Ultrasound Equipment - Needle
Needle Selection
Large bore needles (e.g., 17 G) are more readily visualized and easier to direct under ultrasound. They are preferred for deep blocks e.g., an infraclavicular block when the angle of needle insertion is steep (> 45 degrees). Smaller bore needles (e.g., 22 G) are more difficult to visualize, but easily visualized for more superficial blocks e.g., the axillary block, when the angle of needle insertion is shallow.
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A 17 G Tuohy needle inserted in plane with the ultrasound transducer at an approximately 45 degree angle |
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A 22 G insulated needle inserted in plane with the transducer at an approximately 45 degree angle |
Insulated needles may be used during ultrasound guided nerve blocks if nerve stimulation is desired. Furthermore insulated needles are generally short bevel needles that are less sharp than the hypodermic needles. They are therefore less likely to produce paresthesia upon nerve contact than sharper hypodermic needles.
Echogenic biopsy needles are available but are not specifically designed for nerve blocks at the present time. Echogenic insulated needles will be available soon. Needles with echogenic tips may greatly enhance visualization especially when the needle is inserted using the out of plane approach (perpendicular to the ultrasound beam).
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An example of the echogenic tip needle by Hakko™ Medical Co. LTD (Japan).
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