Comparison of Prescribed and Measured Dialysate Electrolyte Levels in the Hemodialysate

Introduction

In India, end-stage renal disease is present in approximately 130,000 patients, 120,000 of whom are on hemodialysis (HD) [1]. HD requires a large volume of freshly prepared dialysate (D) to remove uremic solutes and electrolytes, such as potassium and phosphorus, and to add bicarbonate. The three components of the hemodialysate are acid concentrate (Part A), base concentrate (Part B) and Association for the Advancement of Medical Instrumentation (AAMI) standard product water, which are mixed in a proportionating ratio [2]. The acid concentrate contains chloride salts of sodium (Na⁺), potassium (K⁺), calcium (Ca⁺⁺) and magnesium (Mg⁺⁺); dextrose monohydrate; and acetic acid/citric acid, whereas the base concentrate contains NaHCO₃ (sometimes along with NaCl) [2].

The measured concentration of electrolytes in the hemodialysate should be close to the prescribed concentration. The final dialysate sodium (DNa⁺) should be within ±2.5% of the prescribed concentration, whereas the measured dialysate Ca⁺⁺, K⁺ and Mg⁺⁺ should be within ±5% of the prescription [3]. If any component of the hemodialysate (acid concentrate, base concentrate or AAMI standard water) has an improper composition, it can affect the electrolyte composition of the hemodialysate and lead to adverse clinical outcomes [4, 5]. Few studies have compared the prescribed and measured DNa⁺ and DCa⁺⁺ [6, 7]. The difference between the measured and prescribed DNa⁺ depends on the type of HD machine and the method of DNa⁺ estimation [8]. However, no studies have compared the prescribed and measured electrolyte concentrations other than Na⁺ and Ca⁺⁺ in the haemodialysate. An improperly functioning water treatment plant can contribute to the discrepancy between the measured and prescribed dialysate electrolyte concentrations. For example, a malfunction in the softener can increase the concentration of Ca⁺⁺ in reverse osmosis permeate and dialysate, resulting in a condition known as hardwater syndrome [9, 10].

Dialysate conductivity is a valuable tool for monitoring the delivered DNa⁺ as it is correlated with DNa⁺ (1 mS/cm of dialysate conductivity is approximately 10 mmol/L DNa⁺ in the haemodialysate) [11]. To the best of our knowledge, this study is the first to examine the discrepancy between measured and prescribed dialysate electrolytes other than Na⁺ and Ca⁺⁺. This study aimed to compare the measured and prescribed electrolyte concentrations in the haemodialysate and to determine the factors responsible for the differences.

 

Methodology

Study design

Retrospective single-centre study

Study period

From July 1st, 2020, to January 15th, 2021.

Inclusion criterion

Data on all dialysis solutions with available measured dialysate electrolyte values were included in the study.

Exclusion criterion

Dialysate solutions with missing prescribed dialysate electrolyte data were excluded.

Study protocol

Data collection commenced after clearance from the hospital ethics committee of the Pondicherry Institute of Medical Sciences (PIMS), Puducherry (Reg. No. ECR/400/Int/Py/2013). All data on dialysis solution electrolytes (measured and prescribed), including Na⁺, Ca⁺⁺, K⁺, Mg⁺⁺, Cl⁻ and HCO₃⁻ concentrations, as well as dialysate conductivity over the prescribed duration, were collected from the hospital records of the Nephrology Department. Data regarding the chemical analysis of reverse osmosis (RO) water and acid concentrate were acquired from hospital records. Data on the analysis methods for dialysis solution electrolytes were obtained from the Biochemistry Department of PIMS.

