OB Study Guide Questions Flashcards
Questions from the comprehensive OB study guide... a ton of shit... There is still a lot on info to fill in some of the things I skipped from the SG, be sure to check it out if you have questions or deficiencies. Thank you for your time, now get to work!
Cardiovascular changes in pregnancy?
- 10th week of gestation~ 10% - 3rd trimester ~ 40-50% - Post delivery as high as 60-80% - Increases: -Stroke volume (30%) -Heart rate (15-25%) -Placental and ovarian steroids
Hemapoietic changes in pregnancy?
- Increased IVF volume/constituents o- Begins @1st trimester - - - 1500ml by term o- Plasma volume increases ~ 45% o- Erythrocyte volume increases ~ 20% o- Plasma protein (albumin) concentration-decreases o- Dilutional effect of increased IVF volume
Respiratory changes in pregnancy?
Capillary engorgement Edematous vocal cords/arytenoids Min Vent 50% incr 1st trimester (decr resting maternal PaCO2) Decr. FRC 3rd trimester (incr atelectasis) Incr MV + decr. FRC = Incr. Alv. conc. of inhaled anesthetics
Renal changes in pregnancy?
o 3rd Month of Pregnancy o 50-60% Increase RBF Glomerular filtration rate o 50% decrease (upper normal limits) Blood urea nitrogen Creatinine concentrations
GI changes in preg?
Commonly experience esophagitis, GERDS Gastric fluid volume and gastric fluid pH “full stomach” Reglan 10 MG IV, Zantac 50 mg IV, Bicitra 30 mL PO
CNS changes in preg?
o Decreased anesthetic requirements – Engorgement of epidural veins – Decreased epidural space – Decreased volume of CSF - Exaggerated spread of local anesthetics - Decrease in dose requirement by 30% to 50%
Periph nerv sys changes inpreg?
- Pregnancy induced analgesia (MAC 40% lower in pregnancy) - elevation in pain threshold
Endocrine chagnes in preg?
Thyroid gland enlarges 50-70% Estrogen induced increase in thyroid binding globulin results in a 50% increase in T3 and T4 concentrations Mean blood glucose usually remains the same, but can decrease in third trimester (due to greater demands by fetus)
Effect of preg on plasma protein content?
Plasma albumin decreases from 4.5 to 3.9 g/dL during 1st trimester. Globulins decline by 10% in the first trimester and rise throughout the remainder of pregnancy to 10% above prepregnancy levels at term. This can affect the amount of available protein binding sites for highly protein bound drugsdue to the fluctuations throughout pregnancy
Affect of preg on inhalational agents?
MAC is decreased by 15-40% (volatile halogenated agents) due to (1) elevated progesterone levels (2) ↑’d CNS serotonergic activity (3) activation of the endorphin system
Affect of preg on IV anesthetics?
(1) Induction dose of thiopental ↓ by 35% (due to same mechanisms as inhaled agents), elimination T1/2 prolonged to 26 hrs vs. 11 hrs due to larger Vd. (2) Propofol pharmacokinetics are unchanged by pregnancy. (3) Succinylcholine’s elimination T1/2 is not altered due to 1st order kinetics and faster recovery due to larger Vd. (4) ↑’d sensitivity to vecuronium and rocuronium noted ↑ clearance and shortened elimination T1/2 also noted. (5) Atricurium pharmacokinetics are unchanged by pregnancy
Affect of preg on local anesthetics?
engorgement of epidural veins w/ ↓ of epidural space ↓ CSF vol. in subarachnoid space ↑ intra-abdominal pressure facilitates spread of LA thereby ↓ing dose by 30-50%
Factors affecting maternal uptake and elimination of anesthetics?
Inc. MV and Decr. FRC=more rapid induction and emergence
Which nerves carry pain in 1st stage labor? 2nd stage? 3rd stage?
1st: T10-L1 Sympathetic (cervical dilation pain); S1-4 somatic nerves (vaginal perineal pain) 2nd: Pelvic musculature and ligaments send via sacral plexus 3rd: Pudendal nerve ?
Definitions of 1st, 2nd, 3rd stages of labor?
1st: Regular contractions - cervical dilation 2nd: Dilation - birth of man-child 3rd: Birth of man-child - delivery of placenta and associated afterbirth
Factors that affect placental transfer of drugs?
Mat-fet concentration gradients mat protein binding Molecular weight Lipid solubility degree of ionization of substance
When should IV drugs be administered (in relation to contraction) to decrease fetal exposure and uptake?
Administering IV drugs during a contraction decreases fetal exposure and uptake due to a marked decrease of maternal blood flow to the placenta during this time.
How will fetal acidosis affect drug delivery in the fetus?
