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OB > Labor, Vaginal & Cesarean Delivery > Flashcards

Labor, Vaginal & Cesarean Delivery Flashcards

1
Q

What are the three stages of labor?

A
  1. Beginning of regular contractions to full cervical dilation (10 cm)
    subdivided into latent phase (dilation to 2-3cm), and
    active phase (up to 10cm)
  2. Full cervical dilation to delivery of the fetus
  3. Delivery of the placenta
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2
Q

What is a laboring mother always considered?

A

A full stomach! Always RSI

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3
Q

According to the ASA guidelines, a healthy mother may:

A

1) drink a moderate amount of clear liquids throughout labor, and, 2) eat solid food up until the point a neuraxial block is placed

*The mother is NPO if surgery and general anesthesia is to be utilized

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4
Q

Does an epidural prolong the first stage of labor?

A

No

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5
Q

Does an epidural increase the need for a c-section

A

No

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6
Q

What can be given to help labor progress?

A

Oxytocin

Oxytocin is released from the posterior pituitary and helps contractions

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7
Q

The perineum is innervated by the ____ nerve

A

pudendal nerve (s2-s4)

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8
Q

Which block is not appropriate for the first stage of labor?

A

the pudendal nerve (s2-s4)

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9
Q

What needs to be anesthetized during the second stage of labor (the uterus is still contracting)?

A

T10-S4

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10
Q

The first stage of labor pain originates from _____ and the second stage of labor originates from _____.

A

The first stage of labor pain originates from T10 - L1 and the second stage of labor originates from T10 - S4.

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11
Q

What are the analgesic options for the first and second stages of labor?

A

1st stage: neuraxial blockade, paravertebral lumbar sympathetic block, and paracervical block

2nd stage: neuraxial blockade and a pudendal nerve block

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12
Q

What has made a comeback for a non-invasive alternative for labor anesthesia?

A

nitrous oxide…self administered 50% nitrous, 50% oxygen

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13
Q

What is the CSE technique, and what does the dual benefit provide?

A

Combined spinal-epidural technique, and it provides the ability to prolong the duration of anesthesia with an indwelling epidural catheter. It is particularly useful in labor and delivery

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14
Q

Labor pain in stage 1

A

1st stage: pain begins in the lower uterine segment and the cervix

pain signals to the T10-L1 posterior nerve roots

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15
Q

Labor pain in stage 2

A

adds in pain (existing pain in the lower uterine segment and cervix) from the vagina, perineum, and pelvic floor

pain impulses travel from the perineum to the s2-s4 posterior nerve roots

neuraxial procedure that covers T10-L1 during the 1st stage must be extended to cover S2-S4 during the 2nd stage of labor (total coverage = T10-S4)

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16
Q

Describe pain in the 1st stage of labor

A

Visceral C-fibers, hypogastric plexus

T10-L1, dull, diffuse, cramping

neuraxial, paravertebral, paracervical

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17
Q

Describe pain in the 2nd stage of labor

A

pudendal nerve

S2-S4

Sharp, well localized

neuraxial, pudendal nerve block

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18
Q

What are the consequences of uncontrolled pain?

A

increased maternal catecholamines (htn and reduced uterine flow)

hyperventilation - left shit of oxyhgb curve (reduced oxygen to fetus)

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19
Q

Why is nitrous oxide so great?

A

when given alone (not with opioids, it is NOT associated with hypoxia, loss of airway reflexes, or unconsciousness

Also preserves uterine contractility and does not cause neonatal depression

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20
Q

What is the most common approach to the combined CSE approach

A

the “needle-through” approach

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21
Q

What is the epidural extension technique?

A

the injection of saline into the epidural space immediately after the local anesthetic is administered into the subarachnoid space

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22
Q

Does hypnosis help labor pain?

A

15% are easy to hypnotize, 15% are impossible

may be of some benefit in labor but not useful by itself

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23
Q

psycho-prophylaxis (lamaze)

A

involves breathing and eye focus, commonly combined with other forms of analgesia

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24
Q

acupuncture

A

opioid peptide release has been demonstrated and maybe the gate control theory. Aims at correcting energy flow imbalances

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25
Q

Parenteral Analgesic Techniques

A

Problems:

Nearly all opioids cross the placenta and depress the fetus.

