Antenatal Foetal
wellbeing by Doppler study!!! To whom to trust?? Is it arterial Doppler changes
(Umbilical artery, MCA changes ) or
venous Doppler changes ( Umbilical veins,
,Ductus venosus & Tricuspid flow ) Point
1:-How
many of members believe that “a decrease in the cerebral placental Doppler
ratio provides an early and sensitive marker of redistribution of cardiac
output which often precedes overt growth delay by up to 2 weeks.
Point 2 :-What is
the sequence of changes due to hypoxemia of foetus :-The reduction of fetal
growth velocity usually but not always mirrors in the following order A) elevation in umbilical artery blood flow
resistance and is B) followed by decreasing middle cerebral artery
impedance.
Point 3: We shouldn’t make a hurried decision as soon
as umb artery undergoes some adverse changes!!! We should keep in mind that Fetal Doppler
assessment that is based on the umbilical artery alone is no longer appropriate
particularly in the setting of early onset IUGR prior to 34 weeks.
POINT 4: Then how we should assess foetal condition
and be assured about health of foetus?? Ans:
Incorporation of middle cerebral artery and venous Doppler provide the
best prediction of acid base status, risk of stillbirth and the anticipated
rate of progression.
Point 5: Whenà there will
be foetal hypoxemia but a normal pH. Ans:-In growth restricted fetuses with an
elevated Doppler index in the umbilical artery , with Doppler evidence of brain sparing in MCA with the presence of normal venous Doppler
parameters(like Ductus) is typically
associated with hypoxemia but a normal pH.
Point
6:-How much relevant is venous
Doppler of Umb venous
flow ? :à Yes. The abnormal venous Doppler parameters, including that of Umb veins
are the strongest Doppler predictors of stillbirth. Reasons are even among
fetuses with severe arterial Doppler abnormalities the risk of stillbirth is
largely confined only to those fetuses that haves abnormal venous Doppler’s.
But Venous Doppler findings of DV that
are particularly ominous are 1) absence of flow changes or 2) reversal of the ductus venous 3) “ a” wave and & 4) biphasic /triphasic umbilical venous
pulsations.
In such settings there is a risk of a
25% stillbirth. But when the study is limited to preterm severe IUGR population
these Doppler findings have a 65% predictive sensitivity and 95% specificity, when
fetal compromise is accelerated there is
a further steady rise in umbilical blood flow resistance venous Doppler indices
escalate over a wide range
Point
7: Oligohydramnios and metabolic academia is
characteristics of ineffective
downstream delivery of cardiac dilatation with whole systolic tricuspid
insufficiency complete fetal inactivity , short term variation below 3.5 m/sec
and spontaneous cardiac late decelerations of the fetal heart rate can be
observed as preterminal events.
How placental
dysfunction is is reflected in Doppler indices?? Ans:- As diagnostic tools 1) elevated umbilical
artery blood flow resistance 2) and /or middle cerebral artery brain sparing
provide evidence of placental dysfunction.
In the fetal
compartment elevation of the umbilical artery Doppler index is
observed when approximately 30% of the fetal villous vessels are abnormal.
What does “Absence
or even reversal of umbilical artery end diastolic velocity: warns us in an
whispering voice?? Ans:- Such changes may occur when 60% to 70% of the villous vascular
tree is damaged. Therefore, the benefit of umbilical artery Doppler , umbilical
artery Doppler , when used in conjunction with standard antepartum testing was
associated with a decrease of up to 38%
in perinatal mortality antenatal admissions, inductions of labor and cesarean
deliveries for fetal distress in labor in women considered at high risk.
What other in
formations we receive from Umbilical vessels??
Ans:-Development of umbilical venous pulsations in fetuses with absent
end diastolic velocities in the umbilical artery was associated with a fivefold
increase in mortality. Researchers have demonstrated that gestational age at
the onset maternal hypertension and the development of pulsations in the
umbilical venous velocities were significantly correlated with the interval of
time between diagnosis and delivery for late decelerations for the FHR.
In summary
Doppler evaluation of the umbilical cerebral and precordial vessels (if
possible) in the growth restricted fetus informs us
:->1) important diagnostic and
prognostic information of in utero foetus. Fetal academia and the risk of
stillbirth are high with progressive elevation of venous Doppler indices.
Risk factor based Screening protocols : Not only
Doppler studies but other methods of foetal surveillance should also be used to
achieve maximum information about foetal oxygenation and hypoxemia .
Advancing Doppler abnormalities indicates acceleration
of disease and requires increased frequency of fetal monitoring. In growth
restricted fetuses, Doppler evaluation is complementary to all other
surveillance modalities.
No comments:
Post a Comment