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40 Cards in this Set
- Front
- Back
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what may obstetrical doppler evaluate?
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-maternal vessels
-fetal vessels -fetal ductus venosus -fetal heart -placenta |
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what are the 2 basic types of doppler u/s?
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-Cw-one crystal transmits and one receives
-PW-single crystal transmits and receives |
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S/D ratio
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-measures peak systole to end diastolic blood flow
-simplist -most widely used |
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RI
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systole-diastole/systole(s-d/s)
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Pulsitility index
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-peak sysole and end diastole/mean max frequency
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If there is increased vascular resistance, what happens to the S/D and P/I ratio?
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-SD increases
-PI increases |
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what happens to the PI with increasing gestational age?
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it decreases
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what is the primary cause of IUGR?
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placenta insufficiency
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factors related to reduced blood flwo to the placenta
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-smoking
-maternal hypertension -drugs -poor nutrition -unknown |
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What happens(with doppler) when there is assymetric IUGR?
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-increased vascular resistance in the aorta and umbilical artery
-decreased vascular resistance in the MCA |
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what does the diastolic flow in the umbilical artery indicate?
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-degee of vascular resistance in the placental bed
-increased placental reisstnace=decreased diastolic flow |
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what happens to the S/D ratio of the umbilical artery with increased gestational age
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there is a decline in S/D ratio
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what diastolic flow of the umbiilicar artery is associated with morbidity and mortality?
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-absent or revesed diastolic flow.
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when is the S/D ratio of the umbilical artery abnormal/
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->3 after 30 wks
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How does a SGA fetus with an S/D ratio of 2.6 compare to an SGA fetus with an SGA ratio of 3.0?
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The SGA fetus w/ a ratio of 2.6 has a much better outcome.
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what are the risks associated w/ an abnromal s/D ratio?
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-preterm delivery
-decreased birth weight -decreased amniotic fluid -SGA -risks associated w/ admission to NICU -born btw24-26 wks=have way poorer outcome |
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how do you obtain the best umbilical artery doppler?
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-close to fetal abdomen9<5cm)
-PW gate placed over umbilical artery -no angle required -waveforms influenced by fetal breathing and heart rate accelerations |
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where will the S/D ratio be higher, at the placental or fetal end of the cord?
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fetal end-because of damping of the pressure pulse as it moves down the cord
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what are elevated S/D ratios associated with?
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-abnormal karyotype
-maternal hypertension -severe growth restiction -fetal distress -perinatal morbidity and mortality |
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what is venous flow in a normal pregnancy like(in the umbilical vein)?
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-constant and low velocity
-variation durng breathing -pulsations are normal in th 1st trimester |
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if there are venous pulsations of the umbilical vein in the second trimester, what is this associated with?
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-IUGR
-congestive heart failure -congestive heart disease -increased mortality |
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@ what level is the MCA visualized?
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-transverse axial view
-slightly more caudal than the BPD level(level of peduncles) |
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what is the flow in the MCA like normall?
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opposite of umbilical artery
normally=low diastolic flow abnormal=high diastolic flow |
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what are normal ductal systolic velocities?
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-50-140cm/sec
diastolic=6-30cm/sec with flow from R to L |
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why do we doppler the ductus arteriosus in utero?
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-useful indetecting early ductal constriction in fetuses of mother's receiveing indomethacin for premature labour
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why would you doppler the maternal uterine artery?
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-if they've had a previous IUGR baby
-can tell if baby has IUGR beore umibilical artery is abnormal |
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where is the uterine artery sampled?
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-where it runs superiorly along the lateral aspect of the corpus
-measure on same side as placenta -performed at 16-22 wks |
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what is considered normal and abnormal for the uterine artery?
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Normal=PI<1.45-narrow peak and significant diastolic flow
Abnormal=PI>1.45 or notching the only way to tell if it's abnormal if it's missing the notch |
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if you see a notch when dopplering the maternal uterine artery in the 1st trimester, what should you suspect?
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-this is normal, but should disappear by second trimester
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if a notch is seen when dopplering the umbilical artery in the second trimester, what should be done to manage this?
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-bed rest in L lateral position
-some studies have shown that the doppler signal returns to normal |
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what does the umbilical artery doppler reflect?
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-downstream resitance to flow
-placental insufficiency |
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what does MCA dopple reflect?
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-blood flow redistribution under conditions of stress
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why is it important to do doppler?
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-studies have shown that dopplwer used as part of OB management has resulted in a reduction of emergency c-sections
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what are the pitfalls w/ dopper?
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-small umbilical artery(2.4mm@ term)
-angle of insonnation -high false negative rate for IUGR -diastolic velocities vary w/ heart rate -indices are higher @ fetal site and lower @ placental site. |
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when (with PIH), will doppler studies be abnormal?
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-w/ severe PIH, doppler is often abnormal, and corrilates well with fetal distress
-doppler changes often precede the findings of a non-stress test by 24 hours -in severe PIH, absent diastolic flow in the AO and umbilical arteries was often associated w/ fetal distress within 24-48 hours |
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how is doppler helpful in discordant twins?
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-not more helpful than EFW
-most vaulable in assessing fetal well being if discordance is detected |
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Indomethacin
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-therapy for preterm labor and polyhydramnios
-disadvantage=causes ductal constriction in fetus |
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maternal antihypertensive drugs
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-cause variable effects on the doppler measurements of the fetal maternal circulation
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smoking
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increase in materal HR and BO, increase in fetal aortic and umbiical blood flow
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digitalis
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givin in cases of hydrops
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