The distribution of dialysate sample data based on prescribed dialysate electrolytes was examined, and the fraction of samples with data on the measured dialysate electrolyte concentrations was determined. Fractions of dialysate samples whose DNa⁺ values were within the permitted limits of the prescribed DNa⁺ (with ± 2.5%) were documented. The number (percentage) of dialysate samples with measured dialysate electrolytes other than Na⁺ (K⁺, Ca⁺⁺, Mg⁺⁺) within the permitted limits of the prescribed respective electrolyte (with ± 5%) was recorded. The measured DCa⁺⁺ distributions in the four subgroups (<1.25 mmol/L, 1.25-1.5 mmol/L, 1.5-1.75 mmol/L and >1.75 mmol/L) were explored. The alterations in DCa⁺⁺/DK⁺ with changes in DNa⁺ or DB (Part B contained NaCl and NaHCO₃) were investigated. The correlation between the measured DNa⁺ and dialysate conductivity was studied.

Statistical analysis

The data distributions of the prescribed and measured dialysate electrolytes were presented as numbers and percentages. The fraction of dialysate samples with electrolytes within the recommended range was expressed as a percentage. Changes (numbers and percentages) in DCa⁺⁺/DK⁺ with alterations in DNa⁺ or DB (including NaCl in the base concentrate) were presented as the mean ± SD/median ± IQR based on the normality of the data, as determined using the Kolmogorov-Smirnov test. The Pearson correlation coefficient was used to evaluate the association between the measured DNa⁺ and the dialysate conductivity. A p-value of <0.05 was considered to indicate statistical significance.

 

Results

Data on 177 hemodialysate samples with available measured dialysate electrolyte values over the 6-month study period were collected from hospital records. Prescribed dialysate electrolyte data were missing for 30 samples. Hence, they were excluded, and the remaining 147 samples were included in the study. Data on the measured dialysate Na⁺, K⁺, Ca⁺⁺ and Mg⁺⁺ concentrations and conductivity were available in 81, 136, 147 and 147 reports, respectively. The predominantly prescribed DNa⁺ and DK⁺ concentrations were 140 mmol/L and 2 mmol/L, respectively. Details of the prescribed DNa⁺ and DK⁺ concentrations are presented in Tables 1 and 2, respectively. In all samples, the prescribed DCa⁺⁺ and DMg⁺⁺ concentrations were 1.5 mmol/L (6 mg/dL) and 0.375 mmol/L (0.9 mg/dL), respectively. In our HD unit, all HD machines are set to the proportionating ratio of acid concentrate : base concentrate : product water = 1:1.83:34. The composition of the acid concentrate per litre, as mentioned in the container, was as follows:

– NaCl: 181 g; Na⁺: 71.77 g
– CaCl₂.2H₂O: 8 g; Ca⁺⁺: 2176 mg
– KCl: 5.5 g; K⁺: 2898 mg
– MgCl₂.6H₂O: 2.75 g; Mg⁺⁺: 325 mg

The NaCl contents per litre of the dialysate contributed by the acid concentrate (Part A) and base concentrate (Part B) were 84 mmol and 20 mmol, respectively. A total of 1.83 litres of the base concentrate contributed 20 mmol and 35 mmol of NaCl and NaHCO₃, respectively, per litre of the final dialysate (a total of 55 mmol/L).

DNa⁺ and DK⁺ were estimated using the ion-selective electrode method. DCa⁺⁺ and DMg⁺⁺ were determined using the BAPTA method and the colourimetric method with chlorophosphonazo-3, respectively, on the Cobas Integra 400 plus. Ca⁺⁺ and Mg⁺⁺ were estimated in RO water and acid concentrate using the EDTA titration method.

The number of samples with measured DNa⁺, DK⁺, DCa⁺⁺ and DMg⁺⁺ values within the permitted range of the prescribed electrolyte concentrations is furnished in Figure 1. Although DCa⁺⁺ values were not within the permitted range of the prescribed electrolyte concentrations for 45.59% of the samples, only 6.8% and 1.36% of the samples had DCa⁺⁺ values >1.75 mmol/L and <1.25 mmol/L, respectively.

