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.AdvPrin A - Spr25 > Uteroplacental & Fetal Physiology Pt. 2 (Exam 2) > Flashcards

Uteroplacental & Fetal Physiology Pt. 2 (Exam 2) Flashcards

(48 cards)

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1
Q

What variables change the rate and amount of transfer of (drugs, toxins, O₂, CO₂, etc.) in the intervillous space?

A
  • Concentration gradient
  • Permeability
  • Restriction of movement (some substances are bound to in the placental tissue to prevent fetal uptake)
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2
Q

What is passive diffusion and what are some substances/drugs move via passive diffusion? (examples)

A

Movement along a concentration gradient

  • O₂
  • CO₂
  • Most anesthetic drugs
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3
Q

In regards to facilitated diffusion, a higher temperature will ______ rate of diffusion.

A

increase

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4
Q

What is facilitated diffusion and what’s an example of a molecule that moves via facilitated diffusion?

A

Movement with the help of carrier proteins still following a concentration gradient

  • Ex: Glucose
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5
Q

What is Active transport?
What is required for active transport?
What are examples of ions that utilize active transport?

A

Movement against a concentration gradient, requiring ATP

Also Requires:

  • Protein membrane carrier
  • Saturation kinetics
  • Competitive inhibition

Ex. Na⁺, K⁺, Ca⁺⁺

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6
Q

What transfer mechanism is characterized by membrane rearrangement, vesicle formation, and the movement of large macromolecules? What does it require?

A

Pinocytosis: cellular engulfment

  • requires energy
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7
Q

What is an example of pinocytosis transfer in pregnancy?

A

Transfer of IgG from mother to fetus

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8
Q

What are the major factors that impact drug transfer across the placenta?

A
  • Blood flow
  • Lipid solubility
  • Protein binding
  • pKa & pH/charge
  • Molecular size

(Also, gestational age, maternal factors, and placental drug metabolism).

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9
Q

What is the primary factor affecting anesthetic drug delivery across the placenta? Why?

A

Blood flow because most drugs are passively transferred.

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10
Q

High lipid solubility results in _______ bilayer penetration.

A

more bilayer penetration

can lead to drug trapping in placental tissue

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11
Q

What drug is an example of high lipid solubility resulting in placental tissue trapping of the drug?

A

Sufentanil

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12
Q

Why are bupivacaine and ropivacaine less likely to cross the placenta?

A

Both are highly protein-bound.

(free unbound fraction of drug equilibrates across placenta)

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13
Q

Albumin binds to _____ and ________ compounds.
α-1 acid glycoprotein binds to ______ compounds.

A
  • Albumin binds acidic & lipophillic compounds
  • α-1 acid glycoprotein binds basic compounds
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14
Q

What is pKa?

A

The pH at which 50% of a drug is ionized & 50% is non-ionized

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15
Q

Do ionized or non-ionized drugs tend to cross the placenta more easily?

A

non-ionized

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16
Q

What is ion-trapping?

A

When the fetus has a lower pH than the mother resulting in drugs being trapped in fetal circulation via H⁺ binding to non-ionized drug.

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17
Q

What is an example of a highly ionized drug that doesn’t cross the placenta easily?

A
  • Succinylcholine

prevents crossing of the drug in the first place

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18
Q

Drugs with a molecular weight of ________ typically cross the placenta.

A

< 500 Da (Daltons)

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19
Q

Most drugs with a molecular weight of _______ do not cross the placenta.

A

> 1000 Da (Daltons)

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20
Q

What are examples of drugs that don’t cross the placenta due to their high molecular weight?

Study These Flashcards
A
  • NDNMB’s
  • Heparin
  • Protamine
21
Q

What anticholinergics readily cross the placenta?

Study These Flashcards
A
  • Atropine
  • Scopolamine
22
Q

What anti-hypertensives readily cross the placenta?

Study These Flashcards
A
  • β blockers
  • Nitroprusside
  • Nitroglycerin
23
Q

What local anesthetic can readily cross the placenta? (in contrast to other LA’s)

24
Q

What drugs/drug classes typically are able to readily cross the placenta?

