I have questions concerning arterial pressure monitoring. I am fairly new to it. I have been trying to pull some information about it. Can anyone give me advice that has been using arterial pressure monitoring and benefited from it.
If the arterial pressure are greater than like -200 or -250 with a 500cc/min blood flow but are getting good kinetics should we still adjust the blood flow?

Heather,

I need to get more information to better answer your questions.
What type of hemodialysis machines does your unit use? What is the blood pump segment size (6mm or 8mm)? Can the hemodialysis machines use true high flow lines? What gauge needles are you using for 500 ml/min blood flow rates?

Deborah



[This message has been edited by Deborah Brouwer (edited 07-05-2000).]

Here's a few more questions...
What do you mean by "good kinetics" ?

Are you doing kinetic modeling at your faciltiy or do you send it out to be calculated ?

Are you doing URR or Kt/V ?

How are your post dialysis BUN samples drawn routinely ?

We use Cobe Centrysystem 3 machines. THe blood pump segment is 6mm. I am not sure what you mean by high flow lines? We use 15 ga needles with the exception of one person. We have our Kt/V calculated at our lab in florida. We do a post bun at end of treatment. Slow pump method where you decrease the flow to 80cc/min for 20 seconds and then draw. We have an URR and a Kt/V result . Our kinetics meet the 1.3 and above. The larger part of our patients are 1.5 and above. Caths tend to be lower on reallly large patients.

Sorry I did not give much info, but I am knew so I don't know what factors play into arterial pressure monitoring.
Thanks

Heather,
Yes, it is all related. The arterial pressure effects the actual delivered blood flow that the patient receives. The delivered blood flow is the extracorporeal flow within the bloodlines and dialyzer. The setting the blood pump reads may not be the true blood flow. As the arterial pressure becomes more negative, the blood pump tubing segment changes from a round to oval shape. This lowers the stroke volume (amount of blood that goes through the blood pump with each revolution) and leads to the lowered actual delivered blood flow.

High flow bloodlines are made for non-Cobe C3 machines and help to reduce the drop in true flow. Large pump segments also can help if the pump segment is made of a tubing material that can retain the round shape. Not all bloodlines are the same.

Cobe C3 machines require the use of the C3 specific bloodlines. The Cobe C3 can only operate with the use of prepump arterial pressure monitoring. Other hemodialysis machines offer prepump arterial monitoring as an optional feature or are unable to monitor prepump arterial pressures.

Did you see the previous post about AP monitoring? Dr. Depner�s article is referenced.

Vascular access is the gatekeeper to quality of life on dialysis. Prepump arterial pressure is a very helpful tool for evaluating the function of a vascular access and to insure adequacy of dialysis.

Please keep posting more questions until you have all your questions answered. This is a very difficult and complex issue. Thanks for your interest.

Deborah




[Note: This message has been edited by Deborah Brouwer]

Debbie is right that the C3 does require that pre-pump arterial monitoring be done, but you should be careful not to exceed
-200 mmHg. This is when delivered blood flow starts to deteriorate.

If you are running blood flows greater than 300 it is generally recommended that 8 mm pump segments be used rather than 6.5 mm.

I am a little surprised that your Kt/V and URR results are as good as they are with 500 QB using 6.5 mm tubing. What are the negative pressures that you see on your patients ?

If you look in the past messages on this discussion board regarding arterial monitoring you will find some excellent pre-pump arterial monitoring references listed.

We usually see about a -250 to -300 arterial pressure. That is what worried me as I started looking into arterial pressure monitoring. So are you saying that the size tubing could falsley alter my reading to a higher negative and if I used an 8mm tubing that the pressure would be less? I think that I understand that arterial pressure monitoring lets us know how much of a blood flow that the graft can offer??? So the smaller tubing could be giving me a false high? Thanks
Heather