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Sciatic nerve block
Dr S. Parthasarathy MD DA DNB PhD
FICA , Dip software based statistics
History
• Victor Pauchet first described the sciatic nerve block
in L'Anesthésie Régionale in 1920:
• "the site of needle insertion for blocking the sciatic
nerve at the level of hip: 3 cm along the
perpendicular that bisects a line drawn between the
greater trochanter and the posterior superior iliac
spine
• Labat described in anesthesia literature
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The labat society = later named
ASRA
Who was labat teacher :
Victor Pauchet
So many approaches later
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Winnie
Raj
Beck
Mansour
di Benedetto
• Inferior division of lumbar L4, L5 and sacral S1, S2, S3 nerves.
• Emerges from the greater sciatic foramen.
• Lies below the piriformis muscle , deep to gluteus maximus m. on
the posterior wall of the pelvis.
• Descends between the greater trochanter of the femur and the
ischial tuberosity.
• Splits into the common peroneal and tibial nerves. This division may
take place at any point between the sacral plexus and the lower
third of the thigh.
• Articular branches arise from the upper part of the nerve and
supply the hip joint.
Inferior division of lumbar L4, L5 and
sacral S1, S2, S3 nerves.
Emerges from the greater sciatic foramen.
Lies below the piriformis muscle , deep to gluteus maximus m.
on the posterior wall of the pelvis.
Descends between the greater trochanter of
the femur and the ischial tuberosity
Splits into the common peroneal and tibial nerves. This
division may take place at any point between the sacral
plexus and the lower third of the thigh.
Osteotome
Indications
• lower-limb surgery, often combined with a
femoral or psoas compartment block.
• distal surgery of the lower extremity
• Post operative analgesia
• Leave out saphenous area
Contraindications
• local infection and bed sores at the site of
insertion,
• coagulopathy,
• preexisting central or peripheral nervous
systems disorders,
• allergy to local anesthetics.
Techniques
• Classic labat approach
• Site – PSIS to GT
• Perpendicular to
midpoint – 5 cm line
• Cross
• GT to sacral hiatus
• Point of intersection
Procedure
• The patient is in the lateral decubitus position with a slight
forward tilt. The foot on the side to be blocked should be
positioned over the dependent leg so that twitches of the foot
or toes can be easily noted.
• After cleaning with an antiseptic solution, local anesthetic is
infiltrated
• The anesthesiologist performing the block should assume an
ergonomic position to allow precise needle maneuvering and
monitoring of the responses to nerve stimulation
Change ??
• The patient is positioned as for the posterior
approach, with the extremity to be blocked uppermost
and with a greater inclination of the trunk to a semi
prone position.
• The dependent limb should be straightened at the
knee and hip and the limb to be blocked should be
flexed at both the knee and hip.
1 cm thick nerve – 20 ml
is OK
• Needle perpendicular
• Gluteus maximus
contraction
• Negotiate greater sciatic
foramen
• Dorsal flexion ?
• Plantar flexion – tibial
component
• Hamstring twitch is OK
Press the
fingers
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Local twitch – GL. Max
Hits bone
Nothing in 10 cm
Genital paresthesia
Hamstring twitch
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Go deep
Go lateral and caudal
Cranial and lateral
Cranial and lateral
OK
Pearls
•Inadequate skin anesthesia despite an apparent timely
onset of the blockade can occur.
•It can take up to 30 minutes for full sensory–motor
anesthesia to develop.
•Local infiltration at the site of the incision by the surgeon
is often all that is needed to allow the surgery to proceed.
• Where the bone breaks
• The continuous sciatic block technique is
similar to the single-shot technique
• Block needle angulated caudad
• 1. 5 ma current
• Locate the nerve
• Passage of catheter
• Caudad
• 5 cm beyond
• Continuous infusion is initiated after an initial
bolus of dilute local anesthetic
• Ropivacaine 0.2% is commonly used for this
purpose (15–20 mL).
• Diluted solutions of bupivacaine or Lbupivacaine- (motor blockade ? ).
• The infusion is initiated at 10 mL/h or 5 mL/h
when a patient-controlled analgesia (PCA)
dose is planned (5 mL
Parasacral - Mansour approach
Parasacral anatomy
Raj technique
• Patient in supine position,- lithotomy or a person
holding .Landmarks: Midpoint of a line between the
greater trochanter and ischial tuberosity.
• Tips:
• Needle is introduced perpendicular to the skin.
• Nerve is located at a depth of 5 to 7 cm.
• Stimulation of the tibial or common peroneal nerve
(hamstrings may be direct muscle stimulation).
In between two bony prominences
Subgluteal ??
Classical sub gluteal PNS
Go down – some more
Above and below
Anterior – beck approach
• supine patient whose leg is in the neutral
position
• Line joining ASIS and pubic tubercle
• Divide into three – medial point draw a line
caudolateral
• Meet the second line from GT to LT
• Nerve stimulator
• 22-gauge, 12-cm needle is
inserted so that it contacts the
femur at its medial border.
Once the needle has contacted
the femur, it is redirected
slightly medially to slide off the
medial surface of the femur.
• At approximately 5 cm past the
depth required to contact the
femur, a paresthesia or motor
response should be sought to
ensure successful block
• 25 ml
• Difficult
• Deep nerve
• Children – supine
• No need to change
Position after GA
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Don’t rest the foot
Keep some pillow below the ankle
We can see the twitch
Anterior approach – hamstring is not reliable
Nothing felt for 12 cm – go lateral
Beck – but USG
• 5- 7 cm above
• Division
• Superficial – T
• Posterior to
popliteal vessels
Biceps and semite
• Can block without USG
also
• 5 cm above the
midpoint of the base of
a triangle
• See for twitch
2 – BF , 3 = SM
Popliteal sciatic block
lateral approach
Saphenous at midthigh ( adductor
canal)
Saphenous
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Superior patella border
Extend the leg
Find sartorius
2 cm above
2 pop ups
10 ml
Saphenous nerve
• In the leg
• 1 cm depth
• Close to the saphenous
• vein
What is left out ??
• Complications
• Why ?
• Rare
• Vascular injury – dysthesia – one to two weeks
Summary
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Sciatic nerve anatomy
Indications
Types of block
USG modifications
Encircle
Volume
Time of onset ??
Complications