#11: Community-Acquired Pneumonia: The Alveoli Strike Back

October 28, 2020 | By Justin Berk

A comprehensive review of pneumonia with Dr. Lipsett

Summary

Join us on a voyage of diagnosis, triage, and treatment of community-acquired pneumonia! Dr. Susan Lipsett delves into the nuances of triaging patients, teasing out viral versus bacterial pneumonia, and choosing the right antibiotic.

Credits

• Written and Produced by: Maximilian Cruz MD
• Infographic: Maximilian Cruz MD
• Cover Art: Chris Chiu MD
• Hosts: Justin Berk MD; Chris Chiu MD
• Editor: Justin Berk MD; Clair of Nodderly.com
• Guest(s): Susan Lipsett MD

Pneumonia Pearls

1. While most of CAP is viral, there is no reliable way to delineate viral from bacterial, which is why we often treat the majority of CAP with antibiotics.
2. If you are going to use antibiotics, the recommended 1st line therapy is high-dose amoxicillin for 7 days.
3. While CXRs are not great to diagnose CAP, a clear CXR can be useful to rule out CAP.
4. The only clinical findings that have been associated with a diagnosis of bacterial pneumonia are hypoxemia and increased work of breathing.
5. Oral cephalosporins are often unnecessarily broad, and are less effective at treating S. pneumoniae than amoxicillin!
6. If you see a child with a viral illness who suddenly worsens, think about superimposed bacterial pneumonia.
7. S. pneumoniae and M. pneumoniae are the most common isolates in presumed bacterial CAP.
8. If a child with CAP fails to improve and/or worsens after 36-48h of treatment, consider obtaining a CXR or US to evaluate for complications such as an empyema.

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Time Stamps

• 7:15 CAP definition
• 10:40 CXR in Diagnosis
• 12:40 Other Imaging in CAP
• 13:20 Outpatient Management of CAP
• 14:32 Other Diagnostic Work-up
• 20:55 Triaging disposition
• 26:27 Asthma Episode Promo
• 27:00 Antibiotic Treatment
• 30:58 PCN Allergy
• 31:30 Azithromycin
• 33:30 Treatment failure
• 36:00 CAP complications
• 41:40 Management of pleural effusions
• 46:55 Discharge goals/criteria
• 48:20 Transition to PO on discharge
• 51:04 The Future of Pneumonia Treatment
• 54:49 Outro

Diagnosis of Pneumonia

Definition of CAP

While there is no single universal definition of CAP, the simplest definition is: any infection of the lower airways that is acquired outside of the hospital. While we often synonymously use CAP for “bacterial community acquired pneumonia”, it is important to remember the CAP can be due to many etiologies: viral, typical bacterial, atypical bacterial, fungal. 

Etiology

Often CAP is used as a synonym for bacterial CAP, however there are many pathogens that cause CAP, including typical bacteria, atypical bacteria, viral, and fungal pathogens. Viral pathogens are the most common cause of CAP, especially in younger children. The 2 most common causes of bacterial CAP in children are Mycoplasma pneumoniae and Streptococcus pneumoniae. Expert opinion: While M. pneumoniae was the most common bacterial isolate in the CDC’s EPIC study, it is increasingly unclear how often it is truly pathogenic, as studies have shown that  a lot of asymptomatic children harbor M. pneumoniae. (See our TWDFNR episode!)  It is also important to note that many institutions don’t have access to pathogen testing to detect M. pneumoniae.

Diagnostic criteria

The Pediatric Infectious Diseases Society (PIDS) and Infectious Diseases Society of America (IDSA) guidelines don’t specifically comment on diagnostic criteria for bacterial versus viral versus atypical CAP. Trying to differentiate bacterial CAP clinically can be difficult, in one systematic review the only findings that were associated with a diagnosis of bacterial pneumonia were hypoxemia and increased work of breathing. Fever, tachypnea, and auscultatory findings, specifically, were not independently associated with increased likelihood of bacterial pneumonia (Shah et al, JAMA Pediatrics 2017).  

Expert tip: Asthma exacerbations due to viral illnesses can often look very similar to bacterial CAP, always keep this on your differential. You can learn more about this on our first #TWDFNR episode here. 

Workup of Pneumonia

Chest X-ray

Guidelines recommend getting CXRs (PA and lateral) in all patients hospitalized for CAP, but recommend against routine CXR in the outpatient setting. However, there is evidence that a negative CXR excludes CAP in the majority of children (Lipsett et al, Pediatrics 2018). Expert opinion: A negative CXR in a child with low-medium clinical suspicion for CAP may allow you to safely observe without antibiotic therapy. Use shared decision making with family, and explain that a negative CXR may help you avoid unnecessary antibiotic use, and all of its potential side effects, in their child.

POCUS

There is some emerging pediatric data supporting its use for diagnosis of CAP, but we don’t know how well it correlates with bacterial CAP yet (Omran et al, Clin Respir J. 2018; Urbankowska et al, Respir Med 2015). Expert opinion: The role of POCUS will continue to expand, and we should have a better idea of how it fits into our algorithms as more data comes out.

