Comparison of Prescribed and Measured Dialysate Electrolyte Levels in the Hemodialysate

Background. The measured electrolyte composition of the dialysate (D) should be in close approximation to that of the hemodialysis prescription. However, to the best of our knowledge, no studies have compared prescribed and measured hemodialysate electrolyte levels other than sodium (Na+) and calcium (Ca++). Objective. To determine the difference between the measured and prescribed electrolyte concentrations in the hemodialysate and the factors responsible for it. Methods. In this retrospective study, data from biochemical analyses of the hemodialysate, acid concentrate and product water were collected. Data on a fraction of samples with measured electrolyte concentrations within the permitted range of the prescribed value were collected, and the reasons for the discrepancy between the prescribed and measured values were analysed. Results. In our study, 91.87%, 59.22%, 54.41% and 6.84% of the samples had DNa+, DK+, DCa++ and DMg++ values, respectively, within the range of the prescribed concentrations. The Ca++ content in the acid concentrate (Part A) and changes in the prescribed DNa+ or DB (part of the dialysate contributed by Part B, which contained sodium chloride and sodium bicarbonate in our study) were responsible for the discrepancy between the prescribed and measured DCa++ values. For an 8 mmol/L (5.7%) reduction in the prescribed DNa+, the measured DCa++ was reduced by 9.07% ± 1.68%. A reduction in the prescribed DB by 8 mmol/L led to an increase in the measured DCa++ of 10.31% ± 2.02%. High measured DMg++ and DCa++ values were observed in certain dialysate samples owing to higher-than-expected magnesium and calcium contents in the acid concentrate. With an 8 mmol/L (5.7%) reduction in the prescribed DNa+, the measured DK+ decreased by 10.56% ± 3.56%. DNa+ was correlated with the dialysate conductivity (R = 0.919) and increased with decreasing prescribed DB. Conclusion. The calcium in the acid concentrate and the prescribed DNa+/DB were responsible for the discrepancy between the prescribed and measured DCa++. The prescribed DNa+ change was responsible for the discrepancy between the measured and prescribed DK+. Furthermore, a strong correlation was observed between the dialysate conductivity and DNa+ in our study, where the dialysate conductivity increased with decreasing DB, while DNa+ remained constant.