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Methods of Anesthesia II > Neuraxial Anesthesia & Local Anesthetic Dosing > Flashcards

Neuraxial Anesthesia & Local Anesthetic Dosing Flashcards

1
Q

adult spinal cord end

A

L1-L2

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2
Q

adult dural sac end

A

S2

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3
Q

kid spinal cord end

A

L2-L3

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4
Q

kid dural sac end

A

S3

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5
Q

layers from skin to CSF 7

A 
1 skin
2 supraspinous ligament
3 interspinous ligament
4 ligamentum flavum
5 epidural space
6 dura mater
7 subarachnoid space
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6
Q

lordosis (convex) is where is spine

A

cervical 7

lumbar 5

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7
Q

kyphosis (concave) is where in spine

A

thoracic 12

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8
Q

kyphosis

A

posterior curvature of spine

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9
Q

lordosis

A

anterior curvature of the spine

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10
Q

scoliosis

A

lateral curvature of the spine

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11
Q

how many cervical vertebrae

A

7

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12
Q

how many thoracic vertebrae

A

12

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13
Q

how many lumbar vertebrae

A

5

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14
Q

how many sacral vertebrae

A

5

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15
Q

how many coccygeal vertebrae

A

4

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16
Q

how many total vertebrae

A

33

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17
Q

how many cervical nerve roots

A

8 pairs

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18
Q

how many thoracic nerve roots

A

12 pairs

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19
Q

how many lumbar nerve roots

A

5 pairs

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20
Q

how many sacral nerve roots

A

5 pairs

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21
Q

how many coccygeal nerve roots

A

1 pair

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22
Q

how many pairs of spinal nerve roots total

A

31

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23
Q

what are nerve roots covered by

A

dural sheath

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24
Q

why is it important that nerve roots are covered by dural sheath? 2

A

1 roots close to spinal cord float in dural sac and pushed away by advancing needle
2 nerve blocks close to intervertebral foramen carry risk of subdural injection

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25
Q

what is the most common starting insertion site for a spinal or lumbar epidural?

A

L3-4 interspace

L4-5 is acceptable; L2-3 may be considered if lower attempts fail

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26
Q

tuffiers line

A

line between superior aspects of iliac crests and estimates L4 body

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27
Q

what is the T10 (umbilicus) dermatome needed for? 3

A

1 spontaneous vaginal delivery (SVD)
2 inguinal surgery
3 testicular surgery

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28
Q

what is the T4 (nipple) dermatome needed for?

A

c-section

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29
Q

why is it convenient that T4 is the most dependent area of the spine in the supine position?

A

lay pts down after spinal then it will go to the correct height usually
it helps prevent the spread of local anesthetic above T4 and prevents high spinal

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30
Q

T5-L1

A

vasomotor tone

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31
Q

what happens when T5-L1 are blocked with spinal or epidural

A

vasodilation and hypotension
“sympathectomy”
nearly all pts with spinals in supine position will have a degree of sympathectomy

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32
Q

are sympathectomies more common with spinals or epidurals?

A

spinals

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33
Q

what is the earliest sign of sympathectomy?

A

nausea and vomiting

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34
Q

T1-T4

A

cardiac accelerator fibers

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35
Q

what can happen if the block rises above T4?

A

significant bradycardia bc you are blocking the sympathetics to the heart

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36
Q

C3-C5

A

phrenic nerve

if the block goes above this then the pt will go apneic

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37
Q

C6-C8

A

hands/fingers

the pt will experience tingling/numbness or weakness in their fingers

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38
Q

what do you do if they start to get numbness in their fingers?

