Ultrasound-Guided Peripheral Nerve Blocks

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Department of Anesthesiology, Yale University School of Medicine, 208051, 333 Cedar Street, TMP 3, New Haven, CT 06520-8051, USA

Thomas M. Halaszynski

Email: Thomas.halaszynski@yale.edu

Keywords

Ultrasound-guided interscalene blockUltrasound-guided supraclavicular blockUltrasound-guided infraclavicular blockUltrasound-guided axillary blockUltrasound-guided femoral nerve blockUltrasound-guided sciatic nerve block

First described in 1978, ultrasound-guided peripheral nerve blockade continues as a new and rapidly growing field in anesthesiology, due in part to the advent of more advanced ultrasound technology developed in the 1990s. This chapter describes commonly performed ultrasound-guided techniques in an easy to follow step-by-step manner. The chapter goals are to impart a recognition and appreciation of how ultrasound use in peripheral nerve block procedures may enhance the application of understanding of human anatomy by anesthesia practitioners and clinicians. Additional references are needed to better understand ultrasound terminology, physics of ultrasound, ultrasound probe selection and equipment, ultrasound knobology, and how to optimize image quality.

Conventionally, peripheral nerve block procedures are performed by eliciting a paresthesia or by nerve stimulation techniques without visual guidance. Such approaches to nerve blockade are highly dependent upon knowledge of surface anatomical landmarks for localization of neural structures. It is, therefore, theorized that regional anesthesia techniques may have an increased success rate, have lower incidence of negative consequences, require smaller local anesthetic volumes, and induce a faster onset of effect when an ultrasound is used in conjunction with anatomical understanding of peripheral nerve anatomy.

Ultrasound-assisted peripheral nerve blockade can:

Identify nerve location, especially in patients with difficult anatomical landmarks
Image nerves in short axis (cross-sectional views)
Provide real-time block needle guidance and direction (allowing needle adjustments in depth and direction)
Real-time imaging of local anesthetic spread upon injection
Identify and appreciate surrounding vital structures (vessels, pleura, etc.)
Reduce the number of needle passes/attempts
Identify aberrant anatomy
May reduce the risk and incidence of inadvertent nerve injury

This chapter describes the following ultrasound-guided nerve blocks:

Upper Extremity Brachial Plexus Nerve Blocks
- Interscalene
- Supraclavicular
- Infraclavicular
- Axillary
Lower Extremity Nerve Blocks
- Femoral
- Sciatic
- Popliteal

Upper Extremity Nerve Blockade

Preparation Technique

Equipment preparation: sterile towels, gloves and gauze pads, antiseptic solution, syringes, 13 MHz linear array transducer, sterile ultrasound sheath, and needles for both local infiltration and nerve block placement
Patient preparation: Monitors “on” and appropriate sedation (midazolam, fentanyl).
Needles: 25G 1.5 in. needle for skin infiltration, and 22G 2–4 in. short bevel needle.
Commonly used agents: 3 % chloroprocaine, 2 % lidocaine, 0.5 % ropivacaine, 0.5 % bupivacaine
Approximate dose: 10–30 ml of local anesthetic.

Interscalene Block

Interscalene blockade targets the brachial plexus at level of nerve trunks or roots, and is used for primary anesthesia and/or postoperative pain management for surgeries on the shoulder/shoulder joint, lateral 2/3rds of clavicle, and proximal humerus surgeries (with or without a continuous catheter). These surgeries include rotator cuff repair, acromioplasty of the shoulder, arthroscopic shoulder surgery, and open reduction and internal fixation (ORIF) of the humerus. NOTE: Interscalene block for wrist, forearm, and hand surgeries often will not provide adequate coverage of the ulnar nerve distribution. However, blockade of ulnar nerve distribution may be achieved by using larger local anesthetic volumes or supplemental blockade of the ulnar nerve at a more distal location.

Ultrasound Anatomy and Needling:

The patient is positioned supine or lateral decubitus with the face turned away from the operative side. The skin is disinfected and the ultrasound probe is covered by a sterile sheath. The ultrasound probe is then placed in the supraclavicular fossa where the brachial plexus is identified next to and posterior-lateral to the subclavian artery. Ultrasound probe is then moved proximally in a cephalad direction and held with a transverse orientation (Fig. 23.1). As the ultrasound probe is moved cephalad, typical divisions of the brachial plexus as seen in the supraclavicular fossa will organize into three nerve roots (C₅, C₆, and C₇).

Fig. 23.1

Suggested initial ultrasound probe position for ultrasound-guided interscalene block

The nerve roots are seen as three round hypoechoic circles usually stacked on top of one another and positioned between the anterior and middle scalene muscles (Fig. 23.2). The carotid artery and the internal jugular vein can be seen anterior and medial to the anterior scalene muscle. The skin at the posterior-lateral end of the probe is anesthetized by subcutaneous infiltration of local anesthetic. The block needle is advanced in-plane with a posterior to anterior direction and advanced until the needle tip is positioned just posterior-lateral to the C₅ and C₆ nerve roots. After negative aspiration, 10–25 ml of local anesthetic is slowly injected in small 3–5 ml aliquots. A continuous single orifice catheter may be inserted to provide continuous infusion of local anesthetic.

