexamethasone (0.15-0.60 mg/kg) immediately, with nebulized epinephrine (0.5 ml/kg of 1:1000 solution) added if there is stridor at rest or respiratory distress. 1, 2, 3

However, given the vomiting component, you must also consider pertussis (whooping cough) as a critical differential diagnosis, as paroxysmal cough with post-tussive vomiting is a hallmark feature of Bordetella pertussis infection, which is particularly dangerous in infants under 6 months. 4, 5

Diagnostic Approach

Key Clinical Features to Assess:

For Croup:

• Sudden onset of barking/seal-like cough 6, 2
• Inspiratory stridor (especially at rest indicates moderate-severe disease) 1, 3
• Hoarseness 6
• Respiratory distress signs: nasal flaring, intercostal retractions, tachypnea 1
• Low-grade fever or no fever 2, 3
• Oxygen saturation <94% indicates need for oxygen therapy 1

For Pertussis:

• Paroxysmal coughing fits followed by vomiting 4
• Inspiratory "whoop" sound (though may be absent in young infants) 4
• Apnea episodes (common in infants <6 months) 5
• Vaccination status (unvaccinated or incompletely vaccinated infants <12 months have highest risk of life-threatening complications) 4

Critical Pitfall:

At 5 months of age, this infant is in the highest-risk category for severe pertussis complications and death. 4, 5 Do not dismiss pertussis based solely on the barking cough—both conditions can coexist or be confused.

Treatment Algorithm

Step 1: Immediate Stabilization

• Assess ABCs rapidly and reassess at frequent intervals 5
• Administer oxygen if saturation <94% via nasal cannula, head box, or face mask 1
• Minimize handling to reduce oxygen requirements 1

Step 2: Croup-Specific Treatment

For All Severity Levels:

• Give oral dexamethasone 0.15-0.60 mg/kg as a single dose (preferred route is oral) 1, 2, 3, 7
• If vomiting prevents oral administration, use intramuscular or intravenous dexamethasone 3
• Alternatively, nebulized budesonide 2 mg can be given if oral route not tolerated 7

For Moderate-to-Severe Croup (stridor at rest or respiratory distress):

• Add nebulized epinephrine 0.5 ml/kg of 1:1000 solution 1, 8
• Monitor for at least 2 hours after last epinephrine dose for rebound symptoms 1
• Effect lasts only 1-2 hours 1
• Do not discharge shortly after epinephrine due to rebound risk 1

Step 3: Pertussis Evaluation and Treatment

If pertussis is suspected (paroxysmal cough with post-tussive vomiting):

• Test for Bordetella pertussis when clinically suspected 4
• Start azithromycin immediately (preferred macrolide for infants <1 month; also appropriate for 1-5 months) 5
• Azithromycin is preferred over erythromycin in infants <1 month due to lower risk of infantile hypertrophic pyloric stenosis (IHPS) 5
• Treatment is most effective when started early (catarrhal phase) 4
• Monitor for IHPS in infants receiving macrolides 5

Step 4: Hospitalization Criteria

Admit to hospital if:

• Three or more doses of racemic epinephrine needed 1
• Oxygen saturation <92-93% 1
• Age <18 months (this patient qualifies) 1
• Respiratory rate >70 breaths/min 1
• Inability of family to provide appropriate observation 1
• Suspected pertussis in infant <12 months (high risk for life-threatening complications) 4, 5

Additional Management Considerations

What NOT to do:

• Do not perform chest physiotherapy (not beneficial) 1
• Do not use humidified or cold air therapy (no proven benefit) 1, 2, 9
• Do not rely on radiographs for diagnosis (clinical assessment is sufficient; reserve imaging for alternative diagnoses) 1, 3
• Do not perform blind finger sweeps if foreign body suspected (may push object deeper) 1

Supportive Care:

• Antipyretics for comfort 1
• Maintain hydration 1
• Provide family education on signs of deterioration 1

Follow-Up

If discharged home:

• Review by physician if deteriorating or not improving after 48 hours 1
• Ensure reliable family able to monitor and return if worsening 1
• If pertussis confirmed, implement contact tracing and prophylaxis for household contacts (especially critical for infants <12 months and pregnant women in third trimester) 5

The dual consideration of croup and pertussis in this age group is critical—treat the croup symptomatically while simultaneously evaluating and treating for pertussis given the vomiting and the infant's high-risk age. 4, 1, 5