Obstetrics Flashcards
Are pregnant women more or less sensitive to local anesthetics for neuraxial anesthesia?
More sensitive (lower doses needed). Uterine compression of IVC causes epidural vein congestion which means less epidural space and lower doses needed; also compresses intrathecal space; progesterone makes nerve fibers more sensitive to LAs
Is the MAC increased or decreased during pregnancy and by how much?
Decreased by 40%
What does a baseline ABG look like for a pregnant women?
7.45/30-32/19-20
Decreased PaCO2 (from increased MV - increased TV and mildly increased RR)
Increased bicarb from compensation
Proteinuria > 300 mg/day is worrisome for what?
Preeclampsia
How are tidal volumes affected in pregnancy?
Increased due to increased AP diameter of the chest
How is the oxygen-dissociation curve affected in pregnancy?
Mother: shifted to the right due to increased 2,3-DPG
Fetus: shifted to the left due to fetal hemoglobin
What makes up FRC?
Expiratory reserve volume (ERC) + residual volume (RV)
How is FRC affected by pregnancy?
Decreased because expiratory reserve volume (ERV) is decreased
Is there autoregulation involved with uterine blood flow?
No; dependent on MAP
What is the normal value for placental oxygen tension?
~40mmHg
When do you worry about aortalcaval compression?
Around 28 weeks
How do you treat aortalcaval compression?
Left uterine displacement (since IVC is to the right of the aorta), avoid T-berg
Difference between fetal respiratory depression with morphine vs. fentanyl?
Morphine is more likely to cause respiratory depression (along with meperidine -> late peaking = >2 hours after birth); fentanyl presents near the time of delivery
What standard induction agent does not readily cross the placenta and affect the fetus?
NMB (both succinylcholine and non-depolarizing) because they are hydrophilic
How do most local anesthetics affect the fetus? Which ones are exceptions to this rule and why?
Most local anesthetics are “trapped” in the fetus because fetal pH (more ionized) is lower than maternal pH; exceptions are chloroprocaine (quickly metabolized) and bupivicaine/ropivicaine (highly protein bound)
What is oxytocin used for and what side effects do you worry about?
Induces contractions
SE: hypotension, possible uterine rupture or fetal hypoxia from increased contraction strength, maternal water intoxication
What is methylergonovine and what side effects do you worry about?
Induces contractions
SE: hypertension (rhymes!)
What is carboprost (Hemabate) and what side effects do you worry about?
Prostaglandin analogue to induce contractions
SE: Bronchospasms
What is magnesium used for in pregnancy and what side effects do you worry about?
Tocolytic
SE: can potentiate NMB
What would >15 mEq/L of magnesium in serum lead to?
SA or AV nodal block
What is terbutaline and what side effects do you worry about?
Beta-2 agonist, tocolytic
SE: tachycardia, hypokalemia
Is ephedrine and/or phenylephrine safe during pregnancy?
Yes
What mediates the pain of the latent phase of labor?
Latent phase: 0-3cm
Mediated by T10-T11
What mediates the pain of the active phase of labor?
Active phase: 3-10cm
Mediated by T10-L1
What mediates the pain of the second stage of labor?
Child being delivered
T10-L1 as well as the pudendal nerves (S2-S4)
Why are NSAIDs contraindicated during pregnancy?
Can theoretically close the ductus arteriosis
How would you run an epidural for a patient with Eisenmenger’s syndrome for labor?
Run only fentanyl (avoid sympathectomy which would be fatal to the patient). AVOID meperidine - has local anesthetic properties
Would you perform neuraxial anesthesia for a patient with idiopathic intracranial hypertension?
Yes (safe and effective)
What anesthetic gas should be avoided prior to delivery?
High-dose nitrous oxide to avoid risk of diffusion hypoxia of the newborn
Why do we use nitrous oxide for OB anesthesia?
N2O does not cause uterine relaxation and allows us to decrease our halogenated volatile anesthetics (decreases uterine tone); beware of high-doses for diffusion hypoxia of the newborn
Variable, Early, and Late decelerations are due to what?
VEaL CHoP
Cord compression
Head compression
Placental insufficiency
What hematologic finding do you worry about in preeclampsia?
Thrombocytopenia with platelet dysfunction; can have elevated INR, d-dimer, PT/PTT
What are the same anti-hypertensives used during pregnancy?
Alpha methyldopa, labetalol, hydralazine, and oral nifedipine
What is the most common cause of preeclampsia mortality?
Cerebral hemorrhage
What do we use in preeclampsia to prevent progression to eclampsia?
Magnesium (calcium inhibition and NMDA inhibition)
How do you clinically follow magnesium administration for preeclampsia?
Monitor for decreased DTRs
What are the effects of magnesium in pregnancy?
- Prolongs muscle relaxant (inhibits Ca++)
- Decreases DTRs
- Venodilates (decreases BP)
- Tocolytic
What effects do you see of magnesium drips with the following serum levels? 4-7 mEq/L, 7-10 mEq/L, 10-13 meQ/L, 15-25 mEq/L, >25 mEq/L?
- Flushing and vasodilation
- DTRs are lost
- Respiratory depression
- Heart block
- Cardiac arrest
During C-section, OB cannot delivery baby and ask for relaxation of the uterus. What do you do?
Give nitroglycerin IV (short acting and rapid onset)
What is placenta accreta vs. increta vs. percreta?
Accreta: placenta attaches to myometrium
Increta: invaded into the myometrium
Percreta: through the myometrium
What is a placenta previa?
Placenta attaches to the uterus low (near or on the os) leading to antepartum painless bleed
Difference between ACLS in pregnant and non-pregnant women?
Uterus should be displaced off the IVC with left uterine displacement (everything else is the same)
When should urgent and elective cases happen during pregnancy?
Second trimester (highest rate of spontaneous abortion is in the first and third trimester)
When does organogenesis occur?
GA 2-8 weeks
When can you start using fetal heart rate monitoring?
After week 16
What is the definition of a category A, B, C, D, and X drug for pregnancy?
A: Safe B: Safe in animals with no humans or not safe in animals but safe in humans C: no data but potential benefits D: possible risk but potential benefits X: Unsafe
What risk to the fetus is there with chronic benzo use during the first trimester?
Cleft palate
