OB Specialty Exam Flashcards
What is uterine blood flow a term pregnancy?
700-800 ml/min
When is the fetus most susceptible to teratogenic effects?
3-8 weeks
How should you treat respiratory depression in an infant born to a heroin addict?
Controlled ventilation
NOT naloxone - don’t want withdrawal
What is the dose of naloxone for a non-addicted newborn?
0.1 mg/kg
When do amniotic fluid embolisms occur?
During labor, delivery, c-section or postpartum
Symptoms of amniotic fluid embolism
Tachypnea, respiratory distress, cyanosis, shock, generalized bleeding (DIC), CV collapse, seizure, pulmonary edema, coma, decreased BP
What are 3 major pathophysiological manifestations of AFE?
Acute pulmonary embolism
DIC
Uterine atony
What 4 clinical features are you likely to see in an AFE?
Dyspnea
Hypoxemia
CV collapse
Coma
Why is morphine not routinely used for labor epidurals?
Long onset time (30-60 minutes)
Why are high doses of epidural morphine not used?
Increased risk of delayed respiratory depression
Analgesia only effective for first stage of labor
What is placenta previa?
The placenta covers the opening to the cervix
When does onset of hemorrhage usually begin with placenta previa?
Near end of 2nd trimester or beginning of 3rd
What is the incidence of placenta previa?
1 in 200 pregnancies
What is the major symptom of placenta previa?
Painless vaginal bleeding
How is placenta previa diagnosed?
Ultrasound
What is the appropriate anesthetic plan for a primipara with placenta previa, active bleeding, and active labor?
C section + GETA
consider intubating with ketamine 0.5-1.0 mg/kg for hemodynamic stability
What kind of regional anesthesia is inefficient at covering 2nd stage labor pain?
Pudendal block
What events occur in 1st stage labor? 2nd? 3rd?
1st - dilation of cervix
2nd- delivery of baby
3rd-delivery of placenta
What causes first stage labor pain?
Visceral pain from uterine contractions and cervical dilation
Sensory dermatomes for labor pain (stages 1-3)?
1- T10-L1
2- T10-S4
3- T10-S4
What causes second stage labor pain?
Stretching and compression of pelvic and perineal structures
What sensory level is needed for a c-section?
T4
What level is needed for a tubal ligation?
T4-5
Down to T10 can be adequate unless it doesn’t cover traction on viscera
What is a normal fetal scalp PaCO2?
40-50 mmHg (same as mom)
What is a normal fetal scalp pH?
7.25-7.35
What is a normal fetal scalp SO2?
30-50%
What is a normal fetal scalp PO2?
18-22 mmHg
What is the most common direct cause of pregnancy related deaths?
Hypertensive disorders of pregnancy
What are the most common morbidities encountered in obstetrics?
Severe hemorrhage and severe preeclampsia
What are the categories scored for APGAR?
A- activity (muscle tone) P- pulse G- grimace A- appearance (skin color) R- respirations
What APGAR scores are considered normal?
7-10
What is average expected blood loss for a vaginal birth?
600 mL
What is average expected blood loss for a c-section?
1000 mL
What procedures generally require general anesthesia?
Bimanual massage of the uterus, manual extraction of retained placenta, reversion of inverted uterus, repair of a major laceration
T6 level
What three drugs are commonly used to treat uterine atony?
Pitocin 20-30 Units/L
Methergine 0.2 mg IM
Hemabate (carboprost) 0.25 mg IM
Which muscle relaxants are safe to give to pregnant women?
Sux - undetectable in baby
Most are fine (highly ionized)
Atracurium and vecuronium are next best
Do inhalational agents cross the placenta?
Yes - a lot. However, little fetal depression occurs when <1 MAC and delivery occurs within 10 minutes
Do induction agents cross the placenta?
Yes! Thiopental, ketamine, propofol, benzos.
Usual induction doses not very detrimental/little fetal effects
Do opiates cross the placenta?
Definitely! Can cause fetal respiratory depression. Morphine does this more than fentanyl. Don’t give to mom until baby is out.
Demerol - bad!! Toxic metabolite not cleared by baby - seizures
Do local anesthetics cross the placenta?
Yes, to some degree. Some ion trapping if fetus is acidotic. Esp. with lidocaine.
Highly protein bound LAs (bupivacaine, Ropivacaine) don’t cross much.
Which anticholinergics cross the placenta?
Atropine, scopolamine
Glycopyrrolate - NO!
Which first line vasopressor is recommended for pregnant women?
Phenylephrine
How is pregnancy induced hypertension defined?
Systolic >140 or diastolic >90.
Or
Increase sbp by 30 or dbp by 15 above patient’s baseline
What is the classic triad of symptoms in pre-eclampsia?
Proteinuria, HTN, edema
When does pre-eclampsia typically occur? When does it resolve?
Occurs after 20 weeks, resolves 48 hours after delivery
What EKG changes are seen with excessive magnesium administration?
Widened QRS
Also - PQ interval prolongation, SA and AV block, cardiac arrest
What is used to treat magnesium toxicity?
Calcium
What percentage of pregnancies are affected by preeclampsia?
