| BackgroundChronic Kidney Disease(CKD)has now become the "global public health issue"that is currently important.Chronic kidney disease not only causes progressive irreversible damage to the kidneys that eventually develops end-stage renal disease requiring alternative treatments such as hemodialysis,peritoneal dialysis,and kidney transplants,but also increases the morbidity aad mortality of cardiovascular disease.The most important cause of death in long-term dialysis patients is cardiovascular and cerebrovascular disease,about 50%of dialysis patients died of cardiovascular and cerebrovascular disease,which is 20 to 30 times that of the general population.According to the report of China Dialysis Cooperation Study(CCSD)in 2010,the results showed that the incidence of hypertension in Chinese dialysis patients was 84.3%,and the new incidence of cardiovascular and cerebrovascular diseases was 57%.Among them,the incidence of ischemic heart disease was 22.7%and the incidence of stroke was 9.6%.The rate of hypertension in patients with peritoneal dialysis was 92.3%,the total incidence of cardiovascular and cerebrovascular diseases was 58.9%,of which the incidence of ischemic heart disease was 27.7%,the incidence of stroke was 13.4%,the incidence of heart failure 47.3%.Among many risk factors of cardiovascular and cerebrovascular events in patients with chronic kidney disease,hypertension and the rapid decline of and residual renal function are important and independent risk factors.Sodium plays an important role in the pathogenesis of hypertension.Studies had reported the impact of sodium on human physiology and health.Sodium chloride determined extracellular fluid volume and was involved in the regulation of blood pressure.Excessive salt or sodium sensitivity was an important cause of hypertension,and reducing sodium intake gradually could significantly resulted in blood pressure decrease in hypertensive patients.Follow-up study found that,in addition to raising blood pressure,excessive salt can lead to blood pressure-independent target organ damage.Observations of the Finnish general population suggested that the relative risk of coronary heart disease increased by 1.5-fold and the all-cause mortality increased by 1.26-fold with sodium intake>100mmol/d,which is independent of blood pressure and other eardiovascular risk factors.Chronic kidney disease(CKD)patients often associated with salt sensitivity.High-salt diet could cause abnormal sodium and water retention,elevate blood pressure,increase renal blood flow and glomerular filtration rate,thereby increasing glomerular pressure and proteinuria.Salt restriction could ease the edema and low blood pressure in patients with chronic kidney disease,and slow the decline of their renal function.Animal experimental studies also suggested that experimental salt injury model mouse increased salt sensitivity,and high salt-intake accelerated the progress of renal injury.In continue ambulatory peritoneal dialysis(CAPD)patients,strict restrictions on sodium intake could lower blood pressure and reduce the associated complications.In 2012,guidelines for antihypertensive treatment published by Kidney Disease Improve Global Outcome(KDIGO)suggested that the daily sodium intake in patients with CKD is less than 90mmol/day(2 g/day,equivalent to 5 g/day of sodium chloride).Residual renal function in patients with chronic kidney disease could effectively remove small molecules and uremic toxins,maintain body water and salt balance,control blood phosphorus levels,correct anemia,reduce the use of erythropoietin,prevent vascular calcification and myocardial hypertrophy,etc.Residual renal dysfunction was an independent risk factor for cardiovascular events in CKD patients.Peritoneal dialysis could better preserve residual renal function in CKD patients.Residual renal function protection is conducive to control volvime load,reduce the severity of ventricular hypertrophy in PD patients.In addition,appetite,dietary protein and total calorie intake were improved,the inflammatory state was reduced in PD patients with residual renal function.The survival rate,all-cause mortality rate was positively correlated with residual renal function in PD patients,so it is essential to protect the residual renal function in peritoneal dialysis patients.Controlling blood pressure,reducing massive proteinuria,and using renin-angiotensin-aldosterone blockers are the important means of delaying the residual renal dysfunction in peritoneal dialysis patients.There were many factors affecting residual renal function in patients imdergoing peritoneal dialysis.The study foimd that would affect the drop-rate of residual renal dysfunction in PD patients,such as proteinuria,the frequency of occurrence of peritonitis,glucose exposure,basal remnant glomerular filtration rate before dialysis,use of diuretics,use of contrast agent and so on.High-salt diet mainly leads to the occurrence of hypertension by increasing the volume load,and can induce the local RAS expression and activation in the kidney.Studies had shown that sodium intake can reduce the activity of RAS,blood pressure,urinary protein,and significantly reduce the incidence of ischemic heart disease,stroke.However,excessive restriction on salt intake could lead to the lack of effective blood volume,which is harmful to the residual renal function.The effect of sodium intake on cardio-cerebrovascular events had a "U" or "J"-type curve,so the effect of sodium intake on residual renal function in PD patients is still controversial.This study intended to explore the relationship between the amoiont of salt intake and the residual renal function,the incidence of cardio-cerebrovascular events in PD patients in the southern Chinese population.The purpose of this study includes the following contents:(1)Assess the effect of salt load on residual renal function.