19 Limitations and Clinical Considerations
Lo Zhen Zhen
Discussing Potential False Positives and Negatives in Ultrasound Interpretation
- False Positives: Occur when fluid is mistaken for pathology; for example, physiological fluid in the pelvis of a female patient may be misinterpreted as hemoperitoneum.
- False Negatives: Can happen in early trauma where a significant amount of fluid has not yet accumulated, or in localized injuries not covered by the standard FAST views.
Addressing the Limitations of FAST and eFAST in the Comprehensive Assessment of Trauma Patients
- Operator Dependency: The accuracy of FAST and eFAST heavily relies on the skill and experience of the operator.
- Suboptimal Views: In some patients, especially those with obesity or subcutaneous emphysema, obtaining clear images can be challenging.
- Complementary Use: While FAST and eFAST are invaluable tools, they should be used in conjunction with other clinical assessments and diagnostic modalities for a comprehensive evaluation.
- Limited Scope: FAST/eFAST is not a comprehensive diagnostic tool and may miss retroperitoneal hematomas and small amounts of fluid.
- False Negatives: Particularly in early trauma presentations.
Tips and Tricks
- Proper Positioning: Ensure the patient is supine for optimal fluid detection.
- Adequate Pressure: Apply sufficient pressure to displace bowel gas, but not so much as to cause discomfort.
- Gain Settings: Adjust the ultrasound gain to optimize the image quality.
Pitfalls
- Mistaking Bowel Gas for Free Air: Distinguish between these by identifying the characteristic appearance of bowel gas.
- Incomplete Exams: Ensure all views are properly assessed.
- Over-reliance on FAST/eFAST: Remember it’s a part of a comprehensive trauma assessment.
Key Takeaways
FAST and EFAST are useful for trauma patients especially in detecting intraperitoneum and intrathoracic injuries
FAST and EFAST are also useful in non-trauma situations such as in cases of ruptured ectopic, ruptured ovarian cyst and ascites.
Understand the limitations of these techniques and their role in the broader context of patient assessment and management.
References
- Gartman, E., |eeditor.|0http://id.loc.gov/authorities/names/n2015031692, & Jankowich, M., |eeditor.|0http://id.loc.gov/authorities/names/n2015182903. (2016). Ultrasound in the Intensive Care Unit. HUMANA.
- Brown, S. M., Blaivas, M., Hirshberg, E. L., Kasal, J., & Pustavoitau, A. (2015). Comprehensive critical care ultrasound. Society of Critical Care Medicine.
- Noble, V. E., & Nelson, B. (2014). Manual of Emergency and Critical Care Ultrasound. Cambridge University Press.
Exercises for FAST and EFAST Chapter
