A Computerized Model to Analyze Transcellular Fluid Shift During Hemofiltration

Abstract

Using urea and inulin as markers, a simple method to calculate intracellular and extracellular fluid volume in patients before and after hemofiltration therapy was developed. During conventional hemofiltration using substitution fluid with a Na+ concentration of 140 meq/l, a decrease in extracellular fluid volume was noted whereas the intracellular fluid volume was unaltered. A computerized mathematical model was developed to analyze transcellular fluid shifts during hemofiltration. This model also indicated a decrease in extracellular fluid volume only, the intracellular fluid volume remaining unchanged. High-Na+ hemofiltration using substitution fluid with an Na+ concentration of 160 meq/l enabled the removal of fluid from both intracellular and extracellular compartments. High-Na+ hemofiltration was expected to normalize the intracellular hydration in uremic patients, and to reduce the decrease in extracellular fluid volume during hemofiltration therapy. High-Na+ hemofiltration could apparently prevent bypotension due to large decreases in extracellular fluid volume by inducing a transcellular fluid shift out of body cells. The computerized model can be a useful tool in the prescription of the optimal Na+ concentration in substitution fluid for individualized hemofiltration therapy.