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Methods of Anesthesia > Neuraxial Anesthesia > Flashcards

Neuraxial Anesthesia Flashcards

1
Q

In adults, the spinal cord ends at

A

L1-L2

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2
Q

In adults, the dural sac ends at

A

S2

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3
Q

In kids, the spinal cord ends at

A

L2-L3

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4
Q

In kids, the dural sac ends at

A

S3

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5
Q

Neuraxial anatomy from layers of skin to CSF

A
  1. Skin
  2. Supraspinous ligament
  3. Interspinous ligament
  4. Ligamentum flavum
  5. Epidural space
  6. Dura mater
  7. Subarachnoid space (contains CSF)
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6
Q

Where is the epidural space

A

Extends superiorly to the foramen magnum and inferiorly to the sacral hiatus

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7
Q

Where is the spine normally convex anteriorly?

A

In the cervical and lumbar regions

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8
Q

Posterior curvature of the spine

A

Kyphosis

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9
Q

Anterior curvature of the spine

A

Lordosis

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10
Q

Lateral curvature of the spine

A

Scoliosis

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11
Q

Number of each vertebrae

A 
7 cervical
12 thoracic
5 lumbar
5 sacral
4 coccygeal
33 total
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12
Q

Number of spinal nerve roots

A 
8 pair of cervical
12 pair of thoracic
5 pair of lumbar
5 pair of sacral
1 pair of coccygeal
31 total
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13
Q

What does it mean if a small portion of nerve roots are covered by dural sheath?

A
  1. Roots close to the spinal cord tend to float in the dural sac and are thus usually pushed away, not pierced, by an advancing needle
  2. Nerve blocks close to intervertebral foramen carry a risk of subdural injection
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14
Q

Most common starting insertion site for a spinal or lumbar epidural in adults

A

L3-L4

L4-L5 is also common and acceptable

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15
Q

What may be considered if L3-5 attempts are unsuccessful for a spinal or lumbar epidural in adults?

A

L2-3

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16
Q

Imaginary line drawn between superior aspects of the iliac crests

A

Tuffier’s line

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17
Q

What does Tuffier’s line estimate?

A

L4 or L4-5 interspace

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18
Q

How do you find the L3-4 space?

A

Palpate the superior aspects of the iliac crests and move up one interspace above Tuffier’s line

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19
Q

What is a T10 level of analgesia for?

A
  1. Spontaneous vaginal delivery
  2. Inguinal surgery
  3. Testicular surgery
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20
Q

What is a T4 level of analgesia for?

A

C-section

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21
Q

The most dependent area of the spine when patients are supine

A

T4

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22
Q

True/false. If the pt is placed supine immediately after the block is given, the normal dose will not go above T4-T6

A

True

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23
Q

Why is it convenient that the spinal drug does not rise above T4-T6 if the patient is placed supine immediately after the block?

A
  1. It will usually go to the perfect height necessary for analgesia for a C-section
  2. It helps prevent the spread of local anesthetic above T4, which helps prevent high spinal or total spinal anesthesia
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24
Q

When T5-L1 nerves are blocked with a spinal or epidural, causing vasodilation and subsequent hypotension

A

Sympathectomy

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25
Q

The earliest sign of more intense sympathectomy

A

Nausea/vomiting

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26
Q

When are sympathectomies usually more severe?

A

With spinal blocks

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27
Q

How do you treat nausea from sympathectomy?

A

Raise the pts blood pressure

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28
Q

Dermatomes where sympathectomy is common

A

T5-L1

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29
Q

Dermatome that contains accelerator fibers

A

T1-T4

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30
Q

What happens if the level of the neuraxial block starts to rise above T4?

A

The patient can have significant bradycardia

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31
Q

Dermatome with phrenic nerve innervation

A

C3-C5

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32
Q

What happens if the neuraxial block goes to C3-C5?

A

The patient will go apneic

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33
Q

How do you know if the block is getting to C6-C8?

A

The patient will experience tingling, numbness and/or weakness in their fingers

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34
Q

How do you decrease the level of the block below C6-C8?

