From the Guidelines
To optimize peripheral nerve and neuraxial ultrasound imaging in morbidly obese patients, use low-frequency curvilinear transducers (2-5 MHz) that provide better depth penetration through adipose tissue, as recommended by the American College of Emergency Physicians 1.
Key Considerations
- For peripheral nerve imaging, apply firm pressure to compress subcutaneous fat and reduce the distance to target structures.
- Utilize tissue harmonic imaging and compound imaging to enhance resolution and reduce artifact.
- Adjust machine settings by increasing depth, reducing frequency, and optimizing gain to improve visualization.
Neuraxial Ultrasound Imaging
- Use the paramedian sagittal oblique approach rather than transverse views, as this provides better acoustic windows through the interspinous spaces.
- Pre-scan patients in the sitting position when possible, as this reduces the skin-to-target distance by stretching adipose tissue.
- Mark anatomical landmarks before the procedure to guide needle insertion even if image quality is suboptimal.
Additional Techniques
- Consider using extended field-of-view technology to better appreciate anatomical relationships in these patients.
- These techniques are essential because conventional approaches often fail in morbidly obese patients due to increased tissue depth and acoustic impedance from adipose tissue, which attenuates ultrasound signals and reduces image quality. While other studies discuss the evaluation and management of severely obese patients undergoing surgery 1, the most relevant guideline for optimizing peripheral nerve and neuraxial ultrasound imaging in morbidly obese patients is provided by the American College of Emergency Physicians 1.
From the Research
Optimizing Peripheral Nerve Ultrasound Imaging and Neuraxial Ultrasound Imaging in Morbidly Obese Patients
To optimize peripheral nerve ultrasound imaging and neuraxial ultrasound imaging in morbidly obese patients, several guidelines and tips can be considered:
- Use of high-frequency probes: High-frequency probes can provide better resolution and penetration in obese patients, allowing for more accurate imaging of peripheral nerves 2.
- Adjustment of ultrasound settings: Adjusting the ultrasound settings, such as increasing the gain or using a higher frequency, can help improve image quality in obese patients 3.
- Use of magnetic resonance neurography (MRN): MRN can provide excellent soft tissue contrast and depict the entire nerve in 3 dimensions, making it a useful adjunct to ultrasound imaging in obese patients 4.
- Preprocedural neuraxial ultrasound: Preprocedural neuraxial ultrasound can help identify the lumbar intervertebral space and predict the needle insertion depth required to reach the epidural or intrathecal space, reducing the risk of complications in obese patients 5.
- Skilled operators: The use of skilled operators is crucial in obtaining high-quality ultrasound images, particularly in obese patients where image quality may be compromised 4, 6.
Tips for Specific Ultrasound Imaging Techniques
Some specific tips for peripheral nerve ultrasound imaging and neuraxial ultrasound imaging in morbidly obese patients include:
- Peripheral nerve ultrasound imaging: Using a high-frequency probe and adjusting the ultrasound settings can help improve image quality, while the use of MRN can provide additional information on nerve anatomy and pathology 4, 2.
- Neuraxial ultrasound imaging: Preprocedural neuraxial ultrasound can help identify the lumbar intervertebral space and predict the needle insertion depth, while the use of skilled operators can reduce the risk of complications 6, 5.
Benefits of Ultrasound Guidance
The use of ultrasound guidance in peripheral nerve blocks and neuraxial anesthesia has several benefits, including:
- Increased success rate: Ultrasound guidance can increase the success rate of peripheral nerve blocks and neuraxial anesthesia by reducing the number of needle passes required and improving the accuracy of needle placement 6.
- Reduced risk of complications: Ultrasound guidance can reduce the risk of complications, such as bloody puncture, by allowing for more accurate needle placement and reducing the number of needle passes required 6, 5.