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Board question: which nerve is not blocked by the axillary block? A: the axillary nerve!
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And also the musculocutaneous nerve, which has to be blocked separately.
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Typical arrangement of nerves around the axillary artery in the axilla (Figure 136-2).
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Variations (Figure 136-3).
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Upper extremity surgery, preferably below the elbow, as the level of the block is not always adequate for elbow surgery, or for a very proximal tourniquet.
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None besides the usual regional anesthesia contraindications.
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- Landmarks: the axillary artery pulse as proximal as possible in the axilla:
- On occasion, a Doppler can be necessary to locate the pulse
- Insert needle through the skin overlying the pulse
- Aim first anterior, toward the coracobrachialis muscle if it can be palpated, and elicit a biceps response at 1.2 mA. Decrease current to 0.4 mA (while adjusting needle position to maintain the response) and inject 5–7 mL of local anesthetic
- Pull needle back to skin and locate two out of three of the nerves that are located in the sheath around the artery (see responses below):
- Typically, the median nerve is anterior to the artery (toward the ceiling when patient supine)
- Ulnar and radial nerves are posterior to the artery (toward the floor with the patient supine), with the radial being deeper
- However, anatomic variations are common. Often, one has to insert the needle, and if no response is elicited, pull it back to the skin, slightly change the angle, and ...