A

place the pt in reverse trendelenburg

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39
Q

T4-T5

A

carina

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40
Q

T6

A

xyphoid process

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41
Q

T7

A

inferior border of scapulae

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42
Q

T8-L1

A

kidney

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43
Q

S2-S4

A

bladder

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44
Q

sympathetic blockade

A

blocking the nerves up to that level will have the ability to produce hypotension and bradycardia

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45
Q

sensory blockade

A

blocking nerves up to that level will produce an absence of pain but NOT of movement/touch

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46
Q

motor blockade

A

blocking nerves up to that level will block the pts ability to move those limbs

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47
Q

levels of sympathetic vs sensory vs motor blockade

A

sympathetic is two levels higher than sensory

sensory is two levels higher than motor

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48
Q

nerves are more easily blocked if they are: 2

A

1 smaller

2 myelinated

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49
Q

differential blockade order from easiest to hardest block

A

autonomic>sensory>motor

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50
Q

what is the goal of an epidural?

A

to stop the needle in the epidural space and not puncture the dura

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51
Q

what type of needle is used for an epidural?

A

17ga tuohy needle

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52
Q

4 epidural advantages

A

1 we can give analgesia as long as necessary
2 more control over analgesic level
3 less profound sympathectomy
4 better preservation of motor function is possible (less dense block)

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53
Q

disadvantages to epidural

A

1 not as dense as spinal (not as comfortable if they have to do a c-section)
2 high propability of PDPH (headache) if needle puncture
3 onset of action is longer for epidurals (several minutes)
4 more potential for local anesthetic toxicity with epidural

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54
Q

walking epidural

A

epidural where it is either:
only narcs
lower dose local
-it preserves motor function, good for post op pain control

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55
Q

spinal anesthesia description (3)

A

1 dura punctured
2 single shot of drug given (preservative free)
3 smaller needles are used

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56
Q

two spinal pencil point needles

A

whitacre

sprotte

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57
Q

whitacre needle

A

smallest opening

CSF aspiration slow and hard

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58
Q

sprotte needle

A

longer opening
CSF aspiration easier
higher chance of injecting epidurally

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59
Q

spinal cutting type needle

A

quincke

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60
Q

quincke

A

cuts through ligaments better but makes larger hole in dura

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61
Q

what is the 18ga introducer needle used for

A

the spinal needle can be placed through the introducer to guide it to the correct spot

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62
Q

advantage of introducer needle

A

much less bending of spinal needle

commonly used if spinal needle is smaller than 22ga

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63
Q

22ga spinal needle advantage and disadvantage

A

advantage-
18ga introducer not needed
disadvantage-
higher risk of spinal headache

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64
Q

common uses for the 22ga spinal needle

A 
elderly pts (lower risk of headache)
obese pts
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65
Q

advantage to 25ga spinal needle

A

way less likely for spinal headache

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66
Q

what is the most common size spinal needle for adults?

A

25ga

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67
Q

disadvantage to 25ga spinal needle

A

more likely to bend when passing ligaments ** used with introducer

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68
Q

advantage to 27ga spinal needle

A

smallest hole in dura and least likely headache

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69
Q

disadvantage to 27ga spinal needle

A

highest chance of bending through ligaments

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70
Q

when is the 27ga spinal needle used?

A

CSE

combined spinal epidural where it is placed through the espocan needle

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71
Q

continuous spinal anesthesia

A

rare

catheter into intrathecal space and repeated doses given

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72
Q

problem with continuous spinal anesthesia

A

microcatheter must be used bc the needles are so small

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73
Q

what is the risk associated with microcatheters

A

neurotoxicity and cauda equina syndrome

pooling of local anesthetic

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74
Q

practical use of continuous spinal anesthesia

A

accidentally wet tap someone and just thread the catheter into the intrathecal space and give lower doses

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75
Q

4 management steps of continuous spinal anesthesia

A

1 sterile technique critical
2 catheter threaded 2-3cm intrathecal space
3 analgesia is usually maintained with local anesthetic boluses NOT infusion
4 appropriate dosing intervals are anywhere from 45-90 min

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76
Q

what should you do before and after each injection

A

flush with previously aspirated CSF after each injection

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77
Q

baricity

A

how dense (heavy) the drug is compared to CSF and the density determines whether the drug will sink or rise

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78
Q

3 types of baricity

A

hyperbaric
hypobaric
isobaric

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79
Q

hyperbaric

A

spinal drug is denser than CSF and drug will sink

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80
Q

how to make drug hyperbaric

A

adding an equal volume of 10% dextrose/glucose to the local anesthetic

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81
Q

hyperbaric spinal for supine position

A

the hyperbaric drug tends to move to T4 because it is the most dependent area of the spine

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82
Q

how do we know that glucose must interfere with the hyperbaric drugs absorbtion?

