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Apex Review > Neuraxial blocks 3 > Flashcards

Neuraxial blocks 3 Flashcards

1
Q

_____ is the primary determinant of epidural block height

A

Volume

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2
Q

The initial dosing for epidural is

A

1-2 mL per segment to be blocked

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3
Q

The “top-up” dose for epidurals is

A

50-75% of the initial dose

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4
Q

A “top-up” dose should be administered

A

before the block recedes more than 2 dermatomes

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5
Q

The volume of the epidural space is smaller in the thoracic region when compared to the lumbar region. Therefore, for a given volume of local anesthetic, you’ll achieve ______ spread in the thoracic region as compared to the lumbar region.

A

Greater

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6
Q

________ is the primary determinant of epidural block density

A

Concentration

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7
Q

The following drugs can be used for epidural dosing

A

2-chloroprocaine 3%
lidocaine 2%
ropivacaine 0.1-0.75%
bupivacaine 0.0625-0.5%
levobupivacaine 0.0625-0.5%

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8
Q

Describe the onset of action for chloroprocaine, lidocaine, ropivacaine, bupivacaine, and levobupivacaine for epidural use.

A

2-chloroprocaine- 5-15 minutes
lidocaine- 10-20 minutes
ropivacaine, bupivacaine, and levobupivacaine 15- 20 minutes

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9
Q

Identify the MOST appropriate techniques for subarachnoid block in a patient scheduled for hemorrhoidectomy.
a. lidocaine 5% in 7.5% dextrose and the sitting position
b. bupivacaine 0.3% in water and the jackknife position
c. Tetracaine 0.2% in water and the sitting position
d. procaine 10% in water and the jackknife position

A

a & b.

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10
Q

______ describes the density of a local anesthetic solution relative to the CSF

A

Baricity

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11
Q

When injected inside the subarachnoid space, a hyperbaric solution will

A

sink

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12
Q

When injected inside the subarachnoid space, a hypobaric solution will

A

rise

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13
Q

When injected inside the subarachnoid space an isobaric solution

A

will remain in place

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14
Q

As a general rule, solutions in dextrose are______

A

hyperbaric

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15
Q

As a general rule, solutions in saline are _____

A

isobaric

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16
Q

As a general rule solutions in water are______

A

hypobaric

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17
Q

_________ is an exception to the general rules of baricity because it contains many molecules making it hyperbaric

A

Procaine 10% in water

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18
Q

If we are using a hyperbaric solution and we keep the patient in the sitting position after the block,

A

a hyperbaric solution will sink and anesthetize the sacral nerve roots causing a saddle block

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19
Q

If we lay a patient supine after a block with a hyperbaric solution, the solution will

A

slide down the lumbar lordosis and eventually pool in the sacrum and the thoracic kyphosis (pools low)

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20
Q

If we keep the patient in the sitting position after a hypobaric block, the solution will

A

rise towards the brain

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21
Q

How does neuraxial anesthesia affect respiratory mechanics?
a. impaired inspiration
b. impaired expiration
c. no impairment
d. impaired inspiration and expiration

A

D. - accessory muscle function is reduced by neuraxial blockade

22
Q

Systemic effects of neuraxial anesthesia to the cardiovascular system include

A

hypotension
vasodilation
variable effect on HR & CO
bradycardia

23
Q

How can neuraxial anesthesia result in bradycardia?

A

inhibition of cardioaccelerator fibers at T1-T4
unloading of ventricular mechanoreceptors–> Bezold-Jarisch reflex
unloading of the stretch receptors in the SA node

24
Q

What are the respiratory effects of neuraxial anesthesia.

