Block - Femoral Nerve ( FNB )

Background

FNB (3 in 1) block should be performed under ultrasound guidance [BestBets]
Used for #NOF, shaft of femur or fractures of the patella
Obtain IV access before performing this technique (risk of LA toxicity)

Equipment:

Something to clean the skin
1% lignocaine in one syringe, with a 25G needle for skin infiltration
0.5% Bupivacaine in another syringe(22G anaesthetic needle for the nerve block)

LA toxicity

The toxic dose for Lignocaine is 3 mgs per kilo or 20 mls of 1% Lignocaine for an adult
In a child = 1 ml of 1% plain Lignocaine for each year of the child's age
Before any regional anaesthesia ensure you are familiar with the signs / management of LA Toxicty

Monitoring

Patients receiving a FIB should be closely monitored during and after (for a minimum of 1 hour) the procedure; for both signs of local anaesthetic toxicity and sedation effects of other analgesia that may have been given.

Vital signs should be recorded at minutes 5, 10, 15, 30 and 60 post procedure.

Procedure

Very gently, slightly abduct the femur on the affected side
Identify the femoral artery and keep one finger on it
The nerve lies lateral and deep to the artery (see diagram)
Clean the skin
Infiltrate the skin with lignocaine
Infiltrate around the nerve in a fan-like fashion with Bupivacaine
Aspirate frequently to avoid intravascular injection
If you puncture the femoral artery compress it for 5-10 minutes
If the bleeding stops continue with the block
Wait 10-20 minutes before manipulating the limb into a splint
Monitor the patient for local anaesthetic toxicity

Max dose of local anaesthetic Bupivacaine 2 mg/kg ( = 0.4 ml/kg of 0.5% bupivacaine ) .

You can use a mixture of lignocaine and Bupivacaine. If mixture used then maximum dose should be 2mg/kg in total.

Beware

The RCEM have issued an alert re death after a fascia iliaca block. Please ensure you:

Site, side, dose and time of block
Frequency of post procedure observations:@ 5, 10, 15, 30 &60 mins post procedure

FNB in anticoagulated patients

Femoral block technique probably safe [ESRA/ASRA statement 2018] especially when balancing risk/benefit for elderly patients with NOF
Use small regional anaesthesia needles (22G) and ultrasound guidance
Target the nerve rather than the iliacus plane/muscle
Avoid vessel puncture (doh!)

"Femoral nerve" block