Study These Flashcards
A
  • Anticholinergics
  • Anti-hypertensives
  • VAA’s
  • Benzo’s
  • Ephedrine
  • Induction agents
  • Tylenol
  • Neostigmine
  • Warfarin
25
What drugs **DO NOT** readily cross the placenta?
- **Glycopyrrolate** - Heparin - Succinylcholine - NDNMBD's - Sugammadex* - Phenylephrine
26
What drugs should be used to reverse paralysis in pregnant patients? Why?
**Neostigmine & Atropine** Glyco does not cross the placenta, thus neostigmine will cause severe fetal bradycardia with neostigmine administration. Use atropine to avoid this.
27
What is a teratogen?
Substance that increases the risk of a fetal defect
28
When during development are teratogens most likely to cause fetal defect?
~15 - 60 days gestational age
29
Which anesthetics drugs are proven teratogens?
**None** However, we like to minimize or eliminate fetal exposure to anesthesia in the 15 - 60 days gestational period.
30
What drug that we commonly use is not regulated by the FDA?
N₂O (medical gas, not drug), so it is not classified
31
What is the teratogenicity profile of benzodiazepines?
Class D FDA Rating (positive evidence of risk) - Probable cleft palate formation from GABA activity - Chronic exposure (not a one time low dose) *Especially Diazepam*.
32
How does meperidine affect the fetus?
- Neonatal CNS depression - Can cause seizures due to normeperidine (metabolite) accumulation
33
How does morphine affect the fetus?
- ↓ maternal respirations = ↓ fetus O₂ - fewer fetal heart rate accelerations (not a good sign)
34
What opioid can be really useful for maternal sedation? Why?
Remifentanil Maternal sedation without significant neonatal effects *Rapid metabolism = minimal fetal exposure*.
35
What is P50 ?
The partial pressure of O₂ at which Hgb is 50% saturated with O₂ * quantifies the affinity of hemoglobin for oxygen
36
At ____ mmHg of partial pressure of oxygen, 50% of **fetal hgb** are saturated.
19mmHg
37
What is the P50 of **adult Hgb**?
27 mmHg PO2
38
How does the P50 of HbF compare to that of HbA?
HbF = 19 mmHg HbA = 27 mmHg HbF will preferentially **pick up O₂** from the mother's blood.
39
A lower P50 will result in a ________ oxygen affinity.
higher
40
What concept is linked with the increase of CO₂ and decrease of pH (acidity) resulting in a _______ affinity of Hgb for oxygen.
Bohr Effect * decreased affinity = increased unloading (Right shift in curve)
41
The presence of CO₂ and blood acidity in fetal blood will _______ the release of O₂ from maternal hemoglobin.
enhance ***R**ight shift = **R**elease*
42
What happens as the CO₂ content of fetal blood decreases?
CO₂ diffuses down concentration gradient into maternal blood → Fetal blood becomes alkaline → curve shifts left → facilitates more O₂ uptake (↑O₂ affinity) by HbF. *Left shift = Lock*
43
How will maternal hyperventilation affect fetal oxygenation?
Hyperventilation = hypocapnia/maternal alkalosis → maternal oxyhemoglobin curve shifts left and prevents as much O₂ from getting to the baby (decreased unloading)
44
What are examples of drugs that are non-ionized and can become ion-trapped when becoming more ionized in fetal circulation?
* Local anesthetics * opioids *these weak bases are more non-ionized in maternal blood and become more ionized in more acidic fetal blood leading to inability to easily cross back into maternal blood*
45
Do benzodiazepines readily cross the placenta or not?
BZDs readily cross the placenta
46
Do opioids readily cross the placenta or not?
opioids readily cross the placenta
47
Is sugammadex a good choice for paralytic reversal in the pregnant patient?
sugammadex has not been widely studied in the pregnant population and is not recommended
48
What specific opioid agonist-antagonist is discussed to be useful for pain relief in the pregnant patient?
Butorphanol (stadol) * blocks and activates pain receptors * provides pain relief with less fetal side effects

.AdvPrin A - Spr25 (33 decks)

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