US Journal Club September, 2019: Lung Ultrasound

Paper 1

Lung Ultrasound Integrated with Clinical Assessment for the Diagnosis of Acute Decompensated Heart Failure in the Emergency Department: A Randomized Controlled Trial

Pivetta, E et al. European Journal of Heart Failure, 21: 754-766. doi:10.1002/ejhf.1379

Full Text

  • Background information
    • Acute decompensated heart failure (ADHF) is a common presentation to the Emergency Department, accounting for more than 4 million ED visits in 20161. The diagnosis can be made with a combination of history, physical examination, chest x-ray (CXR) and laboratory studies including pro-BNP. POCUS can supplement diagnosis by evaluating for pulmonary edema on lung ultrasound.
  • What was the objective of this study?
    • To compare the diagnostic accuracy of combining lung ultrasound and clinical assessment versus the “traditional” heart failure diagnostic work-up including clinical assessment with CXR and BNP.
  • Methods and study design
    • Randomized, prospective, multicenter parallel group trial
    • Two centers in Italy
    • Initial clinical evaluation performed including:
      • History & physical
      • Arterial blood gas and EKG
    • Physician then was asked to decide if etiology was ADHF or non-ADHF → patients randomized to CXR and BNP group or lung US group → final “integrated” diagnosis then assigned after work-up
    • Treating physicians had access to both lung US and CXR/BNP but only after their diagnosis had been assigned
    • Physicians had performed at least 40 lung US exams
    • Used curvilinear probe and an eight-zone protocol
    • 3 or more B-lines in 2 or more zones was considered positive for interstitial fluid
    • Two blinded physicians reviewed the medical records and discharge diagnosis
    • Inclusion criteria:
      • Age > 18 years
      • Presenting to the ED with acute dyspnea or acute on chronic dyspnea in last 48 hours
    • Exclusion criteria:
      • Mechanically ventilated patients (invasive or non-invasive) at time of first evaluation
      • Trauma
  • What was the primary outcome?
    • Accuracy of clinical assessment and lung ultrasound compared to clinical assessment and chest x-ray with BNP
    • Secondary outcome was time needed for evaluation of assessment
  • Results
    • 532 total eligible patients with 518 enrolled
    • 43.2% of patients had final diagnosis of ADHF
      • 38.5% in CXR/BNP group and 48.1% in lung US group
    • 90.7% were admitted and in-hospital mortality was 7.9%
    • Sensitivity and specificity of BNP/CXR was 85% and 89.4% respectively (LR 8.0)
    • Sensitivity and specificity of lung US was 93.5% and 95.5% respectively (LR 20.9)
    • Median number of positive lung zones was 6 in the ADHF group versus 1 zone in the non-ADHF group
    • The median time to formulate a diagnostic hypothesis was 104.5 minutes in the CXR/BNP group compared to 5 minutes in the lung US group
  • Discussion
    • Combining lung US with clinical evaluation outperforms the “standard” diagnostic work-up using CXR and BNP for the diagnosis of ADHF
    • Adding lung US to the work-up was able to reclassify 8.9% of ADHF and 4.5% of non-ADHF patients
    • Lung US significantly reduced the time to diagnosis
    • Generalizability was increased by allowing patient management to be individualized to each physician 
  • Were there any limitations?
    • Study enrolled patients with acute dyspnea so missed other presentations of ADHF
    • Were not able to enroll consecutive patients due to the need for availability of lung US team
    • No standard criteria was used to determine ADHF in the final diagnosis 
    • Not a U.S. population which may limit generalizability
  • Take home points
    • Lung US is a non-invasive and rapid method for evaluating interstitial fluid and can supplement the history, physical, EKG and ABG for diagnosing ADHF
    • This study found eight-zone lung US to be more accurate than CXR and BNP in determining diagnosis of ADHF
    • Using lung US dramatically reduced the time to final diagnosis
    • Some limitations of the study are narrow inclusion criteria, non-consecutive enrollment and a non-US population which may limited generalizability  

Sources

  1. National Hospital Ambulatory Medical Care Survey: 2011 Emergency Department Summary Tables. https://www.cdc.gov/nchs/data/ahcd/nhamcs_emergency/2011_ed_web_tables.pdf (23 November 2018).

