Upper Extremities Study Guide

Question 1

Define peripheral nerve block.

Answer 1

when a local anesthetic is injected near the nerve, or nerves, that control sensation and movement to a specific part of the body.

Question 2

How are peripheral nerve fibers classified?

Answer 2

A, B, and C

(A is sub-divided into A-alpha, A-beta, A-gamma, and A-delta)

Question 3

How do they differ anatomically?

Answer 3

A and B fibers are myelinated.

C fibers are not myelinated. so sad. :(

Question 4

How do they differ functionally?

Answer 4

Question 5

What are the advantages of a peripheral nerve block over central nerve blocks (spinal / epidural)? (3)

Answer 5

• restricts the numbed area to the specific site of the surgery, or to one extremity, as opposed to numbing both legs.
• better post-operative pain control (limiting the need for strong pain medications)
• earlier discharge from the recovery room and hospital

Question 6

What are the basic principles and techniques underlying successful peripheral nerve block?

Answer 6

• patient consent
• proper equipment (nerve stimulator, ultrasound machine, airway equipment, etc)
• local anesthetic and any adjuncts or additives
• knowledge of anatomical landmarks

(i wasn’t sure if this is the what the question was asking, but it sounded good to me)

Question 7

What are the risks in performing a peripheral nerve block? (3 that i could think of)

Answer 7

• intravascular injection
• local anesthetic toxicity
• intraneural injection (nerve damage)

Question 8

How can the risks from peripheral nerve blockade be minimized?

Answer 8

• use of a nerve stimulator
• use of ultrasound
• know the freakin’ anatomy and the landmarks
• don’t be a retard

Question 9

Should paresthesias be used as an indicator of nerve localization in peripheral nerve blocks?

Answer 9

yes, paresthesias can be used when blocking the radial, ulnar, median, and musculocutaneous nerves.

Question 10

How is a nerve stimulator used to facilitate peripheral nerve blocks?

Answer 10

• it elicits muscular twitches in muscle groups served by targeted nerves (basically, they get served)
• constant stimulation of the nerve below 0.5mA but above 0.2mA generally results in a safe, reliable block

(fun terms for knowledge: reobase and chronaxie

reobase - the minimum current necessary to achieve threshold potential over a long pulse

chronaxie - the minimum duration of stimulus at twice the reobase for a specific nerve to achieve threshold potential)

Question 11

peripheral nerve blocks vs. general anesthesia: in what situations are peripheral nerve blocks indicated, or contraindicated, and how are they advantageous over general anesthesia?

Answer 11

indicated in patients you don’t want to put to sleep for fear of them not coming off the vent, or they are too fragile (severe COPD, muscular dystrophy, etc)

contraindicated if the patient doesn’t want it, infection at the injection site, etc.

advantages: patient requires less medication overall and they have less side-effects to deal with, they maintain their own airway, better pain control, etc.

Question 12

What are the toxic limits for local anesthetics used for peripheral nerve blocks?

Answer 12

Lidocaine - 4.5mg/kg w/o epi (300mg max), 7mg/kg w/ epi (500mg max)

Ropivacaine and bupivacaine - 2.8mg/kg w/o epi (175mg max), 3.2mg/kg w/ epi (225mg max)

Question 13

Indications for an interscalene block?

Answer 13

for operations on the shoulder, clavicle, or upper arm

Question 14

What are the landmarks for an interscalene block?

Answer 14

Question 15

Indications for a supraclavicular block?

Answer 15

ideal for procedures of the upper arm, from the midhumeral level down to the hand

Question 16

What are the landmarks for the supraclavicular block?

Answer 16

Question 17

Indications for the infraclavicular block?

Answer 17

ideal for operations distal to the elbow

Question 18

What are the landmarks for the infraclavicular block?

Answer 18

Question 19

Indications for the axillary block?

Answer 19

for forearm and hand operations

Question 20

What is the landmark for the axillary block?

