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Anesthesiology > Regional and Neuraxial Anesthesia > Flashcards

Regional and Neuraxial Anesthesia Flashcards

1
Q

Anterior or posterior nerve roots carry sympathetic outflow? Motor outflow?

A

SNS: Anterior
Motor: Anterior

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2
Q

Where do you expect the C8 dermatome to include?

A

The 5th finger and medial aspect of the arm

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3
Q

A-alpha nerve fibers are responsible for what? Are they large or small and myelinated or unmyelinated?

A

Motor (thick myelinated)

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4
Q

A-delta nerve fibers are responsible for what? Are they large or small and myelinated or unmyelinated?

A

Pain & temperature (thin myelinated)

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5
Q

C nerve fibers are responsible for what? Are they large or small and myelinated or unmyelinated?

A

Pain & temp (small, unmyelinated)

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6
Q

Why do you have differential blockade with spinal anesthesia when using a hyperbaric spinal anesthetic?

A

Local anesthetic concentration in the intrathecal space at more cephalad levels are lower than in the caudal levels

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7
Q

Where does the sympathetic chain run?

A

T1-L2

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8
Q

Where does the parasympathetic chain run?

A

CN III, VII, IX, X, S2-S4

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9
Q

Why would a patient develop cardiac arrest after neuraxial block?

A

Unopposed vagal influence on the heart

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10
Q

Why would a patient with severe aortic stenosis die after spinal anesthesia?

A

In patients with AS, LVEDP is high -> spinal anesthesia decreases preload and afterload -> decreased aortic diastolic pressure results in decreased LV perfusion -> MI

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11
Q

How does spinal anesthesia affect inspiratory and expiratory mechanics?

A

Decreased both (intercostal and abdominal muscles) -> decreases pulmonary reserve

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12
Q

What do local anesthetics bind to?

A

Intracellular side of the alpha subunit of voltage gated sodium channels during the inactivated or activated states (not resting state)

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13
Q

What does pKa determine for local anesthetics?

A

Onset of action (although concentration and environmental pH also plays a role)

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14
Q

What determines potency of a local anesthetic?

A

Lipid solubility

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15
Q

What determines duration of action of anesthetics?

A

Protein binding, larger doses (longer duration), vasodilatory activity (more vasodilatory = shorter duration i.e. lidocaine)

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16
Q

Rate the following in highest rate of absorption to lowest: IV, caudal, brachial plexus, sciatic, subQ, tracheal, intercostal, paracervical, epidural

A

IV > tracheal > intercostal > caudal > paracervical > epidural > brachial plexus > sciatic (peripheral nerve) > subQ

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17
Q

What kind of local anesthetic was probably used if a patient has an allergic reaction and what compound is it mostly due to?

A

Esters because of PABA formation after metabolism; although some amides contain preservatives (methylparaben) which can also cause an allergic reaction

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18
Q

How are ester local anesthetics metabolized?

A

Metabolized by pseudocholinesterases

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19
Q

What local anesthetic can cause methemoglobinemia?

A

Benzocaine (independent of metabolism?) and prilocaine (metabolized to O-toluidine derivatives which oxidizes iron to the ferric state)

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20
Q

How are amide local anesthetics metabolized?

A

Liver

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21
Q

What is transient neurologic symptoms and what local anesthetic is classic for it?

A

Radicular irritation after spinal anesthesia (i.e. burning and aching in buttocks and lower extremities with NO loss of sensation or motor function); Lidocaine

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22
Q

Intravascular bupivacaine or ropivacaine injections require what treatment?

A

Intralipids; other local anesthetics are less protein bound and are less responsive to intralipids

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23
Q

How long do you need to wait to give a single shot spinal/epidural in patients with once daily lovenox? Twice daily lovenox? When can you restart the lovenox?

A

Once: 12 hours after last dose and restart 6 hours after block
Twice: 24 hours after last dose, and restart 24 hours after block

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24
Q

When can you place an epidural catheter with a patient on lovenox for DVT ppx? When can you remove an epidural catheter? When can you restart lovenox after catheter is in? After catheter is removed?

A

Placement: 12 hours after last dose
Restart: 6-8 hours after catheter placed
Remove: 12 hours after last dose
Restart: 2 hours after catheter removed

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25
Q

How long should clopidogrel be stopped before an epidural is placed?

A

7 days

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26
Q

What INR and aPTT is the cutoff for epidural placement?

A

INR should be less than 1.5

aPTT less than 40

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27
Q

How long do you need to wait for epidural placement in a patient with heparin ppx? When can you restart the heparin?

A

Placement: Anytime; if more than ppx dosing, check aPTT and it should be less than 40
Can restart after 1 hour after catheter placement

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28
Q

The inferior tip of the scapula correlates to what vertebral level? Prominent cervical thoracic process? Superior iliac crest? Posterior superior iliac spine?

A
  1. T7
  2. C7
  3. L4
  4. S2
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29
Q

If a patient is given a hyperbaric lidocaine spinal injection and laid supine, what spinal level would the block travel caudally?

A

T6 (normal kyphosis of the back in the supine patients limit the movement to this level)

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30
Q

Is obesity associated with higher spinal blocks?

A

No

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31
Q

What does adding fentanyl to spinal anesthesia with bupivacaine do for you?

A

Intensifies the sensory blockade and allows for faster onset of anesthesia

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32
Q

How do intrathecal fentanyl and morphine differ?

A

Fentanyl: lipophilic + limited dural crossing and shorter lifespan in CSF + little cephalad spread + early respiratory depression only (within 30 min)
Morphine: hydrophilic + crosses dura slower and longer lifespan in CSF + lots of cephalad spread + 2 respiratory depressions (early and late)

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33
Q

Is pruritis worse with IV or intrathecal administration of opioids?

A

Intrathecal

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34
Q

Which opioids are more prone to cause urinary retention?

A

The more lipophilic the drug, the less likely it will cause urinary retention (morphine > fentanyl)

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35
Q

What cardiovascular effects do you see with meperidine?

A
  1. Atropine-like structure -> increased HR
  2. Cardiac depressant effects
  3. Local anesthetic properties
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36
Q

Intrathecal opioid leads to itching… which would be least effective in treating: ondansetron, propofol, diphenhydramine, naloxone, nalbuphine

A

Diphenhydramine (intrathecal opioid mediated itching is a central mechanism and does not involve histamine release)

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37
Q

Does the addition of epinephrine increase the density of the block?

A

No, only prolongs the duration of action

38
Q

Which local anesthetic can interfere with epidural opioid mediated analgesia?

A

Chloroprocaine

39
Q

Large nerve roots of L5-S2 are responsible for what phenomenon?

A

Sacral sparing in epidural anesthesia

40
Q

What is the greatest risk factor for development of an epidural hematoma: experience, diabetes, not using cap and mask, betadine instead of chlorhexidine, placement of a catheter vs. single shot

A

Catheter placements

41
Q

After a 2cc bupivacaine injection for interscalene block, patient develops a tonic-clonic seizure. Why?

A

Vertebral artery injection (100% of LA goes to the brain)

42
Q

After a 2cc bupivacaine injection for interscalene block, the patient develops Horner’s syndrome. Why?

A

Stellate ganglion block, injecting just off of Chassaignac’s tubercle (C6)

43
Q

What nerve does an interscalene block sometimes miss?

A

Ulnar (C8 & T1)

44
Q

Supraclavicular vs. interscalane, which is better at blocking the ulnar nerve?

A

Supraclavicular

45
Q

Which block has the highest incidence of chylothorax?

A

Infraclavicular

46
Q

Axillary approach for brachial plexus block misses what nerve?

A

Musculocutaneous: lateral forearm coverage

47
Q

How are the nerves oriented around the axillary artery for an axillary nerve block?

A

Medial: superior lateral
Ulnar: superior medial
Radial: deep to the artery

48
Q

What nerve is injured in a wrist drop?

A

Radial nerve (wrist extension)

49
Q

What nerve is responsible for wrist flexion?

A

Median nerve

50
Q

What nerve is responsible for pinching?

