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Principles 2 > Epidural Anesthesia (pt 1) > Flashcards

Epidural Anesthesia (pt 1) Flashcards

1
Q

What is Epidural Anesthesia?

A

The reversible chemical blockade of neuronal transmission produced by the injection of local anesthetics into the Epidural Space.
-Temporary interruption of sensory, autonomic, and motor nerve fiber transmission takes place in the anterior/posterior nerve roots as they pass through the epidural space on their course to the periphery
-Occurs, to a lesser extent, on the spinal cord itself.

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2
Q

Where is the Epidural space located?

A

Between the periosteal lining of the canal and the dura.
-Extends from the base of the skull to the level of the sacral hiatus (S4)

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3
Q

What are the boundaries of the Epidural space?

A

-Anterior: PLL
-Posterior: Ligamentum Flavum & Vertebral pedicles
-Lateral: Intervertebral Foramen

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4
Q

What is the usual distance from Ligamentum Flavum to Dura?

A

-Space is smallest where the cord is present (upper lumbar, thoracic, and cervical), around 2-4 mm
-After cord ends (L2), can be 5-7 mm

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5
Q

What is the usual distance from skin to epidural space?

A

4-6 cm
-But can be 2-9 cm depending on patient size

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6
Q

What if you get blood in your epidural catheter/needle?

A

-Epidural space is highly vascular. Has plexi (collection of veins)
-Have to make sure it’s just a tinge of blood. If not, could be inside a vessel.
-Risk of systemic toxicity if in a vessel.
-If blood doesn’t clear, remove needle and catheter as one and hold pressure, start again one interspace higher.
-Remember: Bupivicaine is the most cardio-toxic LA

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7
Q

How does the fatty tissue in the epidural space impact your anesthetic?

A

-Epidural space has bands of connective tissue that are holding fatty globules together.
-This can divert the catheter in a different direction or potentially obstruct the flow of LA.
-Can inject a few cc’s of saline to “open the space” to prevent getting blocked by a band of connective tissue.
-Opioids can get sequestered in the fat, and may require higher doses for analgesia (opioids need to get into the Substantia Gelatinosa to go up to the cord)

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8
Q

Where are Epidural Veins most prevalent?

A

In the lateral aspects of the epidural space, rather than at the midline.

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9
Q

What is the pressure in the Epidural Space?

A

Slightly negative pressure
-1 to - 7 cmH2O except in the sacral area.

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10
Q

Where are the narrowest and widest portions of the Epidural Space?

A

-Narrowest: C5 (1-1.5 mm)
-Widest: L2 (5-6 mm)

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11
Q

T/F: There is epidural space in the cranium

A

False; the epidural space within the cranium is a potential space.

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12
Q

What is a Tuohy needle?

A

-18 gauge needle
-Blunt, curved to push away dura after passing through ligamentum flavum.

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13
Q

What size are most Epidural Catheters?

A

Usually 19 or 20 gauge.
-Plastic, flexible, marked in cm

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14
Q

How much should you thread your epidural catheter past the needle, into the epidural space?

A

3-5 cm

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15
Q

What happens if you don’t thread your epidural catheter far enough into the epidural space (<3 cm)?

A

Dislodgement risk

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16
Q

What happens if you thread your epidural catheter too far into the epidural space (>5 cm)?

A

Can exit the epidural space via the intervertebral foramen.

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17
Q

T/F: If you need to reposition your catheter, you can pull it back through the needle.

A

FALSE: don’t do this. May shear off tip (bad)

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18
Q

List the structures in order that the needle passes through for an Epidural block?

A

-Skin
-Subcutaneous tissue
-Supraspinous Ligament
-Interspinous Ligament
-Ligamentum Flavum
-Epidural Space

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19
Q

What are the 2 ways that LA works in the Epidural Space?

A

1) LA acts at nerve roots, and dorsal ganglia beyond the intervertebral foramen
2) LA acts on dorsal and ventral rootlets and spinal cord after diffusing through CSF

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20
Q

Why does epidural anesthesia take longer to set up?

A

It has to diffuse into or across the dural cuff or root sleeve into the CSF, where it reaches the spinal cord.
-Need larger volumes for epidural (Epidural is 10-20 mL vs Intrathecal is 1-2 mL).

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21
Q

How many mLs of LA should you inject per segment blocked?

A

1-2 mL of LA per segment

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22
Q

If you want a block to a T4 sensory level from an L4-L5 injection site, how many mLs do you need to inject?

A

-12 segments to reach T4
-12 x 1-2 = 12-24 mL of LA

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23
Q

What populations need are at risk for a higher block and need a decreased dose?

A

-Elderly: have smaller spaces overall
-Pregnancy
-Obesity
Dose slowly

24
Q

T/F: The catheter tip is pointing cephalad, so that’s the only direction the LA will spread.

A

False, LA goes caudal and cephalad.

25
Q

What is the duration of action of Chloroprocaine?

A

50-70 minutes

26
Q

What is the duration of action of Prilocaine?

A

90-130 minutes

27
Q

What is the duration of action of Lidocaine?

A

90 - 150 minutes

28
Q

What is the duration of action of Mepivacaine?

A

120 -160 minutes

29
Q

What is the duration of action of Bupivicaine?

A

200-260 minutes

30
Q

What is the setup for performing an Epidural?

