Ultrasound for peripheral nerve blocks
- Edward Yap, MD
Edward Yap, MD
- HS Assistant Professor
- Department of Anesthesia and Perioperative Care, UCSF School of Medicine
- Andrew Gray, MD, PhD
Andrew Gray, MD, PhD
- Professor of Clinical Anesthesia
- UCSF School of Medicine
Ultrasound imaging is increasingly used to guide peripheral nerve blocks. Ultrasound guidance allows real-time visualization of nerves, surrounding structures, and the needle-tip to maximize block success and minimize complications. Unlike other imaging modalities (ie, magnetic resonance imaging [MRI] and computerized tomography [CT]), ultrasound equipment is portable and carries no risk of ionizing radiation.
This topic will discuss the basic principles of ultrasound imaging, the equipment used, and techniques for ultrasound guidance for peripheral nerve block. Ultrasound guidance for venous access, obstetric ultrasound, echocardiography, and other clinical applications for ultrasound are discussed separately. (See "Principles of ultrasound-guided venous access" and "Echocardiography essentials: Physics and instrumentation" and "Ultrasound examination in obstetrics and gynecology".)
Techniques for specific peripheral nerve blocks and other issues common to all peripheral nerve blocks are also discussed separately. (See "Upper extremity nerve blocks: Techniques" and "Lower extremity nerve blocks: Techniques" and "Nerve blocks of the scalp, neck, and trunk: Techniques" and "Overview of peripheral nerve blocks".)
The following are definitions of commonly used ultrasound-related terms.
●Ultrasound – The term "ultrasound" refers to sound waves of a frequency greater than that which the human ear can detect; namely, frequencies greater than 20,000 cycles/second, or Hertz (Hz). Medical imaging requires sound waves of much higher frequency, between 1 and 20 million Hertz (ie, between 1 and 20 megahertz [MHz]).
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- THE WAY ULTRASOUND WORKS
- ULTRASOUND EQUIPMENT
- Ultrasound machines
- - Spatial compound imaging
- - Doppler modes
- ULTRASOUND TECHNIQUE
- Preparation for scanning
- - Ergonomics
- - Time out
- - Gel
- - Scout scan
- - Sterile technique
- Needle orientation
- Ultrasound artifacts
- Image acquisition
- - Transducer manipulation
- - Finding the nerve or space
- - Optimizing the image
- Manipulating the transducer
- Minimizing artifact
- Maximizing machine settings
- - Visualizing the needle
- Injection of local anesthetic
- SUMMARY AND RECOMMENDATIONS