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2-General Anesthesia Exam 2 > Subarachnoid Blocks > Flashcards

Subarachnoid Blocks Flashcards

1
Q

What is the goal of needles?

A

to cause as little damage as possible

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2
Q

What are the types of needles for subarachnoid block needles?

A

Cutting and non-cutting needles

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3
Q

What are the types cutting needles for subarachnoid block needles?

A
  • Quincke-Babcock
  • Pitkin
  • Greene*
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4
Q

What are the types noncutting needles pencil point) for subarachnoid block needles?

A
  • Sprotte
  • Pencan
  • Whitacre
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5
Q

What is the gauge range for subarachnoid block needles?

A

22-29 (most commonly used 25-27g)

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6
Q

What is the length range for subarachnoid block needles?

A

from 3.5-5 inches (most commonly used 3.5 inches)

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7
Q

What are the two disadvantages to cutting needles?

A
  • Can pierce cauda equine roots without provider knowledge

- Increases risk of tip deviation after insertion

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8
Q

How must you hold a cutting needle?

A

Must remember to hold bevel lateral to dural tissue fibers to minimize risk of post-dural puncture headache, although rates of PDPH much higher with cutting needles overall

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9
Q

What are the characteristics of subarachnoid cutting needles?

A
  • Less able to appreciate entry into dura

- May introduce skin contaminants into subdermal tissue

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10
Q

What are the two positioning strategies for subarachnoid blocks?

A

Lateral decubitus and sitting position

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11
Q

What are the two approaches for a subarachnoid block?

A

midline & the paramedian approach

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12
Q

What are the layers of anatomy that must be transversed posterior to anterior when placing a midline subarachnoid block?

A 
Skin
Subcutaneous fat
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Dura mater
Subdural space
Arachnoid mater
Subarachnoid space
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13
Q

What are the layers of anatomy that must be transversed posterior to anterior when placing a paramedian approach subarachnoid block?

A 
Skin
Subcutaneous fat
Paraspinous muscle
Ligamentum flavum
Dura mater
Subdural space
Arachnoid mater
Subarachnoid space
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14
Q

What is the paramedian approach subarachnoid block?

A

the needle tip is directed toward the spinal canal 1 cm lateral to the caudal aspect of the interspace

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15
Q

What determines the distribution of medications administered in the subarachnoid block?

A

distribution is determined by the chemical and physical characteristics of the solution in relation to the chemical and physical characteristics of the patient’s CSF and subarachnoid space

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16
Q

What is another term for subarachnoid block?

A

Intrathecal

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17
Q

What is the normal daily production and pressure of CSF?

A
  • 500ml of CSF produced daily by the choroid plexuses in adults
  • Normal CSF pressure is 10-20 cmH20
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18
Q

What is the specific gravity of CSF?

A

1.004-1.009

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19
Q

What is the CSF specific gravity dependent on?

A

Varies based on temperature (increase temp = decrease specific gravity) and location of fluid

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20
Q

What is the decease in specific gravity from a degree rise in temp by Celsius

A

Decreases ~0.001

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21
Q

What happens to the specific gravity with increases in age?

A

Increases as age increases

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22
Q

What effect does hyperglycemia and uremia have on specific gravity of CSF?

A

Hyperglycemia and uremia increase specific gravity

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23
Q

What effect does Jaundice and liver issues have on specific gravity of CSF?

A

decrease specific gravity

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24
Q

What is true about the local anesthetics solutions administered by the intrathecal or epidural route?

A

must be sterile and preservative free

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25
Q

What is baricity?

A

The resting position of two fluids with differing specific gravities when the fluids are mixed in a single container (e.g. CSF and LA in subarachnoid space)

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26
Q

What is the baricity compared to?

A

Baricity of the injected solution is compared with that of the CSF

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27
Q

What are the characteristics of isobaric?

A
  • The ratio of the specific gravity of a local anesthetic to the patients CSF equals 1
  • E.g. Dissolve drugs in normal saline
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28
Q

What are the characteristics of hyperbaric?

A
  • The solution falls or sinks
  • Baricity >1.0015
  • E.g. Dissolve drug in 5-8% dextrose
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29
Q

Define hyperbaric.

