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JW: Principles of Anesthesia I > Exam 1- Neuraxial Principles (6/6/23) > Flashcards

Exam 1- Neuraxial Principles (6/6/23) Flashcards

1
Q

What are the benefits of epidural anesthesia over spinal?

A
  • Predictable dermatome spread
  • Slower onset of autonomic blockade (slower hypotension)
  • Unlimited duration
  • Varying concentration of LA for analgesia or surgical anesthesia
  • Maintain ambulation and voiding if the epidural is placed above T10 (segmental blockade)
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2
Q

What are the disadvantages of epidural anesthesia?

A
  • Longer time to perform the technique
  • Slower onset of effect
  • Less dense block
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3
Q

What are the indications of epidural anesthesia?

A
  • Upper and lower extremity surgery
  • Can be used as a sole anesthetic or adjunct to GA (big lung cases).
  • Post-op as a continuous infusion with or without patient-controlled epidural analgesia.
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4
Q
A
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5
Q

The epidural space extends from the _____ to the _______.

A
  • From the skull to the sacral hiatus
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6
Q

What makes up the epidural space?

A
  • Fat
  • Areolar tissue
  • Lymphatics
  • Veins/ Blood vessels
  • Nerve roots
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7
Q

Why is blood vessel puncture common in pregnant patients during epidural block procedures?

A
  • Engorgement of the epidural veins from caval compression
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8
Q

What can be done to open up the potential epidural space?

A
  • Injection of saline (5 mL)
  • Injection of air (1-2 mL)
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9
Q

Compare needle entry during an epidural block for cervical/lumbar region and thoracic region.

A
  • Cervical/lumbar approach will be directed horizontally
  • Thoracic approach needle pointed cephalad (40 degrees)
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10
Q

The safest point of entry into the epidural space is below the level of the ________.

A
  • spinal cord
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11
Q

A line drawn between the superior aspect of the ________crosses either the spinous process of L4 or the L4-5 interspace.

A
  • iliac crests
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12
Q

How does a drug’s pKa affect the onset of local anesthesia?

A
  • The closer the pKa is to the physiological pH, the faster the onset of the effect.
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13
Q

What LA is the exception to the pka and pH rule for epidural onset?

A
  • Exception: 2-chloroprocaine (pka: 9.0) 3%
  • This is due to the high concentration of chloroprocaine at 3%

Faster onset than lidocaine

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14
Q

What is sham feeding?

A
  • Sham feeding is any procedure that mimics normal food consumption but where food and drink are not actually digested or absorbed (ie: chewing gum).
  • Sham feeding is a preventive measure for ileus
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15
Q

List the route of LA from fastest to slowest.

A
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16
Q

LA is injected into the epidural space via needle or catheter where the drug diffuses through the dural sheath of _______, __________, __________, and ______where nerve transmission is altered.

A
  • Spinal nerves
  • Roots
  • Rootlets
  • CSF
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17
Q

Generally, with epidural blocks, there is no _________ relationship with LA dosing.

A
  • positional
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18
Q

What are the determinants of block spread in epidural anesthesia?

A
  • Site of injection
  • Volume dose of LA
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19
Q

What conditions will require a lower dose of LA for epidural anesthesia due to lower CSF volume?

A
  • Age
  • Pregnancy
  • Obesity
  • Little Person (Tyrion Lannister)
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20
Q

Why is a reduced volume of local anesthetic solution used during thoracic epidural block?

A
  • Lower volume of LA d/t the potential of a higher block and hemodynamic instability
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21
Q

During an epidural block, how much volume of LA is required per segment?

A
  • 1-2 ml per segment

For example, to achieve a T4 sensory level from an L4-5 injection, approximately 12–24 mL of local anesthetic should be administered (incremental dosing)

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22
Q

What is the volume used for incremental dosing for epidural blocks?

A
  • 5 mL of LA
23
Q

Incremental dosing with 5 ml avoids:

A
  • Accidental “High spinal”
  • Hypotension from rapid autonomic blockade (cardiac arrest)
  • Local Anesthetic toxicity

If epi is added to LA, it can be used as a marker/indicator that medication has been injected into the blood vessel. (↑HR)

24
Q

What are the purposes of using additives for Epidural Anesthesia?

A
  • Prolong epidural block
  • Improve the quality of the block
  • Accelerate onset of block
25
Q

________ increases the duration of useful neuraxial anesthesia with all the agents

A
  • Epinephrine
26
Q

Epinephrine will have the greatest effect with what local anesthetic?

A
  • Lidocaine
  • 2-Chloroprocaine
27
Q

How do you speed the onset of an epidural block?