A

shorter time to peak concentration

shorter duration of action than plain local anesthetics

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83
Q

hyperbaric saddle block pt position

A

allow pt to remain sitting for several minutes after spinal medication

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84
Q

what does a saddle block anesthetize?

A

sacral nerves
buttocks
perineal area
inner thighs

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85
Q

what types of procedures are saddle blocks used for

A

genitourinary

2nd stage labor pain

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86
Q

hypobaric drug

A

spinal drug is lighter than CSF and drug will rise

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87
Q

how do you make a drug hypobaric

A

add sterile water

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88
Q

how much sterile water do you add to a drug to make it hypobaric

A

depends on source!!
larger volume
3mL per 1mL
1mL per 1mg

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89
Q

what is the most common use for a hypobaric spinal?

A

hip surgery

pt in lateral position with operative hip up

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90
Q

isobaric spinal drug definition

A

spinal drug has the same specific gravity as CSF and will remain at the level of injection

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91
Q

how do you make a drug isobaric?

A

add equal volume of CSF or normal saline to the local

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92
Q

does baricity apply to spinals and epidurals?

A

no just spinals

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93
Q

how long until the baricity of the spinal settles?

A

10-15min

then shouldn’t rise or sink based on position

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94
Q

CSE

A

combined spinal epidural technique

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95
Q

CSE technique 4

A

1 advance CSE tuohy needle into epidural
2 27ga spinal needle through into the intrathecal space perform spinal block
3 thread epidural catheter
4 spinal for operative anesthesia, epidural for postop

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96
Q

what is a common needle set for the CSE?

A

espocan kit
tuohy needle with hole
27ga spinal needle

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97
Q

advantages CSE 3

A

1 denser block for procedure than just epidural
2 use the smallest spinal needle and smaller chance of headache
3 postop analgesia with epidural in case dont want to use duramorph in spinal

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98
Q

disadvantage to the CSE

A

can’t perform a test dose through the epidural catheter bc the pt is already numb from the spinal

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99
Q

dural puncture epidural technique 5

A

1 epidural needle placed
2 spinal needle though tuohy and punctures dura
3 spinal needle removed without dosing
4 epidural catheter placed
5 some of the local anesthetic leaks into the intrathecal space through the small hole

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100
Q

advantages to dural puncture epidural technique 3

A

1 faster sacral onset
2 greater sacral spread of local
3 lower incidence of unilateral block

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101
Q

disadvantage dural puncture epidural technique

A

small chance of post dural puncture headache

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102
Q

epidural summary points

A

longer analgesia possible
more control of analgesic level
more gradual, less profound sympathectomy
less dense block

103
Q

spinal summary points

A

limited analgesic duration
single shot (cant alter dose)
rapid potent sympathectomy
denser block

104
Q

sacral hiatus

A

site of needle insertion

105
Q

what is the sacral hiatus covered by?

A

sacrococcygeal ligament

106
Q

sacral cornu

A

bony pominence to either side of sacral hiatus

palpate these for landmarks

107
Q

is a caudal block a spinal or epidural?

A

epidural block but differs because
performed at sacral level
dosed with single shot of drug

108
Q

caudal block technique 5

A

1 palpate sacral hiatus
2 insert needle through sacral hiatus at 45 deg angle
3 advance sephalad until pop
4 advance cannula over the needle and remove needle
5 aspirate before inject

109
Q

when is it possible for the epidural to cause spinal cord or nerve root damage?

A

in the lumbar or thoracic region

110
Q

what will happen when epidural needles get too close to nerve roots?

A

patients experience parasthesias and the anesthetist can redirect

111
Q

can lumbar and thoracic epidurals be done when the patient is asleep?

