A Computerized Model to Analyze Transcellular Fluid Shift During Hemofiltration

Abstract

Using urea and inulin as markers, we have developed a simple method to calculate intracellular and extracellular fluid volume in patients before and after hemofiltration therapy. 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. Furthermore, we have developed a computerized mathematical model to analyze transcellular fluid shifts during hemofiltration. This model also indicates 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 has enabled us to remove fluid from both intracellular and extracellular compartments. Thus, high-Na+ hemofiltration is expected to normalize the intracellular hydration in uremic patients, and to reduce the decrease in extracellular fluid volume during hemofiltration therapy. Our data therefore suggest that high-Na+ hemofiltration could prevent hypotension due to large decreases in extracellular fluid volume by inducing a transcellular fluid shift out of body cells. Our computerized model can be a useful tool in the prescription of the optimal Na+ concentration in substitution fluid for individualized hemofiltration therapy.

Management of Patients with Renal Failure Complicated by Cerebral Oedema

“…Similarly, during haemodialysis there is a preferential movement of solute from the extracellular compartment resulting in a greater fall in plasma osmotic pressure [18], which may lead to the passage of water into the intracellular compartment resulting in cerebral oedema, whereas haemofiltration has been reported to result in a reduction in the extracellular volume without any change in the intracellular fluid volume [19].…”

Prediction of Postdialysis Serum Sodium Concentration and Transcellular Fluid Shift Without Measuring Body Fluid Volumes

“…Model prediction of the postdialysis levels of serum "a+], BUN, Posm, and magnitude of transcellular fluid shifts and sodium removal Assuming that only Na+ is important as an effective osmotic substance in the extracellular fluid to induce a transcellular fluid shift and that urea is freely permeable to the cell membrane, serum "a+], BUN, Posm, ICF, and ECF during HD are simulated as previously described (7,8). In t h s model prediction, the predialysis body fluid volumes must be known.…”

“…Since the effective osmolality reaches equilibrium in both the extracellular and intracellular fluid, and the absolute amount of effective osmotic substance within the cells is assumed constant in our model (7,8): Since the effective osmolality reaches equilibrium in both the extracellular and intracellular fluid, and the absolute amount of effective osmotic substance within the cells is assumed constant in our model (7,8):…”

“…Using the estimated predialysis body fluid volumes, TBFo, ICFo, and ECFo, as described above, the postdialysis levels of serum " a + ] , BUN, Posm, TBF, ICF, ECF, and QNa+ (serum "a+] x ECF) can be predicted based on our computer model (7,8) without measuring body fluid volumes. 1-3 above, TBFo can be estimated if A and B are known.…”

Hemofiltration in Multiorgan Failure Syndrome Secondary to Sepsis: A Critical Analysis of Heterogeneity

“…In turn, hemodialysis solved the problem of the marked cardiodepressive effects of lactic acidosis [44] as well as the meta bolic alterations derived from renal failure [40]. Mean while, the clearing of interstitial edema during hemofiltra tion [45] would imply a significant step towards a return of the cellular environment to a situation of physiological homeostasis.…”