A

Place them in reverse Trendelenburg

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35
Q

Carina dermatome

A

T4-T5

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36
Q

Xyphoid process dermatome

A

T6

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37
Q

Liver dermatome

A

T6-T11

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38
Q

Inferior border of scapulae dermatome

A

T7

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39
Q

Kidney dermatome

A

T8-L1

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40
Q

Orchiectomy dermatome

A

T10

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41
Q

Bladder dermatome

A

S2-S4

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42
Q

Blocking the nerves up to that level will have the potential to produce hypotension and bradycardia

A

Sympathetic (autonomic) blockade

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43
Q

Blocking nerves up to that level will produce an absence of pain

A

Sensory blockade

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44
Q

Blocking nerves up to that level will block the patient’s ability to move those limbs

A

Motor blockade

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45
Q

Sympathetic blockade is typically 2 levels (higher/lower) than sensory blockade

A

Higher

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46
Q

Sensory blockade is typically 2 levels (higher/lower) than motor blockade

A

Higher

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47
Q

If a patient has a sensory block at T4, where would their motor and sympathetic block be?

A

Motor up to T6, sympathetic up to T2

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48
Q

When are nerves more easily blocked?

A

If they are smaller and myelinated

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49
Q

In spinal nerves, local anesthetic inhibition follows the sequence:

A

Autonomic > sensory > motor

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50
Q

What does the local anesthetic inhibition sequence mean?

A
  1. It is easiest to block autonomic nerves
  2. It is easier to block smaller pain nerves than it is to block larger motor nerves
  3. It is possible for a patient to move even if they can’t feel pain
  4. It’s not likely for a patient to have feeling if they can’t move
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51
Q

Goal with an epidural

A

Stop the needle at the epidural space (do not puncture the dura)

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52
Q

Needle for epidural

A

Large 17ga Tuohy needle to allow for threading of catheter into epidural space

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53
Q

Epidural advantages (compared to spinals)

A
  1. We can give analgesia as long as necessary
  2. We have more control over the analgesic level
  3. Patients experience a less profound sympathectomy
  4. This is a better preservation of motor function
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54
Q

Epidural disadvantages compared to spinals

A
  1. Not as dense as a spinal block
  2. Very high probability for post dural puncture headache if the dura is accidentally punctured (larger the needle, the larger the hole in the dura, larger CSF leak, higher chance for PDPH)
  3. Onset of action for local anesthetics is longer
  4. More potential for local anesthetic toxicity
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55
Q

What is a “walking epidural”

A

Epidural dosed with either
1. Narcotics only, or
2. Lower doses/infusion rates of local anesthetic
that preserves motor function and allows patient to walk

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56
Q

Outline of spinal block

A
  1. Dura punctured with spinal needle
  2. Single “shot” of drug is given
  3. Smaller needles are used (27ga, 25ga, 22ga)
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57
Q

Needle size for spinals

A

27ga, 25ga, 22ga

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58
Q

Spinal needle options

A
  1. Whitacre
  2. Sprotte
  3. Quincke
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59
Q

Pencil point needle with smallest opening for spinals

A

Whitacre

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60
Q

Pencil point needle with longer opening for spinals

A

Sprotte

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61
Q

Cutting tip needle for spinals

A

Quincke

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62
Q

Spinal needle where CSF aspiration will be the hardest/slowest

A

Whitacre

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63
Q

Spinal needle where CSF can be easier to aspirate, but a higher chance of injecting epidurally

A

Sprotte

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64
Q

Spinal needle that cuts through ligaments better, but makes a larger hole in the dura

A

Quincke

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65
Q

Introducer needle size for spinals

A

18ga

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66
Q

Purpose of the 18ga introducer needle

A

Much less bending of the spinal needle, commonly used if the spinal needle is smaller than 22ga (25, 27ga)

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67
Q

Advantage of 22ga spinal needle

A

18ga introducer is not needed

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68
Q

Disadvantage of the 22ga spinal needle

A

There is a higher risk of spinal headache due to the larger hole in the dura

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69
Q

Common uses for the 22ga spinal needle

A
  1. Elderly patients

2. Obese patients

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70
Q

Why is a 22ga common for elderly patients?