A

no they must be awake to reduce the risk of nerve injurt

112
Q

can caudal blocks be done when the patient is asleep?

A

yes because they are so far away from the spinal cord or roots

113
Q

what is the most popular block for children?

A

caudal block

114
Q

3 advantages to caudal blocks

A

performed on asleep pts
more reliable perineal anesthesia (than lumbar)
less likely dural puncture and nerve damage

115
Q

5 disadvantages to caudal blocks

A 
dural can still be punctured
rectum can be punctured
technically more difficult in adults
twice as much local anesthetic required than lumbar epidural
higher risk of urinary retention
116
Q

8 factors that affect neuraxial spread of local anesthetics

A 
1 total mg dose
2 total volume injected
3 addition of epi
4 addition of narcotic
5 height of patient
6 positioning
7 weight of patient
8 age
117
Q

how does total mg dose affect spread?

A

higher doses spread more

118
Q

how does volume injected affect spread

A

the higher volume will spread more

119
Q

does dose or volume have greater affect on spread

A

dose

120
Q

how does the addition of epi spread the block?

A

it prolongs the block but doesnt raise the level

121
Q

how does addition of narcotic affect the block

A

increases the density “strength” of the block

122
Q

how does the height of the patient affect the block

A

the shorter you are the more likely it will travel too high

123
Q

how does trendelenburg effect block

A

more cephalad spread of local

124
Q

how does reverse trendelenburg effect block

A

less cephalad spread of local

125
Q

how does lateral effect block

A

block will be more one sided

126
Q

how does the weight of the patient effect spread of block

A

the more obese (heavy) the patient: higher it will spread and a lower local dose is required

127
Q

why does local anesthetic spread higher in heavier patients?

A

increased intraabdominal pressure
compression of inferior vena cava
engorgement of epidural veins
decreases CSF volume

128
Q

how does age effect spread of block

A

geriatric pts have: lower dosing requirements and shorter onset (reduced CSF volume; decrease in nerve fibers and decreased conduction velocity)

129
Q

8 absolute contraindications to neuraxial anesthesia

A 
1 refusal
2 infection at injection site
3 serve hypovolemia
4 coagulopathy (epidural hematoma)
5 severe aortic stenosis
6 severe mitral stenosis
7 sepsis
8 elevated ICP
130
Q

what could infection at injection site or sepsis lead to

A

meningitis or epidural abscess

131
Q

what must the platelet count be for OB before neuraxial blockade?

A

> 80,000- 100,000

132
Q

why should aortic/mitral stenosis be avoided with neuraxial blocks?

A

sympathectomy drops preload and afterload and those should be maintained with aortic stenosis

133
Q

why avoid neuraxial block in patients with elevated ICP?

A

cant tolerate sympathectomy
high MAP is needed to perfuse the head with elevated ICP
Cerebral perfusion pressure= MAP-ICP

134
Q

relative contraindications for neuraxial anesthesia 4

A

1 neurologic deficiencies (MS) (worsening symptoms)
2 sepsis
3 previous back surgery (may effect spread)
4 severe COPD (may rely on accessory muscles to breath)

135
Q

11 potential complications of neuraxial blocks

A 
pruritus
nausea and vomiting (from hTN)
urinary retention
parasthesia (short term)
nerve/ spinal cord injury
backache
PDPH
transient neurologic symptoms (TNS)
cauda equina syndrome (CES)
epidural abscess
epidural hematoma
136
Q

what is the incidence of back pain following spinal anesthesia?

A

25%

137
Q

possible etiologies of back pain: 5

A 
1 regular common backache from needle or lying flat
2 transient neurologic symptoms (TNS)
3 cauda equina syndrome (CES)
4 epidural abscess
5 epidural/spinal hematoma
138
Q

what is a epidural abscess caused by

A

infection potentially after back surgery or neuraxial block

139
Q

what are the symptoms of a epidural abscess

A

back pain intensified by spine percussion
signs of infection (fever, increases WBC)
sensory AND motor deficits

140
Q

how is an epidural abscess diagnosed?

