Tips and Tricks for Optimizing Technical Performance in Ultrasound-guided Peripheral Nerve Blocks

Educational Objectives

The goal of this program is to improve performance of ultrasonography-guided peripheral nerve blocks. After hearing and assimilating this program, the clinician will be better able to:

1. Visualize anatomic structures and the tip of the needle during ultrasonography-guided peripheral nerve blocks.

2. Apply principles of ergonomics to enhance control when performing ultrasonography-guided peripheral nerve blocks.

3. Optimize image quality in ultrasonography.

Summary

Introduction: clinical success requires selection of appropriate patient, block, and surgery; ensure that management of pain integrated into perioperative care (effects of all blocks eventually end)

Challenges in performing nerve blocks using ultrasonography: recognition of sonoanatomy — enhanced through taking workshops and performing ultrasonography with many patients; clinician should recognize patterns; scanning phase characterized by identification of target and structures to be avoided, selection of optimal view, and planning route for needle; insertion of needle — follow tip of needle as it travels to target; injection of local anesthetic agent — appropriate location allows achievement of desired clinical effect

Visualization: we see only structures we look for; we look for only structures that we know exist; interpretation of images during ultrasonography involves recognition of patterns; experience and knowledge of surface and deep anatomy essential; nerves difficult to visualize during ultrasonography, but almost all nerves have consistent relationships to structures easy to visualize (eg, muscle, fascia, vessels, bone); bone hyperechoic; arteries pulsatile; veins compressible; fascial planes appear as bright, reflective, white lines; surface anatomy informs guiding location of probe; be aware of course of nerves; placing probe perpendicular to axis of nerves and vessels usually optimal to reveal recognizable patterns

Positioning: coordinate use of probe and needle in both hands while looking at screen; probe and needle manipulated in 3 dimensions, but visual information presented on screen in 2 dimensions; ensure proper alignment; needle may be advanced across or along line of sight; research suggests that advancing needle along line of sight provides better alignment of needle and beam in in-plane position; advancing needle across line of sight also may be appropriate and improves with practice; advancing needle along line of sight allows holding needle and probe in same hands regardless of side of patient being visualized

Ergonomics: important for coordination and alignment; position bed at proper height, stand squarely, and hold shoulders parallel; hold probe in most comfortable hand; hold probe low to facilitate good control; rest hand on patient at all times to optimize stability; goal control while being relaxed

Optimization of quality of image: ensure that frequency, depth, gain, and focus appropriate; applying pressure improves visibility of structures by reducing depth to target and optimizing contact between probe and skin; press hard enough to compress veins, but avoid discomfort in awake patient; avoid compressing vessels in vascular access procedures; tilting optimizes visibility of nerve because of anisotropy; nerves do not travel parallel to skin; tilting probe can direct beam perpendicular to nerve and increase reflectivity; goal to define boundaries of nerve; avoid using tilt to align beam with needle (use small sliding motions); rotation chiefly used to align entire shaft into view of beam and typically not strictly necessary if visualization of tip possible

Planning approach: identify target and which structures to avoid; majority of structures mobile and can be pushed aside with blunt needle or injection of fluid

Insertion of needle: consider small diameter of objects being aligned; use micromovements to align objects; consider ergonomics; use just enough gel to eliminate air between probe and skin; excessive quantity of gel creates slippery surface and makes control difficult; few drops of saline adequate for central lines

Identifying tip of needle: moving tip easier to visualize; both hands should continuously make small movements; needle winking in and out of view during advancement normal

In-plane approach: insert needle parallel to beam; expect to see entire shaft; positioning of target on screen depends on desired angle of trajectory; shallower angle provides more visible needle, but path to target longer; length of needle in tissue can affect ability to maneuver; “sweet spot” between 30° and 45° for majority of blocks; very deep block may require steeper angle; insert needle as close to center of short edge of probe as possible; steep angle may be required to puncture skin and then be adjusted to desired trajectory; changing trajectory once needle enters muscle difficult; bevel of needle should face upward (generates double echo to help identify tip)