A
  1. Geriatric patients carry a lower risk of spinal headache

2. Larger needles can pass through calcified ligament more easily

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71
Q

Why is a 22ga more common in obese patients

A

a larger needle is less likely to bend/break when passing through the excess tissue

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72
Q

Advantage to 25ga spinal needle

A

It’s less likely for the patient to get a spinal headache

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73
Q

Most common size of spinal needle for adults

A

25ga

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74
Q

Disadvantage to 25ga spinal needles

A

More likely to bend when passing through spinal ligaments, especially if they are calcified, so it is commonly used with an 18ga introducer

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75
Q

Advantage to 27ga spinal needle

A

Creates the smallest hole in the dura, least chance of spinal headache

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76
Q

Disadvantage to 27ga spinal needle

A

Has the highest chance of bending through the spinal ligaments, so wouldn’t want it by itself and wouldn’t want to use an 18ga introducer because it doesn’t pass through ALL spinal ligaments

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77
Q

When is a 27ga spinal needle commonly used?

A

When performing a combined spinal epidural block where is Tuohy needle is used as the introducer needle. The 27ga will only need to pass through ligamentum flavum

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78
Q

Rare technique that provides repeated doses of local anesthetic into the intrathecal space through a catheter

A

Continuous spinal anesthesia

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79
Q

What is needed to run a continuous spinal infusion?

A

Threading a microcatheter (24-32ga) into the subdural space

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80
Q

Problem with the microcatheters

A

Associated with neurotoxicity and cauda equina syndrome

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81
Q

What did the FDA advise against for continuous spinal anesthesia?

A

All small bore catheters (smaller than 24ga)

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82
Q

The only real practical use for continuous spinal anesthesia

A

If an anesthetist unintentionally punctures the dura with a Tuohy needle during epidural placement

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83
Q

Management of continuous spinal anesthesia

A
  1. Sterile technique is critical
  2. Catheter should be threaded 2-3 cm into the intrathetcal space
  3. Analgesia is usually maintained with local anesthetic boluses instead of an infusion and titrated to effect
  4. Appropriate dosing intervals are anywhere from 45-90 minutes
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84
Q

Dose of local anesthetic via continuous spinal infusion

A

Approximately 1/10th of epidural infusion rate and titrated to effect

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85
Q

Refers to whether the drug will sink or rise when injected into the CSF

A

Baricity

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86
Q

When the spinal drug is denser than CSF and the drug sinks

A

Hyperbaric

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87
Q

How are drugs made hyperbaric?

A

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

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88
Q

Where do hyperbaric drugs tend to move?

A

T4

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89
Q

Peak concentration and duration of action of hyperbaric solutions

A
  1. Shorter time to peak concentration

2. Shorter duration of action than plain local anesthetics

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90
Q

Performed by allowing the patient to remain sitting for several minutes after injecting hyperbaric spinal medication

A

Saddle block

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91
Q

What does the saddle block anesthetize?

A

Sacral nerves, buttocks, perineal area, inner thighs

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92
Q

When is a saddle block used?

A

For genitourinary procedures and to relieve 2nd stage labor pain

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93
Q

The spinal drug is ligher than CSF and the drug will rise

A

Hypobaric spinal

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94
Q

How do you make a drug hypobaric?

A

By adding sterile water

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95
Q

Most common use for hypobaric spinal

A

Hip surgery

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96
Q

Spinal drug has the same specific gravity as CSF, so it remains at the level of injection

A

Isobaric

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97
Q

How are drugs made isobaric?

A

By adding equal volume of CSF or normal saline to the local anesthetic

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98
Q

How long does it take for baricity of the spinal to settle?

A

10-15 minutes

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99
Q

Combined spinal epidural technique

A
  1. Advance a CSE Tuohy needle into the epidural space
  2. Thread a small needle through a small hole in the CSE Tuohy needle and performs a spinal block, and removes the spinal needle while keeping the epidural needle in plcae
  3. Thread an epidural catheter after the patient has been dosed with spinal drugs
  4. Use the spinal for operative anesthesia and the epidural for postoperative anesthesia
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100
Q

Advantages to CSE

A
  1. Denser block for a procedure than an epidural alone
  2. Allows the spinal to be performed with a 27ga spinal needle, leading to the smallest chance of PDPH
  3. Allows post op analgesia with an epidural in case the anesthetist does not want to use Duramorph in the spinal
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101
Q

CSE disadvantage

A

Cannot perform a test dose through the epidural catheter to make sure it is in the right place because the pt is already numb from the spinal block by the time the epidural is threaded