A

ct scan

141
Q

treatment of epidural abscess

A

surgical decompression via laminectomy

142
Q

how are the symptoms of epidural abscess and epidural hematoma different?

A

hematoma has faster onset and the WBC count should be normal

143
Q

how are epidural hematomas treated

A

immediate surgical evacuation

144
Q

what is transient neurologic symptoms?

A

someone who experiences back pain without motor deficits

resolves on own

145
Q

what are some hypothesis about what causes TNS

A

lithotomy position
intrathecal vasoconstrictors
highly concentrated local
lidocaine

146
Q

which is more serious CES or TNS?

A

CES because it includes back pain and motor deficits and/or bladder and bowel dysfunction

147
Q

etiology of CES

A

nerve root/spinal cord trauma
highly concentrated local anesthetics
continuous spinal anesthesia through microcatheter

148
Q

which needs a neurology consult? CES or TNS

A

CES

149
Q

post dural puncture headache

A

more likely to occur with wet tap from tuohy needle during epidural
less likely with spinal because headache is proportional to the size of the hole

150
Q

if someone gets a wet tap what is the likelihood of PDPH

A

80% chance

151
Q

what are the two options for if you wet tap a patient

A

thread catheter ~2cm intrathecally for continuous spinal anesthesia
remove needle and start another epidural higher level

152
Q

if you are older are you more or less likely to get a PDPH?

A

less likely as you get older

153
Q

symptoms of PDPH

A

headache bilateral frontal occipital and extends to neck

aggravated by standing or sitting

154
Q

why does standing make the headache worse

A

venous return decrease
epidural veins engorge
push out more CSF and worsen the headache

155
Q

3 treatments for PDPH

A

autologous blood patch
analgesics, caffeine, generous fluid admin
neostigmine and atropine combination

156
Q

what is the gold standard for PDPH treatment

A

blood patch, 90-99 success rate

157
Q

regional anesthesia advantages (compared to GA) 4

A

1 decreases anesthetic requirements (decreases postop N/V)
2 decrease respiratory complications
3 decreased surgical blood loss
4 decreases incidence of thrombosis

158
Q

how many “i” in esters

A

one

159
Q

how many “i” in amides?

A

more than one “i”

160
Q

how are esters metabolised

A

plasma esterases

161
Q

what do esters produce as a byproduct and why does that matter

A

p-aminobenzoic acid PABA

it is associated with allergic reactions

162
Q

how are amides metabolized?

A

by the liver

163
Q

which is more likely to cause an allergic reaction? tetracaine or marcaine?

A

tetracaine because it is an ester

164
Q

what is the pH of local without epi

A

6-7

acidic so it prolongs shelf life

165
Q

what is the pH of local with epi

A

4-5

more acidic because epi is unstable in basic environments

166
Q

what local is most dramatically prolonged by the addition of adrenergic agonists

A

tetracaine (pontocaine)

167
Q

how long does adding phenylephrine to tetracaine increase the duration of block

A

70-100%

168
Q

how long does adding epi to tetracaine increase the duration of block

A

40-60%

169
Q

how long does adding clonidine to tetracaine increase the duration of block

A

50-70%

170
Q

what are the 4 most common local anesthetics for labor epidural dosing

A

marcaine
ropivacaine
lidocaine
chloroprocaine

171
Q

marcaine advantages 2

A

motor sparing

longest lasting

172
Q

what is marcaine usually diluted to?

