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Principles II, Exam 1 > Anesthesia For OB > Flashcards

Anesthesia For OB Flashcards

1
Q

What is the ultimate goal

A

Perfusion of uterus

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2
Q

Obesity in pregnancy

A

50% are overweight

Obesity increases advers effects and rate of c-sections

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3
Q

Respiratory changes

A
  • Thoracic cage circumference increases 5-7 cm, inc in AP diameter
  • Relaxin, relaxation of ligamentous attachments of the ribs
  • Elevation of the diaphragm
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4
Q

Lung volumes changes and capacities

A
  • VT increase
  • RV decrease: diaphragm pushes up the chest
  • ERV decrease
  • FRC decrease by 80% due to elevation of the diaphgram (ERV/RV)
  • Elevated closing volumes
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5
Q

What happens in supine position

A

Exaggerates the effects

-FRC 70% of pp volume

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6
Q

Respiratory changes
MV
Alveolar ventilation

A 
MV  increase ( inc Vt and CO2 production)
Alveolar ventilation increases ( alkalosis )
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7
Q

Heart during pregnancy

A

Leftward, may appear enlarged on X-ray
Grade I, II systolic murmurs due to inc blood flow across valves
Inc HR, so decrease or no change in BP

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8
Q

Maternal blood flow

A
  • Second trimester: max rate of incr, slower in third
  • 35-40% expansion (1L-1.5L) much of this perfuses the gravid uterus
  • EBL 500-1000 L
  • RBC mass inc but at slower rate than plasma (relative anemia of preg)
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9
Q

Autotransfusion

A
  • around 500 cc
  • immediately after delivery
  • decrease in vascular space by same volume
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10
Q

Cardiac output in each trimester

A

1st trimester: 40% inc

2nd trimester: slight incr

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11
Q

Cardiac output during labor

A

15% latent phase
30% active phase
45% expulsion phase
Each contraction increases CO 10-20%

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12
Q

Blood pressure

A
  • No changes
  • Increase renal, uterine and extremity blood flow
  • coload vs preload for SAB
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13
Q

Body wt and composition

A 
17% = 12 kg
Uterus 1kg
Amniotic fluid 1kg
Fetus and placenta 4kg
Blood volume and interstitial fluid 4kg
Fat and protein 4 kg
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14
Q

Aortocaval compression

A

Hypotension, diaphoresis, palor due to obstructed IVC in the supine position- 20th week

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15
Q

What is the effect of vasodilation drugs on aortocaval compression?

A

Drugs will increase symptoms

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16
Q

How does blood returns to heart during aortocaval compression

A

Via the epidural veins and azygos system

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17
Q

What are some effects of aortic compression

Who does it effect

A
  • Partially occluded aorta when supine: HoTn in LE, uterine arteries
  • decreases intervillious blood flow by 20%, dec fetal PaO2
18
Q

What can cause fetal asphyxia, distress

A

Aortic compression

19
Q

What is uterine blood flow related to

A

Perfusion pressure

UPP = UA - UV

20
Q

What is the quick treatment for decrease uterine blood flow

A

Manually displace uterus 15 degrees
Turn pt to left side
10% RUD is more effective

21
Q

What coag factors and when are increased - hemodynamic changes

A

Factors 7,8,10 fibrinogen, leukocytes
Increased after 3 month

Leads to increase incidence of DVT, PE
Gestational thrombocytopenia

22
Q

relative anemia of pregnancy

Why

A

RBC mass increases slower than plasma

Delusional effect

23
Q

GA prego

A
  • MAC decrease 40%, less anesthetic
  • Progesterone level increase 10-20 times
  • Beta endorphins increase during labor
24
Q

Regional anesthesia for prego

A
  1. Swollen epidural veins= high risk for IV injection
  2. Soft LF= lost of resistance best for epidural
  3. Neuro sensitivity to LA: hormonal and acid/base changes
  4. 30-50% dose decrease in LA, 1/3 reduction or more
  5. Lordosis: decr CSF specific gravity may enhance cephalad spread
    - higher risk for high spinal, decrease flow to caudal - narrowing
25
Q

Uterine blood flow originates

Flow rate at term

A

Originates from internal iliac arteries
2 uterine arteries, max dilated
800ml/min at term

26
Q

How is placental blood flow supplied

A

Maternal arcuate artery
Radial arteries
Spiral arteries

27
Q

What is uterine flow proportional to?

A

To the mean perfusion pressure (pressure dependent)

It’s not auto regulated

28
Q

How is arterial uterine blood flow

A
  • Max Vasodilated
  • Capable of vasoconstriction: preeclampsia: doesn’t inc O2 delivery- small babies
  • decrease blood flow to the fetus
  • no way to directly increase uterine blood flow
29
Q

Alpha agonist vs mixed alpha - beta agonist

A
  1. Alpha: potent uterine vasoconstrictor, dec urine blood flow, tx of HoTN with tachycardia, useful in refractory or extreme HoTN
  2. Mixed: protect uterine blood flow, tachyphylaxis, greater venoconstriction
30
Q

What are some factors that increase HoTn

A

Age
Obesity
High block requirements
Pre-op HTN

31
Q

What med BP Rx u should avoid with pregnant women

A

Ace inhibitors decrease BP via steal mechanism

32
Q

Uteroplacental mechanism

A
  1. Spiral arteries: expel blood into intervillious space
  2. Maternal venous sinuses receive blood from intervillious space and return it to the general circulation
  3. Decreased by Prostaglandin inhibitors like Motrin.
33
Q

Placenta characteristics

A

Villous hemochorial
Exchange gases, nutrients, waste w/maternal blood
500g, 3cm thick

34
Q

What is placenta

A
  • Union of maternal and fetal tissues for physiologic exchange
  • Fetus sends deoxygenated blood to the placenta via 2 umbilical arteries; perfuse capillary networks within placental villi that protrude into maternal blood
35
Q

Erythroblastosis fetalis

A
  • Fetus Rh+ RBCs are deposited in the vascular system of an Rh- mother
  • Mom develops antibody to fetus
    Rh+ ABs transferred to fetus which leads to RBC destruction in the fetal spleen
36
Q

What is the umbilical blood flow rate

A

360 ml/min

37
Q

What is the fetal oxygen transfer effected by

A

Decreased by hypoxia, catecholamines, acute cord compression

38
Q

What is the p50 for fetal Hgb

A

P50 is 19 for fetal Hgb

39
Q

When is the biggest increase in CO

A

Immediately after delivery as much as 80% of prepregnancy or 45%
Autotransfusion 500 cc

40
Q

What happens to alpha and beta receptors during pregnancy

A

Down regulation: decreased chronotropic response with epi and iso
- higher doses of vasopressors required

Good: u don’t want vasoconstriction
Receptor issue not volume

Principles II, Exam 1 (8 decks)

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