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Advanced Anesthesia Fall Semester > OB - review > Flashcards

OB - review Flashcards

1
Q

Most physiologic changes occur in the ___ trimester, and most anatomic changes occur in ____

A
  • Physiologic = 1st trimester
    • ​due to hormones secreted by corpus luteum and placenta
  • Anatomic = 2nd and 3rd trimesters
    • ​mechanical changes of the women’s body by enlarging uterus and compression of surrounding structures
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2
Q

Are the physiologic and anatomic changes in pregnancy good or bad?

A

Mostly good.

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3
Q

Respiratory changes in pregnancy (physiologic)

A
  1. Increase in ventilation
    • D/t increased metabolic demand & progesteron eproduction
    • Increase 40% TV
    • increase 15% RR
    • increase 50% MV
      • ​drives maternal PaCO2 to 30-32 (goes into resp alkalosis pH = 7.44)
      • compensated respiratory alkalosis with renal excretion of bicarbonate
  2. Breathing pattern more diaphragmatic
  3. is increased work of breathing
  4. increased use of accessory muscles
  5. chest wall muscle relaxation → chest wall expansion
    • d/t increased progesterone (progesteron mediated)
    • Lung compliance unchanged
    • increase in airway edema → an increase in airway resistance
  6. Increase in O2 Consumption
    • Increase by 30%
    • Oxy-hgb curve shifts to the right (P50 increases from 26-28mmHg)
  7. increased CO2 production
    • increased by 35%
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4
Q

Anatomic respiratory changes in pregnancy

A
  1. Cephalad diaphragm displacement
  2. Weight gain and breast enlargement (pressure on the chest and boobs might get in the way of airway)
  3. Vascular engorgement of the respiratory tract mucosa
  4. Mucus membranes fragile
  5. Edema of nasopharynx, oropharynx, and the cords
  6. Faster small-airway closure
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5
Q

When is edema of the nasopharynx, oropharynx, and the cords most common?

A

During pre-eclampsia

Remember there is HTN and loss of plasma proteins.

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6
Q

Effect of pregnancy on the FRC

A

Decrease by 20%

Less safe apnea time!!

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7
Q

Why can pregnant ladies desat quickly?

A

Low FRC and high O2 consumption rate (30% higher than normal at rest).

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8
Q

We can expect induction during pregnancy to be (faster/slower) than the non-pregnant patient.

MAC should be (increased/decreased) by ____.

A

Faster induction

Decreased MAC by 25-40%

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9
Q

Effects of maternal hyperventilation

A
  • Alkalosis - Shift to the left (will decreased O2 release to the fetus)
  • Constriction of the umbilical and uterine blood vessels
    • This is only a problem with prolonged hyperventilation
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10
Q

Effects of elevating the diaphragm

A

Decreased FRC and displacement of the heart

(look at EKG, listen for murmur, possible dysrhythmia)

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11
Q

Pregnancy and coagulation

A

Overall, it is a hypercoagulable state Increased clotting factors (fibrinogen and factors 5-8)

Platelets remain unchanged or may decrease slightly in 3rd trimester)

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12
Q

CO will be (increased/decreased) during pregnancy

A

Increased

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13
Q

What happens to BP and SVR in pregnancy

A
  • SVR will decreased by 20% - vessels lose their SNS tone → BP may decrease slightly
    • ADH is cleared more rapidly
  • BP maintenance depends on RAAS b/c vessels have lost their SNS tone
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14
Q

Your pregnant patient is lying supine and starts to drop their BP.

What is this and how is it treated?

A

Supine Hypotensive Syndrome

It’s possible compression of vena cava or aorta.

Treatment:

  • Left or right uterine displacement (depending on which vessel is compressed)
  • Hydrate before induction
  • Treat hypotension with ephedrine or phenylephrine
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15
Q

Supine hypotension syndrome is a risk > ____ weeks and can decrease CO by up to ___%

A

20 weeks (but can appear as early as 13-16 weeks)

30%

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16
Q

Plasma volume increases by ___% but RBC volume only increases by ___%.

