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  • Kt /V and access question.

    Lately my Kt/V has been dropping but all the individual lab values are in normal ranges. I have an appointment to check my fistula for any issues but oddly enough, my access numbers during treatment are also in range. Anyone ever had an issue like this?

  • #2
    Hello wherezat,

    Kdt/V calculations are quite complex, and take into consideration specific before and after blood chemistry values, the amount of dialysate processed, fluid removal (before and after weight) and your treatment prescription, e.g. how many times a week do you treat and how much dialysate do you process.

    My Kdt/V can vary from the the low 2.0's to the low 3.0's - a significant difference. The minimally accepted Kdt/V for an HHD patient treating 5X weekly is 2.0. Hemodialysis patients treating in center have a minimally accepted Kdt/V of 1.2. Clearly, the formula for a 3X weekly in center patient is much different than that for home hemodialysis patients.

    If the factors above aren't enough to influence your Kdt/V, another is the cleanliness of your blood at the time of your "before treatment" blood sample. If you have been treating on consecutive days prior to the "before treatment" sample, your blood will be cleaner than if you had not treated for 1 or more days before taking the sample. In this case, the before and after difference is not going to be as significant, which will alone produce a lower Kdt/V.

    My individual nutritional values are excellent because I will treat for at least two days consecutively (generally, nocturnally) prior to the day of my labs. I will also treat nocturnally on the day of my labs to drive my Kdt/V value higher, e.g. more dialysate, more dialyzing time, and typically more fluid removed.

    The mechanics of your fistula will affect the quality of dialysis that you are receiving, but will do so in a manner that should affect nutritional and Ktd/V in like manner. Needle location will affect the quality of dialysis if the arterial and venous sites are less than 2 finger widths apart, which would cause a "pick up" of already cleaned blood from the venous return rather than all of the blood coming from the anastomosis toward the arterial site.


    • #3
      Thanks for the reply.
      What's odd about this and is confusing is the fact that after 4 years of HHD my clearance has dropped over the last 3 months. I've had no changes in my treatment rx, no changes to my medications, no significant variations in my diet and no changes to my access positions.
      The general thought of my neph and vascular is that maybe there is a branch that possibly may be affecting the pull and return circulations but even if there is evidence of a branch it would seem to me that it would have to have become very significant quite rapidly in order to start effecting my clearance within the last few months.
      I just find it hard to think of a change that significant happening without seeing variations in my arterial and venous flow rates.


      • #4
        Hello wherezat,

        I would suggest getting having a fistullogram performed. This is a minimally invasive procedure that is done on an outpatient basis under mild but conscious sedation. The vascular surgeon will inject your fistula with a material that can be observed via X-Ray. The observation will note flow dynamics to determine evidence of restrictions or pooling. Presuming that you are using one set of sites - venous and arterial, on a single vessel, the study will focus on that area and assess influences from lateral vessels that could explain your drop in Kdt/V. You may need to have lateral/run off vessels "tied off" in a separate procedure to restore the proper flow to that portion of the fistula you are using for hemodialysis.

        I'm not certain that the venous and arterial pressures that are measured during dialysis are indicative of flow quality. I have had 4 of 5 of my buttonhole access sites tested with a transonic to determine the pull and push flow/pressure capability of each. Provided the individual sites can sustain a certain range, they are deemed viable for use as either arterial or venous sites - determined by their respective proximity to eachother and your heart, e.g. the arterial access if on the same vessel must be closer to the anastomosis/further from your heart than the venous access to assure that "uncleaned" blood is being pulled from the fistula and "cleaned" blood is being put back into the fistula.


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