A

Ulnar nerve

51
Q

For a 3-in-1 nerve block, what nerves are usually blocked and what do they innervate?

A

Femoral nerve (medial thigh), obturator (medial knee), lateral femoral cutaneous (lateral aspect of thigh), genitofemoral

52
Q

What nerve is missed with a popliteal block for ankle surgery?

A

Saphenous nerve (medial malleolus); need to perform a femoral nerve block

53
Q

What nerve is missed following ankle block if patient has sensation over lateral heel and malleolus?

A

Sural nerve

54
Q

What is the order in terms of loss of conductivity after spinal anesthesia?

A
  1. SNS and PSNS
  2. Sensation (C fibers first)
  3. Motor (A-alpha)
55
Q

What levels do you have blockade of dermatomes and blockade of motors?

A

Pain and temperature is lost 2 dermatomes above the level; motor is lost 2 dermatomes below the level

56
Q

Benefits of spinal/epidural anesthesia over GETA?

A
  1. Decreased hypercoagulable state
  2. Increased tissue blood flow (vasodilation)
  3. Increased oxygenation (normal ventilation)
  4. Increased peristalsis (lower dose of opioids)
  5. Decreased stress response (sympathectomy)
57
Q

Average duration of action of each local anesthetic intrathecally: Bupivacaine, Ropicavaine,Tetracaine, Procaine, Lidocaine

A 
Bupi: 90-120 min (100-150 with epi)
Ropi: 90-120 min (100-150 with epi)
Tetracaine: 90-120 min (120-240 with epi)
Procaine: 45 min (60 min with epi)
Lidocaine: 60 min (90 min with epi)
58
Q

Most important factors for spinal anesthesia?

A
  1. Baricity
  2. Patient position during and after injection
  3. Drug dose
59
Q

Why do we not use lidocaine anymore with spinal anesthesia?

A

Risk of transient neurologic symptoms and cauda equina syndrome

60
Q

What sensory level loss has a higher risk of bradycardia?

A

Sensory level above T6

61
Q

How big is the epidural space in the lumbar, thoracic and cervical spine?

A

Lumbar: 5-6mm
Thoracic: 3-5mm
Cervical: 2mm

62
Q

What is a rough estimate for how much local anesthetic needs to be administered for an epidural?

A

1 cc of local anesthetic per segment blocked

63
Q

What segment level is associated with the following cutaneous landmarks: perineum, lateral aspect of foot, umbilicus, tip of xiphoid, nipple line, 5th finger

A
  1. S2-S4
  2. S1
  3. T10
  4. T6
  5. T4
  6. C8
64
Q

What is the fastest acting but shortest duration local anesthetic for an epidural?

A

Chloroprocaine (2-3%)

65
Q

How early do you need to stop ASA or NSAIDs before an epidural?

A

No contraindication

66
Q

What changes in a local anesthetic solution when you add epi?

A

The pH decreases (more acidic)

67
Q

What condition would greatly increase the half life of lidocaine?

A

Liver cirrhosis

68
Q

Which amide local anesthetic is the least toxic and why?

A

Prilocaine: extrahepatic metabolism and mostly topical use

69
Q

What is the max dose of the following ester local anesthetics: chloroprocaine, procaine, cocaine, tetracaine

A

Chloroprocaine: 12 mg/kg
Procaine: 12 mg/kg
Cocaine: 3 mg/kg
Tetracaine: 3 mg/kg

70
Q

What is the max dose of the following amide local anesthetics: lidocaine, mepivicaine, prilocaine, bupivacaine, ropivacaine

A 
Lidocaine: 5 mg/kg (7 with epi)
Mepivicaine: 5 mg/kg (7 with epi)
Prilocaine: 8 mg/kg
Bupivicaine: 3 mg/kg
Ropivicaine: 3 mg/kg
71
Q

What is a possible complication from liposuction procedures?

A

Since they use a max of 55 mg/kg of local anesthetic (lidocaine), sometimes you can have a large accumulation of LA in the adipose tissues that causes toxicity to occur 6-12 hours after the procedure

72
Q

What toxicity can happen with the preservative sulfite in local anesthetic preparations? EDTA? Methylparaben?

