Home About us Editorial board Search Ahead of print Current issue Archives Submit article Instructions Subscribe Contacts Login 


 
 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 3  |  Page : 783-788

Dialysis sodium gradient: a modifiable risk factor for fluid overload in hemodialysis patients


1 Department of Internal Medicine and Nephrology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Internal Medicine, Faculty of Medicine, Tanta University, Al Gharbia, Egypt

Date of Submission03-Jan-2019
Date of Decision30-Jan-2019
Date of Acceptance02-Feb-2019
Date of Web Publication30-Sep-2020

Correspondence Address:
Ahmed A. B. Z. Omar
Tanta City, Al Gharbia
Egypt
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_441_18

Rights and Permissions
  Abstract 


Objective
The aim was to study the value of dialysis sodium gradient as a modifiable risk factor for fluid overload in hemodialysis patients.
Background
It is important to minimize sodium gradient in hemodialysis patients, as it positively correlates with changes in blood pressure during hemodialysis and intradialytic weight gain (IDWG).
Patients and methods
A cross-sectional analytical study was done on a group of 102 hemodialysis patients divided into three groups: group I included 56 patients with no blood pressure variability, group II included 24 patients who had intradialytic hypotension, and group III included 22 patients who had intradialytic hypertension. All patients attended the Hemodialysis Unit, Zefta General Hospital, Al-Gharbia Governorate, Egypt, during the period from May 2018 to November 2018. Complete history, hemoglobin level, predialysis and postdialysis urea and creatinine, and predialysis sodium were tested.
Results
There were no statistically significant differences between the studied groups regarding sex (P = 0.1939), age (P = 0.192), primary renal diseases (P = 0.189), vascular access type (P = 0.978), dialysis duration (0.976), hemoglobin (P = 0.131), predialytic and postdialytic urea (P = 0.839, P = 0.120), predialytic and postdialytic creatinine (P = 0.584, P = 0.190), ultrafiltration (UF) rate (P = 0.729), UF volume (P = 0.698), IDWG% (P = 0.777), and sodium gradient (P = 0.468). There was a positive correlation between sodium gradient and the mean IDWG%, mean UF volume, and mean UF rate among the studied hemodialysis patients.
Conclusion
There was a positive correlation between sodium gradient and IDWG and consequently UF volume and UF rate.

Keywords: dialysis sodium gradient, fluid overload, hemodialysis, risk factor, ultrafiltration


How to cite this article:
Kora MA, Tawfeek AR, Kasem HA, Omar AA. Dialysis sodium gradient: a modifiable risk factor for fluid overload in hemodialysis patients. Menoufia Med J 2020;33:783-8

How to cite this URL:
Kora MA, Tawfeek AR, Kasem HA, Omar AA. Dialysis sodium gradient: a modifiable risk factor for fluid overload in hemodialysis patients. Menoufia Med J [serial online] 2020 [cited 2020 Nov 26];33:783-8. Available from: http://www.mmj.eg.net/text.asp?2020/33/3/783/296697




  Introduction Top


Conventional hemodialysis remains the most common treatment for end-stage renal disease worldwide and is usually performed for 3–5 h, 3 days per week [1]. It is estimated that up to one-third of the patients on conventional hemodialysis and peritoneal dialysis are volume overloaded [2]. Intradialytic weight gain (IDWG) is often used as a surrogate marker for fluid overload, and studies have shown that a higher IDWG% predicts cardiovascular events [3]. Several mechanisms have been proposed to explain how volume overload leads to increased mortality in the dialysis population, mostly linking volume overload to left ventricular hypertrophy with associated cardiovascular events and more recently, to inflammation, which in turn leads to accelerated atherosclerosis [4]. Higher UF rates and IDWG may also lead to more frequent episodes of intradialytic hypotension, which can be linked to vascular access complications, and inadequate dialysis, but most importantly increased cardiovascular morbidity and mortality [5]. Intradialytic hypotension, which occurs in 10–30% of treatments, ranges from asymptomatic episodes to marked compromise of organ perfusion, resulting in myocardial ischemia, cardiac arrhythmias, vascular thrombosis, loss of consciousness, seizures, or death [6]. Blood pressure (BP) normally declines during the high definition (HD), but ~5–15% of chronic HD patients have a paradoxical rise in BP during the HD session [7]. Intradialytic hypertension has been described variedly, and there is currently no uniformly recognized definition. Multiple studies have suggested that each dialysis patient may have a unique osmolar set point for plasma sodium, and therefore, dialysate sodium (DNa) needs to be individualized [8]. More recently, there has been growing evidence that it is important to minimize sodium gradient in hemodialysis patients as it positively correlates with changes in BP during hemodialysis and IDWG [9]. Therefore, the aim of this work was to study the value of dialysis sodium gradient as a modifiable risk factor for fluid overload in hemodialysis patients.