A

Local anesthetic has a greater specific gravity than CSF

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30
Q

Define hypobaric.

A

Local anesthetic has a lower specific gravity than CSF

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31
Q

What are the characteristics of hypobaric?

A
  • The solution floats
  • Baricity <0.999
  • E.g. Dissolve drug in sterile water
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32
Q

What are the primary factors that affect local anesthetic spread in the CSF?

A
  • Total dose of local anesthetic
  • Site of injection
  • Baricity of the drug (drug choice)
  • Position or posture of the patient (especially when nonisobaric solutions are used
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33
Q

What is duration?

A

primarily a factor of choice of local anesthetic and total dose

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34
Q

What is true about the duraction of highly protein bound medications?

A

(tetracaine, bupivacaine, ropivicaine) have longer durations of action

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35
Q

What can be added to prolong the effects of the medications?

A

Vasoconstrictors

36
Q

What is the typical vasoconstrictor used?

A

Epi 0.1-0.2mL of 1:1000 (1mg/ml)

  • Delays normal uptake of local anesthetics
  • Tetracaine>lidocaine>bupivacaine
37
Q

What is an alternative medication that can be used to prolong duration of intrathecal medications?

A

Can include preservative free opioids or alpha 2 adrenergic agonists to potentially increase duration

38
Q

What is another component that effects the duration of the local?

A

Patient positioning and/or body habitus

39
Q

Review table

A

Nagelhaut 49.3

40
Q

Review table

A

Flood Table 10.3

41
Q

What is continuous SAB?

A

Catheter inserted into subarachnoid space approximately 2-3cm

42
Q

What is continous SAB implicated with?

A

Implicated with cauda equina syndrome with 5% lidocaine

43
Q

What can lidocaine also cause?

A

implicated in causing transient neurologic syndrome (especially 5% solution)

44
Q

What is a symptom of transient neurologic syndrome (especially 5% solution)?

A

Pain originating in the gluteal region then radiating to both lower extremities

45
Q

What is the onset of transient neurologic syndrome (especially 5% solution)?

A

a few hours, up to 24 hours

46
Q

What is the resolution of transient neurologic syndrome (especially 5% solution)?

A

~10days

47
Q

What can be used to treat What is the resolution of transient neurologic syndrome (especially 5% solution)?

A

NSAIDs, opioids, etc.

48
Q

Permanent neurologic injury after spinal or epidural is _______

A

thankfully rare

49
Q

What is transient neurologic symptoms?

A

Moderate to severe pain in lower back, buttocks, posterior thighs 6-36 hrs after complete recovery of spinal anesthetic. Recovery usually takes 1-7 days. )5% lidocaine spinal implicated)

50
Q

What is cauda equina syndrome?

A

Diffuse injury across lumbar-sacral plexus resulting in bladder and bowel dysfunction with bilateral lower extremity sensory and motor impairment (can be permanent).

51
Q

What is a predisposing factor to cauda equina syndrome?

A

Spinal stenosis and lumbar disc herniation/issues may be predisposing factors. (Lidocaine, micro spinal catheters, +/- positioning)

52
Q

What is anterior spinal artery syndrome?

A

Transient. Spasm or thrombosis of anterior spinal artery. Complete paralysis below point of injury. (elderly, peripheral vascular dz, +/- vasoconstrictor use)

53
Q

Where is a high block located?

A

T1-T4

54
Q

What is blocked in a high block? What is a result?

A
  • Sympathetic nerve fibers that innervate the heart are blocked
  • Cardiac accelerators
  • Loss of normal cardiovascular homeostatic reflexes and the ability to compensate for minor cardiovascular stresses
55
Q

What is another side effect of subarachnoid block?

A

Hypotension +/- bradycardia

56
Q

What is a treatment for Hypotension +/- bradycardia

from a SAB?

A

Crystalloids/colloids – 15ml/kg 15 minutes before SAB (or during)

57
Q

What vasproessor agents can be used for Hypotension +/- bradycardia
from a SAB?

