Femoral Nerve Block

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  • Operations of the anterior portions of the thigh, both superficial and deep
  • As an adjunct to general anesthesia and postoperative analgesia for knee joint surgery
  • Combined with sciatic block, can be used for anesthesia of the lower extremity from the level of the mid-thigh down
  • Absolute contraindications
    • Patient refusal
    • Allergy to local anesthetics
    • Infection at the site of injection
  • Relative contraindications
    • Femoral vascular graft
  • Femoral neuropathy
  • Sterile gloves and mask
  • Sterile towels and gauze packs
  • Two 20-mL syringes with stopcocks
  • Tuberculin syringe with 25-gauge needle for local infiltration
  • 22-gauge, 50 mm long, insulated stimulating needle
  • Nerve stimulator with electrode
  • Local anesthetic
    • Choice and concentration of agent is based on whether surgical anesthesia or pain management is desired, because lower concentrations of local anesthetic are required for pain management.
    • Long-acting local anesthetics are a poor choice for ambulatory surgery for minor procedures, because prolonged motor blockade of the quadriceps muscle prevents ambulation and predisposes the patient to falls if he or she attempts to ambulate too early.

The femoral nerve is the largest branch of the lumbar plexus and is derived from the 2nd through 4th lumbar nerves. The nerve descends through the psoas muscle, emerging from the muscle near its lower border and then passing between the psoas and the iliacus muscles. As it travels underneath the inguinal ligament and into the thigh, it is located immediately lateral and slightly deep to the femoral artery, which is easily palpable in the groin. At the femoral crease, the nerve is covered by the fascia iliac and is separated from the femoral artery and vein by a portion of the psoas muscle and ligamentum ileopectineum. The physical separation of the nerve from the vascular fascia at this level explains why a blind perivascular injection of local anesthetic does not spread to the femoral nerve.

At or around the inguinal ligament, the femoral nerve divides into an anterior and posterior bundle. The anterior (superficial) branches innervate the skin covering the anterior surface of the thigh and the sartorius muscle. The posterior (deep) branches innervate the quadriceps muscle, the knee joint, and its medical ligament and give rise to the saphenous nerve, which descends over the medial aspect of the calf to supply sensory innervation down to the medical malleolus of the ankle. The deep branches are primarily motor in function, with articular branches to the hip and knee joints. The superficial branches are primarily sensory and cutaneous in distribution, supplying the anterior, anteromedial, and medial aspects of the thigh, knee, and upper portion of the leg.

Sample excerpt does not include step-by-step text instructions for performing this procedure
The full content of this section includes:
  • Step-by-step text instructions for performing the procedure
  • Clinical pearls providing practical clinical tips from medical experts
  • Patient safety guidelines consistent with Joint Commission and OHSA standards
  • Links to medical evidence and related procedures

  • Continue to monitor all vital signs, carefully observing for s/s of local anesthetic toxicity.
  • Counsel patients about appropriate expected duration of block and adjunct pain medication to ensure optimization of pain control.
  • Caution patients to stand and walk only with assistance until the block is completely gone to avoid falls; when prolonged block is expected, crutches should be advised until the block wears off.
  • Hematoma
  • Local infection
  • Seizures (from systemic injection and local anesthetic toxicity)
  • Neural ischemia and/or neural toxicity
  • Local anesthetic toxicity
    • CNS: tinnitus, confusion, metallic taste in the mouth
    • Cardiac: tachycardia, hypertension, arrhythmia
  • Injury due to falls if patient ambulates before block is completely resolved
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