eFAST for Chest Trauma

By: Annemarie Daecher, MD

Reviewed by: Jonathan Kaplan, MD

Paper #1

Diagnostic accuracy of eFAST in the trauma patient: a systematic review and meta-analysis

Netherton S, Milenkovic V, Taylor M, Davis PJ. CJEM. 2019 Nov; 21(6):727-738. doi: 10.1017/cem.2019.381. PMID: 31317856. 

https://pubmed.ncbi.nlm.nih.gov/31317856/

Introduction and Background: 

  • Traumatic injuries are the most common cause of morbidity and mortality in young adults, with incidence increasing over time
  • eFAST is a widely accepted part of the trauma   assessment to identify pneumothorax, pericardial effusion, intra-abdominal free fluid → early findings can lead to early intervention
  • Many studies on eFAST in trauma with variable sensitivities and specificities, and prior to this there has been no comprehensive systematic review examining the accuracy of all components of eFAST

Purpose/Objectives: 

  • there are a wide range of sensitivities/specificities reported for components of eFAST in trauma. The objective of this study was to review pooled sensitivities and specificities for components of eFAST 

Why is this important? 

  • the eFAST is a commonly used part of the trauma assessment, important to understand limitations as well as strengths 

Methods: 

  • searched Medline and Embase up to October 2018 for studies examining eFAST sensitivity/specificity 
    • 767 records, 119 underwent full text review
    • 75 studies with 24,530 patients satisfied selection criteria 
    • Pooled sensitivities and specificities calculated for pericardial effusion, pneumothorax, intra-abdominal free fluid 
    • Sub-group analysis for intra-abdominal free fluid in hypotensive patients, adult normotensive patients, and pediatric patients 

Study selection:

  • Population of interest: trauma patients (blunt, penetrating, poly) who were assessed in an ED or trauma center, underwent US initially and then underwent gold standard test 
    • US positive for pneumothorax if no lung sliding present or a lung point was seen, gold standard CT
    • US positive for pericardial effusion or intra-abdominal free fluid if hypoechoic fluid present in appropriate anatomic location 
      • For pericardial effusion, gold standard was a CT scan or positive intra-op findings
      • For intra-abdominal free fluid, gold standard was CT scan, positive laparotomy, or positive DPL/DPA
  • Exclusion criteria: studies performed in wrong setting (pre-hospital), in nontrauma patients, if they did not have gold standard comparisons done, or had incomplete data 
  • Primary outcome: Sensitivity and specificity of eFAST

Results: 

  • 767 studies yielded from search, 119 underwent full text review, 75 papers met inclusion criteria
    • 17 studies examined pneumothorax detection, 9 examined pericardial effusion detection, 52 examined intra-abdominal free fluid detection
  • Studies examining pneumothorax included 3653 patients with 4816 data points (some studies used each lung as a data point, 2 data points per patient)
    • Avg. age 39.8 years, 75% male, predominantly blunt trauma
    • Pooled sensitivity for detecting pneumothorax via eFAST was 0.694 (95% CI 0.66-0.72), pooled specificity 0.99 (95% CI 0.98-0.99)
  • Studies examining pericardial effusion included 1031 patients 
    • Avg. age 30 years, 80.6% male, only penetrating trauma 
    • Pooled sensitivity for detecting pericardial effusion via eFAST was 0.912 (95% CI 0.87-0.94) and pooled specificity 0.941 (95% CI 0.922 – 0.957)
  • Studies examining intra-abdominal free fluid included 19,666 patients
    • Avg. age 33.3 years, 68.4% male
    • Of these studies, 6 included only pediatric patients, 8 included patients of all ages (peds and adults), 5 included only hypotensive patients and 1 included only pregnant patients (46% in third trimester)
    • Overall pooled sensitivity for detecting intra-abdominal free fluid via eFAST was 0.742 (95% CI 0.726 – 0.758) and pooled specificity was 0.976 (95% CI 0.973-0.978)
    • Only pediatric patients:
      • Sensitivity for detecting intra-abdominal free fluid via eFAST was 0.709 (95% CI 0.615-0.792) and specificity was 0.951 (95% CI 0.933-0.965)
    • Only hypotensive patients:
      • Sensitivity for detecting intra-abdominal free fluid via eFAST was 0.743 (95% CI 0.681-0.799) and specificity was 0.949 (95% CI 0.926-0.966) 
    • Only adult normotensive patients:
      • Sensitivity for detecting intra-abdominal free fluid via eFAST was 0.76 (95% CI 0.739-0.781) and specificity was 0.98 (95% CI 0.975-0.981)