Fig. 23.2

Interscalene brachial plexus and anatomical relations with the ultrasound probe in the transverse plane. ASM anterior scalene muscle, CA carotid artery, RIJ right internal jugular vein, arrows identify roots/trunks of the brachial plexus and target for injection of local anesthetic

Pearls and Pitfalls

Pearls:

Although it has been described that phrenic nerve involvement occurs in 90–100 % of interscalene blockade procedures, this complication may be prevented or minimized by reducing/eliminating spread of local anesthetic to the anterior and medial nerve roots. Techniques such as depositing the local anesthetic posterior to the brachial plexus, and observing that the injection is not spreading anterior to the nerve roots/trunks, along with minimizing the amount of local anesthetic used to just surround the nerve roots, will decrease the incidence of phrenic nerve blockade.

Pitfalls:

Side effects from an interscalene block include infection, blockade of phrenic nerve (resulting in a hemidiaphram) and the sympathetic chain (located in region of the cervical nerve roots), intravascular injection, local anesthetic toxicity, neuraxial spread/injection (resulting in a “high” spinal), nerve injury, and hematoma formation. Patients may complain of dyspnea if the phrenic nerve is blocked, as it causes ipsilateral diaphragmatic paralysis. For patients with respiratory compromise (severe COPD), blocking one side of the diaphragm may not be a tolerable side effect. In addition, a Horner’s syndrome commonly occurs if the stellate ganglion (sympathetic chain) is blocked, resulting in ipsilateral myosis, ptosis, and anhidrosis. Blockade of the recurrent laryngeal nerve may occur, which causes hoarseness of voice. Severe complications of an intravascular injection (external jugular vein transverses the interscalene groove and vertebral artery is anterior to the cervical nerve roots) from an inadvertent injection (as little as 1–3 ml) of local anesthetic into the vertebral artery may result in seizures.

Supraclavicular Block

Ultrasound-guided supraclavicular blockade typically targets the brachial plexus at the level of nerve divisions. It is used as primary anesthesia and/or postoperative pain management for surgeries on the humerus (distal), elbow, forearm, hand, or wrist (with or without a continuous catheter), and also upper extremity AV fistula surgery. There may be a delay in onset of ulnar nerve blockade or complete sparing of the ulnar nerve. When this block is performed for shoulder surgery, the addition of a superficial cervical nerve block may be required.

Ultrasound Anatomy and Needling:

The patient is placed supine with the head turned away from the side to be blocked. The skin is disinfected and ultrasound probe protected by a sterile sheath. The ultrasound probe is placed in the supraclavicular fossa, parallel to the clavicle (Fig. 23.3), and then the subclavian artery is identified by directing the probe in a lateral to medial direction until an arterial pulsation is detected. The ultrasound probe is usually held in an oblique coronal orientation to achieve a cross-sectional view of the artery. The subclavian artery lies on top of the first rib, which is hyperechoic. The hypoechoic area seen below the rib is the lung. Moderately hyperechoic and shimmering appearance of the pleura can be seen below the first rib in some patients.

Fig. 23.3

Suggested ultrasound probe position for ultrasound-guided supraclavicular block. Blue markings identify the sternocleidomastoid muscle with the clavicular portion most lateral. The needle is inserted in-plane

The brachial plexus (divisions) is posterior and lateral to the subclavian artery arranged as a group of hypoechoic circles, sometimes described as a “cluster of grapes” (Fig. 23.4). The inferior trunk or division of the brachial plexus located in the corner defined by the subclavian artery and the first rib (“corner pocket”) may be difficult to image in some patients. After subcutaneous infiltration of local anesthetic, posterior and lateral to the ultrasound probe, the block needle is inserted in-plane and advanced to the “corner pocket” under constant needle tip visualization in order to avoid a pneumothorax. After negative aspiration, a small aliquot of 3–5 ml of local anesthetic is slowly injected. Injection of local anesthetic in this area allows the brachial plexus to become more superficial and also better ensures blockade of the inferior trunk/division (ulnar nerve). The needle can then be redirected to inject local anesthetic around the rest of the brachial plexus using a total of 15–25 ml of local anesthetic. A continuous single orifice catheter may be inserted to provide continuous infusion of local anesthetic.

Fig. 23.4

Supraclavicular ultrasound anatomy. The brachial plexus at this level (divisions/trunks) appears as hypoechoic circles/ovals in a cluster just lateral to the subclavian artery. Immediately caudad to the 1st rib is the pleura

Pearls and Pitfalls

Pearls:

Blockade of the intercostobrachial nerve in the axilla is necessary if a tourniquet will be used and placed on the upper arm. This approach to the brachial plexus provides a fast onset of effect as well as more complete anesthesia/analgesia of the upper extremity from a single injection.

Pitfalls:

The cupola of the lung may be located in the block placement area, therefore, a pneumothorax is possible. Such a complication should be considered if a patient develops cough or chest pain (even hours after block placement). A phrenic nerve or sympathetic chain blockade is possible, although less common than with an interscalene block. Risk of phrenic nerve or sympathetic chain blockade can be decreased by avoiding local anesthetic spread anterior and medial to the subclavian artery. Bleeding, infection, hematoma formation, nerve injury, and intravascular injection (subclavian vessels are in the region) are potential problems. A supplemental ulnar nerve block may be necessary if the ulnar nerve distribution is missed. A superficial cervical plexus block should be added for shoulder surgery as this approach often misses the skin overlying the shoulder.

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