RenalWEB Home Page renalweb.groupee.net RenalWEB Discussion Forums Nursing / Patient Care Issues Vascular Access VP and Pre-pump AP while on HD set BFR
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Do you change the bloodflow rates for patients using the venous and arterial pressures (pre pump or post pump) as a guide? What VP do you like to see as a max for fistula/graft/catheter at what BRF's? What pre-pump AP do you like to see as a max for fistula/graft/catheters at what BRF's? Example if you have a 3 patients at a BFR of 300 (Fistula/graft and catheter) what would be the max VP and AP you would allow before lowering the BFR? How would that change at a BFR of 400?
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See the post under Dialysis Technical Forum for Real Blood Pump Calibrations- Tom and Joseph talk about Arterial pressure and the effect on the blood flow rates- these two are sharp. Pre pump AP >-250 can greatly effect the real QB within the dialysis circuit. See the post and comments are welcome. This is a very import issue for the vascualr access as well as KT/V issues!
How many of you use pre pump AP? |
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We use prepump lines at my Niles IL clinic. We just recently changed over to monitoring AP, and it was tough getting the techs to keep the monitor line unclamped. They got so many more alarms than usual that they "fixed" it by clamping the AP monitor line. Some monitoring of the techs by our D.O.N., and teaching as well, helped everyone to get with it. We discuss KT/V, URR and other numbers at our monthly QCI meetings, and we should see an upward trend trend soon, I'm thinking. And, thank you for the compliment, Deborah! |
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Well Joesph I am very impressed! Pre pump AP is so important to the safe and effective delivery of an HD tx. Clamping the arterial line to run a "poor or sucking catheter" or fistula/graft is not a safe or good practice. This just avoids the issue of a poor flow from the access- leads to decreased extracoporeal bloodflow, decreased clearance and if bad enough line collaspe or "line sucking" occurs- secondary degassing with possible hemolysis. Would you ever run a treatment without a venous pressure- so why would you do dialysis without a pre-pump Arterial Pressure to see how well the access is working to supply blood into the bloodpump and dialyzer. I wish more dialysis staff understood the importance of pre-pump AP and would use the monitoring correctly. Keep up your efforts. Would like to hear from people not using the pre-pump AP as to why and what questions they have. Any comments about pre pump vs post pump?
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Keep in mind, some machines(Baxter) require a positive pressure arterial line connection to the machine. Fresenius can monitor negative arterial pressure without problems, UNLESS the clinical staff have little or no experience with the practice. Without the baseline knowledge of negative arterial pressure monitoring, many clamp the arteial monitor to avoid the alarms. They think BFR speed is the only consideration for effective clearance.Bottom line, anything greater than -200mmHG should be avoided because of recircultion and blood pump inaccuracies. Can't get the 500BFR without going greater than -200? Lower the BFR and run longer treatments to get that Kt/V or get a better clearing dialyzer. In any case never go greater than -200mmHg art pressure.
[This message has been edited by TecDude (edited 05-07-99).] |
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Good point about the AP increasing with the use of the higher bloodflow rates- you can use larger fistula needles to improve the flow and run with less negative AP's. Do most of you use 17,16,15 or 14 GA needles? Catheters remain the hardest access to get good bloodflows with AP's less than -200. AV fistula/graft that has a >-200 AP might have a low flow within the access. A fistula can stay open with a flow as low as 300 cc/min and if we try to run the blood pump at 400 or 500 the fistula can't supply enough blood to fill the arterial bloodlines. See the Techs BB uner the blood pump calibration-
the techs understand what happens to the blood pump segment when the AP is too negative. (pretty sharp tech on this site!!) |
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Funny you should ask about needle size. We've got one doc who is stuck(no pun intended) on 16G. He thinks clotting times are better than with 15's, and we rib him about it regularly. We have used 17 on occasion but not 14. Yeesh, 14! That's a coffee stirrer. Bet you get a heck of a flow, though! Would be great with parallel dialyzers.
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Joe- you still using parallel dialyzers? I trained on coils and thought parallel dialyzers were so high tech for acutes. Yes 14 ga are big- but 15's work well. Will you Dr. try some 15's and see what happens? could have a patinet use 16 for 1 week and note accurate post neeld eremoval bleeding times and then the next 3 treatments use the 15 ga and compare the post tx times- would be interesting to see if any change.
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I should have said "two dialyzers in parallel". We haven't used plate dialyzers since I've been there, almost 4 years.
Our doc dismisses the idea quickly when asked about 15Ga needles. He's really great about anything else, he's just got a thing about larger needles. Go figure. |
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If you are using 2 dialyzers in parallel you sure could benifit from the 15 ga needles - some units use 14 ga for double dialyzer patients. Would he listen to other MD's using the larger needles? I will see if I can find you some references about the different needle sizes for double dialyzer treatments. Will post if I find any.
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Using dialyzers in parallel is done to improve clearances. 2 hollow fiber large dialyzers are used in the same treatment. The second dialyzer is connected into the bloodlines after the normal placement of the first dialyzer and has the dialysate from the first dialyzer pass through the second dialyzer. This is not a wide spread technique- but is offered at clinics around the US. You can post this question to Patt Peterson under the KT/V board and she might be albe to provide more information and give you a reference for the procedure.
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I hope I understood your starting question correctly.
We monitor access pressures with each tx and do an "access study" weekly. Access studies done q week, @ 200 BF, monitor for VP pressure changes from week to week; usually runs from 40 - 80; helps catch a stenosis or other problem which may occur in grafts and AVF. VP not allowed to run close to or > 300 at prescribed BF; varies BF, but generally runs ~150 - 250. AP monitored on a tx by tx basis, not allowed < -300; most run @ ~ mid 150s - low 200s while at the prescribed BF. We do have a few pts running @ 500BF, with 15g needles, and, of course, their APs and VPs are a bit higher, but are still within limits. Increases in BF ordered according to clearances and recirculation studies. We rarely run someone with 16g needles > 300BF d/t increases in VP and AP and the increased potential for lysis of cells. Thanks Much!! |
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RenalWEB Home Page renalweb.groupee.net RenalWEB Discussion Forums Nursing / Patient Care Issues Vascular Access VP and Pre-pump AP while on HD set BFR
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