Overview

Femoral nerve blocks are useful when managing hip fracture pain. They are an ideal intervention especially in geriatrics.

Femoral nerve blocks should be performed via ultrasound guidance.

Indications

Pain relief for hip, femur, and patella injuries.

Contraindications

Absolute: Allergy to anesthetic.

Absolute: Infection overlying the area to be blocked.

Absolute: Neurologic deficit in the affected extremity.

Relative: Compartment syndrome

• This is not a true contraindication because sensory innervation to the lower leg occurs via the sciatic nerve. Blockage of the femoral nerve should not affect the clinical examination of the lower leg.
• Always Consult with the orthopedist.

Equipment & Dosing

US machine with a high-frequency linear probe

Sterile US probe cover and gel

Sterile gloves

Skin disinfectant

Ropivacaine 0.5%, lidocaine 1%, or bupivacaine 0.25-0.5%

• Ropivacaine is less cardiotoxic than bupivacaine.
• Lidocaine duration 1-2 hours, ropivacaine and bupivacaine ~12 hours
• Always calculate maximum dose, bupivacaine and ropivacaine 3 mg/kg and lidocaine 5 mg/kg

Cardiac monitor

Lipid Emulsion agent (eg: intralipids)

• Local anesthetic systemic toxicity is a rare but potentially fatal adverse event. Bupivacaine increase risk as does direct injection into a vessel

20- to 30-mL syringe

20- or 22-gauge 3.5-in needle

Intravenous Access

Anatomy & Innervation

The femoral nerve is made up of the second, third, and fourth lumbar nerve roots. It passes below the inguinal ligament then bifurcates into the anterior and posterior branches.

These branches provide sensation to the anterior and lower medial areas of the femur, thigh, and knee.

Femoral articular nerves provide sensation to the hip. The femoral nerve lies approximately 1 to 2 cm lateral to the femoral artery in the inguinal crease.

Procedure & Administration

Place the patient supine with the affected leg/hip slightly abducted, if possible.

Pull any adipose tissue out of the inguinal crease with tape.

Place the US machine on the opposite side of the bed.

Locate the femoral nerve using a high-frequency linear probe.

Remember “NAVEL”: Nerve, Artery, Vein, Empty, Lymphatics moving from lateral to medial. Figure 1

Place the US probe parallel to the inguinal crease

• The femoral vein (more medial) will be more compressible than the artery (more lateral).
• Color Doppler mode can also be used to better identify the vessels.

The nerve lies immediately lateral to pulsating artery

• If there appears to be two arteries move proximally until you see one large femoral artery

Once the nerve has been found, place a local skin wheal of anesthetic.

Prep the area using a skin disinfectant and antiseptic.

Place a sterile probe cover over the US probe.

With a needle attached to the anesthetic syringe, enter the skin 1 cm lateral to the probe, with the needle bevel up

• Entry of the needle should generally be at a 45-degree angle but will depend upon the depth of the fascia iliaca.

To best visualize the needle tip, keep the US probe in a transverse orientation, and use an in-plane technique.

Advance the needle slowly, and aim toward the hyperechoic fascia iliaca, which typically overlies the femoral nerve.

• You may feel two “pops” as you penetrate the fascia lata and fascia iliaca.

Once deep to the fascia iliaca, aspirate back to make sure the needle is not in a vessel.

Stay at least 1 cm lateral to the femoral nerve to avoid accidental puncture of a vessel.

Once below the fascia iliaca, slowly inject 3 to 5 ml of anesthetic to confirm location.

• As the anesthetic is injected, it will have a hypoechoic (dark) appearance, and the anterior edge of the fascia iliaca will bulge forward (indicates filling of the fascia iliaca compartment).
• The patient may experience pressure at the injection site but if they experience sharp electric pain, stop injecting, and remove needle 1-2 mm before continuing with infiltration

After confirming location within the fascia iliaca, continue to inject 10 to 20 ml of anesthetic in small 3- to 5-mL aliquots.

• Anesthetic surrounding the nerve distally may give a “donut-like” appearance on US.

VISUALIZE THE INJECTION OF THE ANESTHETIC AT ALL TIMES.

• If you cannot visualize the injection, stop the procedure.
• The patient should start to experience pain relief within 15 minutes and full blockade after 30 minutes.

Complications

Falls secondary to weak and insensate limbs

Infection

Local anesthetic systemic toxicity

Vascular puncture and hematoma

Charting & Documentation

A femoral nerve block requires a procedure note in the medical record

Document:

• Clinical examination before the procedure, including neurologic and vascular examinations of the lower extremity
• Sterile preparation and local anesthetic used
• Needle approach and confirmation of needle placement
• Type and dose of anesthetic injected
• Clinical examination immediately after the procedure
• Complications

Special Considerations

Anticoagulation is not a contraindication, but take care to avoid puncturing a deep vessel.

Discharge Procedure

Patients receiving a femoral nerve block for a hip or femoral fracture are likely to be admitted or transferred to another hospital.

Patients with patella fractures might be discharged home.

All of these injuries are likely to be non-weight bearing if patients are discharged.

Inform inpatient nurse and physician team of block and ideally apply ‘limb alert bracelet on ipsilateral wrist.

Where to Learn More

EMdocs.net

Highland Ultrasound.com

Ultrasound Podcast.com

References

1. References to come