Original Paper Received: October 14, 2014 Accepted: April 23, 2015 Published online: June 27, 2015
Blood Purif 2015;40:59–65 DOI: 10.1159/000430902
Evaluation of Salt Intake, Urinary Sodium Excretion and Their Relationship to Overhydration in Chronic Kidney Disease Patients Andrea E.C. Hallvass a Lígia Maria Claro a Simone Gonçalves a Márcia Olandoski a Fabiana Baggio Nerbass a, b Carlos Alberto Mayora Aita a Thyago Proença de Moraes a Roberto Pecoits-Filho a
a School of Medicine, Pontifícia Universidade Católica do Paraná, Curitiba, and b Nutrition Department, Pro-Rim Foundation, Joinvile, Santa Catarina, Brazil
Key Words Sodium · Fluid overload · Urinary sodium · Chronic kidney disease
Abstract The purpose of this study was to estimate sodium intake in a group of patients with chronic kidney disease (CKD) and to correlate the results with the urinary excretion values of sodium and signs of fluid overload. We included patients with CKD in different stages. Urinary sodium was measured in 24 h urine samples. Body composition monitor (BCM) was used to estimate the hydration status. Sixty patients (38 ± 15 ml/min of GFR) presented 4.14 ± 1.71 g/24 h of urinary sodium excretion. Overhydration was detected in 50% of the patients by the BCM. There was a positive correlation between the measured sodium excretion values and BCM, ICW, ECW and TBW. In conclusion, markers of overhydration evaluated by BCM were positively correlated with urinary sodium excretion. © 2015 S. Karger AG, Basel
© 2015 S. Karger AG, Basel 0253–5068/15/0401–0059$39.50/0 E-Mail [email protected] www.karger.com/bpu
Introduction
Globally, sodium intake has increased alarmingly in recent years. In part, this is due to an increase in the intake of discretionary salt, processed foods, and sodium-based food additives [1]. The World Health Organization (WHO) recommends that sodium intake should be limited to 2,000 mg/day (or 5 g NaCl – sodium chloride) for the healthy population [2]. For black individuals, subjects aged over 50 and people of any age suffering from hypertension, diabetes or chronic kidney disease (CKD), the recommendation is 1,500 mg sodium/day (or 4g of NaCl) [3]. CKD has been identified as a major public health problem worldwide due to its high prevalence [4]. In patients with CKD, a high salt intake is associated with raised blood pressure (BP) and adverse cardiovascular health. Animal experiments, epidemiological studies and clinical trials provide compelling evidence for a detrimental effect of sodium intake on BP among both hypertensive and Roberto Pecoits-Filho School of Medicine, Pontifícia Universidade Católica do Paraná Rua Imaculada Conceição, 1155 Curitiba/Paraná, CEP 80215-901 (Brazil) E-Mail r.pecoits @ pucpr.br
Downloaded by: University of Pittsburgh 198.143.32.65 - 8/8/2015 2:07:51 AM
Material and Methods This is an observational and cross-sectional study, reflecting the initial moment (baseline) of a protocol of a randomized, prospective and controlled study (SALTED). The project was developed in the CKD Clinic of the Catholic University of Paraná. Patients with CKD from any cause followed in the period from June 2010 to April 2013 were included. Non-inclusion criteria were patients undergoing renal replacement therapy, pregnant women and patients younger than 18 years. Also excluded were patients with clinical instability (infections, active autoimmune disease, heart failure or decompensate liver). Eligible patients were contacted and included after signing an informed consent form. The local ethics committee approved the study. Participants reported the prescription drugs continuously in use for more than three weeks and with no change in dosage in this period. Strategies for evaluation were based on 3-day food record. Patients recruited were requested to describe, as detailed as possible, all food and beverages consumed during 3 days, including a day for the weekend. Participants received written and verbal instruction about the technique for collection of 24 h urine samples. On the first morning of the urine collection, participants were asked to discard their first urine specimen and informed to collect all specimens for the next 24 h, up to and including the first urine specimen of the next day. Assessment Methods for Sodium and Laboratory Evaluation At the first visit, patients received a sterilized jar and were instructed to collect 24 h urine (protocol set) the day before the scheduled visit of the study. Patients were instructed to attend the consultation fasting. On the day of consultation, the patient brought the 24 h urine and annotating the 3-day food record. Spot urine and blood samples were also collected at the study visit. For the analysis of discretionary sodium, each 1,000 g of kitchen salt purchased for the family was divided by the number of people living with the patient, and the result was divided by the number of days that the patient reported the duration of salt until the next purchase. This result multiplied by 40% (for sodium chloride added inturn sodium) [11]. The dietary sodium intake was calculated from the 3-day food record (two consecutive days and one day of the weekend). This record was checked by a skilled di-
