Labor & Analgesia Pt. 2 (Exam III) Flashcards
Name the anatomy pertinent to an epidural/spinal.
- Skin
- Subcutaneous tissue
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Epidural space
- Dura mater
What three interspinous spaces are typical for epidural placement?
L2-3
L3-4
L4-5
What are the disadvantages of a continuous epidural?
- 10 - 15 min onset of analgesia (slow)
- Higher drug requirement
- ↑ Maternal LAST risk
- ↑ fetal drug exposure
- Risk of sacral “sparing” slow blockade.
What is the standard “test dose” used for epidurals?
Lidocaine 1.5% w/ 1:200k epi (3mls)
Change in HR indicates intravascular epinephrine.
What would intrathecal placement of an epidural present like when injecting your test dose?
Leg numbness & warmth (Lidocaine 1.5% going intrathecal). Heavy and high spinal risk.
Can a test dose be administered during a contraction?
No because then the change in HR can’t be solely attributed to the test dose.
What are the disadvantages of a CSE (combined spinal epidural) ?
- ↑ risk of fetal bradycardia
- ↑ risk of PDPH
- ↑ risk of neuraxial infection
- Uncertainty of proper epidural catheter placement (until spinal wears off).
Why can fetal bradycardia sometimes occur with CSE ?
- Due to sympathetic blockade & maternal HoTN.
What is a Dural Puncture Epidural?
Similar to CSE but no medications are injected into the spinal space.
What are the advantages of a Dural Puncture Epidural?
- Faster onset than regular epidural
- Transdural migration of medications injected into epidural space
- More rapid anaglesia
- ↓ risk of maternal HoTN and fetal bradycardia compared to CSE.
When is a continuous spinal utilized?
After a “Wet Tap”.
Accidental placement of epidural Tuohy into the spinal space.
What are the disadvantages of a continous spinal?
- Large dural puncture = PDPH
- Risk of other provider mistaking catheter for an epidural catheter instead of a spinal.
What types of pain do epidural local anesthetics treat?
- Visceral Pain: lower uterine & cervical distention
- Somatic Pain: Fetal birth canal descent
Which two LA’s are most commonly used for labor?
Bupivacaine & Ropivacaine
What is a differential block?
- Separation of motor & sensory effects
- Sparing of A-α motor neurons
What are the advantages of Bupivacaine?
- Differential Block
- Long duration
- No tachyphylaxis
- Safety (↓ placental transfer)
What are the disadvantages of neuraxial bupivacaine?
- Slow onset time (10 - 15 min)
- Risk of CV & neuro toxicity
How can the latency time of bupivacaine/ropivacaine be improved?
Addition of a lipophillic opioid.
What epidural dosing of bupivacaine is typical?
0.0625 - 0.25%
10 - 20mls
What are the advantages of Ropivacaine?
- Differential Block (even better than bupivacaine).
- Safety (less toxic than bupivacaine)
What are the disadvantages of ropivacaine?
- Slow onset (10 - 15 minutes)
- CV & Neuro toxicity
What epidural dosing of ropivacaine is typical?
- 0.1 - 0.2%
- 10 - 20mls
Why is lidocaine not routinely used for labor analgesia?
- Poor differential block
- Tachyphylaxis risk
- ↑ placental transfer / ion trapping
What is neuraxial lidocaine useful for?
- Identification of non-functional catheter
- Need for rapid sacral analgesia
- Instrumented vaginal delivery/perineal repair
- Emergent operative delivery
What dose of neuraxial lidocaine is used for emergent operative delivery?
2% Lidocaine 10 - 20 mls w/ 2mls of Na⁺Bicarb
Bicarb (2mls) w/ 18mls of 2% Lido
What will bicarbonate do when paired with lidocaine in neuraxial anesthesia?
Speed up onset
Good for emergent operative delivery.
What dose of lidocaine is used for identification of a non-functional catheter?
5 - 10mls of 2% Lidocaine
What dose of Lidocaine is used for rapid sacral analgesia?
0.5 - 1% Lidocaine 5-10mls
What dose of Lidocaine is used for an instrumented vaginal delivery or for perineal repair?
Lidocaine 1.5 - 2% +/- epinephrine (5-10mls)
What are the advantages and disadvantages of Chloroprocaine?
Advantages:
-Rapid onset
Disadvantages:
- Short duration
- Poor differential blockade
What are the disadvantages of chloroprocaine?
- Short duration of action
- Interferes with bupivacaine/opioids
When is neuraxial chloroprocaine useful?
Emergent instrumented or operative delivery and/or perineal repair
What dose of chloroprocaine is used for emergent instrumented delivery?
10mls of 2-3% chloroprocaine
What are the benefits of neuraxial opioids?
