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Obstetrics > Lecture 2 - Labor Analgesia & Pharmacology > Flashcards

Lecture 2 - Labor Analgesia & Pharmacology Flashcards

1
Q

Pain pathways for 1st stage are:

A

Pain source is mainly lower uterine segment from contractions (T10 - L1 dermatomes)

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2
Q

Pain pathways for 2nd stage are:

A

source is perineal structures via pudendal nerve (S2 - S4 dermatomes)

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3
Q

What is important to know about hypnosis:

A
  • 15% of population easy to hypnotize and 15 % are impossible to hypnotize
  • may be of some benefit in labor but not very useful by itself.
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4
Q

What is important to know about Psychoprophylaxis?

A

(LAMAZE)

  • Involves education and behavioral techniques
  • Combined with other forms of analgesia
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5
Q

What is important to know about Acupuncture?

A
  • During acupuncture opioid peptide release has been demonstrated
  • ??Gate Control Theory?? (over stimulation of an area in pain)
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6
Q

Morphine has what effect on mother and neonate?

A

-immature blood brain barrier increases risk of respiratory depression in the neonate

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7
Q

Meperidine (Demerol) has what effect on mother and neonate?

A
  • Neonate respiratory depression unlikely if given less than 1 hour prior to delivery
  • Contraindicated in pt with seizure or renal issues
  • Kinetics half life is 18-23 hours in neonate
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8
Q

Fentanyl has what effect on mother and infant?

A
  • Respiratory depression may outlast analgesia
  • PCA recipe loading dose 1 - 2 mcg/kg: dose 50 mcg with 10 minute lockout
  • use pulse oximetry
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9
Q

Nalbuphine (Nubain) has what effect on mother and infant?

A
  • Has ceiling effect on resp depression
  • Dysphoria common
  • Treats opioid induced pruritis
  • Mu Opioid antagonist, Kappa agonist
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10
Q

Butorphanol (Stadol) has what effect on mother?

A
  • Sedation Common

- ceiling effect on resp. depression

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11
Q

Volatile agents have what effect on mother and infant?

A
  • Rarely used
  • Dose limit 0.5 MAC
  • Decreased uterine tone
  • Often used with supplemental nerve block
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12
Q

What can be said about Paracervical block?

A

-1st stage of labor
-5 cc of local injected at submucosally at 3 and 9 o’clock position beside cervix
RISKS:
- Accidental injection into uterine artery
-Fetal local anesthetic toxicity
-nerve injury and hematoma

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13
Q

What can be said about pudendal block?

A

-2nd stage of labor
-Good alternative for patients with contraindications for neuraxial block
-injection bil. via trans-vaginal approach under the ischial spines
RISKS:
-Fetal injury
-infection
-hematoma

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14
Q

Amino esters concerns are:

A
  • Metabolized by cholinesterase
  • Para aminobenzoic acid (PABA)
  • One “i” in the name
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15
Q

T/F: Para aminobenzoic acid is a known allergen.

A

TRUE

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16
Q

Amino amides concerns are:

A
  • Amide leadage (metabolized by liver)
  • NO PABA
  • Two “i” in the name
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17
Q

Lipid solubility can do what:

A
  • Increase potency

- Enhances placental diffusion

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18
Q

Protein binding can do what:

A
  • Influence duration
  • Higher protein binding decreases placental diffusion
  • A1-acid glycoprotein (High affinity-low capacity)
  • Albumin (Low affinity-high capacity)
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19
Q

T/F: Local anesthetic agents are all weak acids.

A

FALSE (…all weak bases.)

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20
Q

What will volume and concentration of a local anesthetic dose do?

A

Dictate onset, quality, and duration

Increasing does - faster onset, longer duration

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21
Q

Vasoconstrictors will do what to a local anesthetic?

A

-Prevent absorption via vascular beds, therefore more La available for blockade.

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22
Q

Temperature does what to a local anesthetic?

A

-affects onset, with warmed LA reducing onset time

23
Q

Local anesthetic has what affect on pregnancy?

A

-Smaller amount of local anesthetic are needed
-faster onset of blockade
(Progesterone could possibly be the reason)

24
Q

What local anesthetics are commonly used for labor epidural analgesia?

A
  • lidocaine
  • bupicavaine
  • Ropivacaine
25
Q

What local anesthetics are commonly used for operative epidural anesthesia?

A
  • Lidocaine

- 2 -chloroprocaine

26
Q

What local anesthetics are commonly used for spinal anesthesia?

A
  • Bupivicaine

- Tetracaine

27
Q

Lidocaine concerns in OB are:

A
  • Labor epidural not used for continuous infusion
  • Top up and to test function of epidural catheter
  • Short duration ~45 minutes
  • activate epidural catheter for C-section (15-20 cc of 2%
28
Q

A lot of motor block with lidocaine during a epidural is a good thing.

