Ultrasound Guided Nerve Blocks of Lower Extremity: Techniques and Management - SD

Introduction

My name is Dr. Kho Gandhi. I am from Thomas Jefferson University Hospital in Philadelphia, Pennsylvania.

I am a assistant professor of anesthesiology and director of regional anesthesiology at the hospital.

Today, I'll be talking about ultrasound guided nerve blocks of lower extremity.

Challenges of Joint Replacement

Some of the challenges of joint replacement are that patients have a lot of pain, so we as anesthesiologists and hospital providers need to minimize the patient's pain.

Patients also need to accelerate rehabilitation so that patients do not have excessive scar tissue after surgery.

Patients need to be on anti anticoagulation so that they don't develop pulmonary DVDs and pulmonary embolisms.

And we need to minimize local anesthetic consumption to minimize toxicity, and we need to avoid postoperative complications for patients.

Key Studies on Pain Control and Rehabilitation

Studies have shown specifically this by JAMA in jama by Dr. Muan that patients who are given early physical therapy, regardless of their comorbidities, do better and have better outcomes.

And the key is to control pain and to accelerate rehabilitation.

And patients gain rapid functional improvement if this therapy is begun in early period during the hospital stay.

Xavier Captivia also published in anesthesiology that patients have better pain control, are able to have faster functional recuperation if they have a continuous nerve block or a continuous epidural infusion versus a PCA pain regimen.

They, patients who receive these two forms of therapy are able to have better knee flexion and are able to defer mobilization less than compared to PCA.

However, patients have better knee flexion on day five and discharge, however, at month one and month three, they have minimal differences.

Typical Nerve Blocks of the Lower Extremity

Typical nerve blocks of lower extremity that we do are the lumbar plexus block, the fascia iliac a block, the femoral nerve block.

These nerve blocks are very good for pain of the hip as well as the knee joint.

The sciatic nerve blocks are done for anything below the knee for foot and knees, for foot and back of the knee surgery.

Popliteal nerve blocks are an extension of the sciatic nerve block, and they provide adequate analgesia of the foot for ankle surgery as well as achilles tendon repair.

Advantages of Lower Extremity Catheters

The advantages in lower extremity catheters are that patients have minimal concern for anticoagulation.

Patients can have utilized one leg and the surgical leg is used for physical therapy.

Patients do not require Foleys in the hospital cell setting when they have peripheral nerve catheters, and there's minimal hemodynamic instability compared to epidural infusions.

Lumbar Plexus Block

Anatomy

To review some of the anatomy of the lumbar plexus, the lumbar plexus is derived from L two to L four of the spinal cord.

These nerve roots exit from the spinal cord between the transverse processes of the vertebrae.

They then progress cord add in the belly of the sous muscle to form the terminal nerves.

The lumbar plexus forms the lateral cutaneous nerve, the femoral nerve, as well as the ator nerve.

Benefits and Outcomes

Now, lumbar plexus nerve blocks have been shown to provide adequate analgesia of the hip joint, specifically hip arthroplasty.

When you place a lumbar plexus catheter, patients have very good outcome over the four days after surgery.

They have adequate analgesia.

They have independence from IV analgesia, and they're able to ambulate faster than placebo groups.

Lumbar plexus blocks have also been shown to have good outcomes in knee arthroplasty.

These patients have early recovery when giving lumbar plexus neuro blocks after knee surgery, patients have lower morphine consumption as well as early ambulation.

Technique

On first day when doing a lumbar plexus block, patients are placed in lateral position, and that's best for optimal visualization of the lumbar pl plexus.

The ultrasound probe is often placed three to four centimeters from the midline at the level of the IAC crest.

Now, the ultrasound probe is placed along the longitudinal sagittal position.

And when you are able to place that ultrasound, what you can actually visualize is your erector spine a muscle, and you will see the classic Trident sign.

Trident sign is formed from the transverse process, which gives a acoustic shadowing below the transverse process.

You will be able to visualize the sous muscle and the lumbar plexus is within the first one third of the sous muscle.

Sometimes it is difficult to differentiate them.

However, you could see a hyper coic structures during the performance of this nerve block.

The needle can be placed with the in plain approach and approach the lumbar plexus at one level.

It is often prudent to use a nerve stimulation technique with this procedure.

Fascia Iliaca Block

Applications

Fascia IAC iaca blocks have been done for hip surgeries as well as knee surgeries.

These blocks are fascial compartment blocks.

You are not specifically targeting a nerve, however, you are localizing a, you are localizing the local anesthetic between the fascia lata and the fascia iliac.

And those can be seen well above the at the area of the hip.

And by distributing local anesthetic there, the local anesthetic will spread medially and laterally to block the femoral nerve as well as the ator nerve.

Fascia iac echo compartment blocks have been used in the er specifically for patients that present with hip fractures to provide adequate analgesia to these patients.

Fascia IAC echo block can be easily done by emergency department physicians, and they could provide patients with lower pain scores at 15 minutes, two hours, and eight hours after presentation to the hospital and performance of the nerve block, and also keeps the vitals very stable in the classical approach.