60
Blood Purif 2015;40:59–65 DOI: 10.1159/000430902
etician at the time of consultation and calculated using the Software Avanutri®. The foods were calculated with the software in their fresh form, without discretionary salt. Urinary sodium was measured in urine samples of 24 h through automated method (Architect CI-8200-Abbott Diagnostics®). The sodium intake for 3 days of the survey was obtained by simple averaging. The urinary albumin was measured by immunonephelometry and creatinine using the automated method (Architect CI8200-Abbott Diagnostics®). The glomerular filtration rate (GFR) was estimated by the Modification of Diet in Renal Disease Study equation (MDRD formula) [12]. Assessment Methods for Body Composition and Clinical Evaluation The fluid status was assessed by measuring extracellular volume and total body water (TBW) using a body composition monitor (BCM) indicated for patients with CKD [13], (BCM-Fresenius Medical Care®), and previously utilized HD [14], PD [15] and CKD stages 3 and 4 patients [16]. Briefly, BCM data is based on a physiological tissue model previously described [17]. This method estimates the hydration status (i.e. ECW and ICW) in CKD individuals in comparison to normal control values. BP (mm Hg), weight (kg), height (m) and body mass index – BMI (kg/m2) were also monitored. Patients were instructed to show up on the day of the examination fasting. They all followed the same protocol for the BCM examination, which is described in detail in the manufacturer manual [18]. Statistical Analyses The results obtained in this study were described by mean, median, minimum values, maximum values and standard deviations for quantitative variables and as frequencies and percentages for qualitative variables. To evaluate the association between quantitative variables the correlation coefficient of Pearson, or Spearman when appropriate was estimated. For a comparison of groups in relation to quantitative variables, the Student t-test for independent samples or the nonparametric Mann-Whitney test was considered. The normality condition evaluated was assessed by the Kolmogorov-Smirnov test. To evaluate the variation between the means the ANOVA test was done. p values
Blood Purif 2015;40:59–65 DOI: 10.1159/000430902
Evaluation of Salt Intake, Urinary Sodium Excretion and Their Relationship to Overhydration in Chronic Kidney Disease Patients Andrea E.C. Hallvass a Lígia Maria Claro a Simone Gonçalves a Márcia Olandoski a Fabiana Baggio Nerbass a, b Carlos Alberto Mayora Aita a Thyago Proença de Moraes a Roberto Pecoits-Filho a
a School of Medicine, Pontifícia Universidade Católica do Paraná, Curitiba, and b Nutrition Department, Pro-Rim Foundation, Joinvile, Santa Catarina, Brazil
Key Words Sodium · Fluid overload · Urinary sodium · Chronic kidney disease
Abstract The purpose of this study was to estimate sodium intake in a group of patients with chronic kidney disease (CKD) and to correlate the results with the urinary excretion values of sodium and signs of fluid overload. We included patients with CKD in different stages. Urinary sodium was measured in 24 h urine samples. Body composition monitor (BCM) was used to estimate the hydration status. Sixty patients (38 ± 15 ml/min of GFR) presented 4.14 ± 1.71 g/24 h of urinary sodium excretion. Overhydration was detected in 50% of the patients by the BCM. There was a positive correlation between the measured sodium excretion values and BCM, ICW, ECW and TBW. In conclusion, markers of overhydration evaluated by BCM were positively correlated with urinary sodium excretion. © 2015 S. Karger AG, Basel
© 2015 S. Karger AG, Basel 0253–5068/15/0401–0059$39.50/0 E-Mail [email protected] www.karger.com/bpu
Introduction
Globally, sodium intake has increased alarmingly in recent years. In part, this is due to an increase in the intake of discretionary salt, processed foods, and sodium-based food additives [1]. The World Health Organization (WHO) recommends that sodium intake should be limited to 2,000 mg/day (or 5 g NaCl – sodium chloride) for the healthy population [2]. For black individuals, subjects aged over 50 and people of any age suffering from hypertension, diabetes or chronic kidney disease (CKD), the recommendation is 1,500 mg sodium/day (or 4g of NaCl) [3]. CKD has been identified as a major public health problem worldwide due to its high prevalence [4]. In patients with CKD, a high salt intake is associated with raised blood pressure (BP) and adverse cardiovascular health. Animal experiments, epidemiological studies and clinical trials provide compelling evidence for a detrimental effect of sodium intake on BP among both hypertensive and Roberto Pecoits-Filho School of Medicine, Pontifícia Universidade Católica do Paraná Rua Imaculada Conceição, 1155 Curitiba/Paraná, CEP 80215-901 (Brazil) E-Mail r.pecoits @ pucpr.br