(2)Assess the impact strength of salt load on residual renal function in peritoneal dialysis patients among numerous factors.(3)Assess the risk of new cardio-cerebrovascular events and death under different salt-load conditions.Objection:To find out the relationship between salt intake and the decline of residual renal function,salt intake and new incidence of cardio-cerebrovascular events in PD patients through assessing relevant impact factors.Methods:In this prospective randomized controlled study,volunteers enrolled in this study were recruited from patients who were hospitalized patients or outpatients with peritoneal dialysis at Nanfang Hospital,Southern Medical University from January 1,2016 to December 30,2017.Patients were included:(1)age≥18 years;(2)the duration of CAPD treatment has been≥3 months;(3)urine volume≥100ml/24h,without using diuretic;(4)without history of peritonitis within 1 month;(5)no acute infection or acute infectious disease;(6)without unmaintainable hypertension,heart failiure or malignant tumors or other wasting diseases;(7)On a normal diet,without obvious malnutrition(≥ 60%of ideal body weight);(8)Provide detailed dietary records.Patients were excluded(with any of the following criteria):(1)disagreeing with participating the study or poor compliance;(2)receiving hormone or immunosuppressive therapy or receiving chemotherapy or alkylating agents;(3)vintage of peritoneal dialysis treatment was less than 3 months;(4)urine volume<100ml/24h;(5)peritonitis occurred within 1 month before the study;(6)difficult to control the malignant hypertension or suffer from heart failure;(7)severe malnutrition(<60%of ideal body weight)or severe malnutrition(serum sodium<130mmol/L);(8)may be replaced by hemodialysis or renal transplant in the near future.This research project has been approved by the Guangdong Provincial Institute of Kidney Disease Ethics Committee.All patients were signed informed consent.In this study,33 eligible peritoneal dialysis patients were enrolled.Patients were completed the following examinations:(1)Demographic data included:name,gender,age,date of birth,height,weight,blood pressure,24-hour urine volume,primary disease of end-stage renal disease(renal biopsy pathology is the gold standard for the diagnosis of diabetic nephropathy and hypertensive.If renal puncture is not performed,the patient’s primary disease of ESRD is diagnosed by medical history,clinical manifestations,and biochemical tests and examination results.)(2)Nutritional status:patients were required to eat separately and record the contents of the diet in detail at home for 3 consecutive days,including 2 working days and 1 weekend day.The record should contain all kinds of food what they ate,cooking methods,weight of food,salt,soy sauce and cooking oil.After the record is completed,the dietitian asked and checked the record.Then use the diet calculation software(provided by the Kaitong Company)to calculate the average daily intake of energy,protein,fat,carbohydrates,cellulose,potassium,sodium,chlorine,calcium,Phosphorus,iron,magnesium and other contents;(3)Peritoneal dialysis situation:the start time of PD,peritoneal fluid concentration,dialysis K t/N,residual kidney K t/N,total K t/V,24h urine volume,dialysis creatinine clearance,residual renal creatinine clearance,total creatinine clearance;(4)The use of medication:whether to use ACEI/ARBs antihypertensive drugs and the kinds of antihypertensive drugs;(5)Combining basic diseases:hypertension,diabetes and previous cardio-cerebrovascular events.(6)Blood biochemical indicators:WBC,HGB?PLT;BUN,CR,UA,total carbon dioxide(CO2),fasting blood glucose,K,Na,Cl,Ca,TG,CHOL,alanine aminotransferase(ALT)5 aspartate aminotransferase(AST),serum albizmin(ALB),pre-albumin(PA),C reactive protein(CRP),intact parathyroid hormone(i-PTH),iron,Ferritin,B-type natriuretic peptide(pro-BNP).Urine biochemical indicators:BUN,CR,K,Na,Cl;Peritoneal dialysis:BUN,CR,K,Na,CL(7)Electrocardiogram:left ventricular hypertrophy,myocardial ischemia,heart block or arrhythmia;X-ray examination:cardiothoracic ratio,atherosclerosis;echocardiography:left ventricular mass(LVM),left ventricular mass index(LVMI),ejection fraction(EF%)S interventricular septum thickness(IVST),left ventricular end diastolic diameter(LVDd),left ventricular posterior wall thickness(LVPWT).All the laboratