Needles Used for Nerve Blockade

Needles Used for Nerve Blockade

1. A block needle should be the smallest diameter possible for patient comfort. However, block needles often are inserted into deep tissue and therefore need a more rigid shaft. For most peripheral regional blocks, a 22-gauge needle is preferable. For superficial blocks, such as axillary blocks, a 23-gauge needle is suitable.
2. Short bevel needles (30 to 45 degrees) are associated with decreased nerve trauma and intravascular injection compared with standard A bevel needles and have become standard for peripheral nerve blocks. However, some data suggest that the use of smaller, sharp needles may be associated with less damage in the event of a nerve injury because of a “clean cut” of the nerve. Newer needles with a Sprotte or Whitacre tip may be less traumatic.
3. Insulated needles designed for use in nerve stimulator-guided techniques have a small conductive area at the needle tip, which allows for more accurate nerve stimulation at lower amplitudes of current compared to noninsulated needles.
4. Echogenic needles designed for use in ultrasound-guided techniques feature modifications such as texturing or scoring of the needle's surface to enhance reflection of ultrasound waves and improve needle visibility under ultrasound.
5. Ideal needle length varies by block. Upper- and lower-extremity blocks are best performed with a 50- to 150-mm needle depending on the nerve depth. Brachial plexus blocks usually do not require more than a 100-mm needle and can frequently be accomplished, in the case of interscalene block, with a 25- to 50-mm needle.

Many blocks require depositing a large volume of local anesthetic with a single injection. Connecting a large-volume (20-mL) syringe to the block needle with sterile extension tubing ensures stable needle position during aspiration and injection. For larger volumes of local anesthesia, multiple syringes can be attached with a stopcock.