Maternal and Fetal Physiology Flashcards

1
Q

What are 4 neurological changes the mother experiences?

A
  1. MAC is decreased
  2. Epidural space becomes smaller
  3. CSF volumes are decreased and epidural veins are engorged
  4. Increased sensitivity to LAs
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2
Q

What 5 things happen to mother’s ventilation?

A
  1. TV increased 40% at term
  2. RR increased by 15%
  3. MV increased nearly 50%
  4. PaCO2 decreased to 28-32
  5. FRC decreased by 20%
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3
Q

Does the mother have an overall respiratory/metabolic acidosis/alkalosis?

A

With increased MV, resp alkalosis occurs but compensatory metabolic acidosis occurs via excretion of HCO3 to maintain normal pH.

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4
Q

Why is it important to preoxygenate a mother prior to induction?

A

FRC is decreased coupled with increased maternal oxygen consumption can rapidly lead to maternal hypoxia during induction of GA.

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5
Q

What two things should be kept in mind with ETT selection for mother?

A
  1. Use smaller ETT tube

2. Avoid nasal intubation or instrumentation (due to mucosal venous engorgement).

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6
Q

Does the mother exhibit a left or right shift on oxyhemoglobin curve?

A

Right shift (P50=30).

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7
Q

What 6 cardiovascular changes can be seen in the mother?

A
  1. Increased plasma volume (45%)
  2. PVR drops 15%
  3. CO increases
  4. Response to adrenergic drugs is blunted
  5. Cardiac hypertrophy on CXR
  6. Heart murmurs often present
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8
Q

What happens to mother’s RBC and plasma?

A

Increase in plasma volume (45%) and increase in RBC (20) creates hypervolemia; however, there is a relative anemia (due to plasma dilution).

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9
Q

Is there an increase or decrease in Renin production/secretion in the mother?

A

Increase in renin which increases aldosterone which increases sodium/H2O retention.

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10
Q

T/F: Active phase of labor has the highest cardiac output?

A

False; Postpartum CO can be increased by 80% because the placenta is removed and there is less vascular bed to perfuse/restrict flow

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11
Q

List the phases of labor and their relative increase in cardiac outputs:

A

Latent Phase=15%
Active phase=30%
Second Stage=45%
Postpartum=80%

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12
Q

What is aortocaval compression?

A

Also called supine hypotension syndrome; Both great vessels get compressed while mother is supine.

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13
Q

What are symtomes of Aortocaval Compression?

A
Hypotension
Pallor
Nausea
Vomitting
Diaphoresis
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14
Q

What is the treatment for aortocaval compression?

A

Left lateral uterine tilt position (can also try right lateral if no change in symptoms).

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15
Q

Why are mothers at higher risk of pulmonary embolism?

A

Hypercoagulable state = increased Factors I, VII, VIII, IX, X, XII

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16
Q

What are the 5 hematological changes we see in mothers?

A
  1. Increased Factors I, VII, VIII, IX, X, XII
  2. Decreased factors XI, XIII
  3. Unchanged II, V
  4. PT dec 20%, PTT dec 20%
  5. Cell mediated immunity depressed.
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17
Q

What 3 renal changes can be seen in the mother?

A
  1. RBF and GFR increase by 50% by 16th week
  2. Serum BUN and Crt reduced
  3. Mild glycosuria and proteinuria are common.
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18
Q

Overall, what are the 3 net effects of the GI changes we will see in the mother?

A
  1. Reduced gastroesophageal sphincter tone (LES).
  2. Increased acid production
  3. Slowed gastric emptying
19
Q

What anesthetic consideration are there due to the GI changes in the mother?

A
  1. Increased risk of symptomatic aspiration

2. Treat like full stomach RSI/cricoid/etc

20
Q

T/F: most patients will have less than 25cc w/ a pH of greater than 2.5 in their stomach?

A

False; Most will have greater than 25cc and a pH less than 2.5 in their stomach.

21
Q

What hepatic change can occur with mothers?

A

20% decrease in pseudocholinesterase levels (but there is an increase in Vd which cancels out the problems with DNMBDA).

22
Q

What is the most common elective surgery performed during pregnancy? WHY?

A

Gallbladder removal

Decreased CCK release and contractile response creates sluggish GB and gallstones.

23
Q

What causes mothers plasma glucose levels to be higher and why?

A

Relative insulin resistance allows for more fetal glucose transfer (facilitates offloading ofm\ glucose to fetus)

24
Q

Aside from compensatory mechanisms, how long can a fetus survive once there is no oxygen supply and why?

A

2 minutes because fetal stores are approx 42ml O2 and consumption (without compensatory mechanisms) is 21ml/min.

25
Q

Which direction is the oxyhemoglobin curve shifted in the fetus?

A

Left shift (and also higher amount of hemoglobin).

26
Q

Does maternal or fetal Hgb have a high affinity for CO2?

A

Maternal Hgb

27
Q

In the mother, how much blood flow does the uterus receive?

A

10% of CO (600-700ml/min).

28
Q

What three factors influence uterine blood flow (UBF)?

A
  1. Systemic blood pressure
  2. Uterine vasoconstriction
  3. Uterine contractions.
29
Q

What happens to UBF with neuraxial analgesia?

A

Can increase due to reduction in maternal catecholamines which would reduce vasoconstriction.

30
Q

What affects does N2O and opioids have on UBF?

A

None or very little

31
Q

What effect does propofol have on UBF?

A

Mild decrease in UBF via maternal hypotension.

32
Q

What effect does ketamine have on UBF?

A

No net effect at does less than 1.5mg/kg

33
Q

What effect do volatile anesthetics have on UBF?

A

Decrease UBF secondary to hypotension, but minor effect under 1 MAC.

34
Q

What anesthetic drug can cause uterine vasoconstriction?

A

High serum levels of LAs

35
Q

T/F: Hypoxia and alkalosis can increase L to R shunting

A

False; Hypoxia and acidosis can increase R to L shunting via the PDA

36
Q

Describe the first Stage of Labor?

A

Onset of true labor until complete cervical dilation.

Has a Latent phase and an Active Phase

37
Q

Describe the Latent phase of the 1st stage of labor?

A

Minor dilation 2-4cm, infrequent contractions.

38
Q

Describe the active phase of the 1st stage of labor?

A

Progressive dilation to 10cm and regular contractions (3-5min)

39
Q

Describe the 2nd stage of labor?

A

Time from complete dilation until infant delivered.

40
Q

Describe the 3rd stage of labor?

A

Time from delivery of infant until placenta is delivered.

41
Q

Which type of HR decelerations are most concerning?

A

Late decelerations

42
Q

What is the most common cause of early decels?

A

Head compression= basically a vagal response.

43
Q

What is the main cause of late decels?

A

Compression of vessels/uteroplacental insufficiency

44
Q

What is the main cause of variable decels?

A

Less ominous.

Typically from umbilical cord compression.