Ian McCaslin
Pneumonia is an inflammatory process of the pulmonary parenchyma. It is commonly the result of community-acquired infections both viral and bacterial including Mycoplasma pneumoniae and Chlamydophila species (formerly known as Chlamydia). Although mortality rates from childhood pneumonia in the United States have declined over the past half century, worldwide pneumonia kills approximately 1.2 million children annually, making it the leading cause of death in children under the age of 5 (1,2). Pneumonia is frequently diagnosed in US children, with outpatient visit rates ranging from 74 to 92 per 1,000 children <2 years old to 35 to 52 per 1,000 children 3 to 6 years old (3). Children in the first 2 years of life have higher attack rates, but children in the 2- to 4-year-old age group have a higher incidence of pneumonia complicated by empyema (4).
Low socioeconomic status, poor nutrition, underlying disease, crowded living conditions, and smoke exposure as well as immunocompromise including malignancy, sickle cell disease, HIV, or genetic disorders have all been implicated in increased risk of pneumonia.
Pneumonia may be divided into bacterial and other etiologies (i.e., viruses, fungi, or parasites), but in the majority of cases a microbiologic agent is never identified. Since children do not produce sufficient sputum to obtain an adequate sample for culture, differentiation of infection from colonization is problematic. Nasopharyngeal culture is rarely useful in identifying a presumed bacterial pathogen. Rapid and reliable diagnostic methods are rarely available to the practicing physician. There are well-recognized seasonal variations in respiratory illness with late fall and winter peaks of lower respiratory tract illness due to viruses such as respiratory syncytial virus (RSV) and influenza A or B, but bacterial pneumoniae exhibit less seasonal variation.
A number of epidemiologic studies (5,6) have confirmed the importance of Streptococcus pneumoniae as the agent responsible for the majority of serious bacterial pneumoniae across all age groups beyond the newborn period. Introduction of the heptavalent pneumococcal conjugate vaccine in 2000, followed by the 13-valent vaccine in 2010, have resulted in dramatic reductions in the overall rate of invasive pneumococcal disease, including pneumonia in children <1 year of age (7,8). Rates of mixed infection of S. pneumoniae with either M. pneumoniae or Chlamydophila pneumoniae are relatively frequent in older children, suggesting that the historical classification of clinical pneumonia into “typical” and “atypical” categories should be discouraged. Viruses cause relatively more disease in younger infants and children, whereas M. pneumoniae and C. pneumoniae infections become more prevalent in the school-aged population. The most common viral agent is RSV, and evidence of coinfection of S. pneumoniaewith RSV is common, particularly in younger children. Human metapneumovirus infection is a relatively common cause of respiratory infection in young children, with a spectrum of disease similar to that of RSV (9). Staphylococcus aureus, including community-associated methicillin-resistant S. aureus (CA-MRSA), causes abrupt and severe pneumonia and should be particularly considered during influenza season or in the presence of severe disease (10). Mycobacterium tuberculosis may cause pneumonia in healthy children and is often linked to high-risk exposures. Anaerobic bacteria may be implicated in a host who is susceptible to aspiration, particularly if there is evidence of abscess formation.
CLINICAL PRESENTATION
Symptoms and signs of pneumonia in children vary with age, duration of illness, and underlying condition rather than by bacterial versus viral etiology. Many children with early pneumonia do not have specific respiratory complaints and do not appear severely ill. The “classic” presentation of sudden onset of fever, chills, chest pain, and productive cough is very rare. In fact, febrile children who are ultimately found to have pneumonia frequently present with nonspecific historical and physical examination findings (11). Infants younger than 2 months of age may present with fever and tachypnea and no signs of pulmonary consolidation or clinical evidence of sepsis. Young children usually exhibit some combination of fever, tachypnea, and focal lung findings, associated with a chief complaint of cough, upper respiratory infection symptoms, decreased activity, and poor intake. Older children typically demonstrate a short period of prodromal symptoms, including rhinitis, low-grade fever, decreased appetite, and decreased activity. The proportion of cases of pneumonia due to M. pneumoniae and C. pneumoniae increases in children after 5 years of age (12). Infections with these organisms characteristically progress slowly over 3 to 5 days, with fatigue, sore throat, low-grade fever, and cough. Occult bacterial pneumonia presenting with abdominal pain, vomiting, and dehydration may be mistaken for acute appendicitis.