Technique

The fascia iliac block is done one third the distance from the anterior iliac spine and the pubic tubercle.

By going two centimeters at that one third distance, you're able to actually identify the fascia ica, as well as the fascia lata.

The needle tip can be advanced, the needle can be advanced in plain, and the local anesthetic can be dispersed.

Femoral Nerve Block

Anatomy

Femoral nerve blocks are the bread and butter of what anesthesiologists do in the hospital setting.

The femoral nerve is a divide from L two to L four, the lumbar plexus, and it precedes quad add below the inguinal ligament and divides into the anterior and posterior divisions.

It ovates the quadricep muscle as well as this arterius muscle.

The femoral nerve is lateral to the femoral artery and the vein Above the iliac muscle.

Technique

When scanning for the femoral nerve, one can place the transducer of the ultrasound in the area of the inguinal ligament.

And by scanning the inguinal ligament, you could easily identify the femoral artery as well as the femoral nerve.

Let, let's look at this diagram again.

The femoral artery is here.

The femoral nerve is a large hyper coic bright structure.

It's a large nerve, easy to identify, so that a nerve block could be done at that location.

This is an image of a, this is a video of a continuous femoral nerve catheters that we often do for post-op pain relief after knee surgeries.

All catheters should be done in a sterile fashion.

We typically apply a plastic drape as well as a sterile sleeve or the ultrasound probe.

A linear probe is often enough to identify the femoral nerve different depending on patient anatomy.

The femoral nerve can be visualized here above the profundus branch of the femoral artery.

A needle can be inserted in plain and when stimulating the nerve, you could actually visualize the quadricep twitch.

A catheter is then threaded, and this is a stimulating catheter, which is a different form of catheter, which can still be used to localize the nerve and bolus is given through the stimulating catheter.

Duration and Benefits

So how long should you keep a femoral nerve catheter after total knee replacements?

Studies have shown that maximum benefit for a patient is 48 to 72 hours infusion, and that that helps with passive knee flexion up to six weeks.

Beyond the that, there may not be any benefits on pain, stiffness, and functional ability.

Obturator Nerve

The opterator nerve is usually derived again from the lumbar plexus.

It's sometimes splits high up in the operator canal.

The divisions of the operator nerve vary in different patients.

It could either divide above the foramen or below the formen, so it's really variable with patient anatomy.

The ator nerve can be localized between the adductor muscles, it is the first branch is the anterior branch is between the adductor longus and the adductor brevis.

Another branch is between the adductor brevis and the adductor magness.

In clinical practice, this may not be useful for knee surgeries because the amount of sensory innervation to the knee zone is really variable.

It's just a patch that may be given as part of a sensory iteration.

Most of the add ator nerve is mostly for abduction and motor purposes.

So, for post-op pain relief, it may not be really valuable.

Saphenous Nerve

The saphenous nerve is the only nerve of the femoral nerve that innervates the lower part of the leg, and it gives sensory ovation to the medial aspect of the lower leg.

The saphenous nerve can be blocked within the adductor canal.

If you are to trace the ocular artery branch of the femoral artery and trace it down to the mid thigh level, you could actually see the sartorious muscle, the vast medias muscle, and an adductor longus muscle.

And the sartorious nerve, the saphenous nerve is localized within that adductor canal.

Sciatic Nerve Block

Anatomy

The sciatic nerve is derived from the sacral plexus, and it is lumbosacral plexus, and it is derived from L four to S3.

Need for Sciatic Nerve Block in Total Knee Replacement

The question is, do you really need a sciatic nerve block for total knee replacement?

And the answer is yes.

Studies have shown that fem dang in 2005 has shown that when you combine sciatic nerve blocks or femoral nerve blocks, patients are more comfortable, have less pain and less nausea vomiting.

Same with Ben David, who demonstrated in his study that most of the patients benefit from sciatic nerve catheter catheters with good results when doing a sciatic nerve block.

Technique

The ultrasound probe is can be traced from popliteal area to the high sciatic, high sacral area, and you could actually trace the tibial nerve and the carbon nerve, carbon perineal nerve together, which forms a sciatic nerve, which forms a flat appearing structure and it's hyper coic.

And it could be traced all the way to the infra gluteal or the gluteal area.

Catheter Management and Patient Care

In terms of s in terms of catheters, which catheters are better, again, patients have better outcome.

When you use a 0.2 or 0.4% vacating, there's little difference in outcome between the two, and the satisfaction is high.

However, patients who have higher concentration have more motor block than lower concentration.

Typically what we do is after we insert a catheter, we give a bolus, and that bolus is adequate for primary block patient's.

Catheter is attached to a pump, which provides continuous infusion of local anesthetic at eight to 12 ccs an hour, and we try to aim to provide a sensory block and avoid motor blocks.

We also avoid excessive local anesthetic toxicity.

Patients are monitored in the hospital setting and nursing and patient education is important because if they have an incense limb, they're able, they're prone to getting pos positional nerve injury.

So patient education is indicated for this purposes.

Thank you.