Ep 130 Community Acquired Pneumonia: Emergency Management

While community acquired pneumonia (CAP) is 'bread and butter' emergency medicine, and the diagnosis is often a 'slam dunk', it turns out that up one third of the time, we are wrong about the diagnosis; that x-rays are not perfect; that blood work is seldom helpful; that not all antibiotics are created equal and that deciding who can go home and who needs to go to the ICU isn’t always so clear cut. With this in mind we are taking a deep dive into CAP with Dr. Leeor Sommer and Dr. Andrew Morris, from diagnosis to disposition so that we can better achieve our EM goals of stabilizing sick patients, getting the right diagnosis, initiating the best treatment with the information at hand, prognosticating/appropriately deciding on disposition of patients, and being healthcare and antimicrobial stewards... Podcast production, sound design & editing by Anton Helman; Script writing assistance by Andrew Cameron & Anton Helman. Written Summary and blog post by Alexander Hartt and Anton Helman September, 2019 Cite this podcast as: Helman, A., Sommer, L., Morris, A. Episode 130 - Community Acquired Pneumonia - Emergency Management. Emergency Medicine Cases. September, 2019. https://emergencymedicinecases.com/community-acquired-pneumonia. Accessed [date] Sources of the high misdiagnosis rate of CAP in the ED Some of the reasons why we misdiagnose CAP up to 1/3 of the time in the ED include pressure to make early treatment and disposition decisions (because of time-to-antibiotic "rules" in some jurisdictions), the expectation to have a definitive diagnosis when consulting services for admission, because the classic constellation of symptoms (cough, shortness of breath and fever) is often absent, there are many pneumonia mimics (CHF and PE being the most critical to identify and treat in the ED), early anchoring bias, there is overlap in clinical presentation of viral URI and pneumonia, blood tests may be misleading, CXR has poor accuracy, and there is no single historical or physical exam finding that has high enough likelihood ratio to shift pretest probability significantly. To aid diagnostic accuracy and avoid over prescribing antibiotics, force yourself to consider the diagnosic criteria for CAP: fever, respiratory symptoms and imaging evidence of an infiltrate. Pay close attention to respiratory rate and oxygen saturation – the vast majority of patients with CAP will have an elevated respiratory rate and abnormal O2 sat, but don’t be fooled by the marathon runner - they can maintain perfectly normal vitals with their CAP. Likelihood ratios for physical findings in CAP The highest positive likelihood ratios of clinical findings for CAP from a 2019 meta-analysis are RR≥20 (3.47), fever (3.21) and HR>100 (2.79). Normal vital signs combined with a normal pulmonary examination had a summary estimate -LR = 0.10 in a 2018 metaanalysis. Normal vital signs alone have a -LR = 0.18 for CAP. Pitfall: Using diagnosis of “acute bronchitis” in patients with viral respiratory illness, as it is a non-specific term that sets expectations by patients to be treated with antibiotics for a viral illness. Blood tests for diagnosis and prognosis of CAP are promising statistically but usually not pragmatically useful WBC > 10,400 per mm3 has +LR = 3.4, -LR = 0.52 for CAP, but normal values do not rule out pneumonia and WBC is not included in any of the prognostic decision tools. WBC in the extremes (<4, >20) may be of prognostic significance. CRP of >200mg/L hav been found to have a +LR>5, while <75mg/L have been found to have a -LR<0.2, however,