exam 1 Flashcards
what type of gating is LA for the sodium channel
voltage-gated
normally, sodium ________ a cell, the cell becomes more _____________, and _________________ occurs
sodium enters
cell positive
depolarization occurs
LAs block this! They block impulse propagation!
ligand gated involves a ___________ messenger (neurotransmitter) such as ____
second messenger
Ach
LAs are _____-dependent
dose
larger amount of LA blocks a respectively larger number of channels
true or false
nerve fibers can be sensory, motor, or both
true
how are nerve fibers blocked? in order of:
size
myelination variables
what is blocked FIRST, small or large nerve fibers
small fibers (B or C)
what is blocked FIRST, myelinated or unmyelinated
unmyelinated
what type of fibers do LAs work fastest
B fibers
LAs have a _____________/____________ threshold
functional/minimal
true or false
for LAs, until a minimum dose is met, there will be NO effect
true
true or false
LAs are:
concentration-dependent
dose-dependent
volume-dependent
in order to have an effect
true
AFFERENT neurons are also known as
somatosensory
EFFERENT neurons are also known as
motor
what types of nerves are afferent, efferent, and autonomic
SOMATIC portion of the PNS
what do autonomic neurons do
sensory
motor
autonomic functions: signal brain and spinal cord to control visceral elements (hemodynamics, digestion)
spinal nerves that travel to the thoracic and abdominal compartments
intercostal nerves
outside the spinal cord, spinal nerves =
peripheral nerves
what is the functional unit of the nerve
(individual fiber of nerve)
axon
what type of cells surround the axon
schwann (in layers)
myelin sheaths surround the _______
axon
interspersed among the axon at spaces that are NOT myelinated
nodes of ranvier
where is a primary site for LAs action
nodes of ranvier
“Axon intervals”: voltage gated sodium channels that propagate the nerve conduction
nodes of ranvier
true or false, smallest to largest:
fiber/axon < fascicles (bundles of axons) < fibers (afferent/efferent) < peripheral nerve
true
resting membrane nerve potential
-60 to -90 mV
3 states of sodium channel
1) activated/open
2) inactivated/closed
3) resting/closed
where can LAs NOT act
resting/closed
state of sodium channel also known as “refractory period”
inactivated/closed
what are the largest and fastest fibers
A (especially A alpha)
order of ease of blockade (which occur first, then last)
B fibers, C fibers, then A delta, then A alpha
Recovery or “Wearing Off” of Blockade
A-alpha, then A-delta, then C fibers, then B fibers
sensory/afferent = ______lateral aspect of the cord
dorso
(from the body)
motor/efferent = _______lateral aspect of the cord
ventro
(to the body)
These 2 roots converge to form a spinal nerve before dividing into dorsal and ventral rami which innervate anterior and posterior structures
dorsal root
ventral root
subarachnoid/spinal space
_________ dose
smaller
epidural space
_________ dose
larger
how many pairs of spinal nerves
31 pairs
how many bones
33
cervical NERVES
8*
cervical nerves lie ______ the named vertebral body
EXCEPT for ____, which is _________
ABOVE
(except for the 8th, which is below the vertebral body)
cervical VERTEBRAE
7
thoracic NERVES
12
thoracic VERTEBRAE
12
lumbar VERTEBRAE
5
lumbar NERVES
5
sacral VERTEBRAE
5
sacral NERVES
5
coccygeal NERVE
1
coccygeal VERTEBRAE
4*
cervical spinous processes are pointed _________
caudad (toward the feet)
lumbar spinous processes are pointed _________
straight
landmark:
cricoid cartilage
C6
landmark:
most prominent cervical level called “vertebral prominens”
C7
landmark:
superior angle of the scapula and sternal notch
T2
landmark:
plane of Ludwig; carina; angle of Louis
T4
landmark:
inferior angle of the scapulae
T7
landmark:
xiphoid process
T9
landmark:
umbilicus
T10
landmark:
superior iliac crest
L4
what goes farther, sensation or motor?
