Matthes (Supplemental Video 2)
Matthes (Supplemental Video 2)
INSTRUCTOR: The sciatic nerve block is indicated for intraoperative and postsurgical analgesia for procedures involving the lower extremity. It can be performed through a single injection or continuous infusion of local anesthetic via a catheter. The contraindications are similar to those for other nerve blocks, such as patient refusal, coagulopathy, infection or significant malformation at the block site and hypersensitivity to local anesthetics.
INSTRUCTOR: The sciatic nerve can be blocked at a variety of positions along its course, including the parasacral, transgluteal, subgluteal, anterior and popliteal approaches. The most distal location possible should be selected given the site of the surgical procedure in order to minimize motor weakness. While there are no specific risks associated with the performance of a sciatic nerve block other than those associated with any nerve block, extra care should be taken in performing the block in the popliteal fossa of patients who have had vascular bypass procedures or knee replacements.
INSTRUCTOR: When selecting the appropriate local anesthetic for the block, one must consider both the duration of desire to analgesia and whether or not a surgical level block is necessary. Ropivacaine 0.2% or bupivacaine 0.25% are good options for most patients in whom a longer duration of analgesia is desired. More concentrated solutions, such as 0.5% are required for a surgical level of blockade.
INSTRUCTOR: Typically, the local anesthetic is administered at volumes ranging from 0.2 to 0.5 mLs/kg. To achieve a more rapid onset of analgesia, one may consider adding lidocaine or mepivacaine to the local anesthetic solution. Furthermore, additives such as clonidine, dexamethasone or dexmedetomidine may prolong the duration and density of the block. The anatomic landmarks are the bony prominences of the greater trochanter laterally and the ischial tuberosity, medially.
INSTRUCTOR: The patients should be positioned in an intermediate position between the lateral decubitus and prone position with the operative side up and the hips and knees flexed, as illustrated in this image. Scanning with the ultrasound probe should be performed in the depression between these two structures.
INSTRUCTOR: The equipment needed for an ultrasound-guided sciatic nerve block includes an ultrasound machine with a high frequency curve transducer, a standard nerve block tray, a sterile transducer sleeve and gel, sterile gloves, antiseptic solution for the skin, a syringe containing local anesthetic solution, a continuous catheter kit, and a dressing.
INSTRUCTOR: The person performing the block should have a direct line of sight between the needle, the ultrasound probe and the machine, which should be positioned on the opposite side of the patient. This is an ultrasound view depicting the key anatomic structures in this block. The sciatic nerve is identified as a hyper-echoic structure deep to the gluteus maximus muscle between the greater trochanter and the ischial tuberosity.
INSTRUCTOR: Now, let's take a look at an actual sciatic nerve block being performed on a 3-year-old patient presenting for a surgical procedure on her left lower extremity. After appropriately positioning the patient as previously described, the patient's skin is cleaned with an antiseptic solution and the block area is isolated with sterile drapes.
INSTRUCTOR: The greater trochanter and the ischial tuberosity are palpated, and the ultrasound probe was placed on the skin between them. The left side of the screen is lateral and the right side is medial. On ultrasound, the greater trochanter is seen in the lower left-hand corner, and the ischial tuberosity is seen on the right side of the screen.
INSTRUCTOR: The block needle is inserted in plain and slowly advanced to the hyper-echoic structure in the lower portion of the screen. Nerve stimulation is used and the foot is observed for twitches as the needle is advanced. Once twitches are observed, the stimulating current is then gradually decreased until twitches are still seen at 0.6 milliamps.
INSTRUCTOR: Next, a small amount of local anesthetic is injected after careful aspiration to confirm spread around the identified nerve. A stimulating catheter is then inserted through the needle and its position is confirmed with both ultrasound and the nerve stimulator. The catheter is then secured and a sterile dressing is applied.