Things We Do For No Reason in Pediatrics #2

March 17, 2021 | By Justin Berk

How to Stop Relying on Blood Cultures and X-Rays!

Summary

If you’re looking to bring your clinical game to the next level, look no further than this next episode where we’ll discuss three huge areas of medical overuse. By the end of the episode, you’ll know pneumonia, cellulitis, blood cultures, and more than you’d ever expect about constipation. We welcome Drs. Leonard Feldman and Carrie Herzke back to the podcast, both TWDFNR authors, to explore and educate us on these topics. Listen along here, and follow us @TheCribsiders on #MedTwitter!

Credits

• Producer: Nicholas Lee, MD
• Writer: Nicholas Lee, MD
• Infographic: Nicholas Lee, MD
• Cover Art: Chris Chiu, MD
• Hosts: Justin Berk MD, Chris Chiu MD
• Editor:Justin Berk MD; Clair Morgan of nodderly.com
• Guest(s): Leonard Feldman MD and Carrie Herzke MD

TWDFNR #2 Pearls

1. There is a low likelihood that a patient with community acquired pneumonia will have a clinically useful blood culture result (with < 2.5% of patients being bacteremic and a contamination rate of 3% of all cultures).
2. The vast majority of CAP in children < 5 years old will be due to viral etiologies.
3. There is no evidence that x-rays help diagnose constipation in children; in fact, it can cause increased admissions for bowel clean outs.
4. Non-purulent cellulitis is oftentimes caused by Strep and can be treated with a second-generation cephalosporin.
5. Purulent cellulitis is caused by MRSA/MSSA and should be treated with TMP-SMX, doxycycline, or clindamycin.

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TWDFNR #2 Show Notes 

Community Acquired Pneumonia and Blood Cultures

Why blood cultures in CAP are usually unnecessary

Blood cultures are often useful in severe infections because they can identify an organism that is driving the illness, allowing the provider to tailor antibiotic therapy towards the pathogenic organism. In fully vaccinated children (particularly HiB vaccination), only 3 of 100 children will grow out an organism, which is oftentimes a contaminant that will not help with your therapy. Overarchingly, 3% of blood cultures drawn in children result in a contaminant.

When are blood cultures in CAP useful?

Dr. Herzke lays out some instances in which blood cultures may be more beneficial than harmful:

1. Patients requiring the ICU (where 8% of patients grow an organism)
2. In complicated pneumonia (13-25% positivity rate; cultures from pleural fluid are typically not useful because they are pretreated)
3. Immunocompromised patients

Dr. Herzke’s bonus Things We Do For Good Reason: Treatment with high-dose ampicillin. It has better coverage and penetration for S pneumo than ceftriaxone!

But should I get a respiratory viral panel?

If most CAP in toddlers is caused by viruses, should I obtain a RVP?

• If it will change your management, then it can be worthwhile
  • Will you treat the flu?
  • Will you stop the antibiotics?
  • Will it change your cohorting (eg semi-private rooms)?

Abdominal X-Rays for Diagnosing Constipation

What is the best way to diagnose constipation? 

In a study of pediatric gastroenterologists, 70% would obtain an x-ray to evaluate for stool burden. Yet, the diagnosis of constipation remains clinical delineated by the history (think Rome IV criteria) and physical examination. Alternatively, the x-ray can be misleading with patients having a “moderate stool burden” who have regular, Bristol 4 stools. Indeed, a study in 2010 evaluated different clinical scores and their ability to differentiate between constipation and non-retentive fecal incontinence, and they found that the x-rays did not aid in the diagnosis, which suggested that patients may be undergoing unnecessary radiation.

Dr. Feldman’s expert opinion: There is currently no evidence that performing a digital rectal examination in patients suspected to have constipation helps in the diagnosis, so you should feel comfortable not making it a routine part of your examination.

When might an X-Ray be useful?

While constipation is a clinical diagnosis, there may be concerning items on your differential (even if less likely), such as small bowel obstruction, where it may be appropriate to obtain an x-ray. Be sure to do so!

Cellulitis, MRSA, and more blood cultures

What is the best approach to cellulitis?

Dr. Herzke lays out her approach to diagnosing and managing cellulitis as follows:

1. Evaluate the patient and ensure that you are treating cellulitis.
2. Rule-out serious etiologies, such as necrotizing fasciitis that would necessitate a completely separate management plan.
3. Determine whether the cellulitis is purulent or non-purulent

Why does differentiating purulent or non-purulent cellulitis matter?

The original studies that examined cellulitis and showed a significant portion of Staph infections were based on wound cultures, meaning that they included predominantly patients with purulent cellulitis. Thus, purulent cellulitis is predominantly caused by MRSA and MSSA; on the other hand, non-purulent cellulitis is predominantly caused by Strep species that are oftentimes not included in the spectrum of activity of oral antibiotics that treat MRSA.

For the treatment of non-purulent cellulitis in the immunocompetent patient, the recommendations state that a cephalosporin is appropriate, specifically cefazolin (IV) or cephalexin (PO). For cephalexin, you can utilize the TID dosing rather than the QID dosing. Sufficient therapy is 5 days rather than the 10 days that is sometimes prescribed.

For the treatment of purulent cellulitis, you can utilize TMP-SMX, doxycycline, and clindamycin, though with clindamycin one must check the susceptibilities for MRSA since it is highly resistant in some patient populations. Dr. Herzke’s expert opinion is that she does not double-cover for Strep in these patients since the pathogenic organism is typically Staph.

Why are blood cultures overutilized for cellulitis?

Cellulitis is typically a localized infection that does not result in bacteremia. Thus, the rate of positive blood cultures is approximately 0.4 to 2.9% in immunocompetent children. Thus, you oftentimes do not identify a pathogenic organism, and there are additional costs. For each contaminated blood culture (3% of all cultures in children), it costs the hospital approximately $8,000 to $11,000 that does not even account for the typical increased length of stay associated with empirically treating a bacteremia. One hospital based study demonstrated that reducing blood culture contamination by one percent saves $50,000 per month.

Cellulitis #protips

• For animal bites, amoxicillin-clavulanate
• For immunocompromised patients who have been exposed to water, consider Vibrio, especially if blistering
• For necrotizing fasciitis, broad-spectrum antibiotics and surgical consultation
• Remember that cellulitis can get slightly worse after antibiotic initiation prior to it improving
• Raise the extremity to help drain (just as helpful as the antibiotics)

Goal

Listeners will explain three clinical scenarios of low-value care and be able to more effectively manage these scenarios in the future.

Learning objectives

After listening to this episode listeners will…  

1. Plot a path towards high value care
2. Describe why the risks may outweigh the benefits for blood cultures in patients with CAP
3. Take a history and examine a child to make a clinical diagnosis of constipation
4. Explain why determining if cellulitis is purulent or not is important and how it affects management
5. Identify situations where blood cultures may be beneficial in CAP and cellulitis.

Disclosures

Dr. Feldman and Herzke report no relevant financial disclosures. The Cribsiders report no relevant financial disclosures. 

Citation

Lee N, Herzke C, Feldman L, Chui C, Berk J. “Things We Do For No Reason in Pediatrics”. The Cribsiders Pediatric Podcast. https:/www.thecribsiders.com/ 3/17/2021