Loss of beat-to-beat variability and decreased movement complicate evaluation.

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26
Q

Problems with parenteral analgesic techniques

A

Routes:

IM and SC are not often used because of delayed onset.

IV offers easier titration and rapid onset and PCA options.

PCA advantages include better satisfaction scores, less neonatal depression, less nausea, and less risk of maternal respiratory depression.

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27
Q

What is the best parenteral analgesic technique?

A

PCA advantages include better satisfaction scores, less neonatal depression, less nausea, and less risk of maternal respiratory depression.

28
Q

Which opioid is NOT used parenterally?

A

Morphine

Immature blood-brain barrier increases the risk of respiratory depression in the neonate.
Not often used for this reason.

29
Q

Which parenteral analgesic techniques are used?

F-N-B

A

Fentanyl: Kinetics rapid transfer across the placenta.
Respiratory depression may outlast analgesia.

Nalbuphine (Nubain): Mu opioid antagonist, kappa agonist.
Has a ceiling effect on resp depression but no real large difference in side effects.
Dysphoria is common.
Used to treat opioid-induced pruritis (5-10 mg iv q 6 H prn).

Butorphanol (Stadol):
Some reports suggest a better analgesic profile than fentanyl.
Sedation is common.
Ceiling effect on resp depression.

30
Q

Respiratory depression may outlast analgesia with ____, Dysphoria is common with _____, and ____ is common with is common with _____.

A

fentanyl, nalbuphine, sedation with butorphanol

31
Q

Are volatile anesthetics used anymore in OB?

A

Rarely used anymore.

Dose limit 0.5 MAC.

Risks of pulmonary aspiration (gasses lower esophageal sphincter tone)

Decreased uterine tone is a side effect.
Nitrous used outside the US commonly.
Often used with supplemental nerve block.

32
Q

What lumbar level is best to cover for obstetrics?

A

For obstetrics lumbar level is best to cover T-10 thru S4 dermatomes

In adults the spinal cord ends at the L1 level.

In 5% of patients it ends at L2/3, therefore spinals should be placed as low as possible and below L3.

If patient complains of paresthesia while spinal is being dosed, remove the needle.

33
Q

Because the spinal cord ends at L2/L3 for 5% of adults, where is the best place to do a spinal?

A

below L3.

If patient complains of paresthesia while spinal is being dosed, remove the needle.

34
Q

Where are most puncture sites actually done at?

A

L2-L3 (58%)

L3-L4 (38%

35
Q

Where is an injection considered safe?

Where is Tuffier’s line?

A

Safe: below L2/L3

Tuffier’s line: L4/L5

36
Q

What are the contraindications to neuraxial blockade?

A

Patient refusal
Infection at site of injection
Coagulopathy (anticoags, liver, thrombocyt..)
Intracranial mass legion
aortic stenosis
existing spinal/neuro pathology
hemodynamic instability

37
Q

Epidural space on avg identified ____ cm deep

A

Epidural space on avg identified 4.75 cm deep

38
Q

Loss of Resistance Technique can be with ____ or with ___. ______ is safer option 3-5 cm deep

A

Loss of Resistance Technique can be with saline or with air. Saline is safer option 3-5 cm deep

39
Q

After space identified thread catheter until ____ of the tip lie in the epidural space

A

After space identified thread catheter until 5 cm of the tip lie in the epidural space

40
Q

The difference between epidural and spinal block is one tissue layer (a few millimeters) but drugs delivered via spinal route are ___x more potent and much smaller needles are used

A

10X

41
Q

Subarachnoid Blocks for Labor can consist of..

A

opioid alone or in combination with local anesthetic agent; (sufenta 5-10mcg or 15-20 mcg fentanyl +/- 2 mg bupivacaine.

Good for cases where delivery expected soon and not enough time available to place epidural.

Combination spinal epidural technique also used.

We will typically ask the height of the patient prior to placing the spinal and do 1.4-2ml of bupivacaine RARE to give 2ml.

42
Q

Subdural block

A

Subdural space between the dura and arachnoid mater.
Variable presentation – minimal to LOC and apnea.
May involve cervical roots, cranial nerves, see trigeminal nerve block, Horner’s syndrome.
If detected – do NOT deliberately dose.
Replace catheter into epidural space.