  Patients and Methods Top


A cross-sectional analytical study was conducted on 102 hemodialysis patients regularly coming to the hemodialysis unit in Zefta General Hospital, Al Gharbia Governorate, Egypt. Cases were selected during the study period from May to November 2018. All study patients were classified according to BP variability into three groups:

  1. Group I consisted of 56 patients with no BP variability
  2. Group II consisted of 24 patients who had intradialytic hypotension
  3. Group III consisted of 22 patients who had intradialytic hypertension.


Ethical consideration

The study was approved by the ethical committee of Menoufia Faculty of Medicine, and an informed consent was obtained from all participants before the study was commenced.

Selection criteria for the patients

The patients included in this study were selected according to inclusion and exclusion criteria.

Inclusion criteria

Patients aged greater than 18 years and undergoing conventional hemodialysis treatments 12 h per week (three sessions 4 h each one) were included.

Exclusion criteria

The following were the exclusion criteria: inadequate dialysis with single-pool Kt/V less than 1.2, change in target weight in the last 2 prior weeks, severe hyperglycemia (plasma glucose >15 mmol/l), liver cirrhosis, active infection or inflammatory disease, and hospitalization for any cause in the 4 weeks before the index study date.

Method of sampling

Sample size was calculated using computer sample block randomization type. Samples were obtained during routine investigations. The samples were collect from veins by venipuncture before dialysis session. No special patient preparation was needed, and fasting was not required. Moreover, postdialytic urea and postdialytic creatinine were assessed. For predialysis sodium, the average of the last 3 monthly values before the index date was used. The sodium gradient was calculated using the prescribed DNa minus the average predialysis sodium.

All cases were subjected to the following:

  1. Complete history, such as, age, sex, primary renal disease, duration of HD, dialysis time, access type for HD, number of BP medications, and family history
  2. Clinical examination, including predialysis weight, predialysis BP, postdialysis weight, and postdialysis BP
  3. Laboratory investigations included the following:


    1. Hemoglobin level, which was assessed using Sysmex KX-21 automatized hematology analyzer (Sysmex corporation, Kobe, Hyogo, Japan) [10]
    2. Predialysis and postdialysis urea and creatinine, which were assessed using the open system autoanalyzer synchron CX5 (Beckman, Brea, California, United States)


    3. IDWG is the difference between current predialysis weight and the postdialysis weight of last session [11], and IDWG% is IDWG/prescribed dry weight [11]

      For the pre-BP and post-BP, IDWG, IDWG% (IDWG/prescribed dry weight), and UF rates, the average of the last six hemodialysis treatments before the index date was taken [11]

    4. Predialysis sodium: for predialysis sodium, the average of the last 3 monthly values before the index date was used. The sodium gradient was calculated using the prescribed DNa minus the average predialysis sodium using Roche Diagnostics AVL 9180 Series Electrolyte Analyzer (Roche Diagnostics, Basel, Switzerland) [11]
    5. Random blood sugar was assessed using Sysmex KX-21 automatized hematology analyzer (Sysmex Corporation)
    6. Serum albumin and liver function (aspartate transaminase, alanine aminotransferase) were assessed using the open system autoanalyzer synchron CX5 (Beckman)
    7. Ca, P, and K were assessed using Roche Diagnostics AVL 9180 Series Electrolyte Analyzer


  4. Radiology: ultrasonography (pelviabdominal) was done to exclude liver cirrhosis.


Statistical analysis

Results were tabulated and statistically analyzed by using a personal computer using Microsoft Excel 2016 and SPSS v. 21 (SPSS Inc., Chicago, Illinois, USA). Statistical analysis was done using descriptive, for example, percentage, mean, and SD, and analytical, which includes one-way analysis of variance test (F-test), χ2-test, paired t-test, and Pearson's correlation test (r). Analytical analyses were done to study the relation between the studied variables. A value of P less than 0.05 was considered statistically significant.