102
Q

Dural puncture epidural technique

A
  1. Place epidural needle
  2. Insert spinal needle through Tuohy needles and puncture the dura
  3. Remove spinal needle without dosing intrathecal medication
  4. Place epidural catheter and hook up to infusion pump
  5. Local anesthetic is primarily in epidural space, but the small puncture in intrathecal space allows some to leak in
103
Q

Advantage of dural puncture epidural technique

A
  1. Faster sacral onset
  2. Greater sacral spread of the local anesthetic
  3. Lower incidence of unilateral block
104
Q

Disadvantage of dural puncture epidural

A

Small chance of post dural puncture headache (very small w/27ga needle)

105
Q

Caudal anesthesia landmarks

A

Sacral hiatus: site of needle insertion, covered by sacrococcygeal ligament
Sacral cornu: Bony prominences to the sides of sacral hiatus

106
Q

Palpated to find sacral hiatus

A

Sacral cornu

107
Q

Performed by inserting a needle through the sacrococcygeal ligament into the sacral hiatus with medication injected into the epidural space

A

Caudal block

108
Q

How does the caudal block differ from a regular lumbar epidural block?

A
  1. Performed at the sacral level

2. Dosed with a single shot of drug (instead of catheter infusion)

109
Q

Caudal technique

A
  1. Palpate the sacral hiatus
  2. Insert the needle through the sacral hiatus at a 45 degree angle
  3. Advance cephalad until a “pop” is felt
  4. Advance the cannula over the needle and remove the needle
  5. Aspirate before injecting
110
Q

Common caudal dose

A

1-1.25 mL/kg of 0.125% marcaine with epi

111
Q

Why is it vital that patients remain awake during lumbar or thoracic epidurals?

A

They can alert the anesthetist to stop and redirect the needle if parasthesias are experienced

112
Q

Why can caudal blocks be safely performed in asleep patients?

A

There is a lower chance of nerve damage and parasthesias because the needle is further from the spinal cord or any nerve roots

113
Q

Most popular epidural block in children

A

Caudal block

114
Q

Advantages of caudal anesthesia

A
  1. They can be performed in asleep patients
  2. They provide more reliable perineal anesthesia than lumbar epidurals
  3. Less likely chance of dural puncture and nerve damage
115
Q

Disadvantages of caudal anesthesia

A
  1. Dura can still theoretically be punctured
  2. The rectum can be punctured
  3. More difficult in adults
  4. Requires 2x as much local as a lumbar epidural
  5. Relatively high risk of urinary retention
116
Q

Factors that affect the strength and spread of the neuraxial local anesthetics (8)

A
  1. Total volume injected (10 mL 1% lido will spread more than 1mL 10% lido)
  2. Total mg dose (higher doses spread faster)
  3. Addition of epi
  4. Addition of narcotic
  5. Height of the patient (more than weight)
  6. Positioning
  7. Weight of patient
  8. Age
117
Q

True/false. Dose has a greater effect than volume in neuraxial local anesthetics

A

True

118
Q

True/false. Epi prolongs the block and raises the block level

A

False. Epi prolongs the block but does NOT raise the block level

119
Q

Effect of narcotic on neuraxial block

A

Increases the density/strength

120
Q

Effect of height on neuraxial block

A

The shorter you are, the more likely the block will travel “too high”
Shorter people receive a lower dose

121
Q

Effect of trendelenburg on neuraxial blocks

A

More cephalad spread of local anesthetic

122
Q

Effect of reverse trendelenburg on neuraxial blocks

A

Less cephalad spread of local anesthetic

123
Q

Effect of lateral positioning on neuraxial blocks

A

Block will be more one sided

124
Q

Effects of neuraxial blocks on obese patients

A
  • The higher the local will spread

- Lower local dose requirement

125
Q

Effects of age on neuraxial local anesthetics

A
  1. Lower dosing requirement for geriatric patients
  2. Shorter onset of epidural and spinal anesthesia in geriatric patients
    (no evidence for differences in duration in elderly)
126
Q

Absolute contraindications to neuraxial anesthesia

A
  1. Patient refusal
  2. Infection at the injection site
  3. Severe hypovolemia
  4. Coagulopathy
  5. Severe aortic stenosis
  6. Severe mitral stenosis
  7. Sepsis
  8. Elevated intracranial pressure
127
Q

Why is infection at the injection site an absolute contraindication to neuraxial anesthesia?