43
Q

Key points

A

20-30% less local is required for pregnant patients

Using a noncutting (pencil-point) needle for spinal reduces incidence of post-dural puncture headache

Dont care for pregnant women supine

Pregnant women have softer ligamentum flavum, accented lumbar lordosis, decreased spinal canal space

44
Q

Esters

A

One “i’
plasma cholinesterase
metabolite PABA is a known allergen

45
Q

Amides

A

Two “ii”
No PABA, rare to have allergic issues
metabolized by liver

46
Q

Lipid solubility influences ____

A

Potency

Increasing lipid solubility enhances placental diffusion

47
Q

Protein binding enhances _____

A

duration

High protein binding decreases placental transfer

48
Q

AI - acid glycoprotein: high ____, low _____

Albumin: low____, high _____

A

AI - acid glycoprotein: high affinity, low capacity

Albumin: low capacity, high capacity

49
Q

The speed of onset is determined by ______

A

pKa

pKa is the pH where 50% of LA is charged (polar) and 50% is uncharged (nonpolar)

50
Q

The closer pKa is to physiologic pH, more LA is in nonpolar form and has a _____ onset

A

Faster

51
Q

How do you artificially raise pH so you are closer to pKa?

A

add bicarb

52
Q

What actually makes the local work once it crosses the membrane?

A

the polar molecule

53
Q

Does warm LA reduce onset time?

A

Yes

54
Q

Neuronal Morphology

A

Small and poorly myelinated neurons are more rapidly susceptible to blockade, e.g. type C fibers.

Larger myelinated fibers require higher LA concentration for blockade, e.g. type A fibers.
Typically a ‘differential blockade’ that prevents pain without eliminating awareness (pressure) of labor.

55
Q

What drugs are commonly used in OB for labor epidurals?

A

Bupivacaine
Ropivacaine
Lidocaine

56
Q

What drugs are commonly used in OB for operative epidural anesthesia?

A

Lidocaine
2-chloroprocaine

57
Q

What drugs are commonly used in spinal anesthesia?

A

Tetracaine
Bupivacaine

58
Q

Lidocaine

A

short duration (45 minutes)

Also used to activate epidural catheter for C-section (15-20 cc 2% lidocaine with epi)

For labor epidurals not used as a continuous infusion

Useful as a top up and to test function of epidural catheter

Lot of motor block (bad)

59
Q

2-Chloroprocaine

A

Do not use in patients with atypical pseudocholinesterase.

The only ester local used in epidural space

Rapid onset, very short duration

Epidural 2-chloroprocaine will interfere with the analgesic effects of subsequently administered epidural fentanyl.

60
Q

Bupivacaine

A

Long duration, less motor block than most other agents.

Produces refractory v-tach/v-fib if large IV dose given.

61
Q

Bupivacaine analogs

A

Levobupivacaine: L-isomer of bupivacaine
Less cardiotoxic.
Recently put on the market

Ropivacaine
Less cardiotoxicity than even levo in animal studies.
May be about 25% less potent than bupivacaine.
Not approved for spinal (neither is levo).

62
Q

Bupivacaine analogs

A

Levobupivacaine: L-isomer of bupivacaine
Less cardiotoxic.
Recently put on the market

Ropivacaine
Less cardiotoxicity than even levo in animal studies.
May be about 25% less potent than bupivacaine.
Not approved for spinal (neither is levo).

63
Q

Epidural Drug Administration

A

Every dose is a test dose! Dose incrementally

Accidental IV injection can be detected early

Epinephrine test doses in obstetrics are controversial.

64
Q

LAST symptoms

A

Tinnitus
Light-headedness
Metallic taste
Circumoral numbness
Convulsions
Loss of consciousness
Respiratory arrest

Increased PaCO2 and acidosis lower seizure threshold.

Acidosis decreases protein binding _ more free LA.

65
Q

LAST treatment

A

20% Intralipid if refractory to standard resuscitation efforts

1.5 mL/kg as an initial bolus, followed by

0.25 mL/kg/min for 30-60 minutes

bolus can be repeated 1-2 times for persistent asystole
infusion rate can be increased if the BP declines

OB (6 decks)

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