Chad D. McCalla
EPIDEMIOLOGY
Pneumonia is more common in early childhood than at any other age and the incidence decreases with age (eg, 40 per 1000 in preschool children, 9 per 1000 in 10-year olds in North America).
Viruses or bacteria usually cause pediatric pneumonia, though in most cases, the causative organism is unknown due to difficulties obtaining appropriate specimens, and age is the best predictor of etiology.
Infants less than 4 months of age are at risk for Chlamydia trachomatis, RSV, other respiratory viruses, and Bordetella pertussis.
In the 1 to 24 months age group, mild to moderate pneumonia can be caused by respiratory viruses as well as Streptococcus pneumoniae, Haemophilus influenzae (less commonly), and Mycoplasma pneumoniae.
Although viral pathogens dominate during years 2 to 5, the above bacterial pathogens are common. By the sixth year through 18 years of age, influenza virus A or B and adenovirus are common.
At any age, severe pneumonia may be caused by Staphylococcus aureus, Strep. pneumoniae, M. pneumoniae, H. influenzae B, and group A streptococci.
Special consideration to unusual organisms must be given to children with immunosuppression (Pneumocystis jiroveci, CMV, fungi), cystic fibrosis (Staph. aureus, Pseudomonas), and sickle cell disease (encapsulated organisms).
Risk factors for pneumonia and disease severity include prematurity, malnutrition, low socioeconomic status, passive exposure to smoke, and day care attendance.
Although the mortality rate is less than 1% in industrialized nations, 5 million children less than 5 years of age in developing countries die each year from pneumonia.
PATHOPHYSIOLOGY
Most cases of pneumonia develop after aspiration of infectious viruses or bacteria into the lower respiratory tract.
Protective mechanisms include nasal entrapment of aerosolized particles, mucus and ciliary movement in the upper respiratory tract, laryngeal reflexes and coughing, alveolar macrophages, activation of complement and antibodies, and lymphatic drainage.
Children who are at a higher risk for pneumonia include those with anatomic abnormalities of the airways, immune deficiencies, neuromuscular weakness, and abnormal mucus production.
CLINICAL FEATURES
Clinical features of pneumonia vary with patient age and underlying health as well as infectious etiology.
Neonates and young infants with pneumonia typically present with a sepsis syndrome. Signs and symptoms are nonspecific and include fever or hypothermia, tachycardia, or bradycardia, tachypnea or apnea, hypoxemia, poor feeding, lethargy or irritability, grunting, vomiting, and shock.
Tachypnea is the most common physical sign in children with pneumonia. In an otherwise well-appearing child, the absence of tachypnea suggests another diagnosis, especially in the absence of respiratory distress, rales, or abnormal breath sounds.
Signs and symptoms of pneumonia in older children include fever, cough, pleuritic chest pain, tachypnea, and abnormal lung examination. Associated signs and symptoms may include malaise, headache, rhinitis, conjunctivitis, pharyngitis, wheezing, and rash.
Occasionally, abdominal pain is the primary complaint of a child with lower lobe pneumonia and respiratory symptoms may be omitted during the history.
The clinical manifestations of bacterial and viral pneumonias overlap, making the clinical distinction between them problematic; no single physical examination finding is diagnostic, though combinations of signs and symptoms have better predictive value: the combination of fever, plus either tachypnea, decreased breath sounds or fine crackles predict radiograph positivity with a sensitivity of 93% to 96%.
DIAGNOSIS AND DIFFERENTIAL
As discussed above, individual clinical signs and symptoms cannot reliably distinguish bacterial from viral pneumonia, and chest radiographs are commonly used for this purpose as consolidation is considered a reliable sign of pneumonia.
Though radiologic distinction among viral, atypical, and bacterial pneumonias is not perfect, viral infections typically reveal diffuse interstitial infiltrates with hyperinflation, peribronchial thickening or cuffing, and areas of atelectasis. Bacterial infections tend to produce focal lobar or segmental infiltrates. Care must be taken to distinguish a normal pediatric thymus from focal consolidation (Figs. 73-1 and 73–2).
FIG. 73-1. Arrows indicate a normal thymus. Rotation, apparent from the location of the heart, trachea, and clavicles, makes this thymus appear to be far right of midline. (Courtesy of BC Children’s Hospital, Vancouver, BC, Canada.)
FIG. 73-2. Anterior-posterior (A) and lateral views (B) shows lower lobe consolidation (arrows). (Courtesy of BC Children’s Hospital, Vancouver, BC, Canada.)
Indications for chest radiography include (1) age 0 to 3 months as part of a “rule out sepsis” evaluation; (2) age <5 years with temperature >39°C (102.2°F), WBC count >20,000/mm3, and no other source of infection; (3) ambiguous clinical findings; (4) suspicion for pulmonary complications (eg, pleural effusion or pneumothorax); (5) pneumonia that is prolonged or unresponsive to treatment; (6) suspicion of foreign body aspiration; suspected congenital lung malformations; (7) follow-up of “round pneumonia.”
Sputum cultures are generally unhelpful as they are difficult to obtain in young children, though they may be helpful for older children with cystic fibrosis or children with tracheostomies.
Rapid viral antigen tests are available for RSV and influenza, and may be useful in reducing the inappropriate use of antibiotics or unnecessary invasive testing of infants and young children with fever.
A CBC may reveal leukocytosis; a left shift is typical for bacterial pneumonia, or atypical, or cleft lymphocytes may be seen in children with viral infection or pertussis.
Blood cultures are positive <10% of the time in children with proven bacterial pneumonia and are not routinely recommended.
The differential diagnosis for pneumonia in children includes congestive heart failure, atelectasis, tumors, congenital pulmonary anomalies, aspiration pneumonitis, chemical pneumonitis (eg, hydrocarbons), foreign body aspiration, diabetic ketoacidosis, GI emergencies (eg, appendicitis), and chronic pulmonary diseases.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Treat hypoxia with supplemental oxygen.
Consider positive pressure support (eg, continuous positive airway pressure) for severe respiratory distress and endotracheal intubation for respiratory failure.
Administer isotonic crystalloid for dehydration caused by increased insensible losses and inability to tolerate oral intake (eg, young infants with significant tachypnea, children with vomiting).
Treat bronchospasm with β-agonists.
Treat bacterial pneumonia with empiric antibiotics selected by likely etiologic agent and whether treatment is inpatient or outpatient (Table 73-1).
TABLE 73-1 Empiric Treatment for Pneumonia in Healthy Children
Most children with pneumonia can be treated as outpatients. Indications for admission include age <3 months, a history of apnea or cyanosis, toxic appearance, severe respiratory distress, pulmonary complications (eg, empyema), vomiting with inability to tolerate oral intake or medication, an unreliable home caretaker, and hypoxemia.
The exact pulse oximetry threshold at which an otherwise well-appearing young child with pneumonia should be admitted to the hospital is unknown, however, POX <90% on room air correlates with an increased risk of amoxicillin treatment failure.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 121, “Pneumonia in Infants and Children,” by Joseph E. Copeland.