A

Ephedrine 5-10mg in bradycardic patients or phenylepherine 50-100mcg in patients with a normal heart rate

58
Q

What could be given before SAB to help decrease the risk of Hypotension +/- bradycardia
from a SAB?

A

Serotonin antagonists – E.g. Zofran 4-8mg immediately before SAB. Thought to block the reflexive decrease in HR caused by the sympathectomy from the SAB

59
Q

What needs to be taken account with hypotension +/- bradycardia?

A

Positioning

60
Q

What is respiratory compromise of SAB?

A

Accessory abdominal and intercostal muscle can become compromised and ability to cough and clear secretions can become inhibited

61
Q

What is a side effect of respiratory compromise?

A

Patient may feel dyspneic

62
Q

What is some side effects of SAB?

A

Nausea, Neurologic risk (e.g. paralysis)

63
Q

What is the 3 unexpected cardiac effects of SAB?

A
  • Pacemaker stretch – decrease venous return leads to decrease stretch and lower heart rate
  • Low pressure baroreceptors in the right atrium and vena cava
  • Paradoxical Bezold-Jarisch reflex - mechanoreceptors in the left ventricle are stimulated and cause bradycardia
64
Q

What is the incidence of post dural puncture headache (PDPH)?

A

0.2-24%

65
Q

What caused the post dural puncture headache?

A

Caused by a decrease in CSF available in the subarachnoid space from a leak created by the dural puncture

66
Q

What happens to the medulla and the brainstem in the post dural puncture headache (PDHD)?

A

lose hydraulic support, drop into foramen magnum, stretch the meninges and pull on the tentorium

67
Q

What are some factors that increase the incidence of post dural puncture headache?

A
  • Use of large, non pencil point needles
  • Use of cutting needles with a bevel direction that is perpendicular to the long axis of the body
  • Multiple punctures
  • Female gender
  • Age
68
Q

The incidence is less than 1% following a subarachnoid block performed with a ________

A

25-gauge spinal needle

69
Q

This increases to nearly 36% when using a _______ or ______needle for diagnostic lumbar puncture

A

20-gauge or 22-gauge

70
Q

Following inadvertent puncture of the dura with a 17-gaugeepidural needle, the incidence of PDPH is approximately _______________

A

75% to 80%

71
Q

What are the ages that make post dural puncture headache (PDHD)?

A
  • Less common >60 years of age

- More prevalent <40 years of age

72
Q

What are some associated side effects of post dural puncture headache?

A
  • Nausea and vomiting
  • Appetite loss
  • Blurred vision or photophobia
  • Loss of hearing / tinnitus / vertigo
73
Q

When can a post dural puncture headache occur?

A

Usually occurs within several hours to the first or second postoperative day

74
Q

What is the location of the post dural puncture headache?

A

Mild to incapacitating bilateral frontal headache

75
Q

Where does the pain radiate in the post dural puncture headache?

A

Radiates from behind the eyes and across the head toward the occiput and into the neck and shoulders

76
Q

What position is a post dural puncture headache?

A

headache is relieved when laying flat

77
Q

When does a post dural puncture headache resolve?

A

Typically self limiting and resolves within 10 days

78
Q

What is the conservative treatment for the post dural puncture headache?

A

-Horizontal position, hydration, oral analgesics, 500mg IV caffeine benzoate, 300mg of oral caffeine or theophylline

79
Q

-Caffeine and theophylline are both _________ derivatives that cause cerebral vasoconstriction

A

methylxanthine

80
Q

What is the IV dose for caffeine of post dural puncture headache?

A

500mg IV caffeine benzoate

81
Q

What is the PO dose for caffeine of post dural puncture headache?

A

300mg of oral caffeine

82
Q

What is the definitive treatment for post dural puncture headache?

A

Epidural blood patch, Associated with a 90% cure rate

83
Q

What is the goal of the post dural puncture headache blood patch?

A

Clot formation seals the dural rent and increases CSF pressure

84
Q

What is the technique for epidural blood patch?

A

Involves injecting 12-15ml of autologous blood at or below the level of the lowest initial needle insertion

85
Q

Epidural blood patch: blood travels in a ________ direction in the epidural space

A

cephalad

2-General Anesthesia Exam 2 (11 decks)

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