Fallacies and Pitfalls of Dialysis Sodium Prescription and Control

Abstract

Dialysate conductivity is routinely used as a surrogate for dialysate sodium concentration. However, dialysis machine manufacturers apply different conductivity temperature correction coefficients. With the same conductivity in dialysis machines manufactured by different manufacturers, dialysate sodium may significantly differ. Also, electrolyte prescriptions are individualized (K, Ca, HCO³) and this is associated with another variation in dialysate sodium in the order of 1–5 mmol/L and both deviations are cumulative and chronic for each patient. Equivalence of the prescribed dialysate sodium and the concentration measured in it is not granted. Both variables differ and it is machine dependent! This paper analyses those variations from a technical point of view and suggests how to detect them and how to deal with or avoid them in clinical practice.

How Geometry Affects Sensitivity of a Differential Transformer for Contactless Characterization of Liquids

“…Therefore, this measurement method has potential in biotechnology and medical technology for the contactless determination of biomass within single-use bioreactors [1,18] or for obtaining tissue information [19][20][21][22][23]. In addition, the differential transformer approach is investigated with respect to continuous in-line monitoring of the sodium concentration in human blood, by measuring the blood plasma conductivity, mainly influenced by the sodium concentration [24][25][26][27]. Continuous monitoring of plasma sodium concentration is particularly important in continuous renal replacement therapy, especially in patients with severe dysnatremia, since both a large deviation from the physiological plasma sodium level [26,[28][29][30] and a rapid change in the concentration can lead to dangerous complications such as central pontine myelinolysis [31,32].…”

Impact of dialysate sodium concentration on vascular refilling

“…Additionally, dialysate sodium setting is not an exact science: considering that sodium is also the main contributor to plasma-water conductivity, dialysis monitors convert conductivity into a "natremia" value displayed on the screen, with a potential variation in dialysate sodium in the order of 1-5 mmol/L on either direction. [25][26][27] This may explain why differences did not turn significant when comparing any profile with neutral profile.…”

Differential Inductive Sensing System for Truly Contactless Measuring of Liquids′ Electromagnetic Properties in Tubing

“…To avoid possible contamination of a sample induced by a sensing system, in some applications it is essential to perform contactless measurements. An example of such an application is the continuous in-line monitoring of blood conductivity as a measure of the sodium concentration of blood serum [ 1 , 2 , 3 , 4 , 5 , 6 ]. Such monitoring is particularly useful for critically ill patients in intensive care units with severe dysnatremia [ 7 , 8 , 9 ].…”

“…In measuring systems that operate above this frequency, the whole blood conductivity is additionally affected by the high concentration of intracellular potassium in red blood cells. Thus, solely measuring the sodium concentration (neglecting the low concentrated electrolytes in extracellular liquid) in the microwave region is not possible [ 3 , 18 , 19 ]. Further examples for requiring a contactless sensing system can also be found in biological and chemical process monitoring [ 20 , 21 ].…”