A

A block could lead to possible meningitis or an epidural abscess

128
Q

Why is severe hypovolemia an absolute contraindication to neuraxial anesthesia

A

There is a good chance the patient would not be able to tolerate the sympathectomy

129
Q

Why is coagulopathy an absolute contraindication for neuraxial anesthesia?

A

It could lead to possible epidural hematoma, which includes thrombocytopenia, or elevated PTT or PT/INR

130
Q

In OB, platelet counts > ____ are generally considered safe prior to neuraxial blockade

A

80,000-100,000

131
Q

Why are severe aortic stenosis and mitral stenosis absolute contraindications to neuraxial anesthesia?

A

Sympathectomy drops preload and afterload, and preload/afterload need to be maintained with stenosis

132
Q

Why is sepsis an absolute contraindication in neuraxial blocks?

A

Block placement can lead to possible meningitis and/or epidural abscess

133
Q

Why is elevated ICP an absolute contraindication to neuraxial blocks?

A

Pts with ICP cannot tolerate the sympathectomy because a high MAP is required to perfuse the head in patients with intracranial hypertension

134
Q

Relative contraindications to neuraxial anesthesia (4)

A
  1. Neurologic deficiencies
  2. Sepsis
  3. Previous back surgery
  4. Severe COPD
135
Q

Complications from neuraxial blocks (11)

A
  1. Pruritus
  2. Nausea & vomiting (from hypotension)
  3. Urinary retention
  4. Parasthesias
  5. Nerve/ spinal cord injury
  6. Backache
  7. PDPH
  8. Transient neurologic symptoms
  9. Cauda equina syndrome
  10. Epidural abscess
  11. Epidural hematoma
136
Q

Incidence of back pain following spinal anesthesia

A

25%

137
Q

Possible etiologies of back pain after spinal anesthesia

A
  1. Common backache from needle or lying flat
  2. Epidural abscess
  3. Epidural/spinal hematoma
  4. Transient neurologic symptoms
  5. Cauda equina syndrome
138
Q

Symptoms of epidural abscess

A

Takes days or weeks to develop

  1. Back pain intensified by spine percussion
  2. Signs of infection
  3. Sensory and motor deficits
139
Q

Diagnosis of epidural abscess

A

CT scan

140
Q

Treatment of epidural abscess

A

Surgical decompression via laminectomy

141
Q

Difference between epidural hematoma and epidural abscess

A
  1. Faster onset of hematoma
  2. White count is normal
  3. Hematoma requires immediate surgical evacuation
142
Q

Back pain without motor deficits

A

Transient neurologic symptoms (TNS)

143
Q

Treatment of TNS

A

Resolves on its own

144
Q

Cauda equina syndrome

A

back pain and motor deficits (paresis of the legs, bladder and bowel dysfunction)

145
Q

Etiology of TNS

A

Unclear, possibly lithotomy position, intrathecal vasoconstrictors, highly concentrated local anesthetics, spinal lidocaine

146
Q

Etiology of cauda equina syndrome

A

Nerve root and/or spinal cord trauma, highly concentrated spinal local anesthetics, and continuous spinal anesthesia through a microcatheter

147
Q

Patients who get a wet tap are up to 80% likely to get ____

A

a PDPH

148
Q

Protocol for PDPH

A
  1. Thread a catheter ~2cm intrathecally for continuous spinal anesthesia
  2. Remove the needle and start another epidural at higher dermatome level
149
Q

Symptoms of PDPH

A
  1. Headache pain that is bilateral, frontal, occipital, and extends into the neck
  2. Pain is aggravated by sitting or standing, and may last for weeks
150
Q

Incidence of post dural puncture headache decreases with ___

A

age

151
Q

Why is PDPH exacerbated by sitting and standing?

A

Venous return decreases in those positions, and decreased venous return engorges the epidural veins and drives more CSF out

152
Q

Treatment for PDPH

A
  1. Autologous blood patch (GOLD STANDARD)
  2. Analgesics, caffeine, steroids and generous fluid administration
  3. Neostigmine (0.02 mg/kg) and atropine (0.01mg/kg) combination
153
Q

When should blood patches be done for PDPH?

