How is hemodialysis ordered?

There are multiple components to hemodialysis, and each session of dialysis must be tailored to an individual patient’s needs. For example, do they need more fluid taken off because they have heart failure? Do they need more potassium in the diasylate because they are persistently hypokalemic? Here are some words that you may see in a renal fellow’s note about the components of dialysis and a brief description of what they mean. If you have a LOT of time on your hands, check out these EBPG guidelines published in 2007.

  • Dialyzer: not actually part of the dialysis rx, but I wanted to include it to help you understand the machinery of receiving dialysis. Here is a helpful overview for patients from Davita about the plastic tube that actually does the work of dialyzing.
  • Duration: how long is the dialysis session? Different patients may only be able to tolerate so much, or they may need longer sessions to filter the fluid more slowly. There is no conclusive evidence that longer dialysis time reduces mortality.
  • Ultrafiltration goal: This refers to how much “excess water” is taken off at each session. It is based on that patient’s estimated dry weight (EDW), although the EDW may be difficult to determine at first. There is no recommendation for an UF goal in the US, but based on observational studies, some countries recommend an arbitrary goal of 750-1000 mL/day in anuric patients.
  • Diasylate solution:
      • Sodium: low sodium concentration may exacerbate hypotension, but high sodium may exacerbate volume overload
      • Potassium: In general, one can expect only up to 70 to 90 mEq of potassium to be removed during a typical dialysis session.
      • Calcium: patients with a low concentration of calcium in their bath may not experience as much intra-dialysis hypotension, gain higher vitamin D levels, and can use more phos binders containing calcium to lower phos levels
      • Bicarbonate: usually adjusted to maintain a serum bicarbonate >23. This is important for reducing acidosis.
  • ultra-coefficient: referred to as KUF, has to do with the amount of fluid crossing the diasyler membrane with regards to time and pressure.  I don’t have enough physics know-how to fully analyze its value, but these people seem to.
  • Diasylate temperature: It is thought that lowering the diasylate temperature makes dialysis easier to tolerate and improves symptoms of fatigue/post-dialysis syndrome. Why? Kind of unclear.

 

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