  Results Top


The current study showed that there were no statistically significant differences among the studied groups regarding sex (P = 0.1939), age (P = 0.192), primary renal dieses (P = 0.189), and vascular access type (P = 0.978) [Table 1].
Table 1: Comparison between studied groups regarding age, sex, primary renal disease, and vascular access type

Click here to view


The current study showed that there were no statistically significant differences among the studied groups regarding dialysis duration (0.976), hemoglobin (Hb) (P = 0.131), predialytic urea (P = 0.839), postdialytic urea (P = 0.120), predialytic creatinine (P = 0.584), and postdialytic creatinine (P = 0.190) as well as the differences between postdialytic and predialytic urea (P = 0.729) and creatinine (P = 0.974) [Table 2].
Table 2: Comparison between studied groups regarding dialysis duration, hemoglobin, and predialysis and postdialysis urea and creatinine

Click here to view


The current study showed that there were no statistically significant differences between the studied groups regarding mean UF rate (P = 0.729), mean UF volume (P = 0.698), and mean IDWG% (P = 0.777). Moreover, the mean sodium gradient of group 1 was −1.81 ± 3.20, in group II was −1.15 ± 3.46, and −2.35 ± 3.46 in group III, with no statistically significant differences among them regarding sodium gradient (P = 0.468) [Table 3].
Table 3: Comparison between studied groups regarding dialysis duration, hemoglobin, and predialysis and postdialysis urea and creatinine

Click here to view


Our results revealed that there was a positive correlation between sodium gradient and the mean IDWG %, mean UF volume, and mean UF rate among the studied hemodialysis patients (P < 0.001 for all). However, sodium gradient was not correlated with AGE (P = 0.675), dialysis duration (years), (P = 0.110), Hb (P = 0.360), urea pre (P = 0.504), urea post (P = 0.711), creatinine pre (P = 0.850), creatinine post (P = 0.388), systolic blood pressure (ΔSBP) (P = 0.623), and diastolic blood pressure (ΔDBP) (P = 0.730) [Table 4].
Table 4: Correlation between both sodium gradient and mean intradialytic weight gains % and other variables among the studied hemodialysis patients (n=102)

Click here to view



  Discussion Top


The current study showed that there were no statistically significant differences between the studied groups regarding sex and age. These results come in agreement with the studies by Inrig et al. [12], Inrig et al. [13], and Shamir et al. [14], which found no statistically significant differences between the studied groups regarding age and sex. However, Yang et al. [15] unlike our results, found that there were significant differences between the studied groups regarding age (P < 0.05); those with intradialytic hypertension more likely to be older.

In the present study, there were no statistically significant differences between the studied groups regarding primary renal dieses, dialysis duration, and vascular access type. Our finding agrees with Inrig et al. [12] who found that no statistically significant differences were observed between the studied groups regarding primary renal dieses and dialysis duration. These results agree with the studies by Yang et al. [15] and Shamir et al. [14], which found similar results.

The current study showed that there were no statistically significant differences between the studied groups regarding Hb, predialytic urea, predialytic creatinine, differences between postdialytic and predialytic urea, and differences between postdialytic and predialytic creatinine. Our finding agrees with Inrig et al. [12] who found that no statistically significant differences were observed between the studied groups regarding Hb and predialytic creatinine and urea. These results come in agreement with the study of Inrig et al. [13] who found that no statistically significant differences were observed between the studied groups regarding Hb and predialytic creatinine and urea. Our results agree with the study of Yang et al. [15] who found similar results regarding Hb. Moreover, Shamir et al. [14] found that no statistically significant differences were observed between the studied groups regarding Hb and predialytic creatinine.

The current study showed that there were no statistically significant differences between the studied groups regarding mean UF rate and mean UF volume. However, Yang et al. [15], unlike our results, found that there were significant differences between the studied groups regarding UF volume (P < 0.05); those with intradialytic hypertension more likely to have smaller ultrafiltration (UF).

The current study shows that mean sodium gradient of group 1 was −1.81 ± 3.20, in group II was −1.15 ± 3.46 and −2.35 ± 3.46 in group III, with no statistically significant differences among them regarding sodium gradient. These results are in agreement with Trinh and Weber [11]. Moreover, Shamir et al. [14] found no statistically significant differences between the studied groups regarding sodium gradient. However, Shah and Davenport [16] showed statistically significant more intradialytic hypotensive episodes per week with DNa less than or equal to 136 mEq/l in comparison with DNa 137–139 mEq/l and with DNa greater than or equal to 140 mEq/l. They commented on higher SBP and increased prescription of antihypertensive medications in those patients dialyzing against the lower rather than higher DNa concentrations, supporting our suggestion that associated with individualized DNa prescription. Moreover, Zhou et al. [17] showed BP and IDWG declined with lower DNa in patients at the same volume status. Suckling et al. [18] showed a decrease in BP when using DNa 135 rather than 145 mEq/l but did not report on symptoms.