The samples with measured DCa⁺⁺ values >1.75 mmol/l had higher than the prescribed DCa⁺⁺ and DMg⁺⁺ values because of the higher-than-expected Ca⁺⁺ and Mg⁺⁺ contents in the acid concentrate, as mentioned in Table 3. The acid concentrate was changed immediately after the problem was identified, and the issue was subsequently resolved. Chemical analysis of the RO water revealed that Ca⁺⁺ and Mg⁺⁺ concentrations were within the recommended limits.

A total of 24 dialysate samples were collected, with a set of four samples obtained from separate HD machines. From each HD machine, four sets of dialysate samples with the same acid and base concentrate solution but different DNa⁺ and DB prescriptions were acquired. The number of DB options in the HD machines ranged from −8 to +8, with −8 indicating a decrease in Part B outflow, thereby reducing its contribution to the final dialysate by 8 mmol/L of Na⁺, typically in the form of NaHCO₃. However, in our study, Part B contained NaHCO₃ and NaCl at a ratio of 35:20. A change in Part B, which contributes to the dialysate (DB), to −8 reduces the Na⁺ output from Part B. This alteration causes a decrease in DNa⁺ contributed by Part B to the final haemodialysate from 55 mmol to 47 mmol per litre of the hemodialysate, maintaining the ratio of NaHCO₃:NaCl (35:20). The four sets of samples from each machine were as follows:

– DNa⁺ 140 mmol/L; DB 55 mmol/L
– DNa⁺ 140 mmol/L; DB 47 mmol/L
– DNa⁺ 132 mmol/L; DB 55 mmol/L
– DNa⁺ 132 mmol/L; DB 47 mmol/L

The above 24 samples were collected when the patients were not undergoing HD.

In 100% of the sample pairs with a DB of 55 mmol/L, a reduction in DNa⁺ of 8 mmol/L within the pair led to a decrease in DCa⁺⁺ of >5% (mean ± SD of absolute change: −0.53333 ± 0.088763). Similarly, in 100% of the sample pairs with a DNa⁺ of 140 mmol/L, a reduction in DB from 55 mmol/L to 47 mmol/L increased the DCa⁺⁺ by >5% (mean ± SD of absolute change: 0.55 ± 0.1). The above details are provided in Table 4.

In all (100%) sample pairs with a DB of 55 mmol/L, a reduction in DNa⁺ by 8 mmol/L within the pair led to a decrease in DK⁺ of >5%. However, for all pairs with a constant DNa⁺, a reduction in DB from 55 mmol/L to 47 mmol/L did not lead to a similar direction of change in DK⁺. These details are presented in Table 4.

A strong correlation was observed between dialysate conductivity and DNa⁺ (Pearson correlation coefficient = 0.919 at the 99% level of significance) (Figure 2). On keeping DNa constant in three pairs of dialysate samples, with DB changing within the pair from 55 to 47, the mean increase in dialysate conductivity was 0.3 mS/cm for an 8 mmol/L decrease in DB.

The proper functioning of the acid and base concentrate pumps was confirmed by the engineers of the relevant company. The conductivity metre of the HD machine was also verified to function correctly and was found to be within ±0.2 mS/cm.

S. No.	Prescribed DNa+ (mmol/L)	No. of samples (%)	No of samples with measured DNa+ available (with %)	% of samples with measured DNa+ within the permitted range of the prescribed DNa+
1.	127	2 (1.36)	2 (100)	100
2.	128	5 (3.40)	5 (100)	100
3.	129	3 (2.04)	3 (100)	100
4.	130	11 (7.48)	11 (100)	90.99
5.	132	12 (8.16)	6 (50)	83.33
6.	133	3 (2.04)	3 (100)	66.67
7.	136	1 (0.68)	1 (100)	100
8.	137	1 (0.68)	1 (100)	100
9.	138	3 (0.68)	2 (66.67)	100
10.	140	104 (70.74)	45 (43.26)	88.88
11.	142	1 (0.68)	1 (100)	100
12.	145	1 (0.68)	1 (100)	100

Table 1. Distribution of dialysate samples based on the prescribed and measured DNa⁺

S. No.	Prescribed DK+(mmol/l)	No. of Samples	No of samples with measured DK+ available (with %)	% of samples with measured DK+ within allowed margin of prescribed DK+
1.	2	131	120 (91.60)	61.66
2.	3	14	14 (100)	42.85
3.	3.5	2	2 (100)	50

Table 2. Distribution of dialysate samples based on the prescribed and measured DK⁺ values.

