Tuesday, 25 August 2020

Doppler studies of different foeatl arteries and veins and how best to detect hypoxaemia earliest ??

 

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.

 

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