In the present study, there were no statistically significant differences between the studied groups regarding mean IDWG%. Our finding agrees with Inrig et al. [12] who found that no statistically significant differences were observed between the studied groups regarding mean IDWG%. Moreover, Shamir et al. [14] found no statistically significant differences between the studied groups regarding mean IDWG% (P = 0.02). However, Inrig et al. [13] found statistically significant differences between the studied groups regarding mean IDWG% (P < 0.001), unlike our results.

Our results revealed that there was a positive correlation between sodium gradient and the mean IDWG %, mean UF volume, and mean UF rate among the studied hemodialysis patients (P < 0.001 for all). Our findings are consistent with the current literature demonstrating a positive correlation between the sodium gradient and parameters of fluid overload in hemodialysis patients [19],[20],[21]. These associations of a high sodium gradient with fluid overload are likely explained by a high DNa concentration leading to an elevated postdialysis serum sodium level with the consequence of increased thirst and fluid intake [22]. Moreover, Hecking et al. [23] found a positive association between DNa concentration and IDWG. Our results are in line with Munoz Mendoza et al. [22] who also found a direct correlation between IDWG and sodium gradient, with no associations with the frequency of intradialytic hypotension episodes. Other studies have equally shown that a higher sodium gradient was associated with fluid overload and adverse outcomes [9]. However, previous studies have assessed the association of patient-level variables with IDWG [24]. Wong et al. [25] also considered facility practices. Of the facility factors analyzed, DNa concentration had the strongest association with IDWG. Their analysis showed a trend of declining DNa concentration across regions, with the greatest reductions in both relative IDWG and DNa concentration. However, DNa concentration accounted for only 0.13 greater relative IDWG per 1-mEq/l greater DNa concentration, which suggests it played only a partial role in explaining the decline in IDWG [8]. Finally, multiple studies have suggested that each dialysis patient may have a unique osmolar set point for plasma sodium, and therefore, DNa needs to be individualized. More recently, there has been growing evidence that it is important to minimize sodium gradient in hemodialysis patients as it positively correlates with changes in BP during hemodialysis and IDWG [8],[9],[22],[26].


  Conclusion Top


The current study concluded that there was a positive correlation between sodium gradient and IDWG and consequently UF volume and UF rate.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Saran R, Li Y, Robinson B. US Renal Data System 2014 annual data report: epidemiology of kidney disease in the United States. Am J Kidney Dis 2015; 66:1–6.  Back to cited text no. 1
    
2.
Hur E, Gungor O, Musayev O, Usta M, Toz H, Asci G, et al. Bio impedance spectroscopy for the detection of hypervolemia in peritoneal dialysis patients. Adv Perit Dial 2011; 27:65–70.  Back to cited text no. 2
    
3.
Lee MJ, Doh FM, Kim CH, Koo HM, Oh HJ, Park JT, et al. Intradialytic weight gain and cardiovascular outcome in incident hemodialysis patients. Am J Nephrol 2014; 39:427–435.  Back to cited text no. 3
    
4.
Hung SC, Kuo KL, Peng CH, Wu CH, Lien YC, Wang YC, et al. Volume overload correlates with cardiovascular risk factors in patients with chronic kidney disease. Kidney Int 2014; 85:703–709.  Back to cited text no. 4
    
5.
Flythe JE, Xue H, Lynch KE, Curhan GC, Brunelli SM. Association of mortality risk with various definitions of intradialytic hypotension. J Am Soc Nephrol 2015; 26:724–734.  Back to cited text no. 5
    
6.
Lewicki M, Kerr PG, Polkinghorne KR. Blood pressure and blood volume: Acute and chronic considerations in hemodialysis. Semin Dial 2013; 26:62–72.  Back to cited text no. 6
    
7.
Inrig JK. Intradialytic hypertension: a less-recognized cardiovascular complication of hemodialysis. Am J Kidney Dis 2010; 55:580–589.  Back to cited text no. 7
    
8.
Lomonte C, Basile C. Do not forget to individualize dialysate sodium prescription. Nephrol Dial Transplant 2011; 26:1126–1128.  Back to cited text no. 8
    
9.
Jin H, Lee SY, Lee SN, Song JH, Kim MJ, Lee SW. Effect of dialysate sodium concentration on sodium gradient and hemodialysis parameters. Electrolyte Blood Press 2014; 12:66–73.  Back to cited text no. 9
    