	Expected electrolyte value (mg/L)	Measured electrolyte value (mg/L)
Elemental Ca++ per litre of the acid concentrate (in mg/L)	2176 mg	3290 mg
Elemental Mg++ per litre of the acid concentrate (in mg/L)	325 mg	1010 mg

Table 3. Expected and measured Ca⁺⁺ and Mg⁺⁺ in the acid concentrate (per litre) for dialysate samples with a prescribed DCa⁺⁺ of 1.5 mmol/L but measured DCa⁺⁺ >1.75 mmol/L.

	Change in DCa++ (%) mean+ SD	% of pairs seen >5% change in DCa++	Change in DK+ (%) mean ± SD	% of pairs seen > 5% change in DK+
With an 8 mmol/L fall in DNa+	−9.07 ± 1.68*	Decrease in 100% pairs	−10.56 ± 3.56**	Decrease in 100% pairs
With an 8 mmol/L fall in DB total (including NaCl in the base concentrate)	10.31 ± 2.02	Increase in 100% pairs	NA***	Increase in 41.66% pairs Decrease in 16.67% pairs

Table 4. Changes in the measured DCa⁺⁺ with changes in the DNa⁺/base concentrate rate. **The minus sign suggests a decrease in the electrolyte concentration; ***NA (not applicable) due to an inconsistent response.

 

Discussion

Post-dialysis concentrations of various electrolytes in the blood depend on the electrolyte composition of the hemodialysate. In maintenance hemodialysis potassium and phosphorus move from the patient’s blood compartment to the dialysate, whereas bicarbonate moves from the dialysate to the blood compartment (Figure 3).

Few studies have compared the prescribed and measured DNa⁺ and DCa⁺⁺ concentrations in the haemodialysate [6–8]. This study is likely to be the first to compare prescribed and measured hemodialysate electrolytes other than Na⁺ and Ca⁺⁺. The measured DNa⁺ should be within 2.5% of the prescribed DNa⁺; for other electrolytes, the measured value should be within 5% of the prescribed values [3]. Compared with the study by Gul et al., where only 57% of the DNa⁺ samples were within 2.5% of the prescribed value, in our study, 91.87% of the samples were within the permitted range (±2.5% of the prescribed DNa⁺) [3, 6]. In our research, data on measured dialysate HCO₃⁻ and Cl⁻ were not available, which could have explained the narrow difference between the prescribed and measured DNa⁺.

Few studies have compared measured and prescribed DCa⁺⁺. In 54.41% of the dialysate samples, the measured DCa⁺⁺ was within the permitted range of the prescribed DCa⁺⁺ (i.e., ±5%) [3]. In our study, only two samples exhibited DCa⁺⁺ values of <1.25 mmol/L. In both the dialysates prepared from Part A and Part B, when the prescribed DNa⁺ was 140, the measured DCa⁺⁺ was 5.5 mmol/L, and when it was reduced to 132 meq/L, the measured DCa⁺⁺ was <1.25 mmol/L. DCa⁺⁺ <1.25 mmol/L should be avoided because it is associated with high mortality, and we have not used this dialysate for patient treatment. A total of 61.9% of the samples had DCa⁺⁺ within the recommended range (1.25-1.5 mmol/L) [12]. Only 11 samples had DCa⁺⁺ values >1.75 mmol/L. Assessments attributed this observation to the higher-than-expected Ca⁺⁺ concentration in the acid concentrate; hence, it was not used for patient treatment. Only one study has stated that a higher-than-expected Ca⁺⁺ content in the acid concentrate is a cause of increased dialysate calcium [13]. The role of softener malfunction in high levels of measured DCa⁺⁺ has been investigated [9]. Measured DCa⁺⁺ higher than the prescribed value can result in severe dialysis-associated hypercalcaemia-related clinical features, such as encephalopathy, intra-dialytic hypertension, arrhythmias, vomiting and abdominal pain. These complications can be life-threatening, emphasising the significance of measuring dialysate electrolytes before using a new batch of Part A [9, 10, 13].

