OB Flashcards
Describe the parturients blood gas levels:
pH - no change
PaO2 - increase - 104-108
PaCO2 - decrease - 28-32
Bicarb - decrease - 20
Describe O2 consumption in the parturient in the different stages of labor:
Term - increase 20%
First stage of labor - increase 40% over prelabor
Second stage of labor - increase 75% over prelabor
Describe CO of the parturient:
Increase 40% (10% goes to uterus)
HR increases 15%
SV increases 30%
Discuss CO during labor (as compared to pre-labor values)
1st stage: increases 20%
2nd stage: increases 50%
3rd stage: increases 80%
When does CO return to pre-labor values after birth?
24-48 hours
When does CO return to pre-pregnancy values?
About 2 weeks
How do twins affect CO?
Increase CO 20% above a single fetus pregnancy
Do MAP, SBP, or DBP change in the parturient?
MAP = no change (increased blood volume + decreased SVR = net even)
SBP = no change
DBP = decreased 15%
To which parturient should you apply left displacement of the uterus?
Anyone in the second or third trimester
How does intravascular fluid volume change in the parturient?
Increases 35% to prepare for hemorrhage in labor; creates dilution anemia
How do plasma volume and erythrocyte volume change in the parturient?
Plasma - increases 45%
Erythrocyte - increases 20%
What clotting factors increase in mom?
1, 7, 8, 9, 10, 12
What clotting factors decrease in mom?
11 and 13
What changes occur in antithrombin, protein s, and protein c?
antithrombin and protein s decrease. no change in protein c.
What changes occur in moms fibrinolytic system?
increased fibrin breakdown
Describe the parturients hematologic change overall?
Mom makes more clot, but she breaks it down faster.
How do PT and PTT change?
Decrease by 20%
Normal PT at term - 9.6-12.9s
Normal PTT at term - 24.7-35.0s
What occurs with platelet count?
Unchanged or decrease up to 10% due to hemodilution and consumption
How does MAC change in the parturient?
Decreases 30-40%
Does gastric volume increase or decrease in the parturient? Why?
Increases due to increased gastrin
How does gastric pH change in the parturient? Why?
Decreased due to increased gastrin
How does LES tone change in the parturient? Why?
Decreases due to increased progesterone and estrogen. Cephalad displacement also contributes.
Describe gastric emptying changes in the parturient:
No change before onset of labor; decreases after labor begins
What renal functions increase in the parturient and why?
GFR - increased blood volume and CO
Creatinine clearance - increase blood volume and CO
Glucose in urine - increased GFR and decreased renal absorption
What renal functions decrease in the parturient and why?
Creatinine and BUN - increased creatinine clearance
How many mL/min of blood flow does the uterus receive?
700-900 mL/min, which accounts for 10% of CO
How does serum albumin change in the parturient? How does this affect the free fraction of highly protein bound drugs?
Albumin is decreased, so the free fraction is increased.
Is pseudocholinesterase increased or decreased in the parturient?
Decreased (no meaningful effect on sux metabolism)
What is uterine blood flow dependent on?
Does NOT auto regulate, so dependent on MAP, CO, and uterine vascular resistance (low resistance system)
What reduces uterine blood flow?
Decreased perfusion. Ex: maternal hypotension (sympathectomy, hemorrhage, aortocaval compression)
Increased resistance. Ex: uterine contraction, hypertensive conditions that increase uterine vascular resistance
What drug characteristics favor placental transfer?
Low molecular weight <500 Daltons
High lipid solubility
Non-ionized
Non-polar
What drugs do not cross the placenta?
Heparin
Insulin
NMBs
Glycopyrrolate
Describe Stage 1 of labor:
Beginning of regular contractions to full cervical dilation (10cm)
Describe Stage 2 of labor:
Full cervical dilation to delivery of the fetus
Describe Stage 3 of labor:
Delivery of the placenta
When do the latent and active phases of labor occur?
Stage 1:
Latent ends when the cervix dilates to 2-3 cm
Active begins 3-10 cm
Why is lidocaine not popular for labor analgesia?
Produces strong motor block (good for C-section)
What local anesthetic reduces the efficacy of epidural morphine and why?
2-chloroprocaine. It antagonizes opioid receptors (mu and kappa)
What is the dosing of epidural opioids?
Fentanyl bolus - 50-100 mcg
Fentanyl infusion - 1.5-3 mcg/mL
Sufentanil bolus - 5-10 mcg
Sufentanil infusion - 0.2-0.4 mcg/mL
Discuss opioid spinal dosing:
Fentanyl: 15-25 mcg
Sufentanil: 1.5-5 mcg
Morphine: 125-250 mcg
Meperidine: 10-20 mg
Discuss spinal adjunct medications and doses:
Epinephrine: 2.25-200 mcg
Clonidine: 15-30 mcg
Discuss epidural bolus dosing of adjuncts:
Epinephrine: 25-75 mcg
Clonidine: 75-100 mcg
Neostigmine: 500-750 mcg
Discuss epidural continuous infusion dosing of adjuncts:
Epinephrine: 25-50 mcg/hr
Clonidine: 10-30 mcg/hr
Neostigmine: 25-75 mcg/hr
What are 3 ways a patient can develop a total spinal?
- An epidural dose injected in the subarachnoid space
- An epidural dose injected in the subdural space
- A single shot spinal after a failed epidural
How does a total spinal present?
Rapid progression of sensory and motor block
Dyspnea, difficulty phonating, and hypotension
Loss of consciousness
What does a fetal heart rate of 110-160 indicate?
Normal acid-base balance and intact CNS and ANS of the fetus
What does a fetal heart rate of <110 indicate?
Bradycardia.
Fetal causes: asphyxia or acidosis
Maternal causes: hypoxemia or drugs that decrease uteroplacental perfusion
What does a fetal heart rate >160 indicate?
Tachycardia.
Fetal causes: hypoxemia, arrhythmias
Maternal causes: fever, choriamnionitis, atropine, ephedrine, terbutaline
At what magnesium level does loss of deep tendon reflexes occur?
7-12 mg/dL