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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 • • • • The labat society = later named ASRA Who was labat teacher : Victor Pauchet So many approaches later • • • • • 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 • • • • • Local twitch – GL. Max Hits bone Nothing in 10 cm Genital paresthesia Hamstring twitch • • • • • 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 • • • • • 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 • • • • • • 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 • • • • • • • • Sciatic nerve anatomy Indications Types of block USG modifications Encircle Volume Time of onset ?? Complications