sensation (dermatomes)
true or false
there is OVERLAP in nerve function
true
plexus:
cervical
C1-C4
plexus:
brachial
C5-T1
plexus:
lumbar
T12-L4
plexus:
sacral
L4-S4
the brachial plexus is located between the __________ and ________ scalene muscles
anterior
middle
Triceps
Supination
Extension of wrist
Extension of other fingers
ABduction of thumb
radial
Follows the track of the brachial artery (lying MEDIAL to it)
Pronates
Flexion of wrist + elbow
Flexion of fingers and thumb
ABduction of thumb
mediaN
Formed from C8-T1
Follows the brachial artery following the posterior aspect of the medial epicondyle
Flexion of wrist, ring, and pinky finger
Flexion of thumb
ADduction of fingers + thumb
ulnar
nerve:
Formed from L2-L4
femoral
nerve:
Formed from L4-S3
tibial
nerve:
Formed from L4-S2
common peroneal
nerve:
Formed from tibial + common peroneal
Extension of hip
Flexion of knee
Plantarflexion of ankle
Dorsiflexion of ankle
All movements of the toes
sciatic
why block a plexus, instead of an individual nerve (2)
- In case there is an anomaly
- Convenience (they are very close together)
binds to the lipid side with carbon OXYGEN
ester
Metabolism: plasma/pseudocholinesterases
Caution with: pseudo cholinesterase deficiency; risk of toxicity due to SLOWER metabolism!
ester
Less stable; shorter ½ life; shorter acting
More easily hydrolyzed/broken apart
ester
Allergies are MORE likely
- Metabolites para-amino benzoic acid (PABA); causes reaction
ester
binds to the lipid side with carbon NITROGEN + HYDROGEN
amide
Metabolism: P450 enzymes (liver)
Caution with: liver disease, protein binding issue, enzyme inducing issue!
amide
More stable; longer ½ life; longer acting
Less likely to be hydrolyzed/broken apart
amide
Some allergies can still occur, rarer
* Due to preservatives such as methylparaben in the LA
amide
most common LAs for allergies:
amide
prilocaine
most common LAs for allergies:
ester
procaine
what is the longest acting ester
tetracaine
_________ are more lipophilic and protein bound of the LAs
longer acting
amides
lipophilic portion (ring)
aromatic ring
linker region (classifies LA)
ester or amide
lipophilic region of LA
hydrocarbon chain
ionizable/hydrophilic region of the LA
tertiary amine
when does metabolism of LAs occur
during “uptake”
once the non-intravascular injected LA gets into circulation/plasma/bloodstream
what is the exception, the only one that does NOT get metabolized by pseudocholinesterase for esters
cocaine (metabolized in the liver)
An LA can have a long clinical effect until it gets into the bloodstream
DECREASES toxicity!
slow uptake
true or false
we want to SLOW the UPTAKE process
true
example: epi
where are plasma/pseudo cholinesterases found
OUTSIDE the NMJ
(in the plasma)
what is Ach metabolized by
acetylcholinesterase drugs (inside the NMJ)
what is the best LA group for true allergic patients
preservative-free amide LA
what 2 LAs are common culprits of methemoglobinemia
benzocaine (hurricane spray)
prilocaine
signs of methemoglobinemia (3)
tachypnea
low PO2 “blue blood”
LEFT shift (inability of Hgb to carry oxygen)
presents like a PE
treatment for methemoglobinemia
methylene blue (1-2 mg/kg IV)
the pH at which ½ of the drug is unionized and ionized
pKa
If a pH solution (patient) is ________ than the pKa of the drug, then the LA becomes more ionized/hydrophilic, and is LESS able to enter the nerve and have its effect
LOWER
with infections, the LA onset is _________ and _______ dense
slower and less dense
another term for lipid-solubility in LAs
alkalization
what 3 things are associated with lipid philicity
binds better to tissue
longer duration
higher potency
_________________ is what allows sodium channel to close
hydrophilicity
When a drug has a HIGH pKA, it becomes more _____________ to enter the nerve for action
high pKa= more DIFFICULT
a HIGH pKa = more ___________/____________
ionized/hydrophilic
this can be exaggerated when pH is lower or with additives that make the pH lower
LAs enter the nerve, ______________________________, ionized portion binds
equilibration of non-ionized and ionized portion = pKa equal
3 factors of duration/longevity of action of LAs
1) starting dose
2) tissue distribution (lipid solubility)
3) drug metabolism = delay of uptake
true or false
the larger the dose of LA, the longer the duration
true
increased blood flow is ____________ related to duration of action
inversely
opposite
systemic absorption of LA can be affected by 3 things
site of injection (vessel rich vs vessel poor)
dose
properties (pKa, pH, lipophilicity, protein binding)
HIGH protein binding (adherence to tissue) ___________ uptake*
decreases uptake (makes it last longer!)
