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