A

-Same as spinal (airway management, hypotension, emergency situation)
-IV fluid management (bolus)
-Monitors on
-Sitting or lateral position
-Need assistant to help with position
-Bed at comfortable height

31
Q

How do you identify your landmarks for an Epidural?

A

-Superior aspect of iliac crests = L4/L5 interspace
-Find midline spinous process
-Find largest interspace above/below. Usually it’s L2-L3

32
Q

Describe the steps to performing an Epidural.

A

-Lubricate glass LOR syringe with NS and add a bubble of air
-Prep the skin: 4 inches circumferential and let dry
-Drape
-Skin wheal with LA
-Place non-dominant hand against patient’s back with thumbnail just below where you felt interspace
-Insert Epidural needle with curve pointing up just above thumbnail at a 10-15 degree angle, slightly cephalad
-Needle will feel more secure/anchored as you enter the interspinous ligament/ligamentum flavum.
-Remove stylet
-Attach glass syringe filled with saline
-Non-dominant hand inserts needle slowly
-Dominant hand taps and puts pressure on plunger to feel LOR
-Plunger empties out effortlessly. Note where you lost resistance
-Remove glass syringe, thread epidural catheter
-Add catheter in 3-5 cm into epidural space.
-Administer test dose
-Put patient in desired position
-Continue to dose (if safe, aspirate every time)

33
Q

When does LOR usually occur?

A

At 4-6 cm

34
Q

What is the Hanging Drop Technique?

A

Keep a drop of NS in the hub of the catheter, and it will get sucked in due to negative pressure in the epidural space.

35
Q

What do you chart?

A

-LOR at ___ cm
-How much catheter is in
-Position of catheter in curved back position and at neutral position

36
Q

What should you do before injecting anything?

A

Always aspirate to look for blood and CSF!

37
Q

What is the purpose of the test dose?

A

To ensure that you are in the Epidural Space.
-If in the intrathecal space, effects will occur really quickly. Epidural nerve block takes time
-Lidocaine is given to ensure you’re NOT in the Dura
-If in the Subarachnoid space, patient will have difficulty moving legs and will feel a little warmth.
-Also want to ensure you’re not in an epidural vein.

38
Q

What are the components of an Epidural Test Dose?

A

-Lidocaine 1.5% (15 mg/mL). Usually 3 mL (45 mg)
-Epi 1:200,000

39
Q

Why is Epinephrine added to the test dose?

A

-If you’re in an epidural vein, the Epi will increase the HR
-HR increase can be 10-20 beats above baseline for a few minutes (but caution to avoid erroneous increases in HR like stress or contractions)
-Will experience numbness of the tongue, ringing in the ears, and/or dizziness if vascular injection.

40
Q

What should you do if, on your test dose, the patient’s legs feel warm/heavy?

A

Stop injecting, remove the catheter, and start over!

41
Q

How much LA and how often do you inject in an Epidural?

A

3-5 mL of LA at a time, with 3-5 minutes in between doses.

42
Q

How do you perform a Caudal block?

A

-Patient is prone or extreme lateral
-Identify the sacral hiatus, sacral cornu (2 inches above the coccyx)
-Sacral hiatus is covered by the Sacral-Coccygeal ligament
-Use a 22g short beveled needle, 45 degrees to the skin
-Will feel LOR or a pop going through S-C ligament
-Then, needle is in epidural space.
-Drop the angle of the needle so that it is in the same plane as the patient’s sacrum
-Advance the needle a few cms and inject the drug
-15 min for block to set up
-Good for perineal/rectal surgeries in adults
-Used in peds in combo with GA (0.5 - 1 mL/segment)

43
Q

What dermatome level do you want to block to for Upper abdominal surgery?

A

T4

44
Q

What dermatome level do you want to block to for intestinal, Gyn, and urologic surgery?

A

T6

45
Q

What dermatome level do you want to block to for a TURP?

A

T10

46
Q

What dermatome level do you want to block to for a vaginal delivery or hip surgery?

A

T10

47
Q

What dermatome level do you want to block to for thigh surgery or lower leg amputation?

A

L1

48
Q

What dermatome level do you want to block to for Foot/ankle surgery?

A

L2

49
Q

What dermatome level do you want to block to for Perineal and anal surgery?

A

S2-S5 (saddle block)

50
Q

Which LA can be utilized to create a “walking epidural”?

A

Bupivicaine 0.0625 - 0.125 can get you a nice sensory block without motor.
-Can switch to 2-Chloroprocaine fast if need to convert to C/S (fast onset)

51
Q

What is the Concentration, Onset, and DOA for 2-Chloroprocaine?

A

-C: 3%
-O: 5-15 min
-D: 30-90 min

52
Q

What is the Concentration, Onset, and DOA for Lidocaine?

A

-C: 2%
-O: 10-20 min
-D: 60-120 min

53
Q

What is the Concentration, Onset, and DOA for Ropivacaine?

A

-C: 0.1 - 0.75%
-O: 15-20 min
-D: 140-220 min

54
Q

What is the Concentration, Onset, and DOA for Bupivicaine?

A

-C: 0.0625-0.5%
-O: 15-20 min
-D: 160-220 min

55
Q

What is the Concentration, Onset, and DOA for Levobupivacaine?

A

-C: 0.0625-0.5%
-O: 15-20 min
-D: 150-225 min

Principles 2 (45 decks)

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