Identifying tip of needle (continued): jiggling — staccato, gentle, in and out motion; penetration of structures unlikely; motion may be transmitted to excessively large area and make precisely locating tip difficult; seesawing motion — most often used by speaker; anything at tip of needle lifted through same arc as motion of hub; nothing beyond tip moves; does not cause significant trauma to tissues; safe near vessels and nerves; tactile and visual pops — may be noted as fascia penetrated; hydrolocation — small volume of fluid injected; small amount of fascia surrounds every nerve; especially effective if visualization of needle not otherwise possible; volume of fluid 0.5 mL; use gentle probing motions while advancing needle; avoid sharp, pronounced, jabbing motions

Out-of-plane approach: tip of needle moves outside beam as it advances; moving probe over large area necessary to track needle; tip and shaft of needle look similar (little white dots); acoustic shadow visible when visualizing shaft, but not tip; slide probe away and toward needle to locate tip; potential to image shaft greater with shallow compared with steep angle; steeper angle minimizes errors (except with shallow [≈1-cm] targets); for central lines, steep angle minimizes risk of penetrating dome of pleura; rely on indirect cues to locate tip of needle; primary motions jiggling and side-to-side “waggle”; pops and hydrolocation also important; when targeting nerves, compartmental spread should be visible with injection; advance layer by layer; jiggle to confirm position above each layer; focus on feel instead of screen while penetrating each layer; relax forward pressure and bounce to reassess position after penetration of each layer; slide probe back and forth to locate tip of needle

Injection and delivery of local anesthetic agent: identify fascial envelope or compartment of nerve; fill it without touching nerve (if possible); avoid breaching epineurium; penetrate perineural and extraneural connective tissue to enter nerve sheath; sheath contains local anesthetic agent and guides its spread; present for every nerve and plexus; avoid forced contact with nerve; aim slightly away from nerve; tenting observed, because needle blunt and fascia tough; nerve should roll away; advance in smooth controlled manner; “pop” should be felt; pulling back slightly often necessary; hydrolocation should indicate fluid spreading around nerve; repositioning by “walking around” nerve to achieve good spread not necessary if tip of needle within compartment; piercing fascia easier with steeper trajectory; consider scanning along nerve during injection to monitor spread of anesthetic agent

Intraneural injection: reassess location of tip of needle any time patient reports pain; undue resistance to injection typically related to pressing against fascia, but possibility of intraneural location should be considered; hallmark expansion of nerve target; usually extrafascicular; rarely intrafascicular

Intravascular injection: always aspirate; transducer may occlude small veins; ensure that assistant does not “suck back” too hard on plunger (can collapse vein); reassess position if anesthetic agent does not spread as expected during injection

Readings

Chin KJ: Needle and transducer manipulation: the art of ultrasound-guided regional anesthesia. 2010. https://pdfs.semanticscholar.org/5857/13353de041e994b5dad0119278b94c4778da.pdf. Accessed August 1, 2019; NYSORA: Introduction to ultrasound-guided regional anesthesia. https://www.nysora.com/foundations-of-regional-anesthesia/equipment/introduction-ultrasound-guided-regional-anesthesia/. Accessed August 1, 2019; Scholten HJ et al: Improving needle tip identification during ultrasound-guided procedures in anaesthetic practice. Anaesthesia 2017 Jul;72(7):889-904; Strakowski JA: Ultrasound-guided peripheral nerve procedures. Phys Med Rehabil Clin N Am 2016 Aug;27(3):687-715; Tagliafico A et al: Peripheral nerves: ultrasound-guided interventional procedures. Semin Musculoskelet Radiol 2010 Nov;14(5):559-66.

Disclosures

For this program, members of the faculty and planning committee reported nothing to disclose.

Acknowledgements

Dr. Chin was recorded at the Carolina Refresher Course 2019: 32nd Annual Update in Anesthesiology, Pain, and Critical Care Medicine, held June 19-22, 2019, on Kiawah Island, SC, and presented by the School of Medicine, University of North Carolina at Chapel Hill. For information about upcoming CME opportunities from this sponsor, please visit www.med.unc.edu/cpd. The Audio Digest Foundation thanks the speakers and sponsors for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

AN613801

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.