Femoral nerve block

Disclaimer

These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline. 

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Aim

To guide staff in the use of femoral nerve block.

Background

A femoral nerve block is a quick, easy, effective and safe method of providing analgesia to the child with a femoral shaft fracture as the femoral nerve (L2-L4) innervates the shaft and periosteum of the femur.

General

Anatomy

  • The inguinal ligament extends from the pubic tubercle to the anterior superior iliac spine
  • At its mid point, the femoral vein, artery and nerve pass beneath it
  • The femoral vein lies medial, the artery in the middle and the nerve lateral
  • A useful acronym is: NAVY = Nerve, Artery, Vein, Y fronts (!)

Femoral structure, ligaments and arteries 

Femoral anatomy: Left hand side

Principle

  • The femoral nerve lies in its own tissue plane, is quite superficial (usually 1-2 cm deep; never more than 3cm deep, even in older children) and is separated from the femoral vessels by the fascia iliaca
  • Exact identification of the nerve position isn’t necessary
  • Local anaesthetic injected into the correct plane (just deep to the fascia iliaca) will result in effective nerve block by diffusion of anaesthetic, without the vascular compartment being affected.

Femoral canal and surroundings

 

Femoral anatomy: Left hand side

Note: ultrasound guided femoral nerve blocks can be done if you are appropriately trained.

Preparation

Equipment

  • Sterile gloves
  • Dressing pack
  • Skin cleaning antiseptic solution
  • Needle: 23 gauge (blue) short bevel needle or 25 gauge (orange) in an infant
  • Ropivacaine 0.75% or Bupivacaine 0.5% – appropriate dose drawn up in a syringe.

Procedure

Medications

  • For either drug, the lowest dose which provides sufficient analgesia should be used
  • Both drugs come in a range of concentrations
  • If a different concentration solution is used, the volume administered needs to be adjusted accordingly
  Preferred drug  Alternative 
Local anaesthetic  Ropivacaine 0.75%  Bupivacaine 0.5% 
Dose 

0 – 12 years: 0.25mL / kg

>12 years: 10 – 20 mL 
0.2 – 0.4mL / kg (Max 30mL)
Onset of block  Within 10 minutes  within 10 minutes
Duration of block 6 hours  4-6 hours 
Safety  Ropivacaine has a better safety profile   

Positioning and technique

  • Clean the skin with antiseptic solution.
  • Identify the site of injection again (see above in Anatomy section).
  • Keeping one finger on the femoral artery 0.5-1cm below the inguinal ligament, insert the needle perpendicular to the skin, 0.5-1cm lateral to the artery.
  • The plane in which the nerve lies can be found by feeling a ‘pop’ or loss of resistance twice, first when the needle passes through the fascia lata, and then as it passes through the fascia iliaca.
  • Note that the nerve is fairly superficial (1-2cm) and most failed blocks are due to injecting too deep.
  • Aspirate to make sure the needle is not in a blood vessel.
  • Inject the local anaesthetic slowly, while frequently aspirating briefly to make sure the needle tip has not migrated into a vessel.
  • Some authors describe injecting in a fan shaped pattern around the nerve, however this is not necessary since local anaesthetic injected anywhere under the fascia iliac will diffuse to the nerve and result in a successful nerve block.
  • Place an IV dot (dressing) over the injection site.

Bibliography

  1. AMH Children’s Dosing Companion (2015) Australian Medicines Handbook Pty Ltd
  2. Textbook of Paediatric Emergency Medicine 2nd Edition Cameron Elesevier 2012
  3. Practical Fracture Treatment- Ronald McRae , 5th Edition



Endorsed by:  Director, Emergency Department   Date:  Mar 2018


 Review date:   Feb 2021


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