Intro to Blocks/Segna

Question 1

full onset of nerve blocks may not occur for

Answer 1

30 minutes

Question 2

benefits of blocks

Answer 2

1. fast pain relief
2. decreased risk of intraoperative bleeding, stroke, MI
3. decreased intraoperative need for narcotics = less N/V, less constipation, faster wake up, discharge
4. minimal risk - (dont get resp. depression) compared to tradiational pain managemnet
5. may be able to avoid general anesthesia for certain cases (do entire cases under block)

Question 3

rate of absorption in LAs

Answer 3

rate of absoprtion in LAs

• depends on vascularity
• increased vascularity will lead to faster systemic absorption, higher blood levels, shorter time to obtain peak levels,
• also greater risk for toxicity

Intravenous > Tracheal > intercostal > caudal > epidural > brachial plexus > sciatic > subq

Question 4

Patients with hypoalbuminemia

Answer 4

are at a higher risk of LAST because LAs have a high degree of protein binding and the increased free fraction of the drug will predispose them to LAST

Question 5

Clearance of LA is affected by

Answer 5

1. shorter half life
2. lower protein binding - more free drug

elimination rate dependent on concentration of free fraction

Question 6

systemic toxicity

Answer 6

time and dose dependent

• more likely with higher serum levels/faster onset
• main. targets = CNS/ heart

Question 7

true allergy to LA

Answer 7

is extremely rare

• esters -> PABA, cross rxn within group
• amides -> may contain methylparaben.
• no cross sensitivity between esters and amides
• epinephrine often MISTAKE as allergy
• patient should be fully monitored during entire block and at least 15 min after

Question 8

Clinical Symptoms of LAST (Neuro)

Answer 8

• Early:

Circumoral numbness, dizziness, tinnitus, blurred vision

• restlessness, agitation, nervousness, seizures
• CNS depression: slurred speech, drowsiness, unconsciousness
• may bypass earlier symptoms with arterial (esp. vertebral) injections -> seizures

Question 9

Clinical Symptoms of LAST (cards)

Answer 9

• LA-induced dysrhythmias: sodium channel blocking effect of LA
• prolongatoin of impulse conduction may lead to malignant arrhythmias
• lidocaine: less toxic bc fast in/fast out
• bupivacaine: more potent and toxic, fast in/slow out

Question 10

treatment for LAST

Answer 10

1. supportive (correct hypoxemia/acisosis)
2. ACLS protocol - avoid lidocaine
3. Intralipid:

• 20% emulsion
• 1.5mL/kg as initial bolus
• 0.25 mL/kg/min for 30-60 min
• bolus can be repeated 1-2 times for persistent asystole.

Question 11

Commonly used block anesthetics and DOA

Answer 11

1. ropivacaine: 12 hrs (pushed to 24 with adjuncts)
2. bupiviaine: 15 hrs ~ 24 hrs
3. lidocaine: 2 hrs
4. mepivacine: 6 hours

Question 12

supraclavicular block WITH neurostimulation has

Answer 12

a much higher rate of pneumothorax (5%) compared to other UE blocks

Question 13

COPD is relatively contraindicaiton for

Answer 13

supraclavicular block because pleural apex may be higher

Question 14

axillary nerve block has a high rate of failure for

Answer 14

single nerve injections

Question 15

single injection ulnar block

Answer 15

block at elbow

Question 16

single injection of median nerve

Answer 16

travels in antecubital fossa with brachial artery

Question 17

single injection of radial nerve

Answer 17

travels at lateral elbow within brachioradialis

Question 18

ischemia is an important component of

Answer 18

the bier block.

Blocks nerve conduction, may obtain anlagesia with normal saline in 20-25 minutes of ischemia.

Question 19

bier block: mechanisms of action

Answer 19

1. direct action by LA + retrograde flow into endonerium, capillary plexus, eventuallly into nerve trunks
2. compression of nerve trunks (slow component)

Question 20

Most common drugs for bier block

Answer 20

1. 0.5% lidocaine or prilocaine
2. NO epi added

Dosage ->

• UE = 50 mL
• LE = 100 mL

Question 21

in bier block, tourniquet should be kept inflated for a minimum of

Answer 21

20 minutes

Question 22

lumbar plexus is

1. derieved from
2. divdes into

Answer 22

lumbar plexus is

1. derieved from L2,L3,L4
2. divdes into:

• femoral
• lateral femoral cutaneous
• obturator

Question 23

lateral femoral cutaneous

Answer 23

arises from L2-L3, part of lumbar plexus

Motor: NONE

sensory: lateral aspect of thigh

Question 24

femoral nerve

• arises from
• motor
• sensory

Answer 24

femoral nerve

• arises from: L2, L3, L4
• motor:
  
  • anterior branch - sartorius
  • posterior branch: quads
• sensory: anterior thigh

Question 25

obturator nerve

• arises from:
• motor:
• sensory:

Answer 25

obturator nerve

• arises from: L2, L3, L4
• motor: hip adductors
• sensory: distal inner thigh and part of hip

Question 26

larger branch of the sciatic nerve

Answer 26

tibial (L4-S3)

peroneal: L4-S2

Question 27

intercostobrachial nerve

Answer 27

arises from T2

Not anesthetized with any approah to the brachial plexus. Requires a field block.

Question 28

the stellate ganglion is located at

Answer 28

C7

also called “cerivothoracic ganglion”

Question 29

injection of LA into vertebral artery

Answer 29

as little as 1 mL of LA injected into vertebral artery can lead to seizure

Question 30

Vertebral artery injection is most likely with

Answer 30

interscalene block

Question 31

most common complication of supraclavicular block

Answer 31

pneumothorax

Question 32

for an intraclavicular block the needle must pass through

Answer 32

pectoral major and minor

Question 33

3