A

FALSE

29
Q

What is the dose of 2 chloroprocaine for a Csection?

A

15-25 cc of 3% (redose give 5 cc at a time)

30
Q

Details about 2 chloroprocaine:

A
  • Only ester used in epidural space
  • rapid onset, short duration
  • lot of motor block
  • metabolized by pseudocholinesterase
  • interfere with fentanyl’s analgesic effects
  • Not for spinals
31
Q

Bupivaciane dose for epidural is:

A
  • Initial 15-20 mg (7.5 - 10cc of 0.2%)

- Infusion 8-12 mg ( 8 - 10 cc of 0.1%)

32
Q

What can be said about bupivicaine?

A
  • Long duration
  • less motor block than other agents
  • Produces refractory v-tach/v-fib if large IV does given.
33
Q

What about levobupivacaine?

A
  • L-isomer of bupivicaine
  • less cardiotoxic
  • New and very expensive
  • not approved for spinal
34
Q

What about ropivacaine?

A
  • Bupivacaine analog
  • less cardio toxic than levobupivacaine
  • 25% less potent than bupivicaine
  • not approved for spinal
35
Q

T/F: For obstetrics lumbar level is best to cover T-5 thru S4 dermatones.

A

False (…T-10 thru S4 …)

36
Q

In __% of patients the spinal cord ends at L2/L3, therefore spinals should be placed as low as possible and below __.

A

5

L3

37
Q

_________ line passes across the lumber spine between the posterior iliac crests

A

Tuffier’s (L3/L4)

38
Q

What are the contraindication to neurasxial blockade?

A
  • Patient refusal
  • Infection at the site of injection
  • Coagulopathy (Liver failure, anticoagulats, HELLP syndrome, thrombocytopenia …)
  • Intracranial mass lesion
  • aortic stenosis
  • Existing spinal or neurological pathology
  • Hemodyamic instability
39
Q

Epidural spae on average identified at ___ cm deep.

A

4.75

40
Q

After space identified thread catheter until __ cm of the tip lie in the epidural space.

A

5

41
Q

T/F: If placement of the catheter in an epidural fails withdrawal the catheter while leaving the needle in place to reposition.

A

FALSE (Never withdrawal the catheter through the needle!)

42
Q

Difference between epidural and spinal block is one ______ layer (a few millimeteres) but drugs delivered via spinal route are ~ ___ more potent and much smaller needles are used (______ gauge for spinal vs. _____ gauge for epidural)

A

tissue
10x
22-27
17-18

43
Q

Important points about subarachnoid blocks for labor?

A

-More often used for C-section
-Combination of opioid and local anesthetic
(Sufenta 5-10 mcg or fentanyl 10-20 mcg and bupivacaine 2mg)
-Quickly done when there is no time for epidural
-Combination of epidural and spinal are done too.

44
Q

Important points about a combination of spinal and epidural:

A
  • Provides nearly instant relief

- Problem is it makes testing epidural catheter difficult

45
Q

What are the S/S of local anesthetic toxicity for the CNS?

A
  • Tinnitus
  • Light-headedness
  • Metallic taste
  • Circumoral numbness
  • Convulsions
  • Loss of consciousness
  • Respiratory arrest
46
Q

T/F: A higher potency of local anesthetic requires less total dose required for toxicity.

A

TRUE

47
Q

T/F: A decrease in PaCO2 and acidosis lowers seizure threshold when using a local.

A

FALSE (A increase in PaCO2…)

48
Q

T/F: Acidosis decreases protein binding which allows more free local anesthetic.

A

True

49
Q

What are the S/S of local anesthetic toxicity of the cardiovascular system?

A
  • Inhibition of cardiac sodium channels
  • Decrease the rate of depolarization in Purkinje’s fibers and ventricular muscle
  • Decrease duration of action potential and effective refractory period
  • Increased toxicity to bupivacaine and cocaine with pregnancy.
50
Q

What is the treatment for local anesthetic toxicity?

A
  • 20% intralipid if refractory to standard resuscitation efforts
  • Initial bolus of intralipid 20% at 1.5 cc/kg with a infusion of 0.25 mL/kg/min for 30-60 minutes.
  • A bolus can be repeated 1 - 2 times for persistent asystole
51
Q

What is the presentation of a subdural block?

A
  • Uneventful epidural identification and catheter insertion
  • Sensory change over 10 - 2- minutes
  • Excessive spread for volume injected
  • High cephalad spread with poor caudal spread and sacral sparing
  • Asymmetric distribution
  • Minimal or moderate motor block
  • Minimal or easily controlled hypotension
52
Q

Where does a subdural block occur?

A

Between the dura and arachnoid mater

53
Q

T/F: Horner’s Syndrome can be seen in a subdural block?

A

True

Obstetrics (10 decks)

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