Sciatic Nerve Block - Gluteal Region
Ultrasound guided sciatic nerve block in the gluteal region is considered an ADVANCED skill level block.
The sciatic nerve may be difficult to visualize in this region because of the required depth of beam penetration and lower image resolution from the use of a lower frequency transducer. The overlying adipose tissue in the buttock may be sizable, the sciatic nerve may be quite flat in the transverse view and the required angle of needle penetration may be quite steep.
Both In Plane (IP) and Out of Plane (OOP) approaches are available.
IN PLANE (IP) NEEDLE INSERTION APPROACH
For the In Plane approach, insert a 8 cm 22G insulated block needle on the outer (lateral) end of the ultrasound transducer after skin local anesthetic infiltration. Advance the needle along the long axis of the transducer in the same plane as the ultrasound beam. In this way, the needle can be visualized in real time at the time of needle advancement towards the target nerve.
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- Nerve movement may be observed upon needle contact. Additionally electrical stimulation is recommended to confirm needle to nerve contact.
- Observe the pattern of local anesthetic spread around the target nerve in real time during injection. One may adjust needle position half way during injection to optimize local anesthetic spread.
OUT OF PLANE (OOP) NEEDLE INSERTION APPROACH
- For the OOP approach, align the nerve target at the midpoint of the transducer and then insert the block needle in the same location.
- The OOP approach is often used for catheter insertion.
- For both IP and OOP approaches, scanning prior to needling will determine the angle, distance and depth of needle penetration.
- Observe tissue and needle movement as the needle is advanced towards the target. penetration.
- Clear identification of the needle tip can be technically challenging.
- Confirm needle to nerve contact by electrical stimulation and observe local anesthetic spread.
In Plane Needle Approach to the Gluteal Sciatic Nerve
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Arrows = block needle
Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone |
- Aim to deposit local anesthetic around the sciatic nerve circumferentially.
- However, this may be challenging because the sciatic nerve in this region may be flat and thin in cross section. It is common to find local anesthetic on only one side of the nerve after a single injection.
- Injection to the other side of the nerve may require a second needle insertion site. A hypoechoic (fluid) expansion can be seen during local anesthetic injection.
- Expansion in the gluteus maximus muscle indicates superficial intramuscular injection. Advance the needle accordingly.
- Inject 15-20 mL of local anesthetic for postoperative analgesia.
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Pre-injection
Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone |
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Post-injection
Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone
LA = local anesthetic (deep to the nerve) |
Nerve Localization
1. Identification of the Pudendal Vessels
The pudendal vessels are vascular landmarks at the level of the ischial spine. The vessels are usually visualized adjacent to the ischial spine and medial to the sciatic nerve. It is possible to use Color Doppler or Color Power Doppler to identify the pudendal vessels (artery and vein).
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A. Baseline Scan
Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone |
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B. Scan with Color Power Doppler
Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone
Red arrow = pudendal artery and vein |
2. Identification of the Inferior Gluteal Artery
Another vascular landmark at the level of the ischial spine is the inferior gluteal artery. This structure is usually visualized adjacent to the sciatic nerve. This small artery is more lateral than the pudendal artery.
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A. Baseline Scan
Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone
IS = ischial spine |
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B. Scan with Color Power Doppler
Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone
Red arrow = inferior gluteal artery |
1. Scanning Technique and Local Anesthetic Injection
Pre-injection Scan at the Level of the Ischial Spine
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Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone |
Pre-injection Scan BELOW the Level of the Ischial Spine
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Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
HJ = hip joint
IB = ischial bone |
Post-injection Scan at the Level of the Ischial Spine
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Arrowhead = sciatic nerve
GMM = gluteus maximus muscle
IB = ischial bone
LA = local anesthetic |
Gluteal Nerve Block (In Plane Approach)
- Saranteas T, Chantzi C, Paraskeuopoulos T, Alevizou A, Zogojiannis J, Dimitriou V, Kostopanagiotou G: Imaging in Anesthesia: The Role of 4 MHz to 7 MHz Sector Array Ultrasound Probe in the Identification of the Sciatic Nerve at Different Anatomic Locations. Reg Anesth Pain Med 2007; 32: 537-8
- Chantzi C, Alevizou A, Saranteas T, Zogogiannis J, Iatrou C, Dimitriou V: Usefulness of the two to 5 MHz ultrasound probe in examination and block of the sciatic nerve in orthopedic trauma patients: a preliminary study. J Clin Anesth 2007; 19: 486-8
- Chan VW, Nova H, Abbas S, McCartney CJ, Perlas A, Quan XD: Ultrasound Examination and Localization of the Sciatic Nerve: A Volunteer Study. Anesthesiology 2006; 104: 309-14
- Graif M, Seton A, Nerubai J, Horoszowski H, Itzchak Y: Sciatic nerve: sonographic evaluation and anatomic-pathologic considerations. Radiology 1991; 181: 405-8
- Hullander M, Spillane W, Leivers D, Balsara Z: The use of Doppler ultrasound to assist with sciatic nerve blocks. Reg Anesth. 1991; 16: 282-4