- ↓ LA dosage (20 - 30% reduction)
- ↓ latency
- ↑ analgesia
- ↑ duration of analgesia
Which opioids will have a faster onset?
Lipophillic (fentanil, sufentanil, etc)
Which neuraxial opioids will have a later onset (but provide postoperative pain relief) ?
Hydrophillic
Morphine.
What is the dose of neuraxial clonidine?
75 - 100 mcg
What are the advantages of neuraxial clonidine?
- Analgesic
- ↓ LA requirement
- ↑ block quality/duration
- No motor blockade
What are the disadvantages of neuraxial clonidine?
- Maternal HoTN & bradycardia
- Maternal sedation
What is the typical dose of neuraxial dexmedetomidine?
0.25 - 0.5 mcg/mL
What is precedex used for in neuraxial anesthesia?
- ↓ latency
- ↑ duration of block
- ↓ LA requirement
What adverse effects can occur with higher concentration of neuraxial dexmedetomidine?
Maternal sedation & anxiolysis
What is the MOA of neuraxial Precedex?
- Suppressed C-fiber transmission
- Hyperpolarization of postsynaptic dorsal horn neurons.
What is typical dose of bupivacaine in a continuous epidural infusion?
0.05 - 0.125% Bupivacaine
8 - 15 mL/hr
What is typical dose of ropivacaine in a continuous epidural infusion?
- 0.08 - 0.2%
- 8 - 15 mL/hr
What is a PCEA?
Patient controlled epidural anesthetic
- Less motor blockade
- Less dosing by provider
What is the main factor in determination of LA dosing for a spinal?
Patient height & level of anesthesia desired.
How many mg of bupivacaine is being administered to a patient receiving 1.7mls of 0.75% bupivacaine?
1.7 x 7.5 = 12.75mg Bupivacaine
Can opioids be used as a solo agent for neuraxial anesthesia?
Yes
Analgesia w/ no numbness, motor blockade, or sympathectomy.
More commonly used as an additive however.
What is the dose of hyperbaric bupivacaine?
0.75%
What is the dose of isobaric bupivacaine?
0.5%
What is the isobaric dose of spinal ropivacaine?
0.5%
Not commonly used.
What is the dose of spinal dexmedetomidine?
2.5 - 10mcg
What is the purpose of spinal dexmedetomidine ?
- Prolongs analgesia
- ↓ latency
What is spinal dose of epinephrine?
2.25 - 100mcg
What is the purpose of intrathecal epinephrine?
- Prolonged analgesia
- increased motor blockade (with higher dosing)
What would a higher dose of spinal epinephrine (100 - 200mcg) do?
↑ motor blockade
How is neuraxial hypotension typically treated?
- IV fluids
- Positioning
- Vasopressors (last)
What is the most common complaint associated with neuraxial opioids?
Pruritus
Why does pruritus occur with neuraxial opioid administration?
Central μ-opioid receptors
What dose of diphenhydramine (Benadryl) is used for neuraxial opioid pruritus?
Trick question. Itching is not due to histamine release. Benadryl will not work.
What drug is used to treat neuraxial opioid pruritus?
Centrally acting μ-opioid antagonist
- Naloxone 40 - 80mcg IV
- Naltrexone 6mg PO
Partial Agonist-Antagonist
- Nalbuphine 2-5mg IV
- Butorphanol 1-2mg IV
What are the conservative treatment options for a “wet tap”?
- Caffeine
- Laying down (positioning)
What are the more invasive treatment options for PDPH?
Epidural blood patch
Should CSF be reinjected after wet-tap occurs with a Tuohy needle?
No. ↑ risk for infection/pneumocephalus
Why is bupivacaine 0.75% not used for epidural blocks?
Risk for CV toxicity if injected
What are the mild/moderate signs/symptoms of LAST?
- Tinnitus
- Circumoral numbness
- Restlessness
- Difficulty speaking
What is the treatment for LAST?
1.5 mL/kg Lipid emulsion bolus & benzodiazepines
What are the signs/symptoms of a high spinal?
- Agitation
- Dyspnea
- Inability to speak
- Profound hypotension
- Apnea
How is a high spinal treated?
- Ventilation assistance
- Volume resuscitation
- Vasopressors
Pinky/hand numbness is associated with what spinal level?
C8
Cardioaccelerator fibers originate from what spinal levels?
T1-T4
Diaphragmatic ennervation comes from which spinal levels?
C3-C5
Thumb numbness is associated with what spinal level?
C6
What are the signs/symptoms of a subdural block?
- Unexpectedly high blockade w/ patchiness
- Profound HoTN
- Minimal motor blockade
- Horner’s syndrome
- Apnea
- LOC changes