A

in healthy patients has negligible effects on minute ventilation, tidal volume, RR, dead space, and arterial blood gas tension
accessory muscle function is reduced including impairment of the intercostal and abdominal muscles resulting in decreased pulmonary reserve

25
Q

Describe the CNS effects of neuraxial anesthesia

A

drowsiness

26
Q

Describe the neuroendocrine effects of neuraxial anesthesia

A

diminished sympathetic response to surgical stress

27
Q

Describe the gastrointestinal effects of spinal anesthesia

A

relaxation of sphincters and increased peristalsis

28
Q

Describe the effects to the kidney and liver when performing neuraxial anesthesia.

A

as long as systemic blood pressure is maintained, hepatic and renal blood flow and function are unchanged

29
Q

What spinal levels give rise to the cardioaccelerator fibers?

A

T1-T4

30
Q

What reflex contributes to asystole that occurs with spinal anesthesia?

A

Bezold-Jarisch reflex- the heart slows to allow it adequate time to fill

31
Q

How does a spinal to T4 affect minute ventilation in healthy patients?

A

it has a negligible effect

32
Q

What is the most likely cause of apnea due to spinal anesthesia

A

Brainstem hypoperfusion (not phrenic nerve paralysis or high concentrations of LA in the CSF

33
Q

When compared to intrathecal fentanyl, which findings are MORE likely with intrathecal morphine?
a. wider band of analgesia
b. increased risk of nausea
c. late respiratory depression
d. higher plasma concentration
e. faster onset
f. sympathectomy

A

A, B, C

34
Q

An opioid deposited into the intrathecal space can easily

A

diffuse into the spinal cord

35
Q

An opioid deposited into the epidural space must first diffuse across _________ before entering the CSF. Some of the drug also diffuses into the __________.

A

dural cuff; bloodstream

36
Q

Neuraxial opioids inhibit

A

afferent pain transmission in the substantia gelatinosa (lamina 2 of the dorsal horn)

37
Q

Neuraxial opioids do NOT cause:

A

sympathectomy, skeletal muscle weakness, changes in proprioception

38
Q

______ is the most lipophilic opioid, and _____ is the most hydrophilic opioid.

A

Sufentanil; morphine

39
Q

Key characteristics of lipophilic opioids include

A

a shorter duration of action, less spread in the CSF, and risk of early respiratory depression

40
Q

Key characteristics of hydrophilic opioids include

A

longer duration of action, greater spread in the CSF, and risk of early and late respiratory depression

41
Q

When combined with local anesthetics, ______ create a denser block

A

neuraxial opioids

42
Q

Identify the MOST common side effect of neuraxial opioid administration.
A. pruritus
B. respiratory depression
C. urinary retention
D. Nausea & vomiting

A

A. pruritus

43
Q

The four key side effects of neuraxial opioids include:

A

pruritus
respiratory depression
urinary retention
Nausea & vomiting

44
Q

Respiratory depression is more common with_______- in neuraxial opioid administration.

A

high opioid doses
co-administered sedatives
low lipid solubility (hydrophilic)
advanced age
opioid naivety
increased intrathoracic pressure

45
Q

__________ is most common in young males, and it’s more common with neuraxial opioids when compared to IV and IM administration.

A

Urinary retention

46
Q

_________ reduces the efficacy of epidural opioids.

A

2-Chloroprocaine

47
Q

Epidural morphine may _________ in obstetric and postpartum patients.

A

reactivate herpes simplex labialis

48
Q

Any opioid that enters the systemic circulation becomes available to

A

cross the placenta and enter the fetus

49
Q

When treating pruritus related to intrathecal injection of opioids, what medications should be given?

A

can be treated with an opioid antagonist such as naloxone
diphenhydramine doesn’t fix the cause, but its sedative effects may be beneficial

50
Q

Nausea and vomiting is caused by activation of the opioid receptors in the

A

area postrema of the medulla and vestibular appartus

51
Q

Transfer of opioids from the epidural space to breast milk is

A

minimal

52
Q

What is the mechanism of neuraxial opioid-induced urinary retention?

A

inhibition of sacral parasympathetic tone. this causes bladder detrusor muscle relaxation and urinary sphincter contraction

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