Discussion:

  • Identification of pneumothorax using eFAST:
    • Moderate sensitivity (69.4%), good specificity (99%)
    • Positive likelihood ratio 62.57, negative likelihood ratio 0.256
    • Use for rule in, not rule out
  • Identification of pericardial effusion using eFAST: 
    • Excellent sensitivity (98.2%) and specificity (98.5%) with the removal of outlying studies 
    • Positive likelihood ratio 34.0169, negative likelihood ratio 0.110
  • Identification of intra-abdominal free fluid using eFAST:
    • Moderate sensitivity (74.2%), excellent specificity (97.6%)
    • Positive likelihood ratio 20.3, negative likelihood ratio of 0.25 (not much different between pediatric, hypotensive, adult normotensive groups)
  • Two additional recent reviews evaluated parts of the eFAST, reaching similar conclusions
    • Straub et al: detecting of PTX and hemothorax: sensitivity 81%, specificity 98%
    • Stengel et al: examined use of US in blunt thoracoabdominal trauma patients, found sensitivity was 68%/specificity 95% for detecting FF, organ injury, vascular injury; sensitivity 78%/specificity 97% for abdominal FF, intra-abdominal free air 

Conclusions: 

  • eFAST is a helpful tool to rule in pneumothorax, pericardial effusion, and intra-abdominal free fluid but is not sensitive enough to rule out these disease processes 

Limitations:

  • Publication bias, only positive studies published; however studies included low sensitivities/specificities 

Paper #2 

Value of point of care ultrasonography compared with CT scan in detecting potential life-threatening conditions in blunt chest trauma patients 

Jahanshir, A., Moghari, S.M., Ahmadi, A. et al. Ultrasound J. 2020; 12:36. https://doi.org/10.1186/s13089-020-00183-6

Introduction and Background:

  • Thoracic injury accounts fo 20-25% trauma mortality preventable by early diagnosis 
  • Role of ultrasound in trauma: diagnosing early, diagnosing in unstable patients unable to go to CT, reduction of radiation

Purpose: 

  • evaluated caveats of point of care ultrasound in diagnosis of pneumothorax, hemothorax, and contusion

Methods: 

  • prospective study performed in 157 patients with blunt chest trauma in 3 university hospitals 
  • Ultrasounds performed by 2 EM attendings and a EM PGY3
  • Patients included: 18 years + with acute chest trauma (blunt chest trauma isolated to chest/back and multiple trauma patients)
  • Patient with old chest trauma, history of lung fibrosis or those that didn’t undergo CT were excluded (unless they had a chest tube placed to confirm diagnosis)
  • Each lung scanned in at least 4 spaces for evidence of pneumothorax, hemothorax, contusion by B and M modes 
  • Compared PoCUS to CT scan

Results: 

  • 157 patients, 134 were men, mean age 38.3 years old
    • Most common mechanisms: MVC, falls
  • lung ultrasonography and physical exam: accuracy of 91.8%
  • Pneumothorax: PoCUS sensitivity 75%, specificity 100%, PPV 100%, NPV 94.9%
  • Hemothorax: PoCUS sensitivity 45.4%, specificity 100%, PPV 100%, NPV 91.8%
  • Lung contusion: PoCUS sensitivity 51.8%, specificity 100%, PPV 100%, NPV 86.3%
  • Interestingly, combined physical exam and sonography sensitivity was increased to 91.5% for the diagnosis of pneumothorax, hemothorax, contusion and the specificity decreased to 90.8%

Analysis of false-negatives

  • Pneumothorax:
    • Subcutaneous emphysema = clue to suspect PTX but disrupts US signal via scattering
    • Occult PTXs (very small, only seen by CT scan) = clinically significant?
      • Data suggests US doesn’t miss clinically significant PTX
  • Hemothorax: 
    • False negatives can be due to minimal amounts of blood, blood located posteriorly 
    • Concomitant subcutaneous emphysema
  • Pulmonary Contusion:
    • Finding various signs of lung contusion improves US sensitivity
    • Falsely diagnosed in ARDS, cardiogenic pulmonary edema 
    • Contusion can be falsely interpreted in presence of large PTX due  to presence of collapsed lung

Conclusions: 

  • US is specific enough to rule in diagnosis but not sensitive enough to rule out, use US in conjunction with physical exam, clinical findings

Limitations:

  • didn’t include patients with pulmonary fibrosis, excluding patients with underlying disease will skew results 
  • need larger sample sizes 

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