Downloaded by: University of Pittsburgh 198.143.32.65 - 8/8/2015 2:07:51 AM
Material and Methods This is an observational and cross-sectional study, reflecting the initial moment (baseline) of a protocol of a randomized, prospective and controlled study (SALTED). The project was developed in the CKD Clinic of the Catholic University of Paraná. Patients with CKD from any cause followed in the period from June 2010 to April 2013 were included. Non-inclusion criteria were patients undergoing renal replacement therapy, pregnant women and patients younger than 18 years. Also excluded were patients with clinical instability (infections, active autoimmune disease, heart failure or decompensate liver). Eligible patients were contacted and included after signing an informed consent form. The local ethics committee approved the study. Participants reported the prescription drugs continuously in use for more than three weeks and with no change in dosage in this period. Strategies for evaluation were based on 3-day food record. Patients recruited were requested to describe, as detailed as possible, all food and beverages consumed during 3 days, including a day for the weekend. Participants received written and verbal instruction about the technique for collection of 24 h urine samples. On the first morning of the urine collection, participants were asked to discard their first urine specimen and informed to collect all specimens for the next 24 h, up to and including the first urine specimen of the next day. Assessment Methods for Sodium and Laboratory Evaluation At the first visit, patients received a sterilized jar and were instructed to collect 24 h urine (protocol set) the day before the scheduled visit of the study. Patients were instructed to attend the consultation fasting. On the day of consultation, the patient brought the 24 h urine and annotating the 3-day food record. Spot urine and blood samples were also collected at the study visit. For the analysis of discretionary sodium, each 1,000 g of kitchen salt purchased for the family was divided by the number of people living with the patient, and the result was divided by the number of days that the patient reported the duration of salt until the next purchase. This result multiplied by 40% (for sodium chloride added inturn sodium) [11]. The dietary sodium intake was calculated from the 3-day food record (two consecutive days and one day of the weekend). This record was checked by a skilled di-
60
Blood Purif 2015;40:59–65 DOI: 10.1159/000430902
etician at the time of consultation and calculated using the Software Avanutri®. The foods were calculated with the software in their fresh form, without discretionary salt. Urinary sodium was measured in urine samples of 24 h through automated method (Architect CI-8200-Abbott Diagnostics®). The sodium intake for 3 days of the survey was obtained by simple averaging. The urinary albumin was measured by immunonephelometry and creatinine using the automated method (Architect CI8200-Abbott Diagnostics®). The glomerular filtration rate (GFR) was estimated by the Modification of Diet in Renal Disease Study equation (MDRD formula) [12]. Assessment Methods for Body Composition and Clinical Evaluation The fluid status was assessed by measuring extracellular volume and total body water (TBW) using a body composition monitor (BCM) indicated for patients with CKD [13], (BCM-Fresenius Medical Care®), and previously utilized HD [14], PD [15] and CKD stages 3 and 4 patients [16]. Briefly, BCM data is based on a physiological tissue model previously described [17]. This method estimates the hydration status (i.e. ECW and ICW) in CKD individuals in comparison to normal control values. BP (mm Hg), weight (kg), height (m) and body mass index – BMI (kg/m2) were also monitored. Patients were instructed to show up on the day of the examination fasting. They all followed the same protocol for the BCM examination, which is described in detail in the manufacturer manual [18]. Statistical Analyses The results obtained in this study were described by mean, median, minimum values, maximum values and standard deviations for quantitative variables and as frequencies and percentages for qualitative variables. To evaluate the association between quantitative variables the correlation coefficient of Pearson, or Spearman when appropriate was estimated. For a comparison of groups in relation to quantitative variables, the Student t-test for independent samples or the nonparametric Mann-Whitney test was considered. The normality condition evaluated was assessed by the Kolmogorov-Smirnov test. To evaluate the variation between the means the ANOVA test was done. p values
