Pneumonia is the leading cause of infectious death in the US and one of the most common reasons for inpatient admission.
In IM, you'll see it over and over and over.
Here's my approach to the workup and management of inpatient CAP, along with some key pearls.
- Thread -
Check out these @pointofcaremed digital resources on CAP for use at the point of care!
They include admission checklists, HPI intakes, differentials, sample dotphrases for the EHR, and key clinical pearls, along with a podcast and YouTube video with accompanying slides.
First, what even is pneumonia (PNA)?
Simply put, it is inflammation of the lung parenchyma (most commonly caused by an infection) and can affect the alveoli, bronchioles, and interstitium.
The development of PNA is almost always associated with the microaspiration of either airborne pathogens or oropharyngeal secretions.
As such, PNA is often seen in patients with failure of lung-protective mechanisms like cough reflex and mucociliary clearance.
CAP is an infectious pneumonia contracted outside of a hospital setting.
Viruses are the most common cause of CAP.
The most common bacteria are Strep Pneumo, H. Flu, and Moraxella
However, a pathogen is only detected in 38% of patients admitted with concern for PNA.
When evaluating for bacterial CAP, focus on:
1. Evidence of systemic inflammation
- WBC with neutrophil predominance
- fever, chills, malaise
2. Pulmonary Symptoms
- hypoxia, productive cough, dyspnea
- less likely if sore throat or rhinorrhea
3. Opacities on CXR
Historically, some PNAs were noted to be "atypical" - they had milder symptoms, dry cough, interstitial pattern on CXR, and different response to antibiotics.
We now know this difference is because certain organisms preferentially exert their effect on the interstitium.
Confusingly, "atypical" can refer to either the PNA itself or bacteria that often cause it (i.e chlamydia, legionella, and mycoplasma).
Note, however, that "atypical" does not imply uncommon.
While "typical" lobar pneumonias are most commonly caused by strep pneumo, and "atypical" pneumonias by mycoplasma, a pathogen should not be assumed based on imaging alone.
Given that it is challenging to clinically distinguish between the two, the treatment is the same.
Pneumonia can cause hypoxia via infiltration and inflammation in the alveoli and interstitium, causing:
1. decreased ventilation and V/Q mismatch
2. intrapulmonary shunt (right to left) - blood continues to flow to affected areas and does not exchange oxygen
Here's a checklist I use when admitting a patient with suspected CAP.
Key Questions:
- Is this severe CAP requiring ICU?
- Is this actually a PE or ACS?
- Underlying pulmonary disease?
- Risk factors for MRSA or PsA?
- Prior infections or culture data?
- Value of a CT?
Severe CAP Criteria
Need for mechanical ventilation or pressor
OR
3 or more of:
- AMS
- Hypotension requiring resuscitation
- Hypothermia < 36 C
- RR > 30
- O2 requirement
- WBC < 4
- BUN > 20
- Plt < 100
- Multilobar PNA on CXR
CURB-65 and PSI are validated for predicting mortality, not necessarily the ideal site of care.
However, calculating these (along with assessing for severe CAP), can help you get a sense of sick vs not sick.
In the end, nothing trumps clinical judgment.
Here is the most pertinent info to collect for your HPI.
Key Questions:
- Systemic disease vs localized to lungs
- Trajectory of symptoms
- Exposures and unique risk factors
On exam, PNA may result in:
- reduced breath sounds
- bronchophony - increased clarity of voice
- egophany - E sounds like A
- tactile fremitus - vibrations more pronounced
- dullness to percussion
These are due to consolidation and increased density of lung tissue.
When thinking through your differential, its important to consider not only infectious etiologies, but also pneumonia mimics.
Don't miss:
- Severe PNA or sepsis
- MRSA or Pseudomonas
- PE
- ACS
- ADHF
Aspiration pneumonitis is aspiration of aggrevating substances into the airway without infection.
The imaging findings and symptoms are caused by lung parenchyma inflammation - its usually more abrupt, low-grade fever, and classically RML/RLL if upright vs RUL if supine
It's often tough to tell the difference between aspiration PNA and pneumonitis.
Most end up treating for CAP for 48 hours and stopping with rapid racovery.
If the CXR clears quickly, it was likely pneumonitis. CXR findings from pneumonia usually take months to clear.
Cryptogenic Organizing Pneumonia (COP) is a pneumonia-like disease and imaging appearance due to non-infectious chronic inflammation.
Be suspicious in repeat cases of PNAs seemingly unresponsive to abx.
Specifically lookout for a history of RA or amiodarone use.
Here's a sample plan for CAP.
The most important parts:
- Prompt initiation of abx to at least cover for typical and atypical organisms - commonly ceftriaxone and azithromycin
- Source control as needed
- CT if severe or unclear etiology
Urine legionella and pneumoccocal antigens are usually sent if severe CAP or in cases of a known outbreak.
Similarly, BCx are usually only sent in severe CAP or sepsis
Induced sputum cultures are rarely helpful unless you are concerned about resistance
If available, procalcitonin can be sent on admission and at 48 hours to assess trajectory and in cases where you have lower suspicion for bacterial PNA and want to pull off abx sooner.
In general, procal <0.5 makes a bacterial infection less likely.
twitter.com/ROKeefeMD/status/1700177205165543816
Per the CAPE COD trial (lol), patients admitted to the ICU with severe CAP should receive hydrocortisone 200mg daily for 4-7 days based on improved 28-day mortality (6.2% vs. 11.9%).
These patients likely overlap with sepsis patients who also benefit from steroids.
If you remember nothing else,
- Assess for severe CAP
- Viral etiologies are most common
- Its often tough to differentiate between "typical" vs "atypical" pneumonia pathogens
- Start prompt antibiotics if c/f bacterial PNA
- Discharge when afebrile and ~baseline
There are so many amazing reviews, trials, and other educational resources to learn more about CAP and that helped inform this thread. Here are just a few highlights!
The @PyrlsApp CAP Management Algorithm is particularly excellent! A great resource that I'm using more and more.
twitter.com/PyrlsApp/status/1635947748359905280
For making it this far, here's the checklist, differential, and sample EHR dotphrase for admitting a patient with CAP.
You can also find the downloadable PDF on the @pointofcaremed website.