A

0.1-0.24%

173
Q

marcaine disadvantages 3

A

1 less effective at blocking the larger sacral nerves
2 slowest onset
3 very cardiotoxic

174
Q

what is the implication of marcaine being less effective at blocking larger sacral nerves

A

higher chance of losing their effectiveness during stage two labor

175
Q

toxic dose marcaine with and without epi

A

2.5mg/kg w/o epi

3mg/kg w/ epi

176
Q

what is the treatment for marcaine toxicity

A

CPR

intralipid 20%

177
Q

Ropivacaine (naropin) 0.2%

A

similar pharmacology to marcaine

less cardiotoxic and more expensive

178
Q

what is the max dose of ropivacaine

A

3mg/kg

179
Q

advantages of lidocaine 2% or 1.5% with epi

A

more effective at blocking larger sacral nerves

fast onset

180
Q

disadvantages of lidocaine 2% or 1.5% with epi

A

more significant motor blockade (could inhibit pushing)
neurologic symptoms if the toxic dose is exceeded
highest risk of TNS and CES (intrathecal hyperbaric lido)ch

181
Q

what is the toxic dose of lidocaine with epi

A

7mg/kg

182
Q

what is the toxic dose of lidocaine without epi

A

4mg/kg

183
Q

chloroprocaine (3%) advantages

A

fastest epidural onset

minimal drug transfer across placenta

184
Q

when are you most often going to use chloroprocaine

A

emergency c section

185
Q

why does chloroprocaine have such a rapid onset

A

pseudocholinesterase metabolism

186
Q

chloroprocaine 3% disadvantages

A 
highest degree of motor block
shortest duration (redosed frequently)
contraindicated for intrathecal use
187
Q

5 most common situations an epidural is bolused include

A 
initial test dose
loading dose
dose to increase blocks density
raising the block to t4 gradually
raising the block to t4 immediately
188
Q

what should you do before bolusing an epidural?

A

verify they have stable vital signs prior to bolusing and monitor for 10 mins after
aspirate everytime to rule out intravascular or intrathecal injection

189
Q

signs of intravascular injection

A

increase HR
tinnitus
oral/tongue numbness

190
Q

sings of intrathecal injection

A

immediate numbing of the legs

191
Q

what is the initial test dose

A

5mL of 1.5% lido with 1:200,000 epi

192
Q

accidental IV injection ruled out by absence of:

A

tachycardia
mouth/tongue numbness
ringing in ears

193
Q

accidental intrathecal injection ruled out by

A

not having immediate numbness

194
Q

epidural loading dose

A

additional 5mL loading dose after test dose to speed up the onset of block
higher risk of sympathectomy

195
Q

why dose to increase the density of epidural block ?

A

patchy block when it starts to wear off, disconnect pump and bolus 5mL

196
Q

when would you raise the epidural block gradually to t4?

A

non emergent c section

197
Q

how to raise the epidural block level gradually

A

gives initial 10mL of local, wait 3 min check level
give 5mL of local, wait 3 min, check level
give another 5mL of local if still not high enough

198
Q

if local is bolused too fast what will happen

A

risk of high block and hypotension is increased

199
Q

if the anesthetist waits too long in between boluses what happens?

A

the block density will increase but the block wont rise

200
Q

what is the local of choice for raising an epidural block from t10 to t4?

A

lidocaine because fast onset and longer duration than chloroprocaine

201
Q

what are common preservatives in local anesthetics?

A

sulfites (bisulfite, metabisulfite)
parabens (methylparaben)
EDTA

202
Q

do multi dose or single dose vials have preservatives?

A

multidose vials

203
Q

methylparaben

A

bacteriostatic preservative added to multidose vials

potential anaphylactoid symptoms

204
Q

what is methylparaben contraindicated for?

A

epidural and intrathecal

205
Q

what are methylparaben free solutions referred to as?

A

MPF

206
Q

sulfites (and citric acid) are added to what?

A

local that are premixed with epi to prevent degradation of epi
causes more pain on injection

207
Q

what has intrathecal injection of sulfites resulted in?

A

arachadonitis

anaphylactoid rxns

208
Q

what are sulfites contraindicated for?

A

spinals

209
Q

are sulfites okay to use for epidurals?

A

yes

210
Q

what is EDTA used for?

A

prolong shelf life and allow autoclaving to sterilize glass vial

211
Q

what is EDTA been linked to in patients?

A

epidurally injected associated with severe pain at injection site

212
Q

can you use chloroprocaine for spinals?

