CHD - NNP class video notes

What blood vessel in the maternal-fetal vessels carries the most oxygenated blood?

What percentage of blood goes to the lungs in utero
What happens when the ductus arterious closes prior to birth and why does this occur?

Umbilical vein

Only 10%

If DA closes prior to birth, blood goes to the lungs and babies end up with high pulmonary hypertension. This happens to moms who’s had high doses of NSAIDS or aspirin in pregnancy

What are the things we do now that helps with the detection of CHDs?

• We’ve increased the number of US we do between 16-19 weeks

• We now do 5th chamber cardiac view (rather than standard that looks at the four chambers) so we can see the outflow tract (esecpically to see if baby had TGA)

• We scan for associated abnormalities and anatomical defects (especially if you add color and doppler scans)

Why can’t we detect VSD murmur until 5 days of age?

Pressure in right ventricle & left ventricle are almost identical in the first 24-48hours (5 days after pulmonary pressures come down)

What are some of the cardiac signs of cyanosis?

1. CHD

2. PPHN

3. Methemoglobinemia

What is Methemoglobinemia? How and why does it occur?
What is the cure and what do we give in the NICU that can cause it? What about at home?

It’s a bedside diagnosis when a baby is clearly cyanotic / blue but O2 sats reading above 95% / stable.

It occurs due to an abnormal state Hgb is in (Ferric state instead of ferrous state). Ferric state cannot bind to oxygen well, so Hgb turns dark blue (once 20-30% are in ferric state hence cyanosis)

Meds that cause it - Nitric oxide | Emla cream for LP or circumcision. At home formula mixed with well water (which is high in nitrate)

We give methylene blue infusion (it turns iron from ferric state to ferrous state

When we do CXR and wondering for ? CHD, what do we look for in the imaging?

1. Cardiomegaly (>55% of the CT ratio)

2. Vascularity (increase or decreased)

3. Silhouette (boot shaped / heart on a string etc) - but may not occur in newborn period

4. gases - particularily CO2 (usually normal or low - rather than high in respiratory issues)

5. Hyperoxia test

What is hyperoxia test?

When you give 100% Oxygen for 10- 15 mins and you do an arterial gas.
If cardiac (CHD) - There will be no changes in the CO2 (which means the baby failed the test)
If respiratory - Co2 will be 100% higher than baseline (40-50)