free drug is more quickly used up
what represents the duration of clinical utility
uptake of LA
what organ removes a large portion of LA (especially lidocaine)
lungs
after injection into tissue, it is how long the LA stays in the tissue (around the nerve) before it gets absorbed into circulation/plasma and taken away for metabolism
clinical duration of action
Rates of Uptake from Fastest to Slowest*
(shortest to longest duration)
IV (inadvertent) > tracheal > intercostal > caudal/sacrum > epidural > brachial plexus > femoral = tied with sciatic
what LA disables pseudo/plasmacholinesterase
dibucaine
the higher the dibucaine number, the __________
better
example: dibucaine 80; 80% of enzyme (plasmacholinesterase) is inhibited
what drugs are affected by plasma cholinesterases (4)
remifentanil
esmolol
Sch
esters
toxicity with LAs is due to ______________ of inhibitory neurons
depression
signs of LAST (5)
SNS symptoms:
ringing in ears
circumoral numbness
tongue numbness
seizures, hyperexcitation
resp arrest, cardiac collapse
(DECREASED conductance)
LAST can cause smooth muscle _______________
relaxation
which type of LAs are associated with cardiac toxicity (3)
high-protein binding
longer acting drugs
bupivacaine
.25% is _____mg/ml
2.5
toxicity of LAs occur __-__ minutes from time of injection
1!!-5 min
this is often due to it being intravascular (IV)
how can you prevent toxicity of LAs (7)
- Frequent aspiration
- Avoidance of excessive dosing
- Use of ultrasound
- Test-dosing for epidurals
- Incremental dosing
stay below MAX dose
use less lipophilic drugs
A form of toxicity in the INTRATHECAL space; nerve roots
permanent
loss of function
intractable pain
cauda equina syndrome
causes of cauda equina syndrome or TNS (3)
LAs in prolonged exposure
Mechanical processes such as infection, compression/hematoma, or structural changes
Subarachnoid catheters (particularly with lidocaine, high concentration 5%)
Resolvable within a few weeks
loss of function
intractable pain
transient neurologic symptoms (TNS)
“Sympathectomy”
LAST
LAs are additive**
if giving 2, you need to 1/2 it
what is the most lipophilic LA
bupivacaine
4 drugs and 1 thing to do for LAST treatment
benzos (best option)
propofol (10%)
20% lipid solution/chelating agent
paralytic
oxygenation/ventilation/control airway
CARDIAC treatment for LAST
smaller doses of epi
100 mcg
what is the best method to sustain a patient for LAST
cardiac bypass
What can exacerbate severity of LAST (5)
seizure threshold (HIGH PaCO2)
high PaCO2, hypoventilation
acidosis
hypoxia
hyperkalemia
what is the best treatment for LAST
respiratory
hyperventilation
true or false
toxicity is NOT a “large dose”
true
often, it is a higher % concentration
how are LAs discussed (2)
% concentration
volume
g/____ml
100ml
LA additives:
steroids (1)
duration/improve blockade
LA additives:
alpha 2 agonist (2)
clonidine + dex
less pain (potency)
duration/improve blockade
(neurodepressive)
LA additives:
opioids (3)
lessen pain (potency)
pontentiation/cumulative effect
speed of onset (efficacy)
does NOT affect density or duration
synergistic with LAs
LA additives:
sodium bicarb (2)
lessen pain (potency)
speed of onset (efficacy)
LA additives:
epi (3)
safety
lessens pain (potency)
duration
which is more prominent, alpha 2 agonists or epi
alpha 2 agonists
Has a unique metabolite; o-toluidine; this is a pre-cursor for methemoglobin
prilocaine
permanently non-ionized (lipophilic ALWAYS; rapid onset)
has the ability to cause methemoglobinemia
secondary amine
BENZOcaine
o Not used anymore
o Historically was used regularly for sub-arachnoid block (spinal)
reports of neurotoxicity
5% lidocaine
Has a particular propensity to cause cardiac effects (high affinity) more than other LAs
Has a LONG duration of action, highly lipid-soluble
BUPIVacaine
Behaves similarly to bupivacaine with respect to onset/time/duration
However, it has less cardiotoxic effects and generally has less pronounced motor block potency
Second generation
Safer
ROPIVacaine
EMLA cream
eutectic mixture (LOWER boiling point)
_____________+______________
lidocaine + prilocaine
how far in advance does EMLA cream need to be applied
1 hour
o A sustained release LA
o Designated for infiltration, this LA is found to have prolonged duration of action, presumably due to DELAYED uptake!
