OB (3/10) Flashcards
pregnant women experience what musculoskeletal changes
lumbar lordosis –> back pain, stretch of lateral femoral cutaneous nerve, and affects the center of gravity
MAC of inhaled anesthetics ___________ by 40% in the pregnant pt
decreases
what hormones increase the pregnant woman’s threshold to pain
progesterone and endorphins
if you have to run gas on a pregnant pt what MAC level should you run
0.5
in the pregnant woman, you need ___________ LA to acquire the same level of blockade
less
T/F: with a neuraxial anesthetic in the pregnant pt, sympathectomy will decrease BP much more than in non-pregnant woman
true
the pregnant woman is dependent on _______________ of the lower extremities to counteract effects of IVC compression and return blood to the heart
venous capacitance
uterine blood flow in early pregnancy is _________ mL/min
50-100 mL/min
at term, uterine blood flow is ___________ mL/min
700-900
_________% of CO goes to the uterus
20
the CO that goes to the uterus, _______% of that perfuses the intervillous space and ________% perfuses the myometrium
90; 10
the increase in CO during pregnancy increases the flow to what organs?
- uterus
- kidneys
- extremity skin and muscle
T/F: blood flow to brain and liver does not change during pregnancy
true
uterine blood supply is mainly from ____________ arteries which arise from the ________________ artery
uterine; hypogastric artery (aka the anterior division of the internal iliac artery)
______________ is the number one determinant of O2 and nutrient delivery to the fetus
uteroplacental blood flow
uterine blood flow = _________________ (formula)
uterine perfusion pressure/uterine vascular pressure
intrauterine growth retardation is a tip that __________________ is an inadequate and can lead to _______________ in adulthood
uteroplacental blood flow; CV disease
chronic disease in uteroplacental blood flow leads to
- intrauterine growth retardation
- pre-eclampsia
- CV disease in adulthood
T/F: trophoblastic invasion of spiral arteries is normal in pregnancy
true
what is the physiologic change that causes the low vascular system in pregnancy?
trophoblastic invasion of the spiral arteries –> loss of smooth muscle and the inability of these vessels to constrict
abnormal or inadequate _______________ in pregnancy is integral to the pathophysiology of pre-eclampsia
trophoblastic invasion
what are the causes of decreased uterine blood flow due to decreased uterine arterial pressure
- supine position
- hemorrhage/hypovolemia
- drug induced hypotension
- hypotension during sympathetic block
what re the causes of decreased uterine blood flow due to increased uterine venous pressure
- vena caval compression
- uterine contraction
- drug induced uterine hypertonus (oxytocin, local anesthetics)
- skeletal muscle hypertonus (seizures, valsalva)
what causes decreased uterine blood flow due to increased uterine vascular resistance
- endogenous vasoconstrictors: catecholamines and vasopressors
- exogenous vasoconstrictors: epinephrine, phenylepherine, LA in high concentrations
_________________ + ______________ = decreased uterine vascular resistance
increased uterine artery diameter; dilated placenta circulation
____________ is when blood flow in the pelvis is preferentially redistributed toward the uterus
“steal”
uterine circulation is MORE responsive to the vasoconstricting effects of _________________ than systemic circulation
alpha adrenergic agonists
effect of propofol and barbiturates on uteroplacental blood flow
small decrease
ketamine effects on uteroplacental blood flow in doses < 1.5 mg/kg
no change
inhalational agents effects on uteroplacental blood flow
- potentially decreases uteroplacental blood flow (d/t decrease in maternal BP)
- small effects when less than 1 hr
local anesthetics effects on uteroplacental blood flow
high doses can cause uterine arterial vasoconstriction (so could decrease flow)
neuraxial anesthesia effects on uteroplacental blood flow
- decreases uteroplacntal flow if maternal hypotension occurs
- increased uteroplacental blood flow via decreasing pain and stress
T/F: placental circulation is completely different than moms
true
the ________________ is an imperfect barrier than allows most all substances to cross to fetus
placenta
mechanisms of transfer across the placenta
- passive transport
- facilitated transport
- active transport
- pinocytosis
the fetus depends on the placenta for what 3 things?
- respiratory gas exchange
- nutrition
- waste elimination
the placenta produces a variety of __________, _________, & ______________ that drives a lot changes seen in mom during pregnancy
enzymes, binding proteins, polypeptide hormones.
the placenta is a ______ vessel cord; consisting of ________ artery and _______ vein
3; 2; 1
what characteristics would allow for increased transfer of drug from mom to fetus?
- < 1000 Da (molec. wt)
- uncharged
- lipophillic
- greater proportion of unionized drug in maternal plasma
- absent placental efflux transporter
- binds with albumin (lower binding affinity)
- high concentration of free (unbound) drug fraction
what drug characteristics will decrease drug transfer from mom to fetus
- large molecular wt (> 1000 Da)
- charged
- hydrophillic
- higher proportion of ionized drug in maternal circ
- placental efflux transporter proteins present
- alpha-1-acid glycoprotein binding type (higher binding affinity)
- low concentration of free unbound drug
factors that affect drug transfer from mom to fetus
- lipid solubility
- protein binding
- tissue binding
- pKa
- pH
- blood flow
_____________ properties of INH anesthetics enhance the transfer the drug across the placenta
lipophilic
inhalational agents have little fetal effect at less than ______ MAC and _________
1; imminent delivery
which anesthetic drugs have little effect on the fetus, and thus are used at usual doses
- propofol
- ketamine
- benzodiazepines
opioid effects in the fetus
- effects vary
- concern for respiratory depression
- if close to delivery, avoid
_____________ anesthetics cross the placenta into fetal circulation quickly
local anesthetics
what drugs (used in anesthesia) DO NOT cross the placenta
- glycopyrrolate
- heparin
- succinycholine
- NDMR
fetal concentration of drugs that cross the placenta are dependent on?
- maternal drug metabolism
- placental drug metabolism
- fetal drug metabolism
- changes is uterine blood flow
what is the main different in fetal and postnatal circulation?
systemic and pulmonary circulations are NOT completely separated in teh fetus
T/F: fetus has no effective oxygen reservoir
true - thus mom = gasline for O2 to fetus