Bloodwork

The guidelines recommend against blood tests as an outpatient. One older study suggested a leukocytosis >20,000 in febrile children revealed occult pneumonia on CXR, while another found WBC to be higher in children with pneumococcal versus viral pneumonia, however these were both pre-PCV13 vaccination so likely less relevant now. 

One study found that typical bacterial CAP had higher procalcitonin levels than atypical and viral (Stockmann et al, JPIDS 2018). Expert opinion: Dr. Lipsett does not routinely get procalcitonin/CBC in kids with suspected pneumonia, but if admitting and already placing IV, will usually send CBC and/or procalcitonin. In the outpatient setting, shared decision making is useful to determine the extent of workup.

Blood cultures

The guidelines recommend blood cultures on children being admitted to the hospital for moderate to severe CAP (low quality evidence). Expert opinion: Blood cultures have largely been put to rest, and are not useful in admitted patients with mild or uncomplicated CAP who are not critically ill. The chances of a “positive culture” being a contaminant are significantly higher than the likelihood of a true pathogen in this population. Also, most of the pathogens detected on blood cultures are susceptible to first line therapy for CAP anyways, so they are very unlikely to ever change management.

Viral testing

There is a lot of variation between institutions in regards to testing for viral pathogens. Some do viral pathogen PCR testing for cohorting purposes. There is evidence that viral testing can decrease the workup we do looking for bacterial causes in respiratory illnesses (See section “Testing for Viral Pathogens” pp. e22-e23 in the guidelines for a great summary). It is also likely that you are seeing more viral testing uniformly during the current COVID-19 pandemic. 

Disposition 

Admission criteria

General admission criteria recommended in the guidelines include hypoxemia, moderate respiratory distress, infants less than 3-6 months of age with suspected bacterial CAP, and presence of a moderate to large pleural effusion. 

Expert tips:

One approach is to ask yourself two main questions:

• Do they need something we can’t give them at home? Think: supplemental oxygen, IV hydration, IV antibiotics, etc. 
• Are they at significant risk of clinically worsening? Think:  significantly increased work of breathing, hypoxemic, dehydrated, overall ill-appearing, significant medical comorbidities, incompletely immunized, etc.

Other things to consider: 

• Do they have access to a car? 
• Do they have a PCP they actually see?
• If you prescribe an antibiotic, will they be able to fill it?

You can always watch in the ED for 1-2 hours to make sure their trajectory isn’t worsening. While guidelines recommend admitting if under 3-6 months, Dr. Lipsett will consider discharge with close outpatient follow-up if they are well-appearing, and have good follow-up in place. Just keep in mind they are incompletely immunized, and can change clinical course quickly. 

Treatment

When do I reach for the antibiotics?

The recommendation is only to use antibiotics if you think you are dealing with bacterial CAP. While viral is the most common etiology of CAP in children <5, we don’t have a great way of teasing out which presentations are bacterial versus viral and so you will often see providers in both the outpatient and acute care setting treat with antibiotics. A recent study showed that in ambulatory kids treated for CAP, almost 50% received azithromycin and 25% received oral cephalosporins, so we have work to do in prescribing the right drug for the main bug!

Editor comment: One recent study found that among children with suspected CAP discharged from the ED, receipt of antibiotics or antibiotic prescription did not lead to differences in treatment failure (Lipshaw et al, Pediatrics 2020).

Your First, Second, and Third Best Friend: Amoxicillin

Guideline recommended first-line therapy for bacterial CAP is amoxicillin. Treatment of bacterial CAP is largely targeted towards S. pneumoniae, and amoxicillin is really effective at treating this bug!. There is some regional variability, but there is very little that high-dose amoxicillin can’t overcome (blast from the past: resistance to beta-lactams in S. pneumoniae is mediated by changes to PBPs, which you can overcome with high-doses of amoxicillin). 

High-dose amoxicillin dosing = 90 mg/kg per day. There is some debate as to dividing into BID vs TID dosing; most ID purists will say TID for best pharmacokinetics for extended killing time for S. pneumoniae. 

Cephalosporins: IV ≠ PO 

Using oral cephalosporins as first-line coverage for uncomplicated bacterial CAP has become increasingly common. There are two problems with this; first they are usually overkill in broadness of coverage, which contributes to antibiotic resistance; secondly they are actually not as effective as amoxicillin at treating S. pneumoniae! 

It is important to note that while oral cephalosporins (think: cefdinir) are not as effective for S. pneumoniae, IV ceftriaxone does have very good coverage of S. pneumoniae.  There are situations in which you may want to reach for an oral cephalosporin (unvaccinated child, better Moraxella coverage, concern for resistant H. influenzae, etc), but these are less likely if you’re dealing with uncomplicated bacterial CAP. 

Mycoplasma? Azithromycin? 

Guidelines are vague due to lack of great evidence, and recommend you use macrolides in kids who you suspect have atypical CAP. One systematic review did not find sufficient evidence to support or refute treatment (Biondi et al, Pediatrics 2014). Right now there are more questions than answers, but we probably overprescribe azithromycin.

Penicillin Allergy

If true concern for penicillin allergy, you can use cephalosporins or azithromycin (but azithromycin has high strep resistance in some regions, so be careful!). 