Fetal pH is 0.1 lower than maternal, making weakly basic drugs cross placenta in nonionized form then become ionized in the fetus. Due to the gradient, they thenhave difficulty moving back to the mother (against the gradient). This is called ion trapping.
What are the determinants of uterine blood flow?
Uterine Blood Flow (UBF)=Uterin perfusion pressue/Uterine Venous return (UBF=UPP/UVR)
Is uteroplacental blood flow autoregulated?
the placental circulation displays limited autoregulation ability. What this means is that placental blood flow will most likely decrease with reductions in maternal blood pressure.
Three factors to decrease uterine blood flow?
Systemic BP Uterine Vascular Pressure Uterine Vascular Resistance
How does extreme maternal hyperventilation affect uterine oxygenation?
Mechanical hyperventilation may limit gas exchange between the mother and the fetus in two ways: (1) it can significantly decrease the uterine blood flow by decreasing maternal cardiac output and blood pressure, and (2) in theory, it can decrease transplacental oxygen delivery by causing maternal respiratory alkalosis, which shifts the maternal oxyhemoglobin dissociation curve to the left.
Causes of pain in 1st stage of labor? Which dermatomes would that be?
Several lines of evidence suggest that pain during the first stage of labor is transduced by afferents with peripheral terminals in the cervix and lower uterine segment rather than the uterine body, as is often depicted. T10-L1 dermatomes
Causes of pain in 2nd stage of labor? Which nerve fibers? Affect on uterine blood flow?
Distension, ischemia, and frank injury in or around the perinuem.
Innervation from vaginal surface of cervix, vagina, and perineum:
Pudendal nerve (S2-4)
SNS outflow results in increased CO and SVR, leading to a reduction in uteroplacental perfusion.
Sedative of choice during C-Sect w/ regional anesthetic?
.Most women do not require sedatives, BUT if they HAVE to have it, use a small dose of benzo (midazolam 0.5-2 mg) and/or opioid (fentanyl 25-50 mcg)
When is GETA the technique of choice for a C-Sect?
.Meternal hemorrhage or fetal distress
What causes supine hypotensive syndrome? What is the treatment?
Uteral compression of aorta and vena cava
LUD w RHE
S/S of supine hypotensive syndrome (aortacaval compression syndrome)?
Decreased BP/CO
Decreased blood flow to lower extremeties
Unchanged blood flow to upper extremeties
Increased brachial artery pressure
Possible tachycardia followed by bradycardia
Which LAs are used in OB?
Spinal: Lidocaine, tetracaine, ropivacaine, levobupivicaine, bupivicaine
Epidural: 2-chloroprocaine, lidocaine, mepivicaine, bupivicaine, ropivicaine, levobupivicaine, etidocaine (M&E infrequently)
Which LA is least cardiotoxic, fastest acting, and safest for use in OB?
Ropivicaine
In an epidural, how much should we decrease the dose?
Subarachnoid 25%
Large dose epidural unaltered
Small dose epidural reduced
Physiologic mechanisms behind “anemia of preg”?
Dilutional:
Plasma volume increases 50%, but RBC increases only 30%
When does the greatest increasein CO occur in preg?
During labor and delivery
What happens to CO immediately after delivery?
CO may be as muh as 75% above predelivery measurements
Does preg mimic restrictive or obstructive disease?
Restrictive
6 resp system variable that do NOT change during preg?
Vital capacity
Resp rate
FEV1
FEV1/FVC
Flow-Volume loop
Closing capacity
Most frequent complication of epidural/spinal anesthesia for labor & delivery?
Epidural:
Hypotension, limited/patchy block, dizziness, restlessness, tinnitus, seizures, loss of conc., CV collapse, high block
Spinal:
Hypotension, high spinal, patchy block
Contraindications for spinal/epidural anesthesia?
Patient refusal
Coagulopathy
Uncontrolled hemorrhage
Infection at needle site
Relative: systemic maternal infection, elevated ICP, prior spinal instrumentation with hardware, neuro dx
What is induction to delivery time?
Induction of labor (maybe of anesthesia?) to delivery of fetus
Dysfunctional labor: 20 hrs in nulliparous, 14 hrs in multiparous
What is uterine incision to delivery time?
.From when the incision is made until the baby is out (3 minutes seems to be a critical time, babies out after 3 min tend to be depressed)
What is Variability?
Small, normal changes in fetal heart rate (FHR)
Range of fetal heart rate?
120-160 in a term fetus (immature is higher)
Brady to 100 is OK if less than 2 min
Brady to 80 is unacceptable.
Understand early, late, variable decelerations…
Early: occurs with contractions. This is OK.
