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Principles of Anesthesia > Spinal & Epidural Lecture 4 > Flashcards

Spinal & Epidural Lecture 4 Flashcards

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1
Q

What is the most common cause of LAST?

A

inadvertent injection in a vein

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2
Q

What is the most frequent symptom of LAST?

A

Seizure (cardiac arrest might come before seizure with bupivacaine)

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3
Q

What type of nerve blocks is LAST more common in?

A

More common in peripheral nerve blocks than in epidurals

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4
Q

What increases risk of CNS toxicity associated with LAST?

A
  • Hypercarbia→ increase cerebral perfusion, increase drug delivery to brain, decrease protein binding= increase free LA that can enter the brain
  • Hyperkalemia→ Neurons more excitable
  • Metabolic acidosis→ Lowers seizure threshold and increases brain drug retention (ion trapping)
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5
Q

What decreases the risk of CNS toxicity from LAST?

A
  • Hypocarbia→ decrease cerebral perfusion reduces drug delivery to bain
  • Hypokalemia→Less excitable neurons
  • CNS Depressants→ benzos and barbs; raise seizure threshold
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6
Q

How does LAST impact heart functions (CV toxicity)?

A
  • Decreases automaticity, conduction velocity, AP duration, and refractory period
  • Depress myocardium by affecting intracellular calcium regulation
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7
Q

What are key factors to determine the cardiotoxicy extent of LAST?

A
  • LA affinity to VG Na+ channels in active and inactive states
  • Rate of dissociation from the receptor to VG Na+ channel
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8
Q

______________ has a high affinity to VG Na+ channel and a slower dissociation rate from the receptor during diastole

A

Bupivacaine (primary reason cardiac toxicity is high and resuscitation is very difficult)

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9
Q

List LA in order of more difficult to least difficult cardiac resuscitation:

A

Bupivacaine > Levobupivacaine > Ropivacaine > Lidocaine

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10
Q

What are the treatments for LAST?

A
  • Manage airway→ 100% O2
  • Treat seizures → Benzos, avoid propofol (cardiac depression in large doses and doesnt replace lipid therapy)
  • Modified ACLS→ Epi can make LAST harder; use <1mcg/kg; amio for ventricular arrhythmias
  • Lipid Emulsion therapy
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11
Q

How is lipid emulsion given?/

A
  • Over 70kg: 100mL bolus over 2-3min followed by 250mL infusion over 15-20min (repeat of double if unstable)
  • Under 70kg: 1.5mL/kg bolus over 2-3min followed by 0.25mL/kg/min infusion (repeat or double if unstable)
  • Continue infusion for 15min after stability maintained
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12
Q

What is the max dose for lipid emulsion therapy?

A

12mL/kg

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13
Q

What is epidural/spinal hematoma associated with? Is it common?

A
  • Preexisiting abnormalities in clotting
  • Traumatic or difficult needle placement
  • Indwelling catheters and long-term anticoagulant
    Low incidence (also hard to study)
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14
Q

Cord ischemia from epidural/spinal hematoma is reversible if laminectomy is performed in <_______ hours

A

8 (need prompt dx and intervention)

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15
Q

What is a major symptoms of epidural/spinal hematoma?

A

Pain

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16
Q

What is arachnoiditis?

A

Inflammation of meninges associated with: - non FDA approved drugs into intrathecal/epidural space
- using non-preservative free solutions
- betadine contamination

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17
Q

Why is arachnoiditis an issue?

A

Leads to extensive sclerosis of arachnoid membranes and constriction of vascular supply

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18
Q

When would you switch from neuraxial technique to general? reason to always have GETA set up

A
  • Failed block
  • “High spinal”
  • LAST
  • Anaphylaxis
  • Severe CV collapse
  • Case exceeds duration of local anesthetic
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19
Q

What are 3 common reasons for failure in achieving spinal/epidural?

A
  • Wrong dose
  • Wrong location
  • Wrong position
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20
Q

Which type of needles use introducers?

A

Smaller needles that might bend (22G doesnt need introducer)

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21
Q

What is in the spinal kit?

A
  • 3.5 inch styleted needle
  • Introducer
  • LA (skin 1% lido, SAB 2mL total)
  • Prep
  • Sterile drapes
  • Needles (22G or smaller (skin) and 18G)
  • Filter needle (draw up SAB med)
    Also need to have sterile gloves, hats for pt and provider, mask for provider
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22
Q

Why is it important to keep the stylet in the needle at all times?

A

If you dont have the stylet in the needle then the little bit of bleeding will start to clot the top of the needle

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23
Q

What are the names of the cutting needles?

Study These Flashcards
A
  • Quincke
  • Pitkin
    try to avoid to prevent PDPH
24
Q

What are the non-cutting needles?