Few findings on physical examination exhibit good interobserver reliability. No single physical examination finding or combination of findings demonstrates adequate sensitivity for the clinical identification of pediatric pneumonia. Fever, respiratory rate, and pulse oximetry are objective, reproducible parameters that may help in the clinical diagnosis of pneumonia, and most children with either bacterial or viral pneumonia exhibit some fever and cough by history or examination (11,13). World Health Organization criteria for the clinical diagnosis of pneumonia are based primarily upon the presence of tachypnea and retractions and demonstrate poor sensitivity for the diagnosis in a US-based population (14). The definition of tachypnea varies with age and is conservatively suggested to be a respiratory rate of >60 per minute in infants, >40 per minute in young children, and >20 per minute in those 5 years and older. While the respiratory rate alone is a poor predictor of pneumonia, infants and children ultimately diagnosed with pneumonia are more often tachypneic than not (15). The presence of hypoxemia, defined as saturation <90% at sea level, is difficult to detect on physical examination (16). Given that hypoxemia is well established as a risk factor for poor outcome in patients with respiratory disease, the simple measurement of oxygenation by pulse oximetry should be included in the initial evaluation of all symptomatic infants and children.
Certain combinations of clinical findings are characteristics of complicated lower respiratory tract disease. Grunting respirations with fever are nonspecific but should prompt further investigation. Rales, retractions, and localized diminished breath sounds are highly correlated with parenchymal disease. The presence of an associated pleural effusion is suggested by unilateral decreased breath sounds and dullness to percussion.
DIFFERENTIAL DIAGNOSIS
A number of conditions may be mistaken for community-acquired pneumonia. Lower respiratory illness characterized by cough, rhinitis, fever, and either wheezing or dry crackles on examination in children younger than 2 years of age is characteristic of bronchiolitis. Caused principally by RSV and human metapneumovirus, bronchiolitis is not improved with antibiotics, and can run a protracted course over 1 to 2 weeks. Sudden onset of high fever and signs of pneumonia after several days of lower respiratory symptoms consistent with RSV should prompt concern for bacterial superinfection and warrants antibiotic treatment. More severe disease can present with cyanosis and signs of respiratory failure, particularly in infants with underlying medical conditions such as congenital heart disease. Reactive airways disease affects nearly 10% of children, and acute episodes of difficulty breathing and cough, particularly at night, are commonly triggered by viral respiratory infections.
Foreign body aspiration, heart disease, and other conditions may be mistaken for infectious pneumonia. A history of a choking episode should be sought in all young children presenting with suspected pneumonia.
Myocarditis is frequently initially misdiagnosed as pneumonia; an ill appearance that suggests pneumonia but is not accompanied by a diagnostic chest film should prompt clinical suspicion and an EKG, and possibly an echocardiogram.
Congenital heart disease is suggested by evidence of diminished peripheral perfusion, congestive heart failure, or evidence of poor growth on examination. Depending upon the specific defect, cardiomegaly on chest radiography or diminished pulse oximetry readings that do not respond to oxygen administration are often supportive of the diagnosis.
ED EVALUATION
In most instances the diagnosis of pneumonia is based upon the history and physical examination alone. A chest radiograph is not required but may be helpful in establishing the diagnosis and excluding noninfectious causes. Radiographs ordered empirically for febrile children younger than 10 years of age with no lower respiratory tract findings, signs of respiratory distress, tachypnea, or hypoxia will reveal an occult infiltrate in approximately 5% of cases (11). Extreme dehydration or early clinical presentation may lead to false negative chest radiography in children subsequently diagnosed with acute bacterial pneumonia.
Chest radiography does not establish the etiology of a community-acquired pneumonia in children. Diffuse peribronchial thickening with hyperinflation of the lungs from air trapping is, however, more consistent with bronchiolitis or a viral etiology in the younger child, whereas focal lobar consolidation and pleural effusion in the older child suggests S. pneumoniae or, less likely, M. pneumoniae. Chest radiographs should always be obtained in patients with suspected or documented hypoxemia who are in respiratory distress. Both blood culture and complete blood count (CBC) with differential should be obtained for the hospitalized patient but are not routinely indicated in the outpatient management of pneumonia. The contribution of routine laboratory testing to patient outcomes can be variable. Knowledge of the peripheral white blood cell count or other acute-phase reactant levels at the time of presentation generally does not assist selection of specific therapy or consideration for admission (16). The prevalence of bacteremia is low, and most positive blood cultures are contaminants (17). Moreover, while bacterial disease is suggested by a peripheral white blood cell count >20,000/mm3, the CBC does not reliably differentiate between specific etiologies of pneumonia.
