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What’s the diagnosis and what’s the gold standard for POCUS??

March 2, 2015 4 Comments

A man in his late 50s presented to an ED a while back during the summers months with a 3 day H/O multiple complaints including rhinorhea, sore throat, dry cough, vomiting, loose stool, right frontal headaches, dyspnea, dysuria, and dark urine. So, a mixed picture. Fever of 100.9 was measured at home. No contacts or travel. Pretty healthy in the past: just hypertension, back problems and a 1/2 ppd smoker.

On exam, he looked sick. HR 115 T 37.8 RR 18 BP 105/63. Sat 90 on R/A. Decreased A/E on left base but otherwise negative exam. CXR showed a LLL pneumonia. Normal WBC. Lab abnormalities included Plt 104, Na 120, Cl 84, Lactate 2.9, AST 442, ALT 133, LDH 2027. Bili and ALP normal. AFib on ECG. Negative urine. Ceftriaxone and Zithromax IV were started. Dropped BP and became more tachy. POCUS scans for shock initiated (RUSH, ACES, UHP protocol…pick your acronym!). The IVC was flat. The cardiac scan was done mostly to look for an empty LV, but this was found instead…at the end of the video, an arrow will point out the main abnormality.

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Pretty obvious pericardial effusion (PCE), eh? Interestingly, the elective echo was negative for effusion. So, what’s the diagnosis?

LLL pneumonia, hyponatremia, and elevated LFTs suggested a presumptive diagnosis of Legionella pneumonia. The IVC scan guided aggressive fluid resuscitation beyond 4 L. Norepinephrine was added. The patient was admitted to the ICU and ultimately improved. Urine antigen testing later confirmed the diagnosis.

So how does one explain the pericardial effusion? PCEs can occur in a minority of Legionella cases. There are a couple of case reports in the literature (1, 2). A PCE can be an extra data point to rule in this diagnosis. If the PCE accumulates quickly enough or is large enough, it can contribute to shock along with sepsis and hypovolemia.

Last point. The POCUS scan and elective echo showed discrepant results. The PCE is blindingly obvious in this case, so I think we know which scan was correct. That brings up a question. Many POCUS studies assessing the accuracy of scans performed by clinicians use elective ultrasound or echos as a gold standard or comparator. Is that a valid gold standard?

Comments (4)

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  1. Lloyd Gordon says:

    Your scan (very good quality in a shocky patient) and the elective one were at different times which accounts for the different findings. As we get better at POCUS, the quality of our scans will approach that of the elective scans. Plus our scans are point of care and can actually impact our care.

    • The elective echo was done 2 days later. Possible but doubtful that the PCE would have disappeared in such a short time frame. Plus it was read 2 days after that. Like you said, POCUS scan more likely to impact patient care.

  2. Rob Devins says:

    Great case Steve. Two questions:
    1. Looks like there is an element of RV free wall collapse.
    When you guys were “live” did you have that sense?
    2. How much later was the “elective” u/s?

    • 1) Ha! Looks like it, eh? Not really, we thought the low BP was more from sepsis/hypovolemia.
      2) 2 days later. Some small chance that it disappeared on its own. In any case, raises the point that the POCUS scan would have been considered a false-positive and judged inaccurate if this case happened to be in a study. Not a valid gold standard if done 2 days later or the elective test is not done with a keen eye to look for the findings we’re interested in.

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