Another finding in our study was the effect of prescribed DNa⁺ and DB (NaHCO₃ and NaCl in base concentrate) on DCa⁺⁺ and DK⁺. With a 5.7% reduction in the prescribed DNa⁺, the measured DCa⁺⁺ decreased by 9.07% ± 1.68%, which exceeds the percentage change in DNa⁺. A 8 mmol/L reduction in prescribed DB led to an increase in measured DCa⁺⁺ of 10.31% ± 2.02%. There was no difference between the prescribed and measured DNa⁺ values in these sets of samples.

The effects of alterations in the prescribed DNa⁺ or bicarbonate on measured DCa⁺⁺ in blood-based renal replacement therapies have not been adequately investigated [7]. No studies seem to have examined the effects of changes in DNa⁺ or DHCO₃⁻ on DCa⁺ or DK⁺ in conventional haemodialysis. Moreover, none of the studies have reported that the degree of change in DCa⁺ or DK⁺ can be greater than that in DNa⁺. Our study is the first to make these observations. The rates of change (%) in the measured DCa⁺⁺ owing to changes in either DNa⁺ or DB are pretty close to each other, probably because of similar changes in the acid concentration pump rates, but in opposite directions.

In 59.92% of the measured samples, the DK⁺ concentration was within the permitted range of the prescribed DK⁺ concentration, but none of the samples exhibited a DK⁺ concentration of <1 mmol/L, which is not recommended [14]. One possible cause for this discrepancy could be the higher or lower K⁺ in the acid concentrate than expected. Nonetheless, this reasoning is merely a conjecture, and data are not available to confirm it. In our study, a decrease in the prescribed/measured DNa⁺ of 5.7% reduced (mean ± SD) the measured DK⁺ by 10.56% ± 3.56%, which surpassed the percentage change in DNa⁺. The effects of alterations in the measured DK⁺ concentrations on the reduction in the prescribed DB were inconsistent, and the reasons could not be ascertained.

The percentage change in the measured DCa⁺⁺/DK⁺ when DNa⁺/DB is altered is calculated as follows: a reduction of DNa⁺ by 8 mmol/L (5.7% change) with DB at 55 mmol/L (NaHCO₃ 35 mmol/L and NaCl 20 mmol) or a reduction of DB total by 8 mmol/L (47 mmol) with DNa⁺ maintained at 140 mmol/L, alters the acid concentrate pump rate and hence changes DCa⁺⁺ and DK⁺ (reduction when DNa⁺ is decreased and increment when DB is lowered), as explained below.

Effect of the change in the prescribed DNa⁺ on the measured DCa⁺⁺

When DNa⁺ is decreased by 8 mmol/L, the reduction in DNa⁺ is caused by a change in NaCl in Part A. The Part A pump rate changes as follows:

In our study, NaCl concentration contributed by Part A per litre of the final hemodialysate is 84 mmol.

Hence, a reduction in Part A pump rate upon an 8 mmol/L reduction in the prescribed DNa⁺ is calculated as follows: (8/84) × 100 = 9.52%.

The calculated % change in the acid concentrate pump rate (9.52%) is higher than the % change in the prescribed/measured dialysate sodium: 8/140 = 5.7% (% change in the acid pump rate depends on the contribution of NaCl by the acid concentrate).

When DNa⁺ is reduced by 8 mmol/L (5.7%), the acid concentrate pump rate is decreased by 9.52%. Hence, instead of 1 L, it should pump 0.904 L of the acid concentrate per 1.83 L of Part B and 34 L of product water output. Hence, the actual proportioning ratio becomes 0.9:1.83:34 (instead of 1:1.83:34), and the volume of the dialysate formed per 0.9 L of the acid concentrate should be 36.73 L.

