Paediatric complicated pneumonia: Diagnosis and management of empyema

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Pneumonia is one of the most common reasons for hospitalization in childhood. Although most bacterial pneumonia will resolve with treatment of the underlying infection, some cases will be complicated by the development of an empyema, defined as intrapleural pus or a moderate to large exudative parapneumonic effusion (stage 1), which can progress to being loculated (stage 2) with further development of a fibrinous peel (stage 3). Small parapneumonic effusions are common and do not require drainage. Although other complications of pneumonia occur (eg, pulmonary abscess or necrotizing lung), those topics are beyond the scope of the present document. The most common pathogen in an immunocompetent host is Streptococcus pneumoniae. Other common pathogens include Staphylococcus aureus and Streptococcus pyogenes (group A streptococcus)^[1]. Methicillin-resistant S aureus (MRSA) can also occur^[1]-[3]. Initial studies after the introduction of heptavalentpneumococcal conjugate vaccine (PCV7) reported an increased incidence of paediatric complicated pneumonia^[4]-[7], caused in part by the emergence of non-vaccine pneumococcus serotypes. The incidence of complicated pneumonia from particularly virulent serotypes (such as 19A) decline with the replacement of PCV7 with the 13-valent conjugate vaccine (PCV13)^[8]-[11].   

Clinical presentation

Children with complicated pneumonia will present with many of the symptoms and signs of uncomplicated pneumonia including tachypnea, fever, cough and respiratory distress. The patient may present with complicated pneumonia or an initially uncomplicated pneumonia that is poorly responsive to antibiotics (persistent fever after 48 h to 72 h of antibiotics without clinical improvement, persistent or worsening respiratory distress and/or hypoxia, or new clinical findings of a pleural effusion). Findings on examination that are consistent with a pleural effusion include decreased breath sounds, decreased chest expansion and dullness to percussion of the affected side.

Diagnosis

A chest radiograph (CXR) should always be the initial imaging modality. Ultrasound provides a noninvasive, radiation-free modality to confirm the presence of a pleural effusion suspected on CXR. As well, ultrasound can estimate the size of the effusion, and differentiate free-flowing effusions from those that are loculated^[12]. Chest computed tomography is associated with significant radiation exposure, and generally does not alter management or predict outcomes; therefore, it should not be performed routinely^[13]. However, chest computed tomography should be considered if an alternative diagnosis, such as malignancy, is suspected. Repeat CXRs are not necessary unless clinical deterioration is evident. 

Laboratory testing

When drainage of fluid is clinically indicated, the fluid should be sent for bacterial culture. The yield from pleural fluid cultures is low because most children have already received antibiotics. However, molecular tests, such as 16S or pneumococcal polymerase chain reaction, may increase yield if available; consultation with a local microbiologist is recommended^[14][15]. Pleural fluid biochemistry is generally unhelpful unless an alternative diagnosis is being considered (e.g., tuberculosis, malignancy). Blood cultures are positive in only a minority of cases (approximately 10%), but they should be collected before antibiotics are administered to potentially guide the choice of antibiotics for children who are sufficiently ill to be hospitalized for pneumonia^[4]. Sputum culture is occasionally helpful when available, but is usually difficult to obtain.

Management

There are no high-quality randomized controlled trials on many aspects of the management of paediatric empyema^[1]. Early initiation of antibiotics either alone or together with a drainage procedure is recommended for all patients. Early procedural intervention is recommended if the patient is in moderate to severe respiratory distress (worsening tachypnea, work of breathing and/or hypoxia) because the pleural fluid often occupies most of the hemithorax and may even cause mediastinal shift^[1]. Early consultation with a paediatric surgeon or interventional radiologist is recommended. Conservative management with antibiotics alone may have a role in milder cases (ie, small effusions, mild respiratory distress, and no mediastinal shift)^[1][16][17]. 