A

After all signs that the local anesthetic has worn off

154
Q

When is the neostigmine/atropine combo effective for PDPH?

A

After only 2 doses

155
Q

Advantages of regional anesthesia compared to GA

A
  1. Decreased anesthetic requirements (dec postop N/V)
  2. Decreased respiratory complications
  3. Decreased surgical blood loss
  4. Decreased incidence of thrombosis (due to dec platelet aggregation)
156
Q

Ester local anesthetics

A
  1. Tetracaine
  2. Chloroprocaine
  3. Cocaine
  4. Novocaine
157
Q

Ester metabolism

A

By plasma esterases and produce p-aminobenzoic acid (PABA) as byproduct

158
Q

Which local anesthetic is more likely to cause allergic reactions?

A

Esters due to PABA

159
Q

Amide local anesthetics

A
  1. Bupivicaine
  2. Ropivacaine
  3. Lidocaine
160
Q

Amide metabolism

A

Liver

161
Q

Why are local anesthetics without epi slightly acidic? (pH 6-7)

A

Acidity prolongs shelf life of the local anesthetic

162
Q

Why are local anesthetics with epi more acidic (pH 4-5)?

A

Epi is unstable in basic environments

163
Q

Longest acting spinal local anesthetic

A

Tetracaine (pontocaine)

164
Q

Epinephrine may prolong tetracaine spinal anesthesia by ___

A

40-60%

165
Q

Clonidine prolongs tetracaine spinal block by ___

A

50-70%

166
Q

Most common local anesthetic we use for spinal anesthesia

A

Spinal marcaine (0.75%)

167
Q

Duration of spinal marcaine

A

2 hours

168
Q

Local that’s ability for duration to be prolonged is LEAST affected by epinephrine

A

Marcaine

169
Q

Should only be considered if the procedure were very short and the anesthetist wanted the spinal to wear off as fast as possible

A

Spinal lidocaine (5%)

170
Q

Why is spinal lidocaine not commonly used for spinal anesthesia?

A

Intrathecal use has been associated with transient neurologic symptoms and cauda equina syndrome

171
Q

Contraindicated drug for intrathecal use

A

Chloroprocaine

172
Q

Most common local anesthetics for labor epidural dosing

A
  1. Marcaine
  2. Ropivacaine
  3. Lidocaine
  4. Chloroprocaine
173
Q

Advantages of epidural marcaine

A
  1. Motor sparing (does not block motor nerves as well)

2. Longest lasting

174
Q

Most common local anesthetic for labor epidurals

A

Marcaine

175
Q

Disadvantages of epidural marcaine

A
  1. Less effective at blocking the larger sacral nerves
  2. Slowest onset of all commonly used local anesthetics
  3. Very cardiotoxic
176
Q

Why do marcaine epidurals have a higher chance of losing their effectiveness during stage II labor?

A

The fetal head is pressing on the pelvis/sacral nerves during stage II labor

177
Q

Toxic dose of marcaine

A

2.5 mg/kg w/o epi

3mg/kg w/epi

178
Q

Bupivacaine toxicity treatment

A
  1. CPR

2. Intralipid 20%

179
Q

Implications of epidural ropivacaine

A
  1. Similar pharmacology to marcaine with similar results
  2. Less cardiotoxic, but more expensive than marcaine
  3. Max recommended dose of ropivacaine is 3mg/kg
180
Q

Advantages of epidural lidocaine

A
  1. More effective at blocking the larger sacral nerves

2. relatively fast onset

181
Q

Disadvantages of epidural lidocaine

A
  1. More significant motor blockade than marcaine

2. Toxic dose causes neurologic symptoms (confusion, tinnitus, oral numbness, seizures)

182
Q

Epidural drug more likely to inhibit parturient from pushing effectively during delivery

A

Lidocaine due to motor blockade

183
Q

Toxic dose of epidural lidocaine

A

4mg/kg w/o epi

7mg/kg w/epi

184
Q

Advantages of epidural chloroprocaine

A
  1. Fastest epidural onset

2. Minimal drug transfer across the placenta

185
Q

What causes rapid onset of epidural chloroprocaine?