Accordingly, the expected Ca⁺⁺ content per 36.73 L of the dialysate when DNa⁺ is reduced by 8 mmol/L should be as follows: 2176 × (100 − 9.52)/100 = 1968.84 mg (1 L of Part A contains 2176 mg of calcium).

Hence, the expected Ca⁺⁺ concentration per litre of the dialysate should be 1968.84/36.73 = 53.60 mg/L = 5.36 mg/dL.

The expected difference between the measured DCa⁺⁺ and the expected DCa⁺⁺

(2176/36.8 = 5.91 mg/L) is as follows: 5.91 – 5.36 mg/dL = 0.55 mg/dL (reduced by 9.30%).

Effect of a change in the prescribed DB (NaHCO₃ + NaCl in Part B) on the measured DCa⁺⁺

When DNa⁺ is 140 and DB is reduced by 8 mmol/L, there should be an increase at an acid concentrate pump rate of 9.52% to keep DNa⁺ unchanged.

Hence, instead of 1 L, the acid concentrate (Part A) pump should provide 1.095 L, and the base concentrate (Part B) should be 1.66 L instead of 1.83 L for 34 L of product water, with an actual proportionating ratio of 1.095:1.66:34. The total dialysate volume per 1.095 L of the acid concentrate should be 36.75 L. Accordingly, the expected Ca⁺⁺ content per 36.75 L of the dialysate in the situation of DB reduction by 8 mmol/L: 2176 × (100 + 9.52)/100 = 2383.15 mg.

Hence, the expected Ca⁺⁺ concentration per litre of the dialysate should be 2383.15/36.75 = 64.84 mg/L = 6.48 mg/dL.

The difference between the measured DCa⁺⁺ and the expected DCa⁺⁺ is 5.91 mg/dL in the above 6.48 – 5.91 mg/dL = 0.57 mg/dL (increased by 9.6%)

Effect of changes in the prescribed DNa⁺ on the measured DK⁺

Accordingly, for a prescribed DNa⁺ reduction of 8 mmol/L (5.7% change), the K⁺ content per 36.73 L (as the acid concentrate should be reduced to 0.9 L instead of 1 L) of the dialysate 2898 × (100 − 9.52)/100 = 2622.11.

Expected potassium concentration per litre of hemodialysate should be 2622.11/36.73 = 71.39 mg/L = 71.39/39 = 1.83 mmol/L (molecular weight of potassium is 39). Expected reduction in measured DK⁺ in the above situation is (2-1.83/2) × 100 = 8.5%.

The measured reduction in DCa⁺⁺ with decreasing DNa⁺ and the measured increase in DCa⁺⁺ with decreasing DB total were 0.53333 (9.07% ± 1.68%) and 0.55 (10.31% ± 2.02%), respectively, which were close to the expected values (9.3% and 9.6% for decreases and increases in DCa⁺⁺, respectively, for the above-mentioned situation). The above calculation explains the mechanism behind the change in the measured DCa⁺⁺ compared with the percentage change in DNa⁺ or DB.

The measured DK⁺ increased by 10.56% ± 3.56% with an 8 mmol/L decrease in DNa⁺, which is quite close to the above calculation of the expected percentage change in DK⁺. However, the change in DK⁺ with a change in DB is not consistent.

The above calculations describe the mechanism behind the change in DK⁺ with the change in the prescribed DNa⁺; nonetheless, there are certain differences between the expected and actual changes, which could not be explained.

The percentage change in DCa⁺⁺ /DK⁺ due to the percentage change in DNa⁺ also depends on the Na⁺ contributed by the acid concentrate. In a dialysis solution in which the acid concentrate contributes 104 meq/L (unlike our study, which was 84 meq/L), if DNa⁺ is reduced by 8 mmol/L (5.7%), the expected change in the acid concentrate pump rate should be (8/104)×100=7.69%, which is less than the expected value in our study of 9.52%. We do not have data related to the above-mentioned solution.