A

Plasma 50%

RBC 20%

Causes a dilutional anemia

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17
Q

Normal blood loss during vaginal birth

A

500cc

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18
Q

Normal blood loss during a c-section

A

500 - 1,000cc

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19
Q

GI changes in pregnancy

A

As a result of physiologic and hormonal changes:

  • Increased gastric volume
    • decreased esophageal and intestinal motility (progesterone mediated)
  • Secretions are more acidic
    • ​gastrin mediated (placentally derived)
  • Stomach is displaced in the thorax, upward and at 45 degree angle to the right.
  • Decreasing tone to the lower esophageal sphincter tone, causing reflux
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20
Q

All parturients greater than ___ weeks are considered full stomachs

A

12 weeks

Aspiration risk continues into the post-partum period, until the body has time to normalize hormonally, physiologically, and anatomically.

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21
Q

Aspiration prophylaxis in pregnancy

A

Give non-particulate antacids, H2 blockers, and/or reglan.

Consider doing regional instead.

If doing GA, do RSI.

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22
Q

Renal Changes in Pregnancy

A

High CO and large blood volume cause an increase in GFR by 60%.

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23
Q

Hepatic Changes in Pregnancy

A

Slight increases in AST and ALT

Bigger changes will be seen in HELLP syndrome (part of pre-eclampsia)

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24
Q

Neuromuscular Changes in Pregnancy

A
  1. Increase in endorphins!
    • Allows us to decrease MAC by 40%
  2. Increased sensitivity to opioids, LAs, and catecholamines
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25
Q

Why is MAC decreased in pregnancy?

A

1) Faster induction
2) Higher endorphins potentiates the effects of the VA

26
Q

Formula for uterine blood flow and normal values for UBF

A

(uterine arterial pressure - uterine venous pressure) / Uterine vascular resistance

UBF during pregnancy: 500-700mL/min

UBF when not pregnant: 50-100mL/min

27
Q

There is a direct correlation between uterine blood flow and

A

fetal umbilical venous O2

28
Q

When will uterine blood flow decrease?

A

Decrease in perfusion pressure (maternal hypotension)

29
Q

Is the uterine vascular bed able to autoregulate?

A

NO!

This is why BP management in parturients is critical

30
Q

We are most worried about fetal ion trapping with these drugs

A

LAs

31
Q

Generally all of our anesthetics will cross the placenta except

A

NMBs

32
Q

What is a protective mechanism that the fetus has against drug OD?

A

Blood from the umbilical vein first goes to the liver

33
Q

What is the baseline fetal HR?

A

120-160

May vary by 5-10bpm and variations are a good and normal thing.

34
Q

Causes of fetal tachycardia

A
  1. Maternal fever or infection
  2. Atropine administration
  3. Late sign of fetal hypoxia
35
Q

LATE decelerations may be from

A

Compromised blood flow to the fetus (maternal hypotension, cord compression, etc)

36
Q

SEVERE decelerations will go below __bpm and last longer than ___

A

70 1 minute

Fetus is in distress! We need to deliver!

37
Q

Treatment for shitty fetal heart rate patterns

A
  1. LUD (left uterine displacement)
    • Compression could be decreasing CO by 30%
  2. O2
  3. Correct any contributing factors
    • treat hypotension
    • stop oxytocin
    • check for prolapsed cord in her vajay
    • assess for vaginal bleeding that could be from the placenta)
38
Q

Stages of Labor

A

1st Stage

  1. From beginning of regular painful contractions to full cervical dilation
  2. Longest stage of labor and divided into two phases
  3. This is mostly visceral pain (Block T10-L1)
  • Latent Phase: 1st and longest part
    • Contractions start and are getting stronger and cervix is thinning –>
  • Ative Phase: Second and shorter phase
    • The cervix is actively dilating to 10cm