Answer 20

Question 21

Indications for a single terminal nerve block?

Answer 21

• for supplementation of local anesthetic to “rescue” a less than adequate block - may be necessary for a patient with conditions that preclude more proximal injections (eg, preexisting wounds or infection) - coagulation abnormailities may also render the more proximal approaches less desirable because of the close proximity of major vascular structures

Question 22

What are the landmarks for radial and median nerve blocks at the elbow?

Answer 22

Question 23

What are the landmarks for an ulnar nerve block at the elbow?

Answer 23

Question 24

What is the landmark for a radial nerve block at the wrist?

Answer 24

Question 25

What are the landmarks for a median nerve block at the wrist?

Answer 25

Question 26

What are the landmarks for an ulnar nerve block at the wrist?

Answer 26

Question 27

What nerve or nerves are missed in performing brachial plexus blocks of the interscalene nerves?

Answer 27

the ulnar nerve is missed

(the phrenic nerve gets smoked every time)

(This block is not appropriate for surgery of the hand and forearm, specifically in the ulnar distribution of C8, T1. Because it is performed at the upper roots of the plexus, the block typically spares the ulnar aspect of the hand.)

Question 28

What nerve or nerves are missed in performing brachial plexus blocks of the supraclavicular nerves?

Answer 28

none of the nerves are missed

(50% of the time the phrenic nerve gets smoked)

Question 29

What nerve or nerves are missed in performing brachial plexus blocks of the infraclavicular nerves?

Answer 29

the phrenic nerve gets missed

Question 30

How is a digital block performed?

Answer 30

digital nerve block is most effectively carried out with the hand pronated. the skin over the dorsum of the finger is less tightly fixed to the underlying structures than it is on the ventral side.

skin wheals are raised at the doroslateral borders of the proximal phalanx, and a blunt-beveled, small-gauge, short needle is inserted at the dorsal surface of the lateral border of the phalanx.

infiltration of the dorsal and the ventral branches of the digital nerve is carried out bilaterally, and a total of 1 to 2 mL at each site should be sufficient for block.

Question 31

What is the most important thing to remember about your choice of local anesthetic with digital blocks?

Answer 31

do NOT use epinephrine-containing solutions!

(otherwise, the finger could lose circulation altogether)

Question 32

Describe the Bier block.

Answer 32

• it’s a technique for IV regional anesthesia that can produce total analgesia of either the upper or lower extremity
• it is best reserved for short procedures (less than 60 minutes)
• based on the premise that if circulation to the limb is blocked and local anesthetic is injected into venous vessels distal to the occlusion, the nerves that typically travel with blood vessels will be anesthetized as the drug diffuses into the extravascular space via retrograde flow

Question 33

How is the Bier block performed? (kind of a long answer, but it makes sense)

Answer 33

• place an IV in the operative extremity (a second IV in the other extremity should already be present
• place a double-cuffed tourniquet on the upper arm of the operative extremity
• the operative extremity is raised above their head for exsanguination - with the arm raised, wrap an Esmarch elastic bandage from the fingertips proximally up to the tourniquet (if a bandage is not available, keep the extremity raised for 4 to 5 minutes)
• inflate the proximal tourniquet to 250 mmHg (or 100 mmHg above their systolic BP), and remove the elastic band
• place the extremity down and slowly inject the local anesthetic (the skin may appear to blanch, this is normal)
• allow 10 minutes to elapse before the start of surgery
• if the patient feels discomfort from the tourniquet, inflate the distal tourniquet, and then deflate the proximal tourniquet

Question 34

What are the potential complications with a Bier block?

Answer 34

• local anesthetic toxicity

(never deflate the tourniquet sooner than 20 minutess after injection, even if the surgery is shorter than that time period; the lidocaine has been injected intravenously and toxicity can occur with early cuff deflation)

(do NOT use epinephrine-containing solutions!)

(do NOT use ropivacaine or bupivacaine!)