LA: Chapter 3 reference PDF

Question 1

Benefits of
regional vs. GA w/ opioids

Answer 1

↑ pain control
↑ patient satisfaction (lol idc)

↓ stress response to surgery
↓ intraop & postop blood loss
↓ PONV
↓ logistic requirements

Question 2

ability of a given local anesthetic to block a nerve is r/t (4)

Answer 2

length of the nerve
diameter
myelination
anesthetic used

Question 3

T/F
Myelinated nerves need to be blocked only at nodes of Ranvier

Answer 3

True
approximately 3 consecutive nodes

Question 4

Myelinated nerves require (more/less) anesthetic to block.

Answer 4

less

Question 5

Differential blockade

Answer 5

pain and temperature block (A-d, C fibers)
while minimizing motor block (A-a fibers)

Question 6

Most local anesthetics have a pKa (less/greater) than 7.4

Answer 6

greater

Question 7

How does protein binding increase DoA?

Answer 7

high affinity protein binding
↓
bound to nerve membranes longer
↓
increased doA

Question 8

T/F
High protein binding increases the risk of primary organ toxicity.

Answer 8

False
binding to serum a1-acid glycoproteins and other proteins decreases the availability of free drug in the blood, reducing the potential
for toxicity in the primary organs

Question 9

Conditions that increase free fraction of LA in the blood

Answer 9

acidosis
decreased serum protein

↑ potential for toxicity

Question 10

Initial (inhibitory/excitatory) symptoms of toxicity are manifestations of escalating drug concentration in the CNS, specifically the ___.

Answer 10

excitatory
amygdala

Question 11

S/S
toxicity

Answer 11

muscular twitching
visual disturbance
tinnitus
light-headedness
tongue/lip numbness
extreme anxiety
screaming
concerns about imminent death

if untreated:
generalized tonic-clonic convulsions
coma
respiratory arrest
death

Question 12

Which is more resistant to toxicity?
CNS
CV system

Answer 12

CV system

Question 13

circulatory collapse ratio

Answer 13

relationship between:
LA blood [ ] causing circulatory collapse
&
LA blood [ ] needed to cause convulsions

smaller ratio = ↓ interval btwn convulsions & circulatory collapse

Question 14

Which has the smaller circulatory collapse ratio?
A) bupivacaine & ropivacaine
B) mepivacaine & lidocaine

Answer 14

smaller ratio: bupivacaine & ropivacaine
more potent, long-acting

Question 15

Ropivacaine (Naropin)

Answer 15

-pKa of 8.2
-chemically similar to mepivacaine & bupivacaine
-pure levorotatory stereoisomer
-less cardiotoxic than bupivacaine
-“safest” long-acting

caution: CV collapse still possible

Question 16

racemic mixture

Answer 16

combination of levorotatory and dextrorotatory molecules

Question 17

Which enantiomer tends to be less toxic?
Levorotatory
dextrorotatory

Answer 17

Levorotatory

Question 18

Which is less 🩷 toxic?
ropivacaine
bupivacaine

Answer 18

ropivacaine

preferred long-acting for PNB anesthesia for many providers

Question 19

Bupivacaine (Marcaine)

Answer 19

-pKa of 8.1
-long-acting
-longest onset
-Low [ ] : sensory block > motor (differential sensitivity)
-low-vol infiltration & spinal anesthesia well established

caution: large-volume epidural or peripheral nerve a/w prolonged resuscitation
following accidental IV injection

Question 20

Mepivacaine (Polocaine)

Answer 20

-pKa 7.6
-intermediate-acting
-rapid onset
-infiltration (similar onset to lido; longer doA)
-one of the least neurotoxic LAs
✅ high-risk cardiac pts
-block success despite suboptimal needle position
-intense motor block (shoulder surgery)

Question 21

Lidocaine (Xylocaine)

Answer 21

-pKa 7.7 (low)
↓
distribution into the exsanguinated extremity

-low systemic toxicity
-rapid onset
-intermediate acting
-moderate W & L solubility = versatile

-caution: transient neurologic syndrome

Question 22

most common LA used for intravenous regional anesthesia

Answer 22

Lidocaine 0.5%

Question 23

Peripheral nerve blocks (PNB)
providers usually prefer ___ acting agents

Answer 23

long

so analgesia lasts well into the postop recovery period

Question 24

Regional Anesthesia
Deep sedation or general anesthesia is avoided because

Answer 24

pt indicators of toxicity or nerve injury are masked

must balance btwn pt comfort & safety during block placement

Question 25

Why add epi to LA?

Answer 25

prolongs block
reduced plasma [ ]
marker of IV injection during single injection blocks

Question 26

What changes in V/S would we see with accidental IV injection of LA w/ epi

Answer 26

↑ heart rate (≥10 beats/min)
↑ SBP (≥15 mmHg)
↓ T-wave amplitude (depression ≥ 25%),

10-15+ μg of IV epi can cause this

Question 27

addition of opioids to intrathecal LA

Answer 27

prolongs sensory anesthesia w/o prolonging recovery from ambulatory procedures

reduces LA requirements for OB

“walking epidural”

Question 28

T/F
Clonidine provides analgesia

Answer 28

True
a2-adrenoceptor agonist
analgesia via a nonopioid receptor

Question 29

Dexamethasone 8 mg as LA additive

Answer 29

enhance the duration of sensory and motor blockade

Question 30

Pretreatment with ____ to increase the seizure threshold to local anesthetic toxicity

Answer 30

benzodiazepines

Question 31

Minimize accidental IV injection by injecting ___ ml every 10-15 seconds

Answer 31

5

Question 32

If seizures occur…

Answer 32

airway maintenance
supplemental O2

propofol (25–50 mg) or thiopental (50 mg)

Question 33

Preventing IV injection:
Initial injection of test dose containing at least ___ epinephrine

Answer 33

5–15 μg

Question 34

Is this important? idk

Question 35

Fiber types and fxn

Answer 35