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Abstract

Background and aims: Controlled hypernatremia can play a role in the management of intracranial hypertension, and can be accomplished with CRRT using hypernatremic replacement fluids. The ability to predict the therapeutic result of a hypernatremic CRRT prescription can help develop operating parameters. Aims: The aim of this study was to develop a mathematical model of CRRT to predict sodium levels with hypernatremic replacement fluids. Methods: A multiscale mathematical model was developed for the simulation of sodium, citrate and bicarbonate dynamics. This model consists of a finite element analysis model with partial differential equations for fluid and solute handling in the hemofilter coupled to a multi-compartment model based on ordinary differential equations that describes fluid and solute handling in the body. The model incorporates blood and dialysate flow, protein transport and osmotic pressure, solute reflection, and diffusive and convective solute transport as well as distribution, transport and elimination of sodium, citrate, and bicarbonate in body compartments. Approval was waived by the IRB. Results: A 3 year old 23 kg pediatric patient with post-traumatic intracranial hypertension was managed with controlled hypernatremia using CVVHD with sodium concentration in replacement fluid and dialysate of 160 mMol/L. Anticoagulation was 4% trisodium citrate. Serum sodium was monitored every 2 hours. Simulations over the initial 12 hours were run using the same operating conditions. Comparison of recorded and predicted sodium levels revealed good agreement over the simulation period. Conclusions: This multiscale model predicted sodium levels during hypertonic CVVHD with reasonable accuracy, taking into account multiple factors affecting sodium levels.