Choice of antibiotics

Antibiotics remain a key component in the medical management of empyema, with initial parenteral therapy to cover the most common pathogens, usually followed by oral therapy. Antibiotic coverage for likely causative organisms is essential. There are no randomized trials pertaining to the choice of antibiotics, specifically in empyema, so the potential choice of agents should be guided by clinical appearance and local prevalence of penicillin-resistant S. pneumoniae and MRSA risk factors. Cefotaxime or ceftriaxone is commonly used depending on local guidelines or antibiograms. Ampicillin may be an option for initial empirical antibiotic treatment in the absence of any of the following situations: high local rates of penicillin-resistant pneumococcus, severe illness, necrotizing pneumonia or lung abscess. The addition of vancomycin (or linezolid) is usually reserved for culture-proven or severe suspected MRSA pneumonia. Although no evidence exists for optimal treatment length for empyemas, a total of three to four weeks’ duration is reasonable if there is adequate drainage and no evidence of additional complications. Transition to oral antibiotics is appropriate when drainage has been completed, and the patient is clinically improving and off oxygen (ie, at or just before discharge). Appropriate oral antibiotics vary depending on local resistance patterns. If the cultures are negative, amoxicillin or amoxicillin-clavulanate is the recommended antimicrobial. Penicillin resistance to S. pneumonia is very low and therefore, amoxicillin given in appropriate doses should be reasonable. Refer to the Canadian Paediatric Society’s practice point “Uncomplicated pneumonia in healthy Canadian children and youth” for antibiotic dosages^[18]. 

It is not uncommon for children with empyemas to have fevers that persist for more than 72 h on appropriate therapy; if the child is otherwise improving clinically, it is usually not a sign of treatment failure.

Choice of procedural intervention

A variety of procedural interventions are used in Canada for the management of empyema. These include chest tube placement with or without fibrinolytics, repeated thoracentesis, video-assisted thorascopic surgery (VATS) and open thoracotomy with decortication. Best evidence based on only a few randomized trial suggests that either early small-bore percutaneous chest tube placement with instillation of fibrinolytics (CTWF) or early VATS leads to best outcome as measured by hospital length of stay^[19]-[21]. CTWF is the most cost-effective choice^[22]. Clinicians should consider local expertise in interventions (eg, a surgeon experienced in performing VATS or an interventional radiologist able to insert a small-bore pigtail catheter), and parental and patient preference when deciding on a treatment. In Canada, tissue plasminogen activator is the fibrinolytic commonly used (at a dose of 4 mg in 30 mL to 50 mL of normal saline daily for up to three days)^[23]. Intrapleural dornase alfa, while effective in adults with empyema, provides no additional benefit in children^[24]. 

Prognosis/Outcome

Complete recovery of pulmonary function with normalization of the CXR, aside from mild residual pleural thickening, is expected in the vast majority of children with complicated pneumonias. Other clinical outcomes such as exercise tolerance and spirometry are expected to normalize. Children should be followed after discharge until they have clinically recovered and their CXRs have returned to near normal, recognizing that the latter may take several months^[1][16][25]. Repeating the CXR at two to three months is reasonable.

Addendum

Other common lab findings in complicated pneumonia include elevated acute phase reactants (ie, WBC, ESR, CRP), thrombocytosis, and hypoalbuminemia. These resolve with clinical improvement, as does transient scoliosis which is sometimes seen on chest radiographs^[26].

Bronchopleural fistula development may complicate management. Patients presenting with necrotizing pneumonia are at particular risk. Consultation with experts in pleural disease management such as surgeons, respirologists, and infectious diseases specialists in such cases is warranted, as well as in cases where pleural abscess is suspected.

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CPS HOSPITAL PAEDIATRICS SECTION EXECUTIVE

Members: Sanjay Mahant MD (president); Isabelle M Chevalier MD (president-elect); Dawn S Hartfield MD (past-president); Eyal Cohen MD; Jeret Keith McLeod MD; Jennifer Walton MD
Liaison: Niraj Mistry MD, Residents Section, Canadian Paediatric Society
Principal authors: Thea K Chibuk MD; Eyal Cohen MD; Joan L Robinson MD; Sanjay Mahant MD; Dawn S Hartfield MD
Update by: Eyal Cohen MD, Sanjay Mahant MD

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References

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Disclaimer: The recommendations in this position statement do not indicate an exclusive course of treatment or procedure to be followed. Variations, taking into account individual circumstances, may be appropriate. Internet addresses are current at time of publication.