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Anesthesia Review Questions > Chp 39 Pregnancy > Flashcards

Chp 39 Pregnancy Flashcards

1
Q

What factors determine anesthetic transfer across placenta into fetal circulation?

A
  • Maternal blood concentration determined by drug dose, location, route of inj, maternal metabolism/excretion
  • Rate of placental transfer from the concentration gradient per Fick equation
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2
Q

What is the most critical factor under veterinarian control during a c section?

A
  • Time from beginning administration of anesthetic to time of delivery of newborn
  • Minimizing time from beginning of uterine exteriorization until delivery crucial for reducing period of decreased uterine blood flow
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3
Q

Fick Equation

A
  • Q/t = KA (Cm-Cf)/D

- Amount of diffused substance per unit time

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4
Q

Fick Equation: Q/t

A

Amount of diffused substance per unit time

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5
Q

Fick Equation: K

A

Diffusion constant of a given substance which takes into account its pKa, molecular weight, lipid solubility, protein binding

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6
Q

Fick Equation: A

A

Surface area for diffusion

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7
Q

Fick Equation: Cm

A

Concentration in maternal uterine blood

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8
Q

Fick Equation: Cf

A

Concentration of substance in fetal blood

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9
Q

Fick Equation: D

A

Thickness of the placental membrane

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10
Q

How does pregnancy affect anesthetic requirement (MAC)?

A
  • Assoc with 25-40% decrease in anesthetic requirement

- Thought to be related to circulating levels of progesterone

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11
Q

Newborns and MAC

A
  • Decreased MAC reduction for first month after birth —> at which time MAC requirement will be at a maximum for that animal’s lifetime
  • Also thought to be related to progesterone that has crossed placenta to fetal circulation
  • MAC values tend to decrease gradually from one month of age until death
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12
Q

Physiologic changes altering response to anesthetics occur during pregnancy: HR

A

Increased

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13
Q

Physiologic changes altering response to anesthetics occur during pregnancy: CO

A

Increased

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14
Q

Physiologic changes altering response to anesthetics occur during pregnancy: blood volume

A

increased

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15
Q

Physiologic changes altering response to anesthetics occur during pregnancy: PCV

A

Decreased

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16
Q

Physiologic changes altering response to anesthetics occur during pregnancy: hgb

A

Decreased

17
Q

Physiologic changes altering response to anesthetics occur during pregnancy: plasma protein

A

Decreased

18
Q

Physiologic changes altering response to anesthetics occur during pregnancy: oxygen consumption

A

Increased

19
Q

Physiologic changes altering response to anesthetics occur during pregnancy: minute ventilation

A

Increased

20
Q

Physiologic changes altering response to anesthetics occur during pregnancy: FRC

A

Decreased

21
Q

Physiologic changes altering response to anesthetics occur during pregnancy: gastric emptying time

A

Increased

22
Q

Physiologic changes altering response to anesthetics occur during pregnancy: gastric pH

A

Decreased

23
Q

Physiologic changes altering response to anesthetics occur during pregnancy: GFR

A

Increased

24
Q

Physiologic changes altering response to anesthetics occur during pregnancy: renal blood flow

A

Increased

25
Q

Which physiologic changes altering the response to anesthetics increase during pregnancy?

A 
HR
CO
Blood volume 
O2 consumption
Minute ventilation
Gastric emptying time 
GFR
Renal blood flow
26
Q

Which physiologic changes altering the response to anesthetics decreased during pregnancy?

A 
PCV
Hgb
Plasma protein
FRC
Gastric pH
27
Q

Discuss effect of pregnancy on epidural analgesic technique

A
  • Preg: increased blood vol, increased shunting of abdominal blood to epidural tissues, increased epidural fat stores (during optimal nutrition)
  • Factors increase volume of epidural blood vessels/fat —> decreases potential vol of epidural space
  • Thus: volume of epidural analgesic injected in pregnant animal at term will migrate more rostrally than the same volume injected into non pregnant animal of similar size, conformation
28
Q

How much should you decrease your epidural injectate volume in pregnant animals?

A

About 1/3 of patients at term

29
Q

Important considerations for canine castrations

A
  • Inhalant at low concentrations
  • If opioids used prior to delivery, reversal in the newborn can be achieved by administering 3-4 drops naloxone sublingually
  • IVF, monitoring important
30
Q

Important considerations for feline c sections

A

Oxymorphone, hydromorphone dose in cats = 0.3mgkg

Can also use 0.3mgkg Butorphanol for less likelihood of an excitatory reaction

31
Q

Important considerations for equine c sections

A

BW used for calculation of doses should be estimated no preg weight

32
Q

precautions for anesthetizing pregnant mares: first and second trimester

A

Generally uneventful

33
Q

Precautions for anesthetizing pregnant mares: third trimester

A
  • Gravid uterus may compress VC —> hypotension when mare is positioned in dorsal recumbency
  • Paramount to attention to monitoring CV function, maintenance of ABP and oxygenation
34
Q

What drugs susceptible to “ion trapping” in the fetal circulation?

A
  • Weak bases cross the placenta into fetal circulation as unionized molecules, enter fetal circulation
  • fetal blood more acidic than maternal blood
  • Drug ionizes in fetal blood, becomes trapped and unable to readily diffuse back across the placenta
35
Q

What are the most commonly used drugs that are weak bases?

A
  • Opioids
  • Use of sublingual or IV injection of naloxone frequently effective in reversing depression in neonates that have been exposed to maternal administration of opioids
36
Q

What precautions should pregnant women take when working near anesthetized animals?

A
  • No convincing studies to document health benefits from reduced exposure to inhaled anesthetics
  • Should use vigilant scavenging equipment, avoidance of areas with IgG anesthetic use, elimination of mask or chamber induction techniques , recovery of patients to their breathing circuit with oxygen attached and use of properly fitted personal face masks for the person equipped with filters effective against hydrocarbons

Anesthesia Review Questions (43 decks)

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