pre and post ductual oxygen saturations

[tinkerbell419]

Hi There, is there anyone who would be kind enough to express what a pre and post ductal oxygen saturation is and how to record these. Where do you place the saturation probe?

Thanks

[Coffee Nurse, BSN, RN]

Why don't you try researching it a bit and come back for clarification if you need it? A simple Google search gave me some useful stuff.

[NicuGal, MSN, RN]

Tell us what you think

and we'll chime in. Look

at fetal circulation and see why this is important í ½í¸€

[tinkerbell419]

Hi There,

Ok so ive spent some time researching on what pre and post ductal oxygen saturations are and this is my understanding so far:

Pre ductal relates to part of the aortic opening which is nearer to the ductus arteriosus. The probe in placed on the right hand. Blood flows to the upper extremities such as coronary afteries and carotid arteries. Pre ductal saturations measure the level of arterial oxygen in the blood after blood leaves the heart but BEFORE it reaches the ductus arteriosus of the aorta where it gets sent to the upper extremities such as the brain etc.

Post ductal relates to part of aortic opening which is distal or further away from the ductus arteriosus. The probe can be placed on either the left or right foot and blood is sent to the lower extremities, femoral arteries and renal arteries. The post ductal saturation measures the level of arterial oxygen in the blood as the blood leaves the heart and after it has passed through the ductus ateriosus of the heart.

I hope ive got it right but not too sure.

[Coffee Nurse, BSN, RN]

Duplicate post

[Coffee Nurse, BSN, RN]

Yes, these things are all true. Do you know why you would measure both, and what the significance (possible causes, and potential effects on the baby) would be if you had a discrepancy between the two?

ETA: The postductal probe measures the oxygen content of blood that has passed the ductus, not passed through it; that blood would recirculate back to the pulmonary arteries and the lungs.

[tinkerbell419]

This is where I get confused but I think you would want both pre and post pretty much equal. Yoy would be looking at a difference no greater than 2 or 3% in the pre and post ductal saturations. If there is a difference of more than 3% then this could cause cardiac problems such as hypertension and put extra pressure on the neonates circulation system.

Is this correct?

[chare]

If you have a saturation gradient across the ductus, does this cause cardiovascular problems?

Or do cardiovascular problems cause the gradient?

[tinkerbell419]

I would say that cardiovascular problems would cause the gradient difference. Is this why its so imperative that we measure pre and post ductal sats on admission so that cardiac problems are picked up? In a healthy baby i would say that tbe pre and postal shouldnt be too different to ea h other.

Ive only just really been introduced to pre and postal saturations so i dont have a deep undetstanding and just starting to try and understand it.

[babyNP., APRN]

Pre and post-ductal sats are the basis for the new screening tool, the critical congenital heart defect screen (majority of states now require it). If you have difference of 4% or greater in pre (right hand) vs post (right foot, left foot, right hand), then the infant should get an echo that's read by a pediatric cardiologist as they are at a higher risk for a congenital heart defect.

There is an algorithm (search for it on the AAP) that one follows about re-testing and all the parameters.

[Coffee Nurse, BSN, RN]

I would say that cardiovascular problems would cause the gradient difference. Is this why its so imperative that we measure pre and post ductal sats on admission so that cardiac problems are picked up? In a healthy baby i would say that tbe pre and postal shouldnt be too different to ea h other.

Ive only just really been introduced to pre and postal saturations so i dont have a deep undetstanding and just starting to try and understand it.

Try thinking about what sort of cardiac problems would demonstrate a difference in pre- and post-ductal sats (another Google job), and then figure out why that would happen. I've always found it helpful to use a diagram of the heart and literally draw the flow of blood to see where red and blue come from and end up.

[tinkerbell419]

Ok thankyou so much for all your replies. I will have a closer look at the cardiovascular system.