09.03 Defects of Decreased Pulmonary Blood Flow

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Tricuspid Atresia (Image)
Tetralogy of Fallot Labelled (Image)
Congenital Heart Defects Cheatsheet (Cheat Sheet)
Cyanotic Defects (Mnemonic)
Hypoxia – Signs and Symptoms (in Pediatrics) (Mnemonic)

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Hey guys, in this lesson we are going to cover the heart defects that cause decreased pulmonary blood flow.

For the most part these defects are caused by blood flow to the lungs being blocked. This causes a change in the normal pressures of the heart. So normally pressure is greater on the left side of the heart on the right side but with these defects pressure on the right side of the heart is a greater because of the blood flow to the lungs. Which means deoxygenated blood will shunt right to left and be circulated throughout the body.

The two defects we will talk about in this lesson are tetralogy of fallot and tricuspid atresia. Under the old system of classifications these would be called cyanotic heart defects because patients are often hypoxic and have cyanosis.

Tetralogy of Fallot is a combo of 4 defects-these are worth committing to memory for tests- 1) Pulmonic Stenosis 2) Right Ventricular Hypertrophy 3) Overriding Aorta 4) Ventricular Septal Defect. You can use the mnemonic device PROVe to help you remember this!

So let’s think about the way these defects will affect blood flow. The pulmonary artery is narrowed so blood can’t easily flow out of the right ventricle. The increases pressure on the right side and causes deoxygenated blood to shunt through the VSD to circulate through the body. The muscle of the right ventricle is thick and overworked which can lead to heart failure. And the overriding aorta- which means the aorta is located over the VSD, so blood from the left side and ride side are exiting the heart- is allowing even more deoxygenated blood to circulate.

As with all heart defects the symptoms and presentation will depend on the size and degree of the defect. Some babies will be born with cyanosis and compromised breathing and perfusion others may present later with failure to thrive and something called a Tet spell. This is when the child does something that increases their cardiac demand- so something like playing or getting upset and crying or the most common cause, trying to feed. Remember, feeding for a baby is like an exercise stress test, so if they have all of these cardiac anomalies they will quickly become hypoxic and cyanotic, turning very noticeably blue. In response to this kids will instinctually squat during which actually decreases systemic vascular return to the heart and also increases peripheral vascular resistance.

Heart failure is common with this diagnosis so be on the lookout for those symptoms of poor cardiac output, pulmonary congestion, and systemic congestion.

Tricuspid atresia is when the tricuspid valve never develops, so there is no communication between the right atrium and the right ventricle. 50% of babies will be symptomatic on the first day of life and 80% are symptomatic in the first month. This all depends on if there is and ASD, VSD or PDA that allows blood to flow and mix. If not they will experience cyanosis much faster. They will also likely have failure to thrive and signs of heart failure will probably be pretty evident.

Babies with ToF need surgery within the first year of life. This surgery is not curative. It is simply trying to fix and make the best of it. Most kids with ToF now experience relatively healthy lives, but they will need to be closely monitored.

If you are taking care of a child with ToF and they start having a TET spell, you need to try and keep the child calm, put them in a knees to chest position, administer oxygen and then give them morphine IV. The knee to chest position helps to increase peripheral vascular resistance and decrease systemic vascular return. This just means that blood flow coming back to the heart is less and this reduces pressure in the right side, reducing the amount of unoxygenated blood that is shunting right to left. The morphine does a couple of things for the patient. First, it calms the child down and reduces the RR which reduces cardiac demand Third, like the knee to chest maneuver, it also decreases systemic vascular return.

Patients with Tricuspid Atresia will also need surgery, but usually surgeons try to wait until the child is older than 1 and is meeting certain weight criteria. So until the surgery can be done, the child needs close monitoring and medications to help keep the heart functioning under as little stress as possible.

After any cardiac surgery patients are at high risk for infection like, infective endocarditis, stroke, hemorrhage and pneumothorax, so post-op care focuses on pain management and monitoring for these complications.

You’re priority nursing concepts for a pediatric patient with a congenital heart defect that causes decreased pulmonary blood flow are perfusion, oxygenation and gas exchange.

Okay, guys so we talked through the congenital heart defects that cause decreased pulmonary blood flow. The ones we covered are Tetralogy of Fallot and Tricuspid Atresia. With these pressure on the right side increases and blood shunts right to left. This means that deoxygenated blood is circulating through the body and this causes hypoxia and cyanosis pretty quickly. Most kids will present with in the first month of life with signs of feeding difficulty and heart failure.

Tetralogy of Fallot has 4 main elements to know. They are Pulmonic Stenosis, Right Ventricular Hypertrophy, Overriding Aorta and VSD. Kids with this defect often have something called a TET spell where they become hypoxic and cyanosed with any kind of increase in cardiac demands like crying or feeding. To treat this put the baby in a knees to chest position, keep them calm, administer O2 and give IV morphine.

Tricuspid Atresia is when there is no tricuspid valve and blood can’t flow from right atrium to right ventricle causing deoxygenated blood to circulate in the body.

Both of these are going to require surgery.

That's it for our lesson on congenital heart defects that decrease pulmonary blood flow. sure you check out all the resources attached to this lesson. Now, go out and be your best self today. Happy Nursing!
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