What are the key considerations for managing an infant with suspected pertussis (whooping cough)?

Managing an Infant with Suspected Pertussis

Immediate Hospitalization and Monitoring

All infants under 12 months with suspected pertussis must be hospitalized immediately for continuous cardiorespiratory monitoring due to the high risk of life-threatening complications including apneic spells, bradycardia, cyanosis, and death. 1

• Implement continuous pulse oximetry and apnea monitoring from admission, as infants can present with apneic spells and minimal cough initially 1
• Monitor respiratory status between paroxysms carefully—infants typically appear deceptively well between episodes despite having severe disease 1
• Place the infant in a private room with droplet precautions (surgical mask within 3 feet) until 5 days after starting antibiotics 2
• Expect hospitalization duration of 2-6 weeks for infants under 6 weeks, with the paroxysmal stage typically lasting 2-6 weeks 3, 1

Antibiotic Treatment

Start azithromycin immediately upon clinical suspicion without waiting for culture confirmation. 4

Age-Specific Dosing:

• Infants <1 month: Azithromycin 10 mg/kg/day for 5 days (preferred over erythromycin due to lower risk of infantile hypertrophic pyloric stenosis) 2, 4
• Infants 1-5 months: Azithromycin 10 mg/kg/day for 5 days 2, 4
• Infants ≥6 months: Azithromycin 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg/day (max 250 mg) on days 2-5 4

Critical Timing Considerations:

• Early treatment (first 2 weeks/catarrhal phase) rapidly clears B. pertussis and decreases coughing paroxysms 4
• Late treatment (>3 weeks/paroxysmal phase) has limited clinical benefit but is still indicated to prevent transmission 4
• Antibiotics eliminate communicability after 5 days of treatment 2, 4

Important Medication Precautions:

• Do not administer azithromycin with aluminum- or magnesium-containing antacids as they reduce absorption 4
• Monitor infants <1 month receiving any macrolide for infantile hypertrophic pyloric stenosis (IHPS) 2
• Avoid erythromycin in infants <6 months due to IHPS risk 4

Diagnostic Confirmation

Obtain a nasopharyngeal aspirate or Dacron swab for culture immediately, as isolation of bacteria is the only certain way to confirm diagnosis. 2, 4

• Culture is most sensitive during the catarrhal phase (first 2 weeks) 2
• PCR testing is available but not standardized for routine clinical use 2
• Paired acute and convalescent sera showing fourfold increase in IgG or IgA antibodies to pertussis toxin or filamentous hemagglutinin can provide presumptive diagnosis 2

Nutritional and Hydration Management

Provide frequent small feedings immediately after coughing episodes to prevent aspiration and maintain nutrition, as post-tussive vomiting leads to substantial weight loss. 1

• Offer smaller, more frequent feeds when the infant is less likely to cough (immediately post-paroxysm) 1
• Consider nasogastric or intravenous hydration if vomiting causes dehydration or significant weight loss 1
• Monitor weight closely as substantial weight loss is a common complication 3

Environmental Modifications

Maintain a calm, quiet environment to minimize coughing triggers, as paroxysms can be precipitated by stimulation and occur more frequently at night. 1

• Reduce environmental irritants and eliminate tobacco smoke exposure 1
• Ensure adequate humidification of inspired air 1
• Anticipate and plan for significant sleep disturbance, as paroxysms increase at night 1
• Position the infant safely for sleep while facilitating secretion drainage 1

Complication Surveillance

Monitor continuously for life-threatening complications that are most common in infants under 2 months (case-fatality rate 1.3%). 2, 3

Respiratory Complications:

• Pneumonia (occurs in ~13% of infants, most common complication) 3, 5
• Apneic spells (52% of hospitalized infants) 6
• Cyanosis (63-68% of hospitalized infants) 6, 7
• Pneumothorax from severe coughing 3, 5
• Pulmonary hypertension (life-threatening, may require ECMO) 6

Neurologic Complications:

• Seizures (3% of infants <1 year) 2
• Hypoxic encephalopathy 3
• Subdural hematoma from coughing pressure 1, 5

Other Complications:

• Subconjunctival hemorrhage 1, 5
• Secondary bacterial pneumonia or otitis media 1
• Elevated lymphocyte count (>60,000/μL associated with mortality) 6

Therapies to AVOID

Do not use long-acting β-agonists, antihistamines, corticosteroids, or pertussis immunoglobulin—these have no proven benefit in controlling coughing paroxysms. 2, 4

Contact Management and Prevention

Administer macrolide prophylaxis to all close contacts, especially household members, using the same dosing regimen as treatment. 2

• Identify the source of infection (typically a sibling or parent in 61% of cases) 7
• Verify and update vaccination status of all household contacts 4
• Symptomatic household contacts should be treated as if they have pertussis 2
• Prophylaxis should be given within 21 days of cough onset in the index patient 2

Critical Pitfalls to Avoid

• Never discharge infants <12 months prematurely—the paroxysmal stage lasts 2-6 weeks and complications can occur throughout 1
• Do not be reassured by the infant's appearance between paroxysms—they often appear relatively well between episodes despite severe disease 1
• Do not delay antibiotic treatment while awaiting culture results—start immediately upon clinical suspicion 4
• Do not assume antibiotics will alter the clinical course if started late—they primarily prevent transmission after the catarrhal phase 4, 8
• Do not overlook incomplete vaccination status—65% of hospitalized infants are unimmunized and 30% incompletely immunized 7