LONGEST DURATION of action (24-48 hours)
good for ortho/joint surgery
liposomal BUPIVacaine (EXPAREL)
what can LAs be used for (5)
nerve blockade
inhibition of vent dysrhythmias
reduction in CBF (high ICP)
pain
blunt resp stimulation
CAUTION to LAs for cardiac patients
heart block/conduction delay (can cause cardiac standstill)
beta blockers
calcium channel blockers
how do we pick which LA to use (2)
onset/duration
safety factor
If you need a LARGE volume of a certain medicine, you need to ____________ the % concentration, so you do not reach the max dose
DECREASE
_______ axis of the needle
LONG
_______ axis of the structure
SHORT
reasons for regional anesthesia (4)
postop pain control
opioid reduction or elimination
avoidance of general anesthesia and airway manipulation
reduction in side effects of GAs (cardiac, lung, PONV)
what are the 2 ABSOLUTE contraindications to regional
patient refusal
coagulopathy
(depending on severity of block and severity of lab value)
what are the 4 RELATIVE contraindications to regional
infection
tolerance for pain (AMS)
risk vs benefit
risk for LAST
infection: pH of the tissue is _________ the pKa
BELOW (more ionized)
what is a patient at HIGH risk for PTX and regional is CONTRAindicated
COPD patient, at home with 4L O2, 50% CPAP at night
what is the best type of skin prep
chloroprep
how much lidocaine should be used for a skin wheel
0.5 to 1ml
1%
30g needle
what type of system is used for a nerve stimulator
2-lead
positive: connected to EKG sticker
negative: nerve
what type of needle is used with a 2-lead system
block/blunt/B needle
conical/rounded in shape
(does NOT have shearing action)
true or false:
block needles only have electrical stimuli at the tip
true
by adjusting the power/milliamp stimulation (turning it DOWN) you make it more ______________
sensitive
how much milliamp do you want
.3 to .5 mA
when do you want to inject LA
right after losing muscle movement
true or false
ultrasound beam lies ONLY DIRECTLY UNDER the probe
true
cross section = ________ axis
short
longitudinal = _______ axis
long
what do you want to use first _________ axis
short axis
with short axis, you can see ________/________ or _________
left/right or WIDTH
with long axis, you can see ________
depth
must be “in-plane”
what is the ONLY upper approach that does NOT have risk of PTX
axillary
paralysis of half the diaphragm
ipsilateral (SAME SIDE)
ipsilateral (SAME SIDE) hemiparesis is related to what nerve
phrenic
temporary, only occur during the duration of the block
uptake of LA into the head and neck may result in sympathetic blockade to nerves affecting facial structures (PNS symptoms!)
horner’s syndrome
3 symptoms of horner’s syndrome
1) drooping of eye (ptosis)
2) pupil CONSTRICTION (miosis)
3) ABSENCE of sweat (anhidrosis)
true or false
horner’s syndrome is temporary
true
5 complications of UPPER regional blocks
1) PTX
2) ipsilateral hemiparesis
3) horner’s syndrome
4) hemorrhage
5) accidental vascular (IV) injection
what approaches have a HIGH risk of hemorrhage (non-compressible)
infraclavicular, central
what approach has LOW risk of hemorrhage
axillary
cervical blockade can cause 5 issues
vertebral artery injection
sub-arachnoid injection
phrenic nerve paralysis (temp)
IV injection
vagus/recurrent laryngeal nerve blockade
what nerve roots are associated with cervical
C2, C3, C4
interscalene blocks:
________
trunks
think InTer (“IT”)
SUPRAclavicular blocks:
___________
divisions
INFRAclavicular block:
_______
cords
axillary block:
_________
branches
what nerve roots are involved in brachial plexus
C5, C6, C7, C8, T1
What are the “distal” plexus approaches
INFRAclavicular
axillary
what is the only block that provides coverage to the shoulder
INTERscalene
what is the landmark for interscalene
cricoid cartilage (C6)
what 2 muscles is the interscalene block between
anterior and middle scalene
which block has the HIGHEST risk for PTX
SUPRAclavicular
what is a UPPER block that is challenging and painful
INFRAclavicular
for axillary block:
which nerve is most SUPERFICIAL
median
for axillary block:
which nerve is most DEEP
radial
for axillary block:
which nerve is on TRICEPS side
ulnar
for axillary block:
which nerve is on BICEPS side
musculocutaneous
which block can use landmark technique,
less precise,
involves intentional puncture of artery
axillary “transarterial”
2 puncture sites
how many mL for intercostal block
3-5 ml per site
how deep of injection (inferior edge of rib)
for INTERCOSTAL block
2-3 mm
which block is ONLY MIXED, not a sole anesthetic
trasversus abdominis plane (TAP)
true or false
TAP block does NOT affect ambulation
true
into what fascial plane do you inject for TAP block
transversus abdominus (fascial plane BEFORE reaching that muscle)
what nerves are blocked in TAP
T9-L1
what are the 3 muscles involved with TAP block
external oblique
internal oblique
transversus abdominis
which block does NOT use ultrasound or landmarks
bier block
IV regional
how long must tourniquet be inflated with bier block
AT LEAST 20 min
who is CONTRAindicated from using bier block (3)
dialysis patients
mastectomy patients
trauma patients
____mL of preservative-free, epi-free lidocaine is used
what ___%
50 ml
0.5%
what 2 things occur with tourniquet release
HYPOthermia
HYPOtension
how many mLs per level for PARAVERTEBRAL block
duration?
