Lower Extremity Nerve Blocks Flashcards
What are the two approaches to the lumbar plexus block?
Posterior and Anterior
What is the name for the posterior lumbar plexus block?
Winnie
What are the two types of anterior lumbar plexus blocks?
3 in 1 and Fascia Iliaca
What are the two types of approaches to the sciatic nerve block?
Posterior and Anterior
Where is the lumbar plexus located?
L1-S1
What are the four major nerves that supply the lower extremities?
Lateral femoral cutaneous
Femoral
Obturator
Sciatic
What are the names of the two branches that the sciatic nerve divides into?
Peroneal and Tibial
What is the name of the nerve the femoral nerve turns into more distal down the leg?
Saphenous
At what point does the sciatic nerve branch into the peroneal and tibial nerve?
Just above the knee
How should the patient be positioned for a posterior approach of the lumbar plexus?
Lateral hips in line with the shoulders
What are the landmarks for a posterior approach of a lumbar plexus block?
L4 is the iliac crest
Posterior Superior iliac spine, draw a line perpendicular to iliac crest (up the butt crack)
Move 4cm laterally
How should the needle be inserted for a posterior approach of a lumbar plexus block?
Perpendicular in all planes
5-6cm to contact bone (posterior surface transverse process)
Re-direct needle to pass caudad or cephalad
What is the desired response to ensure you are in the lumbar plexus?
Quadriceps contraction with symmetrical movement of patella
At what amplitude would the provider know they are in the lumbar plexus?
0.5-1mA
How much LA should be injected into a lumbar plexus block?
25-35mL
How long can it take to develop a full sensory and motor block with a lumbar plexus approach?
Up to 30minutes
Why is the anterior lumbar plexus block also called a 3:1 approach?
It anesthetizes the lateral femoral cutaneous nerve, femoral nerve and the obturator nerve
What is the function of the lateral femoral cutaneous nerve?
Purely sensory
What is the function of the femoral nerve?
Mixed motor/sensory
What is the function of the obturator nerve?
Mixed motor/sensory
Where is the needle insertion for the anterior approach of a lumbar plexus block?
Just below the inguinal ligament which is 1-1.5cm lateral to the femoral artery
What direction should the needle be directed for an anterior approach of a lumbar plexus block?
Directed cephalic at about 60 degrees from the skin
What type of motor response should be seen with an anterior approach of a lumbar plexus block?
Quadriceps contraction with symmetrical movement of patella at 0.5-1mA
How much LA should be injected for an anterior approach of a lumbar plexus block?
Greater than 20mL (30-40)
Why should the provider massage after injecting LA with an anterior approach?
To help distribute LA between the three nerves
Why is it helpful to hold distal pressure after injecting LA in an anterior approach of a lumbar plexus block?
To help LA transverse up the plane
What is the anterior approach also known as the “date block?”
The obturator nerve helps keep knees together
What should the provider do if there is sartorious contraction with stimulation?
Redirect the needle laterally and advance 1-2mm farther
What does a sartorious contraction look like?
Contraction of thigh arising from ASIS suggests anterior branch of femoral nerve
What should the provider do if there is arterial blood aspirated with an anterior approach to a lumbar plexus block?
Move the insertion point 1cm lateral
What is the fascia iliaca approach to a lumbar plexus block?
Blind technique no nerve stimulator or ultrasound, identify anterior superior iliac spine and pubic tubricle
Divide the line in thirds
Take most lateral third and drop down 2cm =insertion point
When performing the fascia iliaca approach, what two pops should be felt when advancing?
Fascia lata and Fascia iliaca
How much LA should be injected in the fascia iliaca approach?
3-40mL
What dermatomes are encompassed in a sciatic nerve block?
L4-5, S1, 2, 3
Where is the sciatic window located and what is its importance?
Around the bone of the pelvis this is where the sciatic nerve enters
What position should the patient be in for a classic sciatic block?
Lateral (Sims) position with operative side uppermost
What are the landmarks for the classic sciatic nerve block?
Posterior superior iliac spine PSIS
Greater trochanter
Connect and mark the midpoint, draw perpendicular in caudad direction
Where should the needle be inserted in a classic sciatic nerve block?
4cm alone perpendicular
What muscle stimulation may been seen initially after insertion of a classic sciatic nerve
Stimulation of the gluteus maximus
What is the desired muscle contraction for a classic sciatic nerve block?
Stimulation of the tibial (plantar flexion) and Peroneal (dorsiflexion) and contraction of the hamstring
What type of patient may have long term sciatic pain?
Those whose sciatic nerve goes over or through the piriformis muscle
If contraction of the toes is not seen with a classic sciatic nerve block, what is an acceptable muscle to confirm placement?
Achilles tendon
What might the problem be if a patient complains of an electric shock down half of the penis/vagina?
Stimulation of the pudendal nerve which lies medial to the sciatic nerve
What are the landmarks for the anterior approach of a sciatic nerve block?
ASIS, Pubic tubercle –> connect and divide into thirds
At junction of medial 1/3 and lateral 2/3 draw a perpendicular line to extend caudally
Line through greater trochanter parallel to first line
How should the leg be position for the anterior approach of a sciatic nerve block?
Patella towards the ceiling
Where is the insertion point for the anterior approach of a sciatic nerve block?
Intersection of perpendicular with line through greater trochanter
How far should the needle be inserted for the anterior approach of a sciatic nerve block?
8-10cm, perpendicular in all planes
What bone might the provider come into contact with for the anterior approach of a sciatic nerve block?
Lesser trochanter, redirect medially
What motor response should be seen for the anterior approach of a sciatic nerve block?
Tibial = plantar flexion and inversion
Common peroneal: dorsiflexion and eversion
