Test 2: Uteroplacental & Fetal Physiology Part 1 (Slides 45-63) Flashcards
Do neostigmine and glycopyrrolate cross the placenta?
Neostigmine does cross
but
Glycopyrrolate does not
Why is atropine used over glycopyrrolate during paralytic reversal for someone who is pregnant?
Atropine will cross the placenta, unlike glyco. This avoids fetal bradycardia caused by neostigmine
What paralytic reversal agent is not recommended in the pregnant population?
Sugammadex (has not been studied in pregnant population)
What is a substance that produces an increase in the incidence of a defect that cannot be attributed to chance?
Teratogen
What must happen to produce a defect from exposure to a teratogen?
Teratogen must be administered in a sufficient dose at a critical point in development
In days, what is the most critical part in development?
15 to approximately 60 days gestational age
What anesthetic drug is a proven teratogen?
None have been proven
How is drug teratogenicity studied?
- Animal models
- Retrospective studies
What are the FDA drug classifications?
- Class A to D
- A being least dangerous
- D being most dangerous
What is the drug classification of N2O?
Not classified because it is not regulated by the FDA since it is a medical gas
What is N2O thought to do in animal model studies?
Thought to be harmful to DNA synthesis in high doses
Has not been found to be associated with congenital abnormalities in humans
What is the basic MOA of benzos
Enhance GABA activity in the CNS
What drug has been shown (retrospecitively) to have an association with first 6 weeks of pregnancy and cleft palate?
Diazepam
Chronic exposure, not a one-time low dose
What FDA class is diazepam
Class D (positive evidence of risk)
What are the fetal effects of meperidine?
- neonatal CNS depression
- Metabolite normeperidine can cause seizures if it accumulates
What are the fetal effects of morphine?
- Decreased maternal respiration, can lead to deoxygenation in fetus
- Fewer fetal heart rate accelerations
What are the fetal effects of remifentanil?
- Maternal sedation without significant neonatal effects
- Rapid metabolism = minimal fetal exposure
What are the fetal effects of Butorphanol (Stadol)?
- Mixed agonist-antagonist both block and activate pain receptors
- Can be used for pain relief without as many side effects to fetus
How does the placenta exchange gas?
Passive diffusion
What is placental O2 transfer dependent on?
Partial pressure of oxygen available
What is placental O2 transfer limited by?
Blood flow to placenta/maternal blood flow to uterus
Will a healthy placenta compensate for low O2?
Yes, to a degree
What is P50?
- Partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen
Does fetal or adult hemoglobin have a higher affinity for oxygen?
Fetal
Does fetal or adult hemoglobin have a higher P50?
Adult
Why does the difference in oxygen affinity between fetal and adult hemoglobin matter?
It allows fetal hemoglobin to efficiently pick up oxygen from maternal hemoglobin in the placenta
What is the P50 of fetal hemoglobin?
~19 mmHg
At 19 mmHg PO2, 50% of the Hgb is saturated with O2
What is the P50 in adult hemoglobin?
~27 mmHg
At 27 mmHg PO2, 50% of the Hgb is saturated with O2
What is the Bohr effect?
Phenomenon that describes how the affinity of hemoglobin for oxygen is influenced by the concentration of CO2 and the acidity (pH) of the surrounding environment
An increase in CO2/decrease in pH will result in a decreased affinity of hemoglobin for oxygen
How will an increase in CO2/decrease in pH effect hemoglobin oxygen affinity?
Decreases affinity
How does a decreased affinity for oxygen effect maternal hemoglobin release of oxygen?
Enhances the release
What is the double bohr effect?
Fetal left shift of oxy hgb dissociation curve
Maternal right shift of oxy hgb dissociation curve
Fetal INCREASE affinity
Maternal DECREASE affinity
As CO2 content of fetal blood decreases –> fetal blood becomes relatively alkaline and shifts the fetal oxygemoglobin dissociation curve to the left. This facilitates more fetal oxygen uptake and essentially locks on to that oxygen
How does maternal hypocapnia be detrimental to the fetus?
- Hypocapnia/ Maternal Alkalosis (Hyperventilation) will cause the maternal oxyhemoglobin curve to shift left
How can maternal hypercapnia be detrimental to the fetus?
- Hypercapnia (CO2 readily crosses the placenta) can result in fetal acidosis and myocardial depression