Similar to previous investigations, our study revealed that dialysate conductivity is strongly correlated with DNa⁺ (R = 0.919) [15]. The hemodialysate conductivity increased by a mean of 0.3 mS/cm for an 8 mmol decline in DB, while keeping the prescribed DNa⁺ constant. For an 8 mmol drop in DB, there should be a 5.1 mmol drop in NaHCO₃ and a 2.9 mmol fall in NaCl (base; NaHCO₃:NaCl3 = 5:20). However, the acid concentrate pump should enhance its flow and increase the NaCl content by 8 mmol/L to keep DNa⁺ fixed despite the reduction in DB. Finally, NaCl should increase by 5.1 mmol/L, whereas NaHCO₃ should decrease by 5.1 mmol/L as seen in the study with concomitant increase in DK⁺, DCa⁺⁺ and DMg⁺⁺ due to acid concentrate pump rate increase. The mean rise in the measured DK⁺, DCa⁺⁺ and DMg⁺⁺ values were 0.1 mmol/L, 0.15 mmol/L and 0.1 mmol/L, respectively. The molar conductivities of NaCl, KCl, NaHCO₃, CaCl₂ and MgCl₂ were 103.67 mS/cm, 128.43 mS/cm, 72.54 mS/cm, 199.89 mS/cm and 180.29 mS/cm at 1 mmol, respectively [16]. From the above values, the expected increase in the dialysate conductivity is 0.219, which is quite close to the surge in the mean measured conductivity, i.e., 0.3 mS/cm. Not many studies have examined the possible reason behind the change in dialysate conductivity with a change in DB with fixed DNa⁺.

 

Conclusion

Measuring the dialysate electrolyte concentration is beneficial as discrepancies between the measured and prescribed dialysate electrolyte concentrations can occur, leading to adverse clinical outcomes. The factors contributing to the disparity between the measured and prescribed DCa⁺⁺ values in our study were the improper electrolyte concentration in the acid concentrate and the alteration in the prescribed DNa⁺/DB ratio. The cause of the difference in the measured DK⁺ concentration from the prescribed concentration was the change in the prescribed DNa⁺. The measured dialysate magnesium was higher than the prescribed magnesium because of the higher-than-expected magnesium concentration in the acid concentrate. The dialysate conductivity was well correlated with DNa⁺ and increased with a reduction in the prescribed dose of DB, whereas DNa⁺ remained unchanged. Our findings emphasise the importance of measuring the dialysate electrolyte concentration in case of clinical suspicion and when using a new batch of Part A or Part B.

 

Abbreviations:

D: Dialysate; DNa⁺: Dialysate Sodium; DK⁺: Dialysate Potassium; DCa⁺⁺: Dialysate Calcium; DMg⁺⁺: Dialysate Magnesium; DB: Dialysate contributed by part B; HD: Hemodialysis.

 

