Inflammatory process of the lungs as a result of bacterial infection. May involve interstitial tissue and pleura but ultimately results in alveolar consolidation
Frequency of bacteria as cause of lower infection ranges from 10-50%
Risk factors include: numerous siblings, cigarette smoke exposure, preterm delivery, and lower socioeconomic status
Bacterial invasion via aspiration or hematogenous spread
Bacterial infection overwhelms host immune response
Host response may be impaired due to presence of viral infections, foreign body, or ETT/tracheostomy
Inflammatory response leads to increased capillary permeability with subsequent alveolar edema and leukocyte accumulation
This leads to decreased compliance with intrapulmonary shunt leading to hypoxemia
Bacteria can reach the blood via the pulmonary lymphatic tissue leading to sepsis
Tachypnea is the most sensitive index of disease severity
Figure 1: Pathophysiology of Pneumonia
Fever, leukocytosis with left shift, respiratory symptoms suggest the diagnosis
Lobar consolidation, multilobar consolidation, abscess, pneumatocele all suggestive of bacterial pneumonia
May be associated with bacteremia (estimates of 2.5-7% in hospitalized pediatric patients with pneumonia) (Myers, Ped Inf Dis 2013)
Sputum samples difficult to obtain from most children due to inability to expectorate a sample
Tracheal aspirates can be helpful with numerous PMN's and organisms on gram stain being suggestive while numerous epithelial cells or few PMN's suggest a poorly obtained specimen (contaminated with oral flora) or colonization, respectively. However, their predictive value for true infection is unclear. (Wilson D, PCCM 2014)
Pleural fluid may be helpful in identifying an organism (via gram stain and culture)
BAL can be considered in severely ill children or those not responding to typical treatment to identify other potential agents (ie fungal infection, PJP, etc.)
Typical pathogens vary by age:
Group B Strep: Newborn infants
Strep Pneumo: Typically children <2 yrs of age (3-5 mo old infants) but can affect all ages
H Flu: All ages, often associated with empyema (40%) and bacteremia
Staphylococcus (MSSA and MRSA): Often preceded by viral infections such as influenza, often associated with pleural effusion/empyema (up to 80%)
Mycoplasma: Most common in school-age children although can occur in young children/infants as well. Can be diagnosed via PCR. Requires atypical antibiotic coverage (ie azithromycin)
Pseudomonas: Often seen in those with underlying pulmonary disease or chronic illness. Also seen with artificial airways (ETT/tracheostomy) and along with staphylococcus, is one of the leading causes of ventilator associated pneumonia.
Antibiotic therapy targeted toward likely organisms, beginning with generally broad coverage
In the PICU we typically initiate vancomycin and pipercillin-tazobactam to empirically cover MRSA, resistant strep, as well as gram negative organisms including pseudomonas
More typical community acquired inpatient regimens include: Ceftriaxone for broad gram positive and gram negative coverage (lacking MRSA, pseudomonas coverage) and azithromycin for atypical organism coverage
Outpatient treatment regimens may include azithromycin as monotherapy, amoxicillin-clavulanic acid, or amoxicillin.
If other organisms are suspected (ie PJP with significant hypoxemia and suspicion for immunocompromise), other agents are used (ie Trimethoprim-Sulfamethoxazole + steroids for PJP)
Respiratory support as indicated
Stages of pleural disease
1: Pre-collection stage - PNA associated with pleuritis
2: Exudative stage - simple parapneumonic effusion (PPE)
3: Fibrinopurulent stage - complicated PPE/empyema
Effusion protein/serum protein ratio greater than 0.5
Effusion lactate dehydrogenase (LDH)/serum LDH ratio greater than 0.6
Effusion LDH level greater than two-thirds the upper limit of the laboratory's reference range of serum LDH
pH <7.2, LDH >1000, glucose <40, positive GS or culture + loculation/septations on imaging
Abx >48hrs before tap lowers culture yield but should not affect biochemistry of fluid
4: Organizational stage - thick pleural peel --> entrap lung --> restrictive lung disease
Optimal imaging modality for pleural disease
U/S should be initially used (CT provided no advantage over U/S)
CT should be reserved for complicated cases
Evaluate for parenchymal abscess
U/S is inadequate due to body habitus
Methods of intervention for PPE
Chest tube w/ chemical debridement
Video assisted thoracoscopic surgery (VATS)
When to intervene
Large effusions (affecting >50% of the thorax on CXR) with or without sxs
Moderate effusions (affecting 25-50% of the thorax on CXR) with persistent or worsening sxs
Any effusions associated w/ loculations
How to drain free flowing simple PPE
Consider single thoracentesis
First thoracentesis fails to adequately drain --> place chest tube
In young children requiring conscious sedation, may be beneficial to just place chest tube first instead of doing thoracentesis to avoid repeat procedures w/ sedation
<14F tubes should be used even for loculated effusions
How to manage empyema
Evidence for below guideline (References 6,7,8)
If VATS performed w/in 48hrs of empyema diagnosis --> reduces hospital stay by 4 days
If VATS performed >4 days after empyema diagnosis --> longer hospitalization and post-op complications
VATS vs. tPA (chemical debridement)
No difference in length of hospitalization
Failure rate of tPA was ~17% --> eventually got VATS
VATS more expensive than tPA
Give tPA (0.1 mg/kg up to 4 mg in 40 ml NS with chest tube placement, clamp tube for 1 hour dwell time, q24h x3 days)
If no clinical improvement --> U/S or CT
If persistent pleural disease --> VATS
If no pleural disease --> continue abx
Abx usually for 2-4 wks (minimum of 10 days after resolution of fever)
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8) Rahman et al. Intrapleural use of tissue plasminogen activator and DNAase in pleural infection. NEJM 2011.