7%
What is the therapeutic range for MgSO4?
4-8 mEq/L
Which of the following anti HTN drugs used to treat severe PIH is not capable of causing increased postpartum hemorrhage?
Nitroprusside, nifedipine, NTG, labetalol, diazoxide
Labetalol
What does HELLP stand for?
Hemolysis
Elevated Liver enzymes
Low Platelets
What does VBAC stand for?
Vaginal birth after c-section
What is a normal maternal PaCO2 in the third trimester?
27-32 mmHg
What is the most common cause of breech presentation?
Prematurity
What percent of maternal peripartum deaths are attributable to anesthesia?
2-3%
What is a normal fetal heart rate?
120-160 bpm
What is a normal fetal heart rate variability?
5-10 bpm
What is the incidence of gestational diabetes?
2-3%
What are two indications for magnesium in pregnant patients?
Anticonvulsant for preeclampsia
Tocolytic agent (prevent preterm delivery)
What is the therapeutic blood level for magnesium?
4-8mEq/L
What are the side effects of magnesium?
Sedation, respiratory paralysis, increased sensitivity to nondepolarizng NMBD, antagonism of alpha adrenergic agonists, antagonism of NMDA receptors
Are early decelerations in fetal HR a problem? What causes them?
No. Caused by head compression -> Vagal response (NOT hypoxia)
Are late decelerations in fetal HR a problem? What causes them?
Yes!
Caused by uteroplacental insufficiency -> hypoxia -> central chemoreceptors -> Vagal discharge
What is a normal oxyhemoglobin p50 for a healthy person?
A pregnant woman?
A fetus?
- 27 mmHg normal
- 30 mom
- 19 baby
What causes a rightward shift in the oxyhemoglobin dissociation curve?
Increase in
- CO2
- H+ ions
- 2,3 DPG
- elevation
- temperature
What is an appropriate volume of hyperbaric bupivacaine (0.75%) for a spinal for c-section? How long will it last?
1.6-1.8 mL (12-13.5 mg)
Lasts 120-180 minutes
What is an appropriate volume of local anesthetic solution for an epidural for c-section?
15-25 mL
What are 3 commonly used LAs for use in epidurals for c-section?
3% chloroprocaine
2% lidocaine + epi 1:200,000
0.5% bupivacaine or Ropivacaine
Name 4 side effects of intrathecal opioids
- pruritus
- nausea/vomiting
- sedation
- respiratory depression
FDA drug classification for use during pregnancy:
Controlled studies show no risk.
Category A
FDA drug classification for use during pregnancy:
No evidence of risk in humans. Either animal findings show risk but human findings do not; or no adequate human studies have been done, animal findings are negative
Category B
FDA drug classification for use during pregnancy:
Risk cannot be ruled out. Human studies are lacking, potential benefits may justify potential risk
Category C
FDA drug classification for use during pregnancy:
Positive evidence of risk. Investigational or post-marketing data show risk to the fetus. Potential benefits may outweigh the potential risk.
Category D
warfarin, valproic acid, lithium
FDA drug classification for use during pregnancy:
Contraindicated in pregnancy. Studies in animals or humans have shown fetal risks which clearly outweigh any possible benefits to the patient
Category X
thalidomide
How does Rh- incompatibility occur?
When the woman is Rh negative and the baby inherits Rh positive blood from the father
When does maternal sensitization to Rh positive blood occur?
Very late in pregnancy or during childbirth. (mixing of baby’s and mom’s blood)
Also: miscarriage, induced abortion, or ectopic pregnancy, or amniocentesis
What is Rh iso-immunization?
Development of antibodies against Rh positive proteins following a blood transfusion
Is Rh incompatibility bad for mom, baby, or both?
Baby.
What are 3 major symptoms of Rh incompatibility in the newborn?
1) anemia
2) swelling of the body (associated with heart failure and respiratory problems)
3) kernicterus (neurologic syndrome)
How is Rh incompatibility prevented?
Immune globulin injection (RhoGam) at week 28 of pregnancy
How are newborns treated for Rh incompatibility?
If mild: aggressive hydration, phototherapy
If swelling present: amniocentesis, intrauterine fetal transfusion, early induction of labor, treatment for congestive failure and fluid retention
If kernicterus: exchange transfusion, phototherapy
Under what weight is considered low birth weight?
Under 2500 grams (5.5 lbs)
What is the extra risk with bupivacaine in regional anesthesia?
High potential for local anesthetic toxicity if injected IV. Difficult resuscitation due to high protein binding and lipid solubility
Which opioid produces the worse fetal respiratory depression?
Morphine
Before what week is birth defined as preterm?
37 weeks
What kind of labor pain is covered by a pudedal block?
2nd stage labor pain
Wha are 3 complications of a pudendal nerve block?
1) hit the fetus with a needle
2) IV injection
3) retro peritoneal hematoma
What are the top 6 risk factors for maternal morbidity?
1) advanced maternal age (>34)
2) non-white ethnic group
3) multiple pregnancies
4) history of HTN
5) previous postpartum hemorrhage
6) emergency C-section