Surgical and anesthesia consents signed

Monitors—blood pressure cuff, ECG, pulse oximeter, capnography

Supplemental oxygen via nasal cannula or facemask

Pillows, blankets, or tables to aid positioning

Skin marker to mark the site laterality and surface landmarks

Sedation to optimize patient comfort—typically midazolam and fentanyl

Rescue drugs and emergency airway equipment available

Antiseptic skin disinfectant

Sterile gloves, mask, hat

Sterile drapes or towels

50- to 100-mm 20- to 22-gauge short-bevel insulated stimulating needle

Small syringe and small gauge needle with lidocaine for skin infiltration

30 mL local anesthetic of choice

Nerve stimulator and/or ultrasound machine with highfrequency linear probe, sterile ultrasound probe cover, and ultrasound gel

Antiseptic skin disinfectant

Sterile gloves, gown, mask, hat

Ultrasound machine with high-frequency linear probe or nerve stimulator

30 mL local anesthetic of choice

Sterile regional anesthesia tray:

Nerve localization can be achieved using peripheral nerve stimulators and/or ultrasound guidance.

Over the past decade, ultrasound-guided nerve blocks have rapidly gained popularity because they provide several advantages compared to the nerve stimulator technique. The use of ultrasound provides direct, real-time visualization of target nerves, needle advancement, and spread of local anesthetic in the desired location.⁶ With continuous catheter techniques, the precise location of the catheter tip can be visualized. Blood vessels and smaller peripheral nerves can be identified and avoided. Research suggests that ultrasound guidance provides an improvement in time required to perform the block, block onset, and block success.^7,8,9,10

For the popliteal sciatic block, ultrasound allows visualization of the precise point where the sciatic nerve bifurcates, which is variable between patients. Identifying this location is helpful in blocking both components of the sciatic nerve.

For these reasons, although this chapter briefly covers nerve stimulator approaches, the focus will be on ultrasound-guided techniques, which have become routinely used in regional anesthesia.

With the in-plane approach, the needle is inserted at the side of the transducer, in line with the ultrasound beam (FIG 2). Because the needle is within the plane of imaging, the entire needle shaft and tip should be seen as echogenic line. In-plane approach is often used due to superior visualization of the entire needle as it is advanced toward the target.

With the out-of-plane approach, the needle is introduced perpendicular to the transducer (FIG 3). The needle crosses the plane of the ultrasound beam such that the needle shaft and tip are seen as an echogenic dot on ultrasound. Needle tip localization is more difficult with this approach. Techniques to help locate the needle tip include looking for tissue displacement, scanning for the needle tip, and injection of fluid to separate tissue planes (hydrodissection). One advantage of using the out-ofplane approach is that the needle traverses only skin and adipose tissue, avoiding muscle.

A wide range of positions can be used during popliteal sciatic nerve blockade. Each is discussed and illustrated in further detail in the following section.

Choice of positioning is typically dictated by a combination of patient comfort, patient mobility, operator ergonomics, and the operator’s personal preference. Body habitus, pain, or the presence of external fixation devices may limit the ability of the patient to assume a lateral or prone position.