Paper 2

Performance comparison of lung ultrasound and chest x-ray for the diagnosis of pneumonia in the ED

Bourcier, Jean-Eudes et al. The American Journal of Emergency Medicine, Volume 32, Issue 2, 115 – 118

Full Text

  • Background information
    • Pneumonia is the number one cause of mortality from infectious disease in Western countries.
    • Chest x-ray is frequently use but has poor sensitivity and specificity, especially in early disease.
    • CT of the chest is considered the gold standard but comes with many downsides including ionizing radiation.
    • Ultrasound has the potential to provide many benefits including speed, cost and lack of ionizing radiation.
  • What was the objective of this study?
    • To assess the potential of POCUS of the lung by attending emergency physicians (EPs) in diagnosing acute pneumonia
  • Methods and study design
    • Observational, single center study conducted in France
    • Inclusion criteria:
      • > 18 years of age
      • Suspicion of acute pneumonia including 3 or more:
        • Tympanic temperature ≥ 38oC
        • Cough
        • Dyspnea
        • Heart rate > 100
        • Oxygen saturation ≤ 92% on room air
    • 10 EPs involved in the study
      • Five were trained included two days of hands-on sessions with theoretical and practical training
    • EPs performed 8-zone lung US using curvilinear probe on an M-Turbo machine immediately after assessment of patient
    • Evaluating for bilateral alveolar-interstitial syndrome to confirm diagnosis
    • All patients subsequently underwent chest x-ray → thoracic CT only if “difficult diagnosis” after x-ray
  • What was the primary outcome?
    • Primary outcome was diagnostic performance of lung ultrasound versus chest x-ray
    • Secondary outcome was agreement between lung ultrasound and chest x-ray versus thoracic CT
  • Results
    • 144 total patients enrolled
    • Sn/Sp for lung ultrasound was 95% and 57%
    • Sn/Sp for chest x-ray was 60% and 76%
    • Of 49 cases with negative CXR, final diagnosis of pneumonia was made 43 times by lung US
    • Of 29 patients who underwent CT, 23 had pneumonia. Of those, ultrasound accuracy was 100%, whereas CXR was 52% 
  • Discussion
    • Authors note significantly higher accuracy of lung US compared to CXR
    • Particularly true in patients with symptoms for less than 24 hours or “difficult to diagnose” pneumonia
  • Were there any limitations?
    • Final diagnosis was not always made with the “gold standard” test, thoracic CT scan
    • Lung ultrasound is poor at evaluating for “deep alveolar lesions” leading to likely false-negatives
    • Non-US population
  • Take home points
    • Lung ultrasound shows promise for detection of acute pneumonia, particularly in patients with symptoms for less than 24 hours when compared to chest x-ray
    • The physicians in this study were trained extensively on lung ultrasound and used an 8-zone scanning protocol which may limit generalizability 

Paper 3

Emergency and Critical Care Applications for Contrast-Enhanced Ultrasound

Kummer, Tobias et al. The American Journal of Emergency Medicine, Volume 36, Issue 7, 1287 – 1294

Full Text

  • Background information
    • There has been a 3.5-fold increase in CT imaging use for trauma patients from 1995 – 2007
    • 16% of all ED patients with an injury undergo CT
    • In the 1960s a cardiology named Dr. Joyner experimented with injected agitated saline during echocardiograms to enhance resolution
    • This evolved into contrast enhanced ultrasound (CEUS) with original contrast material made of micro-bubbles of air within albumin/lipid shell
  • How does this work?
    • New commercially available contrast is made of inert gas surrounded by a lipid shell
    • After injected, can be detected for 5 minutes
    • Contrast bubbles are about the size of RBCs, rapidly eliminated and are not cleared renally
    • Inert gas becomes exhaled and shell is metabolized in the liver
    • Contrast takes advantage of acoustic impedance between blood and gas
    • Approximately 1% side effect rate, mostly nausea and headache
    • Risk of allergic reaction exists, at rate less than IV contrast with CT

The authors presented several studies using CEUS and their applications:

  • Echocardiogram
    • A 2008 prospective study found dramatic improvement in image quality when using CEUS for patients in the surgical ICU
    • Noted to be a decrease in technically difficult echos from 75% to 21% after the use of CEUS
  • Blunt abdominal trauma
    • Studies show improvements in sensitivity and specificity for abdominal trauma with the use of CEUS compared to traditional ultrasound
    • In patients with hepatic trauma, CEUS identified contrast medium extravasation at rate similar to CT with IV contrast 
  • Pediatric patients
    • Significant increase in sensitivity and specificity with CEUS in CT-diagnosed solid organ injury over traditional ultrasound
    • Almost 100% sensitivity and specificity with detection of abdominal solid injury organ with CEUS
  • Use in pregnancy
    • Contrast agents are classified as Category B or Category C
    • Little is known about safety in breastfeeding
    • More studies are needed to evaluate safety in pregnancy
  • Future directions
    • CEUS could be used to enhance several studies including:
      • DVT/Doppler 
      • Distinguishing between pneumonia and other focal findings
      • Active extravasation into hematoma
      • Vascular compromise in ovarian torsion
  • What are some potential limitations?
    • Special ultrasound equipment and software required
    • Guidelines to establish standardization of exams
    • How to evaluate competency for CEUS across various training levels
  • Take home points
    • CEUS is a relatively new US modality which may help with improving image quality and detection of pathologies outside the scope of traditional US
    • CEUS shows promise for trauma patients as contrast can detect active bleeding and solid organ injury approaching rates of CT
    • More data is needed for use in pediatric and pregnant patients
    • May have more use in resource limited settings where CT/trauma surgery are not readily available

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