Peripheral Nerve Blocks Part 1

Question 1

What is the difference between a pain block and an anesthetic block?

Answer 1

pain block decreases pain but does not eliminate sensation, whereas an anesthetic block does

Question 2

What are absolute contraindications to peripheral nerve blocks?

Answer 2

patient refusal, coagulopathy, infection at the site of block, severe hypovolemia, severe aortic or mitral valve stenosis, increased ICP

Question 3

What are frequently used anesthetics for peripheral nerve blocks?

Answer 3

0.5% ropivacaine, 0.75% ropivacaine, 0.5% bupivacaine

Question 4

What does the addition of vasoconstrictors to blocks do?

Answer 4

delays absorption and prolongs block

Question 5

What does the addition of Decadron do to PNBs?

Answer 5

increase DOA

Question 6

What does the addition of bicarb do to PNBs?

Answer 6

decreases onset and increases density of the block

Question 7

What type of needle is usually used for PNBs?

Answer 7

20-22 G short bevel needle

Question 8

Describe how to use nerve stimulators to localize a nerve

Answer 8

start with a stimulus around 1.5 mA and dial down to around 0.5 to ensure motor response is still stimulated (only works on motor nerves, not sensory) - caution: if response still seen at 0.2-0.3 it may be intraneural

Question 9

What is attenuation?

Answer 9

as US waves travel through tissue, it loses energy and amplitude decreases (absorption, reflection, scattering)

Question 10

What is gain?

Answer 10

degree of receiver amplification

Question 11

What are some indications for a Bier block?

Answer 11

short operative procedures for the extremities, pain therapy

Question 12

What kind and how much LA do you use for a Bier block?

Answer 12

12-15 mL of 2% lidocaine OR 30-40 mL of 0.5% lidocaine

Question 13

Describe how a Bier block is performed

Answer 13

1) double pneumatic tourniquet placed over soft cloth on upper arm 2) distal PIV placed 3) arm elevated for 1-2 minutes for passive exsanguination 4) rubber Esmarch bandage wrapped from hand to distal cuff of tourniquet 5) inflate distal cuff, then proximal cuff, then deflate distal cuff 6) remove Esmarch bandage and inject LA 7) arm lowered, IV cannula removed

Question 14

What is the max dose of LA that can be used in a Bier Block?

Answer 14

no more than 3 mg/kg

Question 15

What can you do if a patient starts c/o tourniquet pain during a Bier block?

Answer 15

inflate distal cuff, then deflate proximal duff (NEVER release proximal cuff before inflation of distal cuff- results in rapid loss of anesthesia and risk of LAST)

Question 16

How do you deflate the tourniquet at the end of a Bier block?

Answer 16

should be inflated for at least 20 minutes after LA injection- once ready for release, deflate tourniquet for 10 seconds, and reinflate for 1 minute (results in more gradual washout of LA)

Question 17

What is a stellate ganglion block and why is it performed?

Answer 17

injection of LA in sympathetic nerve tissue of neck located on either side of voice box; blocks sympathetic nerves that go to the arms and face- may reduce pain, swelling, color and sweathing changes in UE and improve mobility

Question 18

What are some conditions a stellate ganglion block is used for?

Answer 18

Reflex Sympathetic Dystrophy (RSD), Sympathetic Maintained Pain, Complex Regional Pain Syndrome, Herpes Zoster (shingles)

Question 19

What is a common side effect of a stellate ganglion block?

Answer 19

Horner’s syndrome (decreased pupil size, eye drooping, decreased facial sweating)

Question 20

What nerves are blocked with a wrist block? How much LA is used?

Answer 20

radial, ulnar, median (5 mL for median and ulnar nerve, 10 mL for radial)

Question 21

Describe how to block the ulnar nerve for a wrist block

Answer 21

1) insert needle under tendon of flexor carpi ulnaris muscle close to distal attachment above styolid process of ulna 2) advance needle 5-10 mm to just past the tendon of flexor carpis ulnaris 3) after negative aspiration, 3-5 mL LA injected 4) subQ injection of 2-3 mL of LA just above tendon of flexor carpi ulnaris to block cutaneous branches of ulnar n.

Question 22

Describe how to block the median nerve for a wrist block

Answer 22

1) insert needle between tendons of flexor palmaris longus and flexor carpi radialis
2) needle inserted until it pierces deep fascia and 3-5 mL of LA injected
* insert needle until it hits bone, then withdraw 2-3 mm to inject LA

Question 23

Describe how to block the radial nerve for a wrist block

Answer 23

inject 5 mL of LA subQ just proximal to radial styloid, aiming medially, then extend infiltration laterally using another 5 mL

Question 24

How long is the onset time for a wrist block?

Answer 24

10-15 minutes (sensory develops faster than motor)

Question 25

What is the indication for a cutaneous nerve block of the upper extremity? How much LA is used?

Answer 25

mostly used as supplement to major blocks of the upper extremity; 5-10 mL

Question 26

Describe the anatomy of the intercostobrachial nerve and how it is anesthetized

Answer 26

lateral cutaneous branch of ventral primary ramus of T2 that communicates with medial cutaneous nerve of arm- provides innervation to skin of axilla and medial aspect of proximal arm; both nerves are anesthetized by subQ infiltration of skin on medial aspect of arm

Question 27

Why is an intercostobrachial nerve block performed?

Answer 27

to supplement brachial plexus block to achieve more complete anesthesia of upper arm

Question 28

Describe how to perform an intercostobrachial nerve block

Answer 28

1.5 inch 25G needle inserted at level of axillary fossa- entire width of medial aspect of arm is infiltrated with LA to raise subQ wheal

Question 29

What are indications for a medial cutaneous nerve block of the forearm?

Answer 29

blockade of lateral antebrachial cutaneous nerve, insertion of AV graft, superficial procedures on volar surface of forearm

Question 30

Describe how to perform a medial cutaneous nerve block of the forearm

Answer 30

1.5 inch 25 G needle used to infiltrate LA subQ over entire medial aspect of arm just below elbow crease

Question 31

What are some indications for a lateral cutaneous nerve block of the forearm?

Answer 31

insertion of AV grafts, superficial procedures on volar aspect of forearm, supplement axillary brachial plexus block in which musculocutaneous block not performed/failed

Question 32

How is a lateral cutaneous nerve block performed?

Answer 32

1.5 inch 25 G needle used to infiltrate LA subQ over entire lateral aspect of arm just below elbow crease