When the Adult Walks into the Peds ED…

Don’t panic! The adult IDSA guidelines recently switched from azithromycin to amoxicillin as first line therapy, so go ahead and pull your same friend amoxicillin out of your pocket! 

2AM page: IV fell out, do we need to put another one in?

Transition those IV antibiotics to PO as soon as you are able to, which is generally as soon as the patient can tolerate taking by PO meds! Some common IV to PO conversions:

Ampicillin → Amoxicillin

Vancomycin → Clindamycin or Trimethoprim/Sulfamethoxazole

Ceftriaxone → Amoxicillin (remember: you would lose some S. pneumo coverage if you transition to an oral cephalosporin)

Duration of Treatment

The last version of the guidelines recommend 10 days of treatment. Expert opinion: there are studies showing shorters courses are likely adequate, and many institutions are coming down to 7 days of therapy. Dr. Lipsett will often treat uncomplicated CAP for 7 days, and complicated CAP for longer than 7-10 days, often up to 14 days, depending on the scenario..

Treatment Failure & Complications

Definition of Treatment Failure

No improvement and/or worsening of symptoms after 48-72 hours. Before moving on consider whether it was viral all along, and now they have worsening bronchospasm (especially in a child with underlying asthma). If you didn’t get a CXR previously, now is the time to get it to evaluate for any evidence of a complicated pneumonia. 

It’s Complicated…

Complicated pneumonia is a spectrum of disease, which includes pleural effusions, necrotizing pneumonia, lung abscesses, and bronchopulmonary fistulas. Since S. pneumoniae vaccination is now so widespread, the incidence of S. pneumoniae pneumonia has decreased, but rates of complications have increased.

Parapneumonic Effusions

Parapneumonic effusion = any pleural effusion secondary to pneumonia or lung abscess. This is probably the most commonly encountered complication.

Complicated parapneumonic effusion = empyema =  when microorganisms actually infect the pleural space leading to pus in the pleural space. 

You can use lung ultrasound (recommended first-line) or lateral decubitus CXR to help determine if it is a simple effusion or an empyema, and also whether there is evidence of loculations. Rarely should you use CT, usually only if there is high concern for lung abscess on CXR or US that you cannot otherwise fully characterize,, or the child is getting sicker despite appropriate therapy. 

Management of parapneumonic effusions is guided largely by size, specifically by degree of opacification of the hemithorax, as well as severity of illness:

Small
Definition: Opacifies <¼ of hemithorax. 
Sx/sxs: Patients usually well-appearing, no respiratory compromise. 
Tx: Antibiotics, generally no drainage necessary.

Moderate
Definition: Opacifies >¼ but <½ of hemithorax. 
Sx/sxs: Often some respiratory compromise. 
Tx: Broad spectrum antibiotics, and if significant respiratory compromise or concern for empyema, some form of drainage (chest tube with fibrinolytics to break up loculations, or VATS).

Large
Definition: Opacifies >½ of hemithorax. 
Sx/sxs: Usually very ill-appearing with significant respiratory compromise.
Tx: Broad spectrum antibiotics and drainage. 

In regards to antibiotic choice in complicated CAP, think of more virulent pathogens, specifically S. aureus and GAS. The classic picture is a child with a viral infection who develops a secondary bacterial infection. This is the time to switch from amoxicillin/ampicillin to a 3rd generation cephalosporin for better coverage of resistant S. pneumoniae and H. influenzae. Consider adding vancomycin for MRSA coverage. . 

Discharge Criteria

Set Goal Posts

Discuss discharge criteria on admission, that way the team and family are on the same page (these can change!). Big picture is trajectory, trajectory, trajectory! Think about what brought the patient into the hospital, and if that is now improved. 

Generally, you want them 1) off supplemental oxygen for 12-24 hours 2) tolerating oral hydration, 3) baseline mentation, and 4) any increased work of breathing should be progressing in the right direction.  It is OK to discharge with a fever, don’t use “afebrile” as a discharge goal! Most importantly, make sure they have close follow-up with their PCP!

Links

1. Peds in Review overview on bacterial CAP

Goal

Listeners will be able to appropriately work up and triage the many different flavors of pediatric community acquired pneumonia (CAP). 

Learning objectives

After listening to this episode listeners will…  

1. Recall that pediatric community acquired pneumonia (CAP) is a diagnosis broadly applied to any lower respiratory tract infection (LRTI) 
2. Differentiate which patients are appropriate for outpatient versus inpatient management
3. Choose an appropriate diagnostic workup in the evaluation of CAP
4. Assess the appropriateness of antibiotic regimens based on understanding of antibiotic spectrum and pharmacokinetics 
5. List the common complications of CAP

Disclosures

Dr. Lipsett reports no relevant financial disclosures. The Cribsiders report no relevant financial disclosures. 

Citation

Lipsett S, Cruz M, Chui C, Berk J. “Community Acquired Pneumonia: The Alveoli Strike Back”. The Cribsiders Pediatric Podcast. https:/www.thecribsiders.com. Original air date: October 2020.

References

Hyperlinked where referenced in notes.