Femoral Nerve Block

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    This guideline has been adapted for statewide use with the support of the Victorian Paediatric Clinical Network

  • See also

    Acute pain management 
    Communicating Procedures to families

    Key points

    1. Paediatric femur fractures are associated with severe pain, which will be exacerbated during necessary transfers and investigations as well as during application of traction
    2. Femoral nerve blocks allow effective, safe and medium duration analgesia
    3. Ultrasound (US) guided blocks are more effective and safer and should be performed if equipment and expertise are available


    • Femur fractures of any aetiology
    • Anterior thigh wounds requiring exploration and washout


    1. Local anaesthetic allergy/anaphylaxis
    2. Open wound or signs of infection at likely injection site

    Potential Complications

    1. Allergy/anaphylaxis
    2. Direct neural trauma from needle/high pressure infiltration of local anaesthetic
    3. Vascular injury eg formation of pseudoaneurysm
    4. Intravenous/intra-arterial infiltration +/- haemodynamic collapse due to local anaesthetic toxicity 


    1. Monitoring – continuous ECG and SpO2
    2. Ultrasound machine – high frequency linear probe (eg 10-15MHz)
    3. Sterile probe cover
    4. Sterile gloves
    5. Needle for injection
      1. Specific nerve block needle if available
      2. Spinal needle with trocar removed
        NB: Caution with Sprotte/Whitacre needles as injection point proximal to tip
    6. Low pressure extension tubing  - optional but improves accuracy of infiltration

    Analgesia, Anaesthesia, Sedation

    1. 1% lignocaine for skin infiltration (1-2 mL)
    2. Local anaesthetic for block (any suitable, dilute both to double volume with normal saline)
      1. Ropivacaine  max 3 mg/kg (eg 0.4 mL/kg of 0.75%)  – gold standard, not always available, longer duration, decreased risk cardiotoxicity
      2. Bupivacaine max 2 mg/kg (eg 0.4 mL/kg of 0.5%)increased risk cardiotoxicity but longer duration of action
      3. Lignocaine max 4 mg/kg (eg 0.4 mL/kg of 1%) or with adrenaline > 7 mg/kg – short duration 2 hrs which may be sufficient eg transfer to theatre, safer for inexperienced user
    3. Consideration of supplementary analgesia for eg, nitrous oxide sedation or IN/IV fentanyl if severe agitation or difficult positioning of lower limb is impairing block insertion 


    • Locate femoral crease: ASIS to pubic symphysis
    • Lateral > Medial: Femoral nerve > artery > vein
    • Palpate artery
    • Needle insertion and superficial local anaesthetic injection site roughly 5cm lateral to artery towards ASIS
    • On ultrasound view femoral nerve has popcorn or honeycomb appearance

      Femoral nerve block

    Femoral nerve block 2 


    Ultrasound-guided(ideally performed with assistant)

    1. Locate landmarks
    2. Prepare ultrasound machine
      • Correct probe
      • Position opposite side of bed from block sign
      • Gel onto probe with cover/large tegaderm applied after
      • Prepare dressing pack with local anaesthetic, appropriate needle, low pressure tubing
    3. Clean area and drape appropriately especially medially
    4. "In-plane" ultrasound probe orientation with marker pointing to ASIS
    5. Observe landmarks (Lateral > Medial)
    6. Infiltrate 1-2 mL of 1-2% lignocaine superficially lateral to artery
    7. Pierce skin with block needle through anaesthetised skin
    8. Advance slowly ensuring tip of needle always visible
    9. When lateral to nerve and between layers of fascia iliaca infiltrate small amount
      • Prior to any injection aspirate without moving needle to ensure not within vessel
    10. Continue to infiltrate local anaesthetic gradually aiming to fully encircle the nerve

    "Blind Technique" – Fascia-Iliaca Block:
    1. Locate landmarks – ASIS to pubic tubercle divided into thirds
    2. Needle insertion point is 1 cm distal to junction of lateral and middle thirds
    3. Injection point is after second "pop" denoting passage through two fascial planes
    4. Aspirate to ensure not in vessel
    5. Gradually infiltrate local anaesthetic stopping every few mLs to aspirate again
    6. If in correct space resistance to infiltration should be minimal, if significant resistance withdraw slightly and re-try

    Femoral nerve block 3

    Post-procedure care

    1. Simple dressing/band-aid for injection site
    2. Review of injection site for formation of pseudoaneurysm – usually within 2 hrs of procedure
    3. Monitoring can be stopped 5-10 minutes post procedure

    Alternatives in case of block failure

    1. Will likely require ongoing opiate analgesia
    2. Immobilisation of lower limb 

    Consider transfer when

    1. If staff unable to safely perform the procedure
    2. Uncontrollable pain
    3. Fracture requiring surgical treatment not able to be performed at presenting hospital
    4. Signs of local anaesthetic toxicity – will need discussion with retrieval team

    For emergency advice and paediatric or neonatal ICU transfers, call the Paediatric Infant Perinatal Emergency Retrieval (PIPER) Service: 1300 137 650.

    Last updated July 2017