Phantom Practice

STEPS TO BUILD A PORCINE PHANTOM

1. Prepare a piece of pork shoulder with the humerus attached.
2. Carve to 20 cm x 12 cm x 8 cm (length x width x height).
3. Remove the skin and deodorize the pork specimen by soaking it in approximately 30 mL of 70% alcohol inside a plastic bag for 8 to 10 hours at 4°C.
4. Use a metal or plastic rod (approximately 1.5 cm in diameter) to create a 10cm long tunnel within the muscle layers approximately 3 cm from the surface.
5. Insert a bovine tendon (approximately 8 cm long and 1 cm in diameter) inside the tunnel; ultrasound appearance of tendon and nerve is similar.
6. Use a smaller tendon for advanced practice.
7. Wrap up the whole phantom in a transparent para film and reinforce exteriorly by a surgical paper towel.
8. Store specimen at 4°C until use.

Short axis (x-section) view

Longitudinal view

In Plane Needle Insertion Practice

A. The needle is inserted in plane with the transducer but the needle image is not seen.

B. Maneuver # 1: Slide the transducer back and forth slowly over the needle until the needle image is seen. Hold the needle steady.

C. Maneuver # 2: Wiggle the needle tip from side to side until the needle is seen. Hold the transducer steady.

Out of Plane Needle Insertion Practice

Please refer to Needle Localization.

Needle Handling

Proper needle handling skills are required for accurate and smooth needle insertion during ultrasound guided nerve blocks. If the operator is not ambidextrous, and prefers to use the dominant hand to handle the needle and inject local anesthetic, then the operator must choose a proper body location and orientation in relationship to the patient.

This is an example of a right handed operator using the right hand to hold the needle for a left sided interscalene block. Note that the operator is standing on the left side of the patient below the clavicle.

This is an example of a right handed operator using the right hand to hold the needle for a right sided interscalene block. Note that the operator is now standing on the right side of the patient above the clavicle. AA = axillary artery.

Needle Selection

Large bore needles (e.g., 17 G) are more readily visualized and easier to direct under ultrasound. They are preferred for deep blocks e.g., an infraclavicular block when the angle of needle insertion is steep (> 45 degrees). Smaller bore needles (e.g., 22 G) are more difficult to visualize, but easily visualized for more superficial blocks e.g., the axillary block, when the angle of needle insertion is shallow.

A 17 G Tuohy needle inserted in plane with the ultrasound transducer at an approximately 45 degree angle

A 22 G insulated needle inserted in plane with the transducer at an approximately 45 degree angle

Insulated needles may be used during ultrasound guided nerve blocks if nerve stimulation is desired. Furthermore insulated needles are generally short bevel needles that are less sharp than the hypodermic needles. They are therefore less likely to produce paresthesia upon nerve contact than sharper hypodermic needles.

Echogenic biopsy needles are available but are not specifically designed for nerve blocks at the present time. Echogenic insulated needles will be available soon. Needles with echogenic tips may greatly enhance visualization especially when the needle is inserted using the out of plane approach (perpendicular to the ultrasound beam).

An example of the echogenic tip needle by Hakko^TM Medical Co. LTD (Japan).
Arrows = echogenic indicators at the needle tip

Body Ergonomics

Proper body ergonomics to handle the transducer and the needle, to view the screen, and to position the patient are essential for block success and to avoid operator fatigue and body injury. Below are some examples of proper and improper body ergonomics.

Proper operator and screen orientation; note that the ultrasound machine is placed directly in front of the operator to provide a direct line of vision.	Improper operator and screen orientation; note that the operatorís head is turned almost 90 degrees to view the ultrasound image on the screen.
Proper body position and bed height for the procedure	Improper body position; the bed is too low for the procedure
Proper transducer holding skill; the hand is placed close to the transducer contact surface	Improper transducer holding position; the hand is high up on the transducer
Proper hand and arm positions; both hands and arms are comfortably supported	Improper hand and arm positions; both the arm holding the transducer and the hand holding the needle are not supported

Perineural Injection

The goal is to place the needle tip on each side of the target nerve (i.e., perineural) but not inside the nerve (i.e., intraneural). Avoid direct head-on needle to nerve contact (figure A).

Aim to inject local anesthetic around the nerve and not inside the nerve (figures B and C). Perineural injection is visualized as an expanding collection of hypoechoic fluid around the nerve. Circumferential spread is generally a good indication of adequate local anesthetic spread ("donut sign").

Figure A shows needle in contact with nerve White arrows = block needle Yellow arrowhead = nerve	Figure B show local anesthetic injection around the nerve LA = local anesthetic White arrows = block needle Yellow arrowhead = nerve
Figure C show local anesthetic injection around the nerve LA = local anesthetic White arrows = block needle Yellow arrowhead = nerve

Recognition of Improper Local Anesthetic Spread

An Illustration of Local Anesthetic Spread During Femoral Nerve Block

Figure A shows an improper injection outside the fascia iliaca (FI). Arrows show tissue expansion outside the fascia. FA = femoral artery

Figure B shows a proper injection deep to the fascia iliaca (FI). Arrows show fluid expansion deep to the fascia. FA = femoral artery

An Illustration of Proper and Improper Local Anesthetic Spread During Popliteal Sciatic Nerve Block

Figure A illustrates improper injection and subsequent hypoechoic local anesthetic spread (asterisk) outside the fascial sheath of the sciatic nerve (hyperechoic structure) in the popliteal region.

Figure B illustrates proper injection (asterisks) inside the fascia sheath of the sciatic nerve.

An Illustration of Proper and Improper Local Anesthetic Spread During Supraclavicular Brachial Plexus Block

Figure A illustrates improper injection and hypoechoic local anesthetic (LA) spread outside the brachial plexus sheath. Arrowheads = nerve trunks FR = first rib PL = pleura SA = subclavian artery

Figure B illustrates proper injection (LA) inside the expanded brachial plexus sheath. Arrowheads = nerve trunks FR = first rib PL = pleura SA = subclavian artery

Recognition of Intraneural Injection

Intraneural injection is manifested by an expansion of nerve diameter (yellow arrowheads) with as little as 1mL of injection (figure B).
Another hint of an intraneural puncture is nerve movement towards the needle as the needle is withdrawn. The nerve should be moving away from the needle under normal circumstances.

Ultrasonographic Appearance of An Intraneural Injection

Pre-injection

Post-injection

Hydro Dissection Technique

The hydro dissection technique is most useful for "dissecting" out the intermuscular or interfascial plane in which a small nerve lies.

Injection of 5-10 mL of fluid (saline or D5W) through the needle can distend and open up the narrow space so that the small nerve is more clearly visualized before local anesthetic injection.

Hydro dissection is particularly useful for blockade of smaller nerves located between muscular planes e.g., 1) ilioinguinal and iliohypogastric nerves; 2) the rectus sheath block; 3) obturator nerve; 4) saphenous nerve and 5) transverse abdominis plane block.

Figure A shows hypoechoic ilioinguinal/iliohypogastric nerves (arrowheads) within the plane between the internal oblique muscle (IOM) and the transverse abdominis muscle (TAM).	Figure B shows needle (arrows) approaching the nerves using the in plane needle approach. It is difficult to tell if the needle tip is indeed inside the intermuscular plane.
Figure C shows injection of a small amount of fluid ("hydro dissection") to open up the narrow plane. A small hypoechoic fluid collection is now seen above the nerves.

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