usg guided nerve block part ii

Femoral Nerve Femoral Nerve BlockBlock

Femoral Nerve Femoral Nerve Origin:Origin:

The femoral The femoral nerve is the nerve is the largest branch of largest branch of the lumbar the lumbar plexus, and is plexus, and is formed from formed from L2,3,4. L2,3,4.

Femoral N. Femoral N. AnatomyAnatomy

Femoral N. Anatomy Key Femoral N. Anatomy Key Points:Points:

VAN – vein, artery, VAN – vein, artery, nerve (from medial nerve (from medial to lateral).to lateral).

Nerve lies on top of Nerve lies on top of iliopsoas muscles. iliopsoas muscles.

Nerve to sartorius Nerve to sartorius m. exits and lies m. exits and lies superficial and superficial and medial to main medial to main body of femoral n.body of femoral n.

FasciaLata

Note fascias lata and iliaca. Fascia iliaca lies between the artery and the nerve – thus they lie in different compartments.

Femoral Nerve Femoral Nerve Cutaneous Cutaneous

DistributionDistribution The femoral nerve The femoral nerve

supplies the anterior supplies the anterior thigh and part of the thigh and part of the medial thigh, then as medial thigh, then as the saphenous nerve the saphenous nerve supplies the medial supplies the medial aspect of the lower aspect of the lower leg and ankle.leg and ankle.

Knee & Hip Bone Knee & Hip Bone InnervationInnervation

Anterior Posterior

Standard Standard Femoral Block Femoral Block

Technique Technique Palpate femoral artery

at inguinal crease. Mark a spot 1 cm

lateral to pulse. Advance needle till

quadriceps twitch obtained.

Issues With Standard Issues With Standard Technique:Technique:

Body SizeBody Size

Sartorious Sartorious TwitchTwitch

Injection should not Injection should not be done when a be done when a sartorius twitch is sartorius twitch is present, because the present, because the nerve may have nerve may have already exited the already exited the sheath.sheath.

Nerve toSartorius m.

Issues With Standard Issues With Standard Technique:Technique:

Injection Outside Injection Outside Sheath:Sheath:

Issues With Standard Issues With Standard Technique:Technique:

Femoral N. Ultrasound Femoral N. Ultrasound Imaging (1):Imaging (1):

Positioning:Positioning: Patient flat, stomach Patient flat, stomach

retracted with wide tape retracted with wide tape if needed. if needed.

Stand on side of block, Stand on side of block, machine on opposite machine on opposite side.side.

Try to line up needle, Try to line up needle, transducer, and US transducer, and US monitor – makes it monitor – makes it easier to image your easier to image your needle.needle.

Femoral N. Ultrasound Femoral N. Ultrasound Imaging (2):Imaging (2):

Holding the Probe:Holding the Probe: Notice the hand is holding Notice the hand is holding

the probe in a way that the probe in a way that the side facing us is easily the side facing us is easily visualized – making it visualized – making it easier to get the needle easier to get the needle lined up with the middle of lined up with the middle of the probe.the probe.

Notice that the hand is Notice that the hand is resting on the patient’s resting on the patient’s skin. This helps keep the skin. This helps keep the probe from sliding around probe from sliding around on the gel.on the gel.

SAX approach.

Imaging:Imaging: Start below crease.Start below crease. Perpendicular to leg, not parallel to crease.Perpendicular to leg, not parallel to crease. Look for femoral artery, white triangle.Look for femoral artery, white triangle.

No! Yes!

The white triangle: The white triangle: anatomic correlationsanatomic correlations

Example Images:Example Images:

Lateral Medial

Try to identify the fascial planes and the nerve.

Lateral Medial

Lateral Medial

Lateral Medial

MedialLateral

Slight rotational and angle Slight rotational and angle adjustments of probe, to get best adjustments of probe, to get best cross section.cross section.

Move probe cephalad to find best Move probe cephalad to find best compromise between femoral nerve compromise between femoral nerve image and depth. (As you move image and depth. (As you move cephalad, the nerve becomes a more cephalad, the nerve becomes a more distinct bundle. However, it can be distinct bundle. However, it can be harder to image as it gets deeper.)harder to image as it gets deeper.)

Fine Tuning Imaging:Fine Tuning Imaging:

LateralMedial

LateralMedial

Another example. Try to identify the fascial planes and the nerve.

LateralMedial

LateralMedial

LateralMedial

Note second artery below femoral artery – the profunda femoris branch.

At this location, femoral nerve is also branching out, and harder to image, so best to move more cephalad.

The probe is being moved cephalad.

Approaches: With Approaches: With StimulationStimulation

OOP

IP

OOP IP

Approaches: No Approaches: No StimulationStimulation

Here, an 18 g Touhy needle is being used – easier to see with US, and easier to feel the 2 pops through fascias lata and iliaca.

OOP IP

Don’t aim for nerve. Aim to pierce fascia iliaca lateral to nerve.Feel fascial pop, then give 1 ml test dose to confirm location.

OOP OOP GeometryGeometry

A good goal for the OOP approach would be that your needle tip approaches the nerve at the point that the ultrasound beam intersects with the nerve. That way, you will be sure to see your test injection. You can measure depth to nerve with US, then use that information as shown.

Example of In Plane Example of In Plane Approach:Approach:

Example of Out of Plane Example of Out of Plane ApproachApproach

Note that the needle isn’t seen here, but tissue movement shows general track of the needle.

Injection:Injection:

More Injection:More Injection:

In Plane – Outside SheathIn Plane – Outside Sheath

An example of a test injection above the fascia iliaca, and probably also above the fascia lata.

Out of Plane – Outside Out of Plane – Outside SheathSheath

An example of a test injection above the fascia iliaca.

One more nice example: a 16 y/o female for an ACL repair.

Post injection. Even though nerve is not completely surrounded with local, the block is still usually good.

Scenario:Scenario:Total Knee ReplacementTotal Knee Replacement Preop meds: celexecob, Preop meds: celexecob,

gabapentingabapentin Spinal anesthesiaSpinal anesthesia Femoral single shot block vs Femoral single shot block vs

cathetercatheter Pre or postop.Pre or postop. Local by surgeon (helps with Local by surgeon (helps with

sciatic mediated pain).sciatic mediated pain).