10.
Geistanger A, Arends S, Berding C, Hoshino T, Jeppsson JO, Little R, et al. IFCC Working Group on Standardization of Hemoglobin A1c, Statistical methods for monitoring the relationship between the IFCC reference measurement procedure for hemoglobin A1c and the designated comparison methods in the United States, Japan, and Sweden. Clin Chem 2008; 54:1379–1385.  Back to cited text no. 10
    
11.
Trinh E, Weber C. The dialysis sodium gradient: a modifiable risk factor for fluid overload. Nephron Extra 2017; 7:10–17.  Back to cited text no. 11
    
12.
Inrig JK, Oddone EZ, Hasselblad V, Gillespie B, Patel UD, Reddan D, et al. Association of intradialytic blood pressure changes with hospitalization and mortality rates in prevalent ESRD patients. Kidney Int 2007; 71:454–461.  Back to cited text no. 12
    
13.
Inrig JK, Patel UD, Toto RD, Szczech LA. Association of blood pressure increases during hemodialysis with 2-year mortality in incident hemodialysis patients: a secondary analysis of the Dialysis Morbidity and Mortality Wave 2 Study. Am J Kidney Dis 2009; 54:881–890.  Back to cited text no. 13
    
14.
Shamir AR, Karembelkar A, Yabes J, Yao Y, Miskulin D, Gassman J, et al. Association of intradialytic hypertension with left ventricular mass in hypertensive hemodialysis patients enrolled in the blood pressure in dialysis study. Kidney Blood Press Res 2018; 43:882–892.  Back to cited text no. 14
    
15.
Yang CY, Yang WC, Lin YP. Post-dialysis blood pressure rise predicts long-term outcomes in chronic hemodialysis patients: a four-year prospective observational cohort study. BMC Nephrol 2012; 13:12–16.  Back to cited text no. 15
    
16.
Shah A, Davenport A. Does a reduction in dialysate sodium improve blood pressure control in haemodialysis patients? Nephrology 2012; 17:358–363.  Back to cited text no. 16
    
17.
Zhou YL, Liu HL, Duan XF. Impact of sodium and ultrafiltration profiling on hemodialysis-related hypotension. Nephrol Dial Transplant 2013; 21:3231–3237.  Back to cited text no. 17
    
18.
Suckling RJ, Swift PA, He FJ, Markandu ND, MacGregor GA. Altering plasma sodium concentration rapidly changes blood pressure during haemodialysis. Nephrol Dial Transplant 2013; 28:2181–2186.  Back to cited text no. 18
    
19.
Santos SFF, Peixoto AJ. Sodium balance in maintenance hemodialysis. Semin Dial 2010; 23:549–555.  Back to cited text no. 19
    
20.
Davenport A. Negative dialysate to sodium gradient does not lead to intracellular volume expansion post hemodialysis. Int J Artif Organs 2010; 33:700–705.  Back to cited text no. 20
    
21.
Kumar S, Khosravi M, Massart A, Potluri M, Davenport A. Are serum to dialysate sodium gradient and segmental bioimpedance volumes associated with the fall in blood pressure with hemodialysis? Int J Artif Organs 2014; 37:21–28.  Back to cited text no. 21
    
22.
Munoz Mendoza J, Sun S, Chertow GM, Moran J, Doss S, Schiller B. Dialysate sodium and sodium gradient in maintenance hemodialysis: a neglected sodium restriction approach? Nephrol Dial Transplant 2015; 26:1281–1287.  Back to cited text no. 22
    
23.
Hecking M, Karaboyas A, Saran R. Predialysis serum sodium level, dialysate sodium, and mortality in maintenance hemodialysis patients: The Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis 2012; 59:238–248.  Back to cited text no. 23
    
24.
Kalantar-Zadeh K, Regidor DL, Kovesdy CP, Van Wyck D, Bunnapradist S, Horwich TB, et al. Fluid retention is associated with cardiovascular mortality in patients undergoing long-term hemodialysis. Circulation 2009; 119:671–679.  Back to cited text no. 24
    
25.
Wong MM, McCullough KP, Bieber BA. Intradialytic weight gain: trends, predictors, and associated outcomes in the International Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis 2016; 69:367–379.  Back to cited text no. 25
    
26.
Penne EL, Sergeyeva O. Sodium gradient: a tool to individualize dialysate sodium prescription in chronic hemodialysis patients? Blood Purif 2011; 31:86–91.  Back to cited text no. 26
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

Top
 
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
Abstract
Introduction
Patients and Methods
Results
Discussion
Conclusion
References
Article Tables

 Article Access Statistics
    Viewed117    
    Printed8    
    Emailed0    
    PDF Downloaded13    
    Comments [Add]    

Recommend this journal


[TAG2]
[TAG3]
[TAG4]