how many cm depth?
5ml
4 hour
1 cm
what is a safe block for the back
erector spinae plane
you want to see the erector spinae MUSCLE in the _______ axis
LONG (like the needle)
erector spinae muscle:
TRANSVERSE PROCESS in the _______ axis
SHORT axis
lumbar plexus
L2, L3, L4
lateral femoral cutaneous nerve
L2, L3
obturator nerve
L2, L3, L4
what are 2 main nerves that come out of the lumbar plexus
obturator
LFCN
what is the drawback of the femoral nerve and LFCN block
canNOT ambulate
tibial nerve causes:
_________flexion
plantar
common peroneal nerve causes:
_________flexion
dorsi
foot drop occurs when injured
common peroneal nerve
femoral nerve block:
nerve is approached _____________ from the femoral artery
and ____________ the inguinal ligament/fascial layer
LATERAL
BELOW inguinal ligament
how many mLs for a femoral nerve block
20-30ml
what is the key target of the fascia iliaca block
lateral femoral cutaneous nerve
(femoral occurs by default)
2 other names for adductor canal block
saphenous nerve block
distal femoral block
true or false
adductor canal block does NOT affect the hip
true
true or false
which block is difficult to see the nerve (this is normal)
adductor canal block
what is the target of the adductor canal block
below/adjacent to the sartorious muscle
very few branches come off the ________ plexus
SACRAL
how many cm along the perpendicular line should the sciatic nerve block occur
5 cm
CAUDAD
where does the sciatic nerve divide:
____cm ABOVE the bend of the knee
10cm
true or false
you still ambulate with a popliteal block
true
which block requires the prone position
popliteal
nerves are _________ to vein/artery
LATERAL
tibial nerve is more ______________,
___________ to the vein and artery
MEDIAL
CLOSER to the vein/artery
common peroneal nerve is more ______________,
___________ to the vein and artery
LATERAL
FARTHER from the vein/artery
true or false
tibial nerve is LARGER
true
true or false
tibial and common peroneal nerves are VERY CLOSE together
true
5 nerves of the ankle
posterior tibial (PT)
saphenous
deep peroneal (DP)
superficial peroneal (SP)
sural
posterior to the PT artery
PT nerve
medial side, anterior to malleolus
saphenous
lateral to anterior tibial artery
DP
lateral, anterior to malleolus
superficial peroneal
lateral, posterior to malleolus
sural
true or false
ankle block is often LANDMARK guided
true
sural sensation
pinky toe
SP sensation
lateral/on the side
DP sensation
between first and second tarsal
PT and saph sensation
medial
How does complete anesthesia of the leg or knee occur
Femoral + sciatic nerve block
As long as you block ________ the site of surgery/pain, you are okay
ABOVE
Which nerve would NOT be covered with a popliteal block
saphenous
What nerve is covered by the Adductor Canal Block/saphenous Nerve Block
femoral
What 6 nerves will the sciatic cover
tibial
common peroneal
PT
DP
SP
sural
what is NOT covered by the interscalene block
ulnar nerve
and
sensory to the hand
what is NOT covered by the supraclavicular block
shoulder
what is NOT covered by the infraclavicular block
shoulder, upper arm
what is NOT covered by the axillary block
shoulder, upper arm, elbow
3 blocks for ANTERIOR KNEE
adductor
femoral
fascia iliaca
3 blocks for ANKLE
popliteal
sciatic
ankle
5 additives
- sodium bicarbonate
- epinephrine
- opioids
- alpha 2 agonist (clonidine)
- steroids (dexamethasone)
adjusts the SENSITIVITY of the probe to the tissue
gain
increases the DISTANCE that the probe scans the tissue
depth
certain probes may DECREASING WIDTH of the scan as DEPTH INCREASES
C6
radial
C7
medial
C8
ulnar
what site has the highest risk of toxicity
tracheal (highest rate of uptake, besides IV)
