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CRRT replacement fluid calculator for hyponatremia

Extreme hyponatremia presents unique challenges during hemodialysis treatment. While conventional dialysis machines are typically limited to a minimum sodium concentration of 130 mmol/L, Continuous Renal Replacement Therapy (CRRT) solutions generally contain 140 mmol/L. For patients with extreme hyponatremia, a lower dialysate sodium concentration is preferred to prevent dangerously rapid increases in serum sodium levels.

This calculator provides guidance for selecting appropriate replacement fluid volume and sodium composition, based in part on research findings.

Clinical Example:

A 50-year-old woman presents with:

  • Severe AKI
  • Sodium level: 100 mmol/L
  • Target maximum sodium concentration: 108 mmol/L

Using CRRT with:

  • Dialysate flow: 1L/hour
  • Dialysate sodium concentration: 140 mmol/L

The calculator recommends either:

  • 0.97L/hour of 1/2 Normal Saline (sodium 75 mmol/L), or
  • 0.296L/hour of D5W (sodium 0 mmol/L)

Reference:

Management of Severe Hyponatremia with Continuous Renal Replacement Therapies.
Clin J Am Soc Nephrol. 2018 May 7;13(5):787-789.
doi: 10.2215/CJN.13281117

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