Late: occurs after contraction starts, lingers until after contraction is over. This is NOT OK.
Variable: occurs with some contractions, but not all… Possibly from umbilical cord compression. Not particularly good…
Fetal scalp pH?
Older method to confirm/exclude fetal acidosis when monitoring suggests fetal compromise.
Components of APGAR score?
A- Appearance
P- Pulse
G- Grimmace
A- Activity
R- Respirations
In a baby born to a heroin-addicted mother, what drug should be avoided in the newborn?
Narcan?
What is organogenesis?
It is the development of organs.(<8 weeks gest. according to Dr. Whats-his-name we saw last week)
What is hemolytic disease of newborn?
(AKA Erythroblastosis fetalis)
Transplacental passage of maternal IgG antibodies against fetal erythrocytes
(Mother Rh -, fetus Rh +) Mother is treated with Anti-D immunoglobulin during and after pregnancy
What is preeclampsia?
New onset of HTN (140/90) & proteinuria after 20 wks gestation
What is eclampsia?
CNS involvement results in new onset of seizures in preeclamptic women
What is severe preeclampsia?
BP > 160/110
Proteinuria >5g/24hr
elevated serum creatine
oliguria
pulm HTN
pulm edema
visual disturbances
IUGR
RUQ/epigastric pain
S/S HELLP syndrome
What is HELLP syndrome?
Hemolysis
Elevated Liver enymes
Low Platelets
Essential pharm interventions of preeclampsia and eclampsia?
MgSO4 (seizure prophylaxis)
Steroids (accelerate fetal lung maturity, surfactant production)
What are the 1st and 2nd causes of death in preeclampsia?
1st: CVA
2nd: Placental abruption
How does preeclampsia affect uteroplacental circulation?
Increased downstream resistance in the uteroplacental bed -> decreases diastolic flow -> increases systolic/diastoli flow ratio -> IUGR
What is uterine atony?
Soft, boggy uterus (most common cause of PP hemorrhage)
List 5 requirements for anesthetic management of uterine atony.
Large-bore IV access
Volume resus
Type & Cross
CBC & CoAgs
Prep for hysterectomy!!!
-Oxytocin, ergot alkaloids, prostaglandins
What is placenta previa?
Implantation of the placenta in advance of the fetal presenting part
(placenta covers the cervical os)
Painless bleeding in 2/3 trimester
DX via US
Double set-up
What is placenta accreta?
Abnormally adherent placenta
What is placenta increta?
.Placental invasion of the myometrium
What is placenta percenta?
Placental invasion of the uterine serosa or other pelvic structures
Predisposing factors for placenta accreta?
Hx of previous C/Sects with current placenta previa
What is abruptio placenta?
A complete of partial speraration of the placenta from the decidua basalis before delivery of the fetus.
Fetal compromise occurs d/t the loss of placental surface area for maternal-fetal exchange.
What is amniotic fluid embolism?
Embolism of amniotic fluid……….
Etiology unclear, but there is a disruption of the barrier between the amniotic fluid and maternal circulation.
(AKA “anaphylactoid syndrome of pregnancy”)
Why does DIC occur?
Theorized that amniotic fluid contains a procoagulant (Factor X activator) as well as possible circulating trophoblast, whih may disrupt the normal clotting cascade
What is amniotic fluid? What is a normal amount? What is an L-S ratio?
Clear fluid that surrounds the fetusin the amniotic sac.
Suspends and protects fetus
Nml volume is 50 ml @ 12 wks to 800 ml @ 38 wks
L-S ratio: lecithin/sphingomyelin ratio-lab test to determine fetal lung maturity; immature lung begins to produe more lecithin than sphingomyelin and the reversal of the ratio signifies the lung is beginning to mature (~34 wks)
What is choriamnionitis?
infection of the placental membranes and amniotic fluid
may lead to systemic infection and possible exclusion of neuraxial anesthesia
What is a tocolytic drug? Name 3 of them.
“Taco-destroying”
or… med given to stop or slow down uterine contractions in preterm labor
CCBs, B-agonists, prostaglandin inhibitors
Mag sulfate
Why is mag sulfate the drug of choice for preeclampsia?
Reduces the risk of full-blown eclampsia, reduces HELLP by reducing fibrin deposition, reduces maternal mortality, all while maintaining uterine blood flow
The preeclamptic patient should not receive which general anesthetic?
Do not give Ketamine to a preeclamptic patient. Ketamine increases sympathetic outflow, further increasing blood pressure.
Name 2 pharm treatments for hypertonic uterus.
Terbutaline (B-agonist) & nitroglycerin
Therapeutic action of oxytocin?
