{"id":152,"date":"2018-04-23T11:40:01","date_gmt":"2018-04-23T11:40:01","guid":{"rendered":"http:\/\/edren.org\/ren\/?page_id=152"},"modified":"2023-03-09T12:22:34","modified_gmt":"2023-03-09T12:22:34","slug":"haemodialysis","status":"publish","type":"page","link":"https:\/\/edren.org\/ren\/handbook\/dialysis-handbook\/dialysis-information\/haemodialysis\/","title":{"rendered":"Haemodialysis"},"content":{"rendered":"
NHS Lothian protocols for care of patients receiving haemodialysis<\/span><\/strong><\/h5>\n

Our Standard Operating Procedure<\/a>.<\/p>\n

Our RIE Dialysis Unit Escalation Policy<\/a>.<\/p>\n

 <\/p>\n

Quantitation and adequacy<\/span><\/strong><\/h5>\n

Measurements of small molecule clearance have become an accepted way of assessing the adequacy of haemodialysis, because a correlation with mortality has been shown in large studies. It is a Renal Association standard that adequacy is checked monthly on all chronic haemodialysis patients.<\/p>\n

Kt\/V for urea*<\/span><\/strong> is the most widely accepted of these measurements, although a simple surrogate for this, urea reduction ratio (URR), is more readily measured and is also widely used. There is a calculator for Kt\/V in Proton.<\/p>\n

* K<\/span><\/strong> is a dialyser-specific figure for rate of urea clearance on an individual dialyser, at a given blood flow and dialysate flow. t is duration of dialysis. V<\/span><\/strong> is the volume of distribution of urea in a patient.<\/p>\n

Urea reduction ratio method<\/span><\/strong><\/p>\n

In the RIE we check Urea Reduction Ratio (URR), calculated as:<\/p>\n

URR = 100 x [1 – Post(Urea)\/Pre(Urea)]<\/span><\/strong><\/p>\n

The Edinburgh unit participates in a multicentre audit with comparison of URR results between all units in Scotland. This is the protocol approved by the Scottish Renal Association:<\/p>\n

    \n
  • The \u2018pre\u2019 sample is taken immediately after cannulation of the fistula with a dry needle and before the dialysis starts. For central venous cannulae, a sample can be drawn from the line after the Heparin lock has been removed. Take care not to contaminate the samples with saline.<\/li>\n
  • The post sample is taken by the stop flow method ie. the dialysate flow is stopped for 5 minutes, leaving the blood pump running, before sampling from the port in the arterial blood line. This is to allow time for the blood in the access to equilibrate with the central circulation, but not enough time for the equilibration from the tissue pool<\/li>\n<\/ul>\n

    Only these bloods should be marked PRE (001) and POST (002) and are done by staff in the dialysis Units on a monthly basis.<\/p>\n

    Bloods taken without this stop flow will overestimate urea clearance on dialysis. Hence, while it may be appropriate to take bloods pre-dialysis on eg. in-patients to save patients venepuncure, and it is often necessary to know post dialysis potassium in out-patients who have not for whatever reason, completed their dialysis prescription, mark these bloods with the time they are taken, not pre\/post or the 001\/002 codes. This is very important as failure to do so causes problems with download of data to the Registry.<\/p>\n

    Problems with Kt\/V & URR<\/span><\/strong><\/p>\n

      \n
    • Small molecule clearance is not the only or even always the most important factor in determining dialysis adequacy.<\/li>\n
    • Fluid balance is important for mortality and is not measured by Kt\/V or URR. It is more affected by dialysis frequency and duration.<\/li>\n
    • Calculations that use measurements of blood urea (instead of dialysate urea) are prone to sampling errors, particularly urea rebound.<\/li>\n
    • V (volume of distribution of urea) is low in wasted, malnourished patients \u2013 high Kt\/V values may be caused by this, rather than by excellent dialysis.<\/li>\n<\/ul>\n
      Kt\/V versus URR<\/span><\/strong><\/h5>\n

      Calculations based on URR alone underestimate Kt\/V because no account is taken of the consequences of ultrafiltration.\u00a0 This removes urea, but is \u2018invisible\u2019 by URR monitoring alone.
      \n
      \nTable:<\/span><\/strong> correlation of URR to Kt\/V corrected for ultrafiltration (NKF K\/DOQI Guideline 2000). Calculated from single-pool, variable volume model with a body weight of 67.3kg, V of 35L, and NPCR of 1.0. Wt\/BWt is the ultrafiltration volume\/post dialysis weight x 100.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
      <\/td>\nURR Values at Kt\/V<\/span><\/strong><\/td>\n<\/tr>\n
      DWt\/BWt\u00a0 %<\/span><\/strong><\/td>\n0.8<\/td>\n0.9<\/td>\n1.0<\/td>\n1.1<\/td>\n1.2<\/td>\n1.3<\/td>\n1.4<\/td>\n1.5<\/td>\n<\/tr>\n
      0<\/td>\n53<\/td>\n57<\/td>\n61<\/td>\n65<\/td>\n68<\/td>\n71<\/td>\n74<\/td>\n76<\/td>\n<\/tr>\n
      1<\/td>\n52<\/td>\n57<\/td>\n61<\/td>\n64<\/td>\n68<\/td>\n71<\/td>\n73<\/td>\n76<\/td>\n<\/tr>\n
      2<\/td>\n50<\/td>\n55<\/td>\n59<\/td>\n63<\/td>\n66<\/td>\n69<\/td>\n72<\/td>\n75<\/td>\n<\/tr>\n
      3<\/td>\n49<\/td>\n54<\/td>\n58<\/td>\n62<\/td>\n65<\/td>\n68<\/td>\n71<\/td>\n74<\/td>\n<\/tr>\n
      4<\/td>\n48<\/td>\n53<\/td>\n57<\/td>\n61<\/td>\n64<\/td>\n67<\/td>\n70<\/td>\n73<\/td>\n<\/tr>\n
      5<\/td>\n47<\/td>\n51<\/td>\n56<\/td>\n60<\/td>\n63<\/td>\n67<\/td>\n70<\/td>\n72<\/td>\n<\/tr>\n
      6<\/td>\n46<\/td>\n50<\/td>\n55<\/td>\n59<\/td>\n62<\/td>\n66<\/td>\n69<\/td>\n71<\/td>\n<\/tr>\n
      7<\/td>\n44<\/td>\n49<\/td>\n53<\/td>\n58<\/td>\n61<\/td>\n65<\/td>\n68<\/td>\n71<\/td>\n<\/tr>\n
      8<\/td>\n43<\/td>\n48<\/td>\n52<\/td>\n57<\/td>\n60<\/td>\n64<\/td>\n67<\/td>\n70<\/td>\n<\/tr>\n
      9<\/td>\n42<\/td>\n47<\/td>\n51<\/td>\n56<\/td>\n59<\/td>\n63<\/td>\n66<\/td>\n69<\/td>\n<\/tr>\n
      10<\/td>\n41<\/td>\n46<\/td>\n50<\/td>\n54<\/td>\n58<\/td>\n62<\/td>\n65<\/td>\n68<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      \nPrescribed Dialysis:<\/span><\/strong><\/h5>\n

      Dialysis should be prescribed on an individual basis.\u00a0 The variables influencing the amount of dialysis required are:<\/p>\n