A

Psuedocholinesterase metabolism

186
Q

Perfect choice for bolusing an epidural for emergency C-section

A

Chloroprocaine

187
Q

Disadvantage of epidural chloroprocaine

A
  1. Produces the highest degree of motor block

2. Has the shortest duration

188
Q

When are epidurals bolused instead of infused?

A
  1. Initial test dose
  2. Loading dose
  3. Dose to increase block intensity
  4. Raising block to T4 gradually
  5. Raising block to T4 level immediately
189
Q

What should you do prior to bolusing an epidural?

A
  1. Verify the patient is stable

2. Aspirate to rule out intravascular or intrathecal injection

190
Q

Signs of intravascular injection

A
  1. Fast heart rate
  2. Tinnitus
  3. Oral/tongue numbness
191
Q

Signs of intrathecal injection

A

Immediate numbing of the legs

192
Q

Why should a patient be monitored for 10 minutes after every epidural bolus?

A

To ensure stable BP because the pt can have sympathectomy and subsequent hypotension

193
Q

What is an initial epidural test dose?

A

5mL dose of 1.5% lidocaine with 1:200,000 epi right after the epidural is placed

194
Q

How is accidental IV injection ruled out with the epidural test dose?

A

In the absence of:

  1. Tachycardia (from the epi)
  2. Mouth/tongue numbness, or a metallic taste in the mouth (from the lido)
  3. Ringing in the ears
195
Q

How do you rule out accidental intrathecal injection from an epidural test dose?

A

If there is no gradual onset of numbness

196
Q

What is the epidural loading dose?

A

5 mL of marcaine or ropivacaine right after the initial 5mL test dose is given

197
Q

Advantage of the epidural loading dose

A

It speeds up the onset of the block

198
Q

Disadvantage of the loading dose

A

It can raise the level of the block above T10 and make a sympathectomy much more likely

199
Q

What can you do if there is a patchy block?

A

Dose ~5mL of local (2% lidocaine)

200
Q

When would you need to gradually raise the level of the epidural block to T4?

A

For a non-emergent C-section

201
Q

How do you gradually raise the epidural block?

A
  1. Give an initial 10 mL of local anesthestic, wait 3 min, check the dermatome level
  2. Give an additional 5mL of local
  3. Give a final 5 mL of local (for total of 20 mL) if block is not high enough
202
Q

When is the risk of high block and hypotension increased?

A

If the local anesthetic is bolused too fast

203
Q

What happens if you wait too long in between epidural boluses?

A

The block density will increase, but the block will not rise

204
Q

When raising an epidural block from T10 to T4, the local anesthetic of choice is probably

A

Lidocaine

205
Q

How do you raise the epidural block level immediately?

A

Bolus 20 mL of epidural anesthetic all at once

206
Q

Best choice of local anesthetic for emergency C-sections

A

20 mL of 3% chloroprocaine (600mg)

207
Q

Common preservatives in local anesthetics

A
  1. Sulfites
  2. Parabens
  3. EDTA
208
Q

True/false. A single dose vial contains preservatives

A

False

209
Q

Bacteriostatic preservative in multidose vials of local anesthetics that can cause anaphylactoid symptoms

A

Methylparaben

210
Q

Preservatives contraindicated for both epidural and intrathecal administration

A

Methylparaben

211
Q

Preservative used for epidural use, but not spinal use

A

Sulfite

212
Q

Purpose of sulfites

A

To prevent degradation of epinephrine in an alkaline pH

213
Q

Preservative used to prolong shelf life and enable manufacturer to autoclave to sterilize the vial

A

EDTA

214
Q

Large volumes of epidurally injected local anesthestic with EDTA has been associated with

A

Severe pain at the injection site

215
Q

Even though chloroprocaine is now EDTA free, it is still contraindicated for

A

Spinal use

216
Q

Preservatives associated with neurotoxicity

A

Sulfites and parabens

217
Q

Added to lidocaine or chloroprocaine to speed up the onset when bolusing

A

Bicarb

218
Q

When would you most want to bring the drug closer to its pKa when bolusing?