2nd Stage

  1. From full cervical dilation to delivery
  2. This is the most painful stage***
  3. This is somatic, stretching pain (Block S2-4)

3rd Stage

  1. From delivery of neonate to delivery of the placenta
39
Q

Staging and neuraxial block requirements

A

1st Stage (T10-L1)

2nd Stage (T10-S4) **notes say S4-S1**

3rd Stage (T10 b/c it involves the vag and uterus)

40
Q

Risks for intense pain during pregnancy

A
  1. Young maternal age (ya so tight)
  2. Increased maternal weight (excess tissue in the way)
  3. Occiput posterior presentation Increased fetal weight (fat baby)
  4. Use of tocolytics
41
Q

Opioids popular in pregnancy

A

Fentanyl and meperidine (Demerol)

Sufentanil not as popular because it can cause fetal bradycardia

42
Q

Common analgesic interventions in parturients

A
  1. Opioids
  2. Ketamine
  3. Agonist/Antagonists (Nubain & Stadol)
  4. Intrathecal Opioids
  5. Epidurals
  6. CSE
43
Q

Can epidurals prolong labor?

A

Yes, it can prolong Stage 1

44
Q

Relative contraindications for regional anesthesia

A
  1. Primary herpes
  2. Obstructive cardiac lesions
  3. R or L intracardiac shunts
  4. Active CNS disease
  5. PIH (pregnancy induced HTN)
  6. MG (possible respiratory compromise)
45
Q

Epidurals should be placed below this level

A

Below L2

46
Q

Does the level of epidural block depend on baracity of the LA?

A

NO.

It would matter in spinals. NOT epidurals!

47
Q

Most common LAs in pregnancy

A

Amides: Lidocaine, bupivacaine, and ropivacaine

Esters: Chlorprocaine, tetracaine, and mepivacaine

48
Q

Epidural concentrations used for bupivacaine

A

.0625% - .25%

Used with or without an opioid

49
Q

Epidural concentrations used for ropivacaine

A

.125% - .5%

50
Q

Benefits of having a continuous laboring epidural (CLE)

A
  1. More constant level of analgesia
  2. More even block
  3. More stable VS
  4. Greater safety
  5. Able to use if need to give surgical block for emergent c-section
51
Q

Procedure for continuous epidural infusion

A
  1. Give test dose with epi. Wait 3-5 min before initiation of bolus (may be difficult to detect b/c mother is probs already tachy from pain)
  2. Give bolus injection
  3. Start continuous infusion once adequate block obtained (at LEAST T10 level)
52
Q

Block above this level will start to affect cardiac accelerators

A

T4

53
Q

Sometimes the first sign of a sympathectomy may be

A

N/V

If your patient starts having N/V after epidural placement - check BP for hypotension. We don’t want SBP

54
Q

Effects of epidural on labor

A

Slows Stage 1

Can halt labor if cervix dilated

55
Q

Caudal Block

A

Type of epidural not common in OB.

Needs high volumes. May be ok in Stage II

56
Q

Paracervical block

A

Usually done by OBGYN

LA injected submucosally in the vagina on either side of the cervix

May be used for Stage I (while cervix is dilating), but there is high risk of fetal bradycardia from LA injection.

57
Q

Pudendal block

A

Good block for Stage II (delivery)

Inject LA on both sides of vagina into the sacrospinous ligament. Good perineal anesthesia.

58
Q

Parturients are most likely easy or difficult airway?

A

Difficult

Edema of oropharynx and cords

59
Q

If doing a spinal block for c-section, you should block at this level

A

T4-6

60
Q

ABG changes

A
  • PaO2 decreased (>100 mmHg)
  • PaCO2 decreased (30-32 mmHg)
  • Arterial pH no change
  • Serum bicarbonate decreased 4 mEq/L (from 26 to 22 mEq/L)
    • ​Compensatory renal excretion of serum bicarbonate

Advanced Anesthesia Fall Semester (10 decks)

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