A
  • Alkalinization by adding 1 meq sodium bicarb for every 10mL of LA
  • Increases pH of LA
  • This will increase the concentration of nonionized base
  • Increase the rate of diffusion of the drug
  • Increase the speed of onset
28
Q

LA used in epidural block: 2-Chloroprocaine
Concentration:
Onset:
Duration:
Duration w/ Epi:

A

LA used in epidural block: 2-Chloroprocaine
Concentration: 3%
Onset: 10-15 mins
Duration: 45-60 mins
Duration w/ Epi: 60-90 mins

29
Q

LA used in epidural block: Lidocaine
Concentration:
Onset:
Duration:
Duration w/ Epi:

A

LA used in epidural block: Lidocaine
Concentration: 2%
Onset: 15 mins
Duration: 80-120 mins
Duration w/ Epi: 120 -180 mins

30
Q

LA used in epidural block: Mepivacaine
Concentration:
Onset:
Duration:
Duration w/ Epi:

A

LA used in epidural block: Mepivacaine
Concentration: 2%
Onset: 15 mins
Duration: 90-140 mins
Duration w/ Epi: 140-200 mins

31
Q

LA used in epidural block: Bupivacaine
Concentration:
Onset:
Duration:
Duration w/ Epi:

A

LA used in epidural block: Bupivacaine
Concentration: 0.5-0.75%
Onset: 20 mins
Duration: 165-225 mins
Duration w/ Epi: 180-240 mins

32
Q

LA used in epidural block: Ropivacaine
Concentration:
Onset:
Duration:
Duration w/ Epi:

A

LA used in epidural block: Ropivacaine
Concentration: 0.75-1.0%
Onset: 15-20 mins
Duration: 140-180 mins
Duration w/ Epi: 150-200 mins

33
Q

Rank the following LA from fastest to slowest onset:

Mepivacaine
Lidocaine
Chloroprocaine
Bupivacaine
Ropivacaine

A

Note that fast onset correlates with short duration and slow onset correlates with long duration.

34
Q

Which LA agent is only used in epidural blocks?

A
  • 2-Chloroprocaine 3%
35
Q

How is 2-Chlorprocaine metabolized?

A
  • Plasma cholinesterase

Esters are metabolized by plasma cholinesterase. Amides are metabolized by the hepatic enzymes.

36
Q

Which LA provides the least dense epidural block?

A
  • Ropivacaine

Walking epidural.

37
Q

Which epidural LA provides the greatest motor function depression?

A
  • Lidocaine
38
Q

Why do you not want to increase LA rate for an epidural block if an OB patient is 8 cm dilated?

A
  • Increasing the LA to the epidural block will depress motor function for the patient to push.
  • Provide PRN opioid analgesia instead
39
Q

Combined Spinal Epidural Kit Tray Set Up

A
40
Q

Why is the tip of the epidural catheter colored?

A
  • In case the tip is sheared off when removing the catheter, x-ray imaging can detect where the catheter is located.
41
Q

What type of needle has the most curvature (30 degrees) and is generally used in an epidural block?

A
  • Tuohy Needle
42
Q

What needle is used when epidural catheter placement is difficult or when the angle is steep (thoracic epidural)?

A
  • Crawford Needle
43
Q

In most cases, what direction should the bevel be pointed during an epidural procedure?

A
  • Bevel pointing cephalad
44
Q

What is the gauge of a Tuohy needle?
How long is each marking?

A
45
Q

What is the best type of catheter to use for epidural placement?

What is the benefit of using this type of catheter?

A
  • Multi-orifice catheter
  • Benefits: Even block
46
Q

How far should the epidural catheter be placed within the epidural space?

A
  • 3-5 cm
47
Q

What is the problem with using plastic catheters for epidural blocks?

A
  • The stiffness of the catheter can cause inadvertent SAB puncture
48
Q

Why is there a stylet in the Thuoy needle?

A
  • To prevent blood clots
49
Q

What is the problem with leaving a long catheter in the epidural space (15 cm).

A
  • Coiling
50
Q

How do you know that the Thouy needle has passed the Ligamentum Flavum into the epidural space?

A
  • Loss of resistance using air or saline
51
Q

Why is a test dose performed with an epidural block?

A
  • A test dose is performed to identify unintentional puncture to the blood vessel or subarachnoid space.

1.5% lidocaine with epi is used as a test dose

52
Q

What are the indications of intravascular injection of LA?

A
  • A change of >20% in HR
  • Tinnitus
  • Circumoral numbness
  • Metallic taste

If any of these symptoms occur, replace the epidural catheter.

Positive Test dose.

53
Q

What are the two methods used to determine the epidural space?

A
  • Loss of resistance technique
  • Hanging drop method
54
Q

What volume of 1.5% lidocaine with 1:200000 epinephrine is used as a test dose?

A
  • 3 mL

JW: Principles of Anesthesia I (61 decks)

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