Oxytocin (Pitocin) is used to induce or augment labor and is a first line drug for tx of uterine atony. It enhances uterine contraction, decreasing bleeding post-delivery.
Which LA accumulates the least in the fetus?
Chlorprocaine
It is an ester LA and is metabolized by plasma cholinersterase very rapidly. A chlorine atom in its structure allow it to be metabolized 3x faster than other ester LAs. (Mother and fetus have active plasma cholinesterase)
Should the OB patient be pre-curarized priorto the delivery of general anesthesia for E-C/Sect?
Nope. It can take way too long, and more sux is needed to be effetive.
Which maternal nerve block will cause the most fetal bradycardia?
Paracervical block.
Mechanism is uncertain: may be related to local anesthetic-induced vasoconstriction of the umbilical artery, fetal manipulation while performing the block, local anesthetic effects directly in the fetus, or sudden increase in uterine tone with injection.
Whic types of blocks can be used for 1st stage of labor pain?
paracervical block
lumbar sympathetic block
epidural block
What is meconium aspiration?
Aspiration of meconium (i love these kinds of questions…)
Fetus inhales his own in-house poops, what a dumb-shit…
Leads to Meconium Aspiration Syndrome: resp distress, cxr shows pulm consolidation and atelectasis
Tx: airway suction, PPV, extracorporeal membrane oxygenation, and inhaled nitric oxide
What nerve is most commonly associated with vaginal delivery?
Pudendal nerve
What is normal blood loss for vaginal delivery? C-Sect?
Vag: 500 mL
C/Sect: 1000mL
Most common causes of fetal distress?
Hypoxia
Precipitating factors of pre-eclampsia?
- Primary Primaparous women (85%)
- Chronic HTN
- Renal Disease
- Insulin Dependant Diabetes
- Obesity
- Hx of preeclampsia
- Hx of close relatives developing the disease
- Conditions associated with rapid uterine rupture
- Hydatiform moles
- Diabetes
- Multiple gestation
PaO2 and PaCO2 in normal fetus?
PaO2: 50-60 mmHg
PaCO2: 40 mmHg
How does fetal heart rate fluctuate with maternal blood pressure?
fetal oxygenation is limited primarily by uteroplacental blood, not maternal oxygenation
2 signs of fetal hypoxia?
Late decels
variable decels w brady
Definitive treatment for preg-induced HTN?
Delivery of fetus and placenta
When is ketamine used for C-Sect?
Placenta previa with hemorrhage (EMERGENT)
Actions to prevent hypotension during C-sect?
Ephedrine
Phenylephrine
Supp O2
LUD
IV fluid bolus
Greatest maternal/fetal danger of using general anesthesia for deliveries?
Death
Epidural opioid effectiveness is decreased when used with which LA?
Chloroprocaine (that’s a bitch, huh?)
may also interfere with epidural bupivicaine…
What does the fetal scalp monitor measure?
Fetal heart rate
Fetal pH
What nerve injury is most commonly associated with vaginal delivery?
Perineal?
Most common “nonOB” procedures performed on OB patients? Least?
Most:
- Cervical incompetence
- Appy
- Adnexal/Ovarian surgery
- Chole
- Bowel obstruction
- Breast surgery
Least:
- Neuro procedures
- Cardiac/ Valve surgery
- Transplant
- Urological
How do you best avoid contributing to malformation of the fetus during surgery?
Have someone relieve you for a break.
OR maintain fetal well-being
(maintain maternal oxygenation, maintainance of nml mat. oxygen tension, oxy-carrying capacity, oxygen affinity, and uteroplacental perfusion)
Four major objectives of anesthetic management in the OB patient which corresponds to fetal wellbeing.
avoidance of teratogenic drugs
avoidance of intrauterine fetal hypoxia and acidosis
prevention of preterm labor
management of anesthesia including fetal monitoring, careful choices of anesthetic drugs (spinal and epidural anesthesia in the first trimester), and ensuring inhaled concentrations of oxygen remain above 50%
What is teratogenicty?
any significant postnatal change in function or form in an offspring after prenatal treatment
What are some documented teratogens?
radiation
CMV
herpes
toxoplasmosis
alcoholism
DM
folic acid deficiency
hyperthermia
ACE inhibitors
anticonvulsants
cocaine
anticoagulants
tetracyclines
androgenic hormones
cyclophosphamide
iodides
lithium
FDA classification of commonly used anesthetics.
Mostly B’s and C’s in clinical doses
At what point is an OB patient no longer considered an OB patient?
Several weeks post partum
Six H’s to avoid during induction and maintenance of the OB patient.
hypoxemia
hypotension
hypertension
hyper/hypocarbia
hypoglycemia
hyper/hypothermia
