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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
What is baricity?
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)
26
What is the baricity compared to?
Baricity of the injected solution is compared with that of the CSF
27
What are the characteristics of isobaric?
- The ratio of the specific gravity of a local anesthetic to the patients CSF equals 1 - E.g. Dissolve drugs in normal saline
28
What are the characteristics of hyperbaric?
- The solution falls or sinks - Baricity >1.0015 - E.g. Dissolve drug in 5-8% dextrose
29
Define hyperbaric.
Local anesthetic has a greater specific gravity than CSF
30
Define hypobaric.
Local anesthetic has a lower specific gravity than CSF
31
What are the characteristics of hypobaric?
- The solution floats - Baricity <0.999 - E.g. Dissolve drug in sterile water
32
What are the primary factors that affect local anesthetic spread in the CSF?
- 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
33
What is duration?
primarily a factor of choice of local anesthetic and total dose
34
What is true about the duraction of highly protein bound medications?
(tetracaine, bupivacaine, ropivicaine) have longer durations of action
35
What can be added to prolong the effects of the medications?
Vasoconstrictors
36
What is the typical vasoconstrictor used?
Epi 0.1-0.2mL of 1:1000 (1mg/ml) - Delays normal uptake of local anesthetics - Tetracaine>lidocaine>bupivacaine
37
What is an alternative medication that can be used to prolong duration of intrathecal medications?
Can include preservative free opioids or alpha 2 adrenergic agonists to potentially increase duration
38
What is another component that effects the duration of the local?
Patient positioning and/or body habitus
39
Review table
Nagelhaut 49.3
40
Review table
Flood Table 10.3
41
What is continuous SAB?
Catheter inserted into subarachnoid space approximately 2-3cm
42
What is continous SAB implicated with?
Implicated with cauda equina syndrome with 5% lidocaine
43
What can lidocaine also cause?
implicated in causing transient neurologic syndrome (especially 5% solution)
44
What is a symptom of transient neurologic syndrome (especially 5% solution)?
Pain originating in the gluteal region then radiating to both lower extremities
45
What is the onset of transient neurologic syndrome (especially 5% solution)?
a few hours, up to 24 hours
46
What is the resolution of transient neurologic syndrome (especially 5% solution)?
~10days
47
What can be used to treat What is the resolution of transient neurologic syndrome (especially 5% solution)?
NSAIDs, opioids, etc.
48
Permanent neurologic injury after spinal or epidural is _______
thankfully rare
49
What is transient neurologic symptoms?
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
What is cauda equina syndrome?
Diffuse injury across lumbar-sacral plexus resulting in bladder and bowel dysfunction with bilateral lower extremity sensory and motor impairment (can be permanent).
51
What is a predisposing factor to cauda equina syndrome?
Spinal stenosis and lumbar disc herniation/issues may be predisposing factors. (Lidocaine, micro spinal catheters, +/- positioning)
52
What is anterior spinal artery syndrome?
Transient. Spasm or thrombosis of anterior spinal artery. Complete paralysis below point of injury. (elderly, peripheral vascular dz, +/- vasoconstrictor use)
53
Where is a high block located?
T1-T4
54
What is blocked in a high block? What is a result?
- 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
What is another side effect of subarachnoid block?
Hypotension +/- bradycardia
56
What is a treatment for Hypotension +/- bradycardia | from a SAB?
Crystalloids/colloids – 15ml/kg 15 minutes before SAB (or during)
57
What vasproessor agents can be used for Hypotension +/- bradycardia from a SAB?
Ephedrine 5-10mg in bradycardic patients or phenylepherine 50-100mcg in patients with a normal heart rate
58
What could be given before SAB to help decrease the risk of Hypotension +/- bradycardia from a SAB?
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
What needs to be taken account with hypotension +/- bradycardia?
Positioning
60
What is respiratory compromise of SAB?
Accessory abdominal and intercostal muscle can become compromised and ability to cough and clear secretions can become inhibited
61
What is a side effect of respiratory compromise?
Patient may feel dyspneic
62
What is some side effects of SAB?
Nausea, Neurologic risk (e.g. paralysis)
63
What is the 3 unexpected cardiac effects of SAB?
- 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
What is the incidence of post dural puncture headache (PDPH)?
0.2-24%
65
What caused the post dural puncture headache?
Caused by a decrease in CSF available in the subarachnoid space from a leak created by the dural puncture
66
What happens to the medulla and the brainstem in the post dural puncture headache (PDHD)?
lose hydraulic support, drop into foramen magnum, stretch the meninges and pull on the tentorium
67
What are some factors that increase the incidence of post dural puncture headache?
- 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
The incidence is less than 1% following a subarachnoid block performed with a ________
25-gauge spinal needle
69
This increases to nearly 36% when using a _______ or ______ needle for diagnostic lumbar puncture
20-gauge or 22-gauge
70
Following inadvertent puncture of the dura with a 17-gauge epidural needle, the incidence of PDPH is approximately _______________
75% to 80%
71
What are the ages that make post dural puncture headache (PDHD)?
- Less common >60 years of age | - More prevalent <40 years of age
72
What are some associated side effects of post dural puncture headache?
- Nausea and vomiting - Appetite loss - Blurred vision or photophobia - Loss of hearing / tinnitus / vertigo
73
When can a post dural puncture headache occur?
Usually occurs within several hours to the first or second postoperative day
74
What is the location of the post dural puncture headache?
Mild to incapacitating bilateral frontal headache
75
Where does the pain radiate in the post dural puncture headache?
Radiates from behind the eyes and across the head toward the occiput and into the neck and shoulders
76
What position is a post dural puncture headache?
headache is relieved when laying flat
77
When does a post dural puncture headache resolve?
Typically self limiting and resolves within 10 days
78
What is the conservative treatment for the post dural puncture headache?
-Horizontal position, hydration, oral analgesics, 500mg IV caffeine benzoate, 300mg of oral caffeine or theophylline
79
-Caffeine and theophylline are both _________ derivatives that cause cerebral vasoconstriction
methylxanthine
80
What is the IV dose for caffeine of post dural puncture headache?
500mg IV caffeine benzoate
81
What is the PO dose for caffeine of post dural puncture headache?
300mg of oral caffeine
82
What is the definitive treatment for post dural puncture headache?
Epidural blood patch, Associated with a 90% cure rate
83
What is the goal of the post dural puncture headache blood patch?
Clot formation seals the dural rent and increases CSF pressure
84
What is the technique for epidural blood patch?
Involves injecting 12-15ml of autologous blood at or below the level of the lowest initial needle insertion
85
Epidural blood patch: blood travels in a ________ direction in the epidural space
cephalad

2-General Anesthesia Exam 2 (11 decks)

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