A

When raising the block level from T10 to T4

219
Q

Disadvantage to bicarb

A

Causes the local anesthetic to precipitate within 6 hours

220
Q

Purpose of alpha agonists with neuraxial anesthesia

A
  1. Prolongs block duration
  2. Limits toxic side effects
  3. Enhances analgesic quality
221
Q

Why does epinephrine have the least effect on the duration of bupivacaine?

A

It is highly lipid soluble

222
Q

What is significant about epinephrine with tetracaine

A

Tetracaine is highly lipid soluble (higher than bupivacaine) but epi has the greatest effect on the duration

223
Q

Associated with greater decrease in BP and can prolong block duration when administered orally

A

Clonidine

224
Q

Morphine without preservatives

A

Duramorph

225
Q

Carries a higher risk of urinary retention when compared to fentanyl

A

Morphine

226
Q

Causes more respiratory depression in fetus than fentanyl

A

Morphine

227
Q

Advantages of neuraxial opioids

A
  1. Analgesia
  2. No motor blockade
  3. No sympathectomy
228
Q

Disadvantages of neuraxial opioids

A
  1. Pruritus
  2. Delayed respiratory depression
  3. Nausea/vomiting
229
Q

Most common complication of neuraxial narcotics

A

Pruritus

230
Q

When is delayed respiratory depression more likely to occur with neuraxial opioids?

A

Following intrathecal morphine than intrathecal fentanyl because morphine is less lipid soluble than fentanyl

231
Q

What is significant about spinal dosing of opioids?

A

Narcotics should NOT be added to the spinal if the procedure is outpatient due to risk of respiratory depression

232
Q

Significance of intrathecal dexmedetomidine

A

Similar analgesia and less pruritus and shivering compared with morphine

233
Q

What determines the form the drug takes on?

A
  1. pH of the environment the drug is placed in

2. The drug’s pKa

234
Q

The more polar/charged the drug is, the (slower/faster) the onset

A

The slower the onset

235
Q

The more nonpolar/non-ionized a drug is, the (slower/faster) the onset

A

Faster

236
Q

If we can get a drug to be 50% ionized, it will have the (slowest/fastest) onset possible

A

Fastest

237
Q

If an acidic drug is placed in a basic environment, it will become (positively, negatively, neutrally) charged

A

Negatively

238
Q

If a basic drug is placed in an acidic environment, it will become (positively, negatively, neutrally) charged

A

Positively

239
Q

What is ideal pH for a drug?

A

The pH of the drug’s environment that will result in 50% ionizations and 50% nonionization which leads to the highest nonpolar portion possible (pKa)

240
Q

Acidic drugs have a (high/low) pKa

A

Low

241
Q

Basic drugs have a (high/low) pKa

A

High

242
Q

It takes a basic environment to prevent a (acidic/basic) drug from becoming positively charged

A

Basic

243
Q

Local anesthetic drugs are (acidic/basic)

A

Basic

244
Q

Local anesthetic solutions are (acidic/basic)

A

Acidic

245
Q

Why is adding acid to local anesthetics good and bad?

A

Good: prolongs shelf life
Bad: Slows down onset by leading to higher portion of ionized/positively charged drugs

246
Q

How can you speed up the onset of local anesthetics?

A

Add bicarb

247
Q

The pH of a drug solution is 4.5. The pKa of a drug is 10.7. Adjusting the pH of the drug to ___ will result in the fastest onset

A

10.7

248
Q

True/false. A drug solution has a pH of 6.5 and a pKa of 5.5. Adjusting the pH of the drug closer to physiologic pH will speed up drug onset

A

False

249
Q

Factors that determine local anesthetic onset

A
  1. How ionized the anesthetic is
  2. How close the local anesthetic’s pH is to the pKa (the closer, the faster)
  3. How close the local’s pKa is to physiologic pH (the closer, the faster)
  4. How lipid soluble the local is
250
Q

Higher lipid solubility for local anesthetics = (slower/faster) onset and (shorter/longer) duration

A

Slower onset, longer duration

251
Q

Higher lipid solubility for other drugs = (slower/faster) onset and (shorter/longer) duration

A

Faster onset and shorter duration

252
Q

Factors that determine local anesthetic potency

A
  1. How concentrated the local anesthetic is (more concentrated = more potent)
  2. How lipid soluble the local is (more potent = more lipid soluble)
  3. The total dose (higher dose = more potent)

Methods of Anesthesia (20 decks)

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