A

Sulfites: anaphylactoid reactions, arachnoiditis
EDTA: low back pain at epidural injection site
Methylparaben: anaphylactoid reactions

73
Q

What is the preservative in 2-chloroprocaine and what can it cause?

A

Sodium bisulfite; can lead to arachnoiditis

74
Q

What is the maximum recommended dose of cocaine?

A

1-3 mg/kg

75
Q

What does adding sodium bicarbonate to lidocaine do?

A

Decreases the pain on subcutaneous infiltration
It also causes more non-ionized forms which results in faster diffusion of LA through cell membrane (unfortunately has conflicting data)

76
Q

How is remifentanil broken down?

A

Nonspecific blood and tissue esterases

77
Q

Is the response to epinephrine as a test dose different if the patient is awake or under GA?

A

Yes, BP and HR responses are reduced under GA

78
Q

What is the dose of intralipid for local anesthetic toxicity?

A

1 cc/kg bolus then infusion of 0.25 cc/kg/min for 10 min

79
Q

Which local anesthetics are in EMLA (eutectic mixture of local anesthetics) cream?

A

Lidocaine and prilocaine

80
Q

Is the S- or R- enantiomer of bupivacaine more cardiotoxic?

A

R-bupivacaine is more cardiotoxic (ropivacaine is actually the S-enantiomer)

81
Q

The pKa of mepivacaine is 7.6. At physiologic pH (7.4), what % of mepivacaine is in the uncharged (unionized) form? 39% or 61%?

A

pH = pKa + log (ionized/unionized)

  1. 6 = 7.4 + log (ionized/unionized)
  2. 2 = log (ionized/unionized) -> thus more ionized than unionized (39% to be exact)
82
Q

What is the advantage of mixing epinephrine to LA just before injection vs premixed epi-LA vials?

A

The premixed vials are acidic to ensure that epinephrine does not get degraded -> LA are mostly ionized -> slower onset of action; thus you get a faster block onset by mixing your own epi before use

83
Q

What proteins is bupivacaine primarily bound to in vivo?

A

Alpha-1-acid glycoproteins (AAG)

84
Q

Intrathecal microcatheters with continuous infusions of 5% lidocaine are associated with what complication?

A

Cauda equina syndrome

85
Q

What patient position puts them more at risk for transient neurologic symptoms after spinal injection of lidocaine?

A

Lithotomy

86
Q

Why would you administer IV lidocaine prior to succinylcholine?

A

Relaxes bronchial smooth muscles whereas succinylcholine only blocks skeletal muscles at the nicotinic receptor

87
Q

What is the mg/mL dose of 1% lidocaine? 0.5% bupivacaine?

A

1% lidocaine = 10 mg/mL

0.5% bupivacaine = 5 mg/mL

88
Q

What type of nerve fibers (large, small, myelinated, unmyelinated) are more resistant to local anesthetics?

A

Large myelinated neurons (A-alpha - motor) are most resistant, followed by smaller myelinated (A-delta - pain/temp), then small unmyelinated (C - pain/temp)

89
Q

After an accidental IV injection of 300 mg mepivacaine, the patient has a tonic-clonic seizure, what is the next best step: chest compressions, intralipids, ketamine, propofol, methohexital

A

Propofol to terminate seizures

Intralipids are good for bupivacaine and ropivacaine toxicity (highly protein bound)

90
Q

Does adding epinephrine affect the duration of action for ropivacaine? Bupivacaine? Tetracaine?

A

Does NOT affect ropivacaine or bupivacaine. It does increase the duration of action of tetracaine

91
Q

What patient characteristics affect local anesthetic spread in the subarachnoid space?

A
  1. Position during and after injection
  2. Height (taller = more)
  3. Spinal column anatomy
  4. Decreased CSF volume (pregnancy, ascites, increased age, etc)
92
Q

After an intercostal block, what would you worry about if the patient suddenly develops respiratory distress?

A
  1. Poor respiratory reserve (secondary to phrenic nerve block - 100% of the time)
  2. Pneumothorax

Anesthesiology (21 decks)

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