ED rapid testing for influenza A and B viruses is recommended during seasonal outbreaks; a positive test can significantly reduce the number of laboratory tests and radiographs ordered, and likewise reduces the number of antibiotic prescriptions (18). Other diagnostic tests such as serology, antigen assay, PCR, and nasopharyngeal swab for culture are considered investigational and are of little benefit in clinical decision making in the outpatient setting (19). Thoracentesis and culture of pleural effusion should be reserved for ill-appearing children or those with immunocompromise who require critical care admission, and in cases where chest tube drainage or operative management is recommended for suspected empyema or abscess.
KEY TESTING
• Early pulse oximetry determination, and oxygen supplementation if <92%
• Influenza A and B rapid diagnosis testing during seasonal outbreaks
• Chest radiography if more severe disease is suspected
• Complete blood count and blood culture if hospitalization is considered
ED MANAGEMENT
After a careful history and physical examination, coupled with a judicious use of radiography and laboratory markers, the emergency physician’s primary tasks are to initiate therapy and determine patient disposition. Ill-appearing patients should be placed on continuous cardiorespiratory monitoring while in the ED and dehydrated patients with pneumonia should be given an intravenous (IV) saline fluid bolus of 20 cc/kg. Initial pulse oximetry readings <92% on room air or an ill appearance should prompt oxygen administration by non-rebreather mask until the response to therapy can be determined. A trial of bronchodilator aerosols may be considered for patients with associated wheezing or history of reactive airways. Antitussive agents are generally ineffective and are not recommended. Purified protein derivative (PPD) placement should be considered for all patients with newly diagnosed pneumonia.
CRITICAL INTERVENTIONS
Infants younger than 8 weeks of age should be hospitalized after culture of blood, urine, and CSF, and empiric administration of IV ampicillin and cefotaxime. Infants aged 8 weeks to 3 months with uncomplicated pneumonia should be admitted to the hospital after culture of urine and blood in the ED followed by administration of IV cefotaxime or ceftriaxone. Narrow-spectrum IV penicillin or ampicillin may be administered to fully immunized children requiring hospitalization in areas where local epidemiologic data demonstrate low-level penicillin resistance for invasive S. pneumoniae. Parenteral antibiotic therapy may be initiated with cefuroxime or ceftriaxone for hospitalized children who are not fully immunized, in regions of higher-level penicillin resistance, or for children with severe infections, including those with empyema (16). Inpatient treatment for infections suspected to be caused by either M. pneumoniae or C. pneumoniae may include IV azithromycin. Children with severe pneumonia require additional empiric coverage for S. aureus , including CA-MRSA. Initial treatment should include IV vancomycin in addition to IV ceftriaxone. These children should be considered for admission to an intensive care unit. Emergency providers should maintain awareness of regional antimicrobial susceptibility reports.
DISPOSITION
Most children with pneumonia can be managed as outpatients, and antibiotic therapy is not indicated for patients with suspected bronchiolitis or if findings are consistent with a viral syndrome. Children beyond 3 months of age with uncomplicated pneumonia may be treated for 10 days with amoxicillin, cefuroxime, or clindamycin in penicillin-allergic patients (16).
For school-aged children where M. pneumoniae and perhaps C. pneumoniae are possible etiologic agents in addition to S. pneumoniae, macrolides including azithromycin or erythromycin are acceptable options. Though not approved for pediatric use, oral levofloxacin appears safe and effective in children with pneumonia if significant resistance to S. pneumoniae is suspected (20). Children in whom fluid intake or compliance is a concern may be given parenteral ceftriaxone (50 mg/kg as a single dose) for coverage of initial 24 hours of therapy.
Printed language-appropriate discharge instructions should be reviewed with caretakers prior to discharge from the ED. Attention to adequate hydration, fever control, medication compliance, and observation for worsening condition should be emphasized. The emergency physician may wish to communicate directly with the primary care provider prior to patient discharge. All children with pneumonia diagnosed in the ED should be reevaluated within 24 hours. Fever often persists for 48 hours into the course of treatment of bacterial pneumonia.
Indications for admission include age younger than 4 months, respiratory compromise, persistent oxygen requirement, inability to retain oral fluids or medication, concerning underlying medical condition, and uncertain home environment. Patients with immunocompromise, large pleural effusion, respiratory distress, evidence of hypoxemia requiring FiO2 greater than feasible in a general care setting, or suspicion of CA-MRSA pneumonia should be admitted to an intensive care unit or transferred to a facility where appropriate monitoring and critical intervention is ensured.
Common Pitfalls
• Failure to diagnose a patient with foreign body aspiration or myocarditis.
• Treating for bacterial pneumonia in the young well-appearing wheezing child.
• Failure to ensure understanding of discharge instructions, including follow-up in 24 hours.
REFERENCES
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