A

no

213
Q

what two things should you check before injecting epudural or intrathecal

A

preservative free

“for spinal or epidural use”

214
Q

can you use a local with preservatives for a bier block?

A

no

215
Q

why is bicarb added?

A

added to lidocaine or chloroprocaine to speed up onset by bringing closer to pKa

216
Q

how long until the local will precipitate when bicarb is added

A

6hr

217
Q

effects of adding alpha agonist?

A

prolongs block duration
limits toxic side effects
enhances analgesic quality

218
Q

what local is effected the most with added epi

A

tetracaine

219
Q

what local is effected the least with added epi

A

bupivacaine

220
Q

if the local is _____ lipid soluble then added epi is less significant.

A

more

221
Q

can alpha agonists cause analgesia?

A

yes by directly inhibiting sensory and motor neurons

222
Q

what does clonidine do to BP

A

greater decrease in BP

223
Q

duramorph

A

morphine without preservatives

224
Q

which causes more respiratory depression in fetus and urinary retention? morphine or fentanyl?

A

morphine

225
Q

advantages of neuraxial opioids

A

analgesia
no motor blockade
no sympathectomy

226
Q

disadvantages of neuraxial opioids

A

pruritus (itch)
delayed respiratory depression
nausea/vomiting

227
Q

the more lipid soluble drugs they have a _____ onset and _____ duration

A

faster onset

shorter duration

228
Q

____ lipid soluble drugs exit the central nervous system quickly

A

more

229
Q

duration of epidural narcotics

A

twice as long as spinal because epidural dose is higher

230
Q

spinal dosing of opioids

A

should not be dosed if it is outpatient procedure

231
Q

what are the three forms a drug can be in?

A

non polar
polar/neg charged (loss of H+)
polar/pos charged (gain of H+)

232
Q

what is the form a drug takes determined by? 2

A

drugs pH

pH of environment the drug is placed in

233
Q

if you have higher degree of nonpolar drug then the onset is

A

faster

234
Q

do the ionized or nonionized portion of the drug cross the lipid membrane?

A

nonpolar (nonionized)

235
Q

if an acidic drug is placed in a basic environment then it will become:

A

negatively charged and slow the onset of the drug

236
Q

if a basic drug is placed in an acidic environment then it will become

A

positively charged and it will slow the onset of the drug

237
Q

what is the highest possible portion of nonpolar drug

A

50%

238
Q

when you place a drug in an ideal pH then it will

A

have the highest portion of nonpolar drug and fastest onset possible

239
Q

pKa

A

pH of the drugs environment that will result in the drug having 50% ionization and 50% nonionization

240
Q

pH of lidocaine

A

6.5

241
Q

pKa of lidocaine

A

7.9

242
Q

what would you do to bring the pH of lidocaine closer to its pKa?

A

add sodium bicarb

243
Q

do basic drugs have a high or low pKa

A

high

244
Q

do acidic drugs have a high or low pKa

A

low

245
Q

the drug will have a ____ onset the closer the drugs pKa is to physiologic pH 7.4

A

faster

246
Q

are local anesthetics by themselves more acidic or basic?

A

basic

247
Q

are local anesthetics in the vial more acidic or basic?

A

acidic

acid added so it wont precipitate

248
Q

adding bicarb to local anesthetic will 4

A

1 bind up excess acid
2 make drug less pos charged
3 increase the pH
4 speed up onset of action

249
Q

how much lower is the pH of local when the solution contains epi?

A

1-1.5 units lower

250
Q

factors that determine the onset of local anesthetic 4

A

how ionized the local is
how close locals pH is to the pKa
how close the locals pKa is to physiologic pH
how lipid soluble the local is

251
Q

effect of higher lipid solubility on local anesthetics onset and duration

A

slow onset

long duration

252
Q

effect of higher lipid solubility on other drugs such as fentanyl onset and duration

A

fast onset

short duration

253
Q

factors that determine local anesthetic potency 3

A 
how concentrated (more=potent)
how lipid soluble (higher=potent)
total dose (more=potent)

Methods of Anesthesia II (13 decks)

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