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Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
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PLACEMENT

Anatomy.

The femoral nerve travels through the pelvis in the groove between the psoas and iliacus muscles, as illustrated in Figure 13-1 . It emerges underneath the inguinal ligament, posterolateral to the femoral vessels, as illustrated in Figure 13-2 . It frequently divides into its branches at or above the level of the inguinal ligament.

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Figure 13-1  Femoral nerve anatomy: anterior oblique view.


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Figure 13-2  Femoral nerve anatomy: at the inguinal ligament.


Position.

The patient is in a supine position, and the anesthesiologist should stand at the patient’s side to allow easy palpation of the femoral artery.

Needle Puncture.

A line is drawn connecting the anterosuperior iliac spine and the pubic tubercle, as illustrated in Figure 13-3 . The femoral artery is palpated on this line, and a 22-gauge, 4-cm needle is inserted, as illustrated in Figure 13-4 . The initial insertion should abut the femoral artery in a perpendicular fashion, as shown in Figure 13-5 (position 1); a “wall” of local anesthetic is developed by redirecting the needle in a fan-like manner in progressive steps to position 2. Approximately 20 mL of local anesthetic is injected incrementally in this fashion. It may also be useful to displace the needle entry site laterally 1 cm, direct the needle tip to lie immediately posterior to the femoral artery, and then inject an additional 2 to 5 mL of drug. This allows block of those fibers that may be in a more posterior relation to the femoral artery. Elicitation of paresthesias occurs variably with this block; however, if one does occur, the medial to lateral injection should still be carried out, as the nerve often divides into branches cephalad to the inguinal ligament.

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Figure 13-3  Femoral nerve block: technique with needle puncture.


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Figure 13-4  Femoral nerve block: technique with needle puncture.


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Figure 13-5  Femoral nerve block: technique with local anesthetic injection.


When using a continuous catheter technique, stimulating catheter block kits or traditional epidural needles and matched catheters may be used in adults ( Fig. 13-6 ). In the latter situation, the epidural needle is positioned with the assistance of a nerve stimulator or using paresthesia elicitation as an endpoint. After the needle is positioned, 20 mL of preservative-free normal saline solution is injected through the needle, and the appropriate-size catheter is then inserted approximately 10 cm past the needle tip. Once the catheter has been secured with a plastic occlusive dressing, the initial bolus injection of drug is carried out, and the infusion is started.

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Figure 13-6  Femoral nerve block: technique using a continuous catheter.


Potential Problems.

Unilateral lower extremity block is often indicated for patients with peripheral vascular disease; thus, a number of patients with prosthetic femoral arteries are suitable candidates for this block. If lower extremity peripheral regional block has been chosen in a patient who has recently undergone placement of a prosthetic femoral artery, efforts should be made to avoid the newly placed prosthesis.

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