Analgesia & Resuscitation : Current Research

Abstract

Background: Sciatic nerve block is classically performed through posterior or lateral approaches. With the increased use of ultrasound, the anterior approach has gained popularity. An anterior approach should be considered in patients after trauma and severe postoperative pain where patient positioning can be challenging. The anatomical landmark techniques can be difficult for anterior approach and cannot always be relied on due to inconsistency in extremely obese population. The presence of large blood vessels in the needle path and increasing use of anticoagulants, call for the use of ultrasound guidance for anterior approach to sciatic nerve. Objectives: Here we describe two cases where an anterior approach was used to place indwelling sciatic nerve catheter under ultrasound guidance. Methods: Patients were positioned supine with some external rotation of the corresponding lower extremity. Skin was prepped using standard technique and ultrasound was used to scan for the sciatic nerve using anterior approach. A curvilinear probe was used to allow for deep tissue scanning. The Sciatic nerve was identified deep to adductor muscle medial to the femur and about 10 cm distal to the inguinal crease. A 6 inch tuohy needle was used to approach the nerve with stimulation elicited at 1 mA or less in each case. Twenty ml of 0.5% ropivacaine was injected and the catheter was inserted 5 cm past the needle tip. Results: The patients had a successful sciatic block and very good pain management post-operatively. The use of ultrasound has made the anterior approach to sciatic nerve more feasible and safer. The nerve could be visualized using real time ultrasonography and catheter was placed safely avoiding damage to major blood vessels and the nerve itself. Conclusion: The anterior approach for the placement of sciatic nerve catheter is safe when facilitated with ultrasound guidance. This technique is very useful in patients who cannot be positioned for the conventional posterior approach to the sciatic nerve. Inserting sciatic nerve catheter using the anterior approach under ultrasound guidance is relatively new and can potentially save time and provide more safety.