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Abstract: FR-PO281

Simplified, Simulated Sodium Kinetic Modeling for Correction of Hyponatremia by Continuous Venovenous Hemofiltration

Session Information

Category: Fluid and Electrolytes

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Uduman, Junior, Henry Ford Hospital, Detroit, Michigan, United States
  • Mohiuddin, Naushaba, Henry Ford Hospital, Detroit, Michigan, United States
  • Zasuwa, Gerard, Henry Ford Hospital, Detroit, Michigan, United States
  • Yee, Jerry, Henry Ford Hospital, Detroit, Michigan, United States
  • Frinak, Stanley, Henry Ford Hospital, Detroit, Michigan, United States
Background

Management of hyponatremic, oliguric patients is challenging using conventional dialytic therapy. Osmotherapy, targeted plasma sodium concentration [Na] elevation, delivered by continuous renal replacement therapy (CRRT), must be safely achieved without overcorrection of [Na], i.e., >6 to 8 mmol/L in 24 hours. Predictive modeling of controlled osmotherapy requires an appreciation of CRRT and ongoing Na kinetics. Utilizing an approach based on near-equivalence of Na dialysance and urea reduction ratio (URR), we developed a model that calculates [Na] elevations precisely using predilution continuous venovenous hemofiltration (CVVH), and contrasts the conventional strategy of using replacement fluid [Na] as the post-treatment goal [Na].

Methods

The model defines the post-treatment [Na] (NaPost) at time (t), thereby defining △Na, the difference between pre-therapy [Na] (NaPre) and NaPost. A [Na] gradient (▽Na = NaRF – NaPre) is defined by URR, derived from Na dialysance (D). Because D approximates KUrea, URR is derived from Watson volume, treatment time, and D, determined by QB (hematocrit-adjusted blood flow rate), QRF (RF rate), and QUF (ultrafiltration rate). URR represents the time-varying decrease of ▽Na, i.e., Napost = [(1 − URR) × NaPre + (URR × NaRF)] and NaRF = NaPre + (△Na/URR).

Results

The model calculates, tabulates, and plots time-varying NaPost. Panel 1 of figure displays model input and output parameters for a hypothetical scenario of an anuric hyponatremic patient with tabulated data and graph in panel 2. Model extensions permit simultaneous initial targeting of NaPost, URR, or effluent dose. Integrated calculations determine RF dilutions or infusion rates of parallel hypotonic solutions when RF solutions cannot be adjusted.

Conclusion

We conclude that safely controlled osmotherapy of oligoanuric, hyponatremic patients by predilution CVVH is feasible, and can determine time-varying NaPost. Validation of the model in various clinical scenarios of hyponatremia is required to support utility.