Peripheral Nerve Blocks

Question 1

hypoechoic background with hyperechoic lines. Compressible

Answer 1

Fat

Question 2

Bright hyperechoic lines

Answer 2

Fascia

Question 3

hypoechoic background with hyperechoic lines. Non-Compressible. Surrounded by hyperechoic lines

Answer 3

Muscle

Question 4

Very bright hyperechoic line with anechoic region beneath.

Answer 4

Bone

Question 5

Hyperechoic and hypoechoic. Honeycomb appearance. Above clavicle more hypoechoic and below clavicle more hyperechoic

Answer 5

Nerves

Question 6

Postganlionic sympathetic and afferent sensory. Only unmyelinated nerve fiber. Autonomic, pain and sensation

Answer 6

C Fibers

Question 7

Preganglionic sympathetic. Autonomic

Answer 7

B Fibers

Question 8

Afferent sensory nerve. Pain and sensation

Answer 8

A(delta)

Question 9

Afferents to muscles and joints. Proprioception

Answer 9

A(Beta)

Question 10

Efferents to muscle spindles. Muscle Tone

Answer 10

A(gamma)

Question 11

Efferents to motor and joints. Motor

Answer 11

A(alpha)

Question 12

Nerve block onset

Answer 12

B >C & A(d) > A(g) > A(b) > A(a)

Question 13

Nerve block recovery

Answer 13

A(a) > A(b) > A(g) > C & A(d) > B

Question 14

LAST (LA Systemic Toxicity ) - Drugs not to use

Answer 14

B-Blockers, Ca Channel Blockers, or LAs

Dont give Propofol

Also, reduce ept to < 1mcg/kg

Question 15

T or F. Heparin 5000 SQ BID and Aspirin/NSAIDs may be administered at any time with no restriction on regional.

Answer 15

True

Question 16

In general must wait anywhere from __-__ half-lives after administration of anticoagulant before regional can be safely performed.

Answer 16

3-5 half lives

Kidney and Liver dysfunction means one should wait longer before regional can be safely performed

Question 17

Current intensity = measured in __. You should start at ___ and dial down. When you get to < ___ it is ok to inject LA

Answer 17

mA, 1.5mA, 0.7mA

Question 18

_____ is used foe sensory vs. motor differentiation and is especially useful in neuropathic patients

Answer 18

Pulse duration = duration of current.

Question 19

Typical pulse duration is about ___microseconds - which will get motor without sensory involvement

Answer 19

100msec

may have to increase for neuropathic pts

Question 20

___ = pulses per second.

Answer 20

Stimulation frequency (Hz) - 2 Hz is typically adequate

Question 21

_____ = pulse duration at which threshold current amplitude is twice that of rheobase

Answer 21

Chronaxie

Important for nerve differentiation

Question 22

_____ = lowest current amplitude with long or infinite pulse duration applied to depolarize (stimulate) a nerve.

Answer 22

Rheobase

Question 23

Equation for current you need in order to stimulate a nerve

I = ______

Answer 23

I =Ir(1 + C/t)

I = Current
Ir = Rheobase
C = Chronaxie
t = pulse duration

Question 24

Block is done at the C5-C7 root/trunk level.
C8-T1 (ulnar nerve) spared.

Block acceptable for shoulder and top half of humerus)

Deltoid/Biceps twitch acceptable

Side effects (ipsilateral horner syndrome, SOB, and hoarseness)

Complications (epidural/subarachnoid spread, paralysis, respiratory failure)

Answer 24

Interscalene Block

Question 25

Block is deeper than the other blocks of the brachial plexus. Thus technically more difficult to visualize with ultrasound Acts at level of cords The best block when performing and upper extremity catheter. Sensory innervations from mid-humerus down. Pneumothorax a major concern

Answer 25

Infraclavicular Block

Question 26

Musculocutaneous nerve, ulnar nerve, median nerve, and radial nerve blocked Technically more challenging because individual nerves have to be anesthetized No risk of pneumothorax Very difficult to place a catheter

Answer 26

Axillary Block

Question 27

Spinal of the arm Acts at the level of the divisions Covers from the mid-humerus down. Does not cover shoulder because the axillary nerve and dorsal scapular nerve are spared Pneumothorax a real concern especially with the land-mark technique

Answer 27

Supraclavicular block

Question 28

Median, Ulnar, and Radial nerves blocked Easily done with nerve stimulation, landmarks, or ultrasound. Great supplemental block if one of the brachial plexus blocks is incomplete

Answer 28

Wrist and Elbow blocks

Question 29

Innervation to anterior thigh and medial aspect of lower leg. Quadriceps contraction ideal (as opposed to sartorial twitch) Anterior and Posterior division Significant quadriceps weakness Ideal for knee replacements and ACL reconstructions Fascia iliaca block only blocks femoral, lateral femoral cutaneous, and obturator 50% of the time.

Answer 29

Femoral Nerve Block

Question 30

In rare situations when there is considerable medial knee pain Obturator nerve divides into anterior and posterior divisions which traverse through the adductor muscles.

Answer 30

Obturator Nerve Block

Question 31

“Femoral nerve block from the back” Reliably blocks femoral, lateral femoral cutaneous, and obturator nerves Advanced block ( Complications include epidural and subarachnoid spread and retroperitoneal hematoma)

Answer 31

Lumbar Plexus Block (Psoas Compartment Block)

Question 32

Difficult to see under u/s guidance Sensory nerve to lateral aspect of thigh Location is 2 cm medial and 2 cm inferior to anterior superior iliac spine

Answer 32

Lateral Femoral Cutaneous Nerve Block

Question 33

The only unmylenated fibers we have

Answer 33

C Fibers

Question 34

Visceral Pain

Answer 34

A-delta

Question 35

Somatic Pain

Answer 35

C fibers

Question 36

Smallest fibers

Answer 36

C fibers

Question 37

___ fibers are stimulated at shorter pulse durations

Answer 37

motor (50-100 micro sec chronaxie)

Question 38

___ fibers are stimulated at longer chronaxie

Answer 38

pain - A(d) - 170 micros sec and C fibers - 400 micro sec

Question 39

Largest and most sensitive nerve in the body (anesthetized with the lowest concentration of local anesthetic and anesthetized for longest duration) Easily injured (torturous course and low blood flow) Posterior cutaneous nerve of the thigh can only be blocked with parasacral approach

Answer 39

Sciatic Nerve Block

Question 40

Several different places nerve can be blocks (above knee, below knee and ankle) Quadriceps sparing (purely sensory nerve) Excellent for foot and ankle surgery

Answer 40

Saphenous Nerve Block

Question 41

5 nerves blocked - Saphenous (fem) - Deep peroneal (sci) - Superficial peroneal (sci) - Posterior tibial (sci) - Sural (sci)

Answer 41

Ankle Block

Question 42

Excellent block for breast and thoracic surgery u/s, landmark, or loss of resistance appropriate technique. Pneumothorax, epidural or intrathecal spread real concerns

Answer 42

Paravertebral Nerve Block

Question 43

If you are doing an interscalene block and your pt starts to hiccup, what should you do?

Answer 43

You hit the phrenic nerve - should aim more posteriorly and laterally

Question 44

If you are doing an interscalene block and rather than getting a deltoid and bicep twitch, you get a shoulder raise, what does that mean?

Answer 44

stimulating accessory nerve - too posterior and need to aim more anteriorly

Question 45

Excellent coverage T10 and below (subcostal tap if higher segmental coverage needed) Umbilical surgeries will need a rectus sheath block

Answer 45

TAP Block