Decreasing blood pump speed when UF off

Chisca, RN · Sep 20, 2014

I found this passage from the fourth edition of Handbook of Dialysis on pg 176. "Slowing the blood flow rate. In the past , part of the intitial therapy for dialysis hypotension was to slow the blood flow rate, a practice developed at a time when plate dialyzers and acetate dialysis solutions were in use and ultrafiltration control systems were not. The practice was believed beneficial at the time because reducing blood flow rates resulted in reductions in (a) dialyzer blood volume, (b) acetate (a vasodilator) transfer to the patient, © ultrafiltration rate, and (d) fistula "steal". The latter refers to the belief that lowering blood flow reduces access flow and allows systemic flow to increase, a concept that is very likely incorrect (Trivedi et al 2005). With current dialysis practice , reduction of the blood flow rate to manage hypotension during dialysis should not be routinely done."

We do not reduce QB to treat hypotension in the center I work in. Blood flow through a mature fistula is at least 600ml/minute so how does reducing the pump speed to 200 have any effect at all on blood pressure or reperfusion?

Travel_Lusting · Sep 20, 2014

Hi Chisca, thank you so much for your response. We were wondering the rationale behind this practice but our co-worker was unable to explain. Thanks especially for the reference.

On another note, I see you run mature fistulas at "at least 600ml/min." What is the maximum speed? In our unit the max is 400ml/min. What are the maximum arterial/venous pressures? Many of our patients return from other units insisting they can have higher blood pump speeds. Right now we are working from outdated policies which we are in the process of amending (insight from other units is great). I have heard of 500ml/min pump speeds (but no higher). Hoping to do some travel work soon, I do not want to be completely shocked when I arrive.

Chisca, RN · Sep 21, 2014

I think I didn't explain clearly but the blood flow through a mature fistula, without being connected to a dialysis machine, is 600 ml/mn and higher which is why I don't feel the dialysis machine flow will have much of an effect on blood pressure. Our nephrologists are slaves to the mighty Kt/v and try to run patients at between 350 and 450 pump speeds. Alot of times they will order "QB best flow". There is alot of controversy over the practice of faster pump speeds as best outcomes come from longer dialysis times but most patients want as quick a treatment as possible. Patients become convinced that faster pump speeds will reduce their treatment times. Management gets paid by the treatment so they want as little time as possible. Mid molecule clearance is also reduced with faster times. Longer treatment times would reduce hypotensive episodes and we would see better patient outcomes but in the US it is hard to convince the dialysis community to change. As far as maximum pump speed the limiting factor is going to be resistance in the circuit and needle size. Blood viscosity is also a variable. With a 15 gauge needle you are not going to be able to run above 450 without exceeding the limits on arterial/venous pressures. My units policy is