Bibliography

1. Varughese S, Abraham G. Chronic Kidney Disease in India: A Clarion Call for Change. Clin J Am Soc Nephrol. 2018 May 7;13(5):802-804. https://doi.org/10.2215/CJN.09180817. PMID: 29382651; PMCID: PMC5969474
2. Kohn OF, Kjellstrand CM, Ing TS. Dual-concentrate bicarbonate-based hemodialysis: know your buffers. Artif Organs. 2012 Sep;36(9):765-8. https://doi.org/10.1111/j.1525-1594.2012.01524.x. PMID: 22924819.
3. Pérez-García R, García Maset R, Gonzalez Parra E, et al; Comisión de Expertos de la Sociedad Española de Nefrología para la creación de la Segunda Edición de la Guía de Gestión de Calidad del Líquido de Diálisis. Guideline for dialysate quality of Spanish Society of Nephrology (second edition, 2015). Nefrologia. 2016 May-Jun;36(3):e1-e52. English, Spanish. https://doi.org/10.1016/j.nefro.2016.01.003.PMID: 26988922.
4. van der Sande FM, Cheriex EC, van Kuijk WH, Leunissen KM. Effect of dialysate calcium concentrations on intradialytic blood pressure course in cardiac-compromised patients. Am J Kidney Dis. 1998 Jul;32(1):125-31. https://doi.org/10.1053/ajkd.1998.v32.pm9669433. PMID: 9669433.
5. Movilli E, Camerini C, Gaggia P, Zubani R, Feller P, Poiatti P, Pola A, Carli O, Valzorio B, Cancarini G. Role of dialysis sodium gradient on intradialytic hypertension: an observational study. Am J Nephrol. 2013;38(5):413-9. https://doi.org/10.1159/000355974. PMID: 24216674.
6. Gul A, Miskulin DC, Paine SS, Narsipur SS, Arbeit LA, Harford AM, Weiner DE, Schrader R, Horowitz BL, Zager PG. Comparison of Prescribed and Measured Dialysate Sodium: A Quality Improvement Project. Am J Kidney Dis. 2016 Mar;67(3):439-45. https://doi.org/10.1053/j.ajkd.2015.11.004. PMID: 26776538.
7. Bacchetta J, Sellier-Leclerc AL, Bertholet-Thomas A, Carlier MC, Cartier R, Cochat P, Ranchin B. Calcium balance in pediatric online hemodiafiltration: Beware of sodium and bicarbonate in the dialysate. Nephrol Ther. 2015 Nov;11(6):483-6. https://doi.org/10.1016/j.nephro.2015.03.006. PMID: 26165800.
8. Shendi AM, Davenport A. The difference between delivered and prescribed dialysate sodium in haemodialysis machines. Clin Kidney J. 2020 Mar 11;14(3):863-868. https://doi.org/10.1093/ckj/sfaa022. PMID: 33777369; PMCID: PMC7986319.
9. Leonard H, Pile T. Hard water syndrome: a case series of 30 patients from a London haemodialysis unit. Clin Kidney J. 2019 May 12;13(1):111-112. https://doi.org/10.1093/ckj/sfz050. PMID: 32082559; PMCID: PMC7025357.
10. Freeman RM, Lawton RL. The hard-water syndrome. Med Instrum. 1974 Jun;8(3):201–3. https://doi.org/10.1056/nejm196705182762003.
11. Locatelli F, Di Filippo S, Manzoni C. Relevance of the conductivity kinetic model in the control of sodium pool. Kidney Int. 2000 Aug 1;58:S89–95. https://doi.org/10.1046/j.1523-1755.2000.07611.x.
12. van der Sande FM, ter Meulen KJA, Kotanko P, Kooman JP. Dialysate Calcium Levels: Do They Matter? Blood Purif. 2019;47(1–3):230–5. https://doi.org/10.1159/000494584.
13. Pathak N, Kumar Nanda S. Calcium levels in acid concentrate are critical – A case series of posthemodialysis hypercalcemia due to high calcium in acid concentrate. J Nephropharmacol. 2024;13(2):e11666. https://doi.org/10.34172/npj.2024.11666.
14. Ashby D, Borman N, Burton J, Corbett R, Davenport A, Farrington K, et al. Renal Association Clinical Practice Guideline on Haemodialysis. BMC Nephrol. 2019 Oct 17;20(1):379. https://doi.org/10.1186/s12882-019-1527-3.
15. Tura A, Sbrignadello S, Mambelli E, Ravazzani P, Santoro A, Pacini G. Sodium Concentration Measurement during Hemodialysis through Ion-Exchange Resin and Conductivity Measure Approach: In Vitro Experiments. PLOS ONE. 2013 Jul 2;8(7):e69227. https://doi.org/10.1371/journal.pone.0069227.
16. Replacement of Renal Function by Dialysis | Walter H. Hörl | Springer [Internet]. [cited 2021 Jan 28]. Available from: https://www.springer.com/gp/book/9781402000836.