Study These Flashcards
A
  • Sprotte
  • Pencan
  • Greene
  • Gertie Marx
25
What are the advantages for using a pencil-point tip in a SAB?
- Drag fewer contaminants into subnormal tissues - "Pop" can be sensed with a pencil point needle - Less risk for PDPH - Less than 1% risk PDPH - Failure rate of 5%
26
What are common problems encounteres with SAB?
- Lack free CSF when spinning 360 degrees - No swirl - Resistance with injection (probably on the side→ pull out needle a little) - Paresthesia - Check swirl halfway - Blood instead of CSF - No block (expired?) - Partial block
27
What should you do if the patient complains they feel it in their foot when trying to start SAB/epidural?
STOP pull out and redirect
28
Checking for CSF swirl only works with what types of LAs?
Hyperbaric
29
What should you do if you get a partial block?
Try to position patient with non-numb side down→ if still not working in 15-20min proceed with GA
30
What needle is used for epidurals?
Tuohy needs (bigger 17-18G and has markings on it)
31
What is different about epidural kit compared to SAB kit?
- Catheter - Tuohy needle with markings - LOR syringe - 20mL syringe - Lido with epi for test dose
32
What are the different epidural needles?
- Tuohy: Most curvature (30 degrees) blunt tip is less likely to puncture subarachnoid space - Hustead: 15 degree curve - Crawford: Preferred when catheter placement is difficult or angle is steep (thoracic) 0 degree curve - Weiss: 15 degree curve and it has "wings"
33
What does each marking on the tuohy needle represent?
1cm (9cm at the hub)
34
Why is a multiport catheter useful when placing an epidural? what is the downside?
- Helps to even distribution of LA in epidural space - Downside= high incidence of inadvertent intravascular placement
35
What is the optimal epidural space length?
3-5cm (need 3-5cm of catheter in the space)
36
What are the catheter marking on the epidural catheter?
5cm (1 dark line) 10cm (2 dark lines) 15cm (3 dark lines) 20cm (4 dark lines)
37
What is a negative and positive aspect of plastic epidural catheters?
- Easier to thread (less expensive) - Inadvertent SAB puncture (stiffer)
38
How can we figure out at what depth the epidural catheter should be secured?
- Measure skin to epidural space with needle marking (total needle length- amount outside the skin) - Add that to the optimal epidural catheter depth (3-5cm)
39
Can you give epidural over a back tattoo?
If tattoo is at least 5 months old (try to aim for area with less ink)
40
How do you know when you are in the epidural space?
As soon as you hit epidural space it will suck air or saline from syringe (LOR) into the potential space
41
How can you make sure to thread the epidural catheter into the space without pulling any of it out when trying to remove the needle?
Hold catheter and push it forward when pulling needle out to counteract pulling
42
When should you do the test dose for epidural?
No recommended to test dose with the tuohy needle→ better to test dose with catheter to know whether catheter was threaded into the right space *want negative test dose*
43
What are important numbers to document when placing epidural?
- Depth to epidural space (skin to space) - Catheter marking at the skin - Catheter depth/length in epidural space (# cm in the space)
44
What are the 2 methods to determine you are in the epidural space?
- Loss of resistance (LOR)→ use saline, air, or both - Hanging drop method (not common practice)→ saline drop placed at the hub of needle and epidural space is identified when drop is sucked into needle by negative pressure
45
What is common composition of epidural test dose?
3mL of 1.5% lidocaine mixed with epinephrine (1:200,000)
46
What should you look for when injecting test dose?
- Accidental IV placement: jump in heart rate by 20% or more, ringing in ears, metallic taste in mouth, numbness around the mouth - Accidental spinal injection: Dense motor block w/in 5 min of test dose
47
What are special considerations for epidural test dose for pregnant patients and cardiac patients?
- Pregnant women: give test dose after contraction to see true increase in HR if intravascular - Pts on heart medication: Big increase in BP (>20mmHg) could also mean needle in blood vessel
48
If lumbar epidural started at L4-L5 how many mL needed to T10 surgery?
Initial dose: 7mL Top up dose: 3.5mL
49
Initial dosing regimen for epidurals?
Initial dose: 1-2mL per segment of spine given in 5mL increments
50
What is the dosing regimen for top-ip dosing with epidural catheter?
- Give top-up dose beofre 2 segment regression has occurred - Give 50%-75% of initial loading dose when 2 segment regression has occurred to maintain block
51
What is the recommended top up time from initial dose for lidocaine, 2-chloroprocaine, mepivacaine, and bupivacaine/ropivacaine?
- Lidocaine: 60min - 2-Chloroprocaine: 45min - Mepivacaine: 60min - Bupivacaine/Ropivacaine: 120min
52
What are common problems encountered with epidurals?
- CSF wet tap (PDPH) - Paresthesia - Cant thread catheter (NS into epidural space to try to open it up then gently turn catheter) - Aspirate blood (check with each dose) - Positive test dose (pull out catheter) - False positive test dose (Give after contraction)
53
What is the order for CSE?
Spinal first then epidural
54
What is the procedure for CSE?
- Tuohy needle as guide to get into epidural space - Then put spinal needle inside tuohy and go until subarachnoid space to place SAB - Pull out spinal needle - Thread epidural catheter
55
Should you use same LA for spinal and epidural when doing CSE?
Yes just different concentrations→ same pharmacokinetics/dynamics
56
When is CSE commonly used?
Teaching hospitals with surgical residence→ provides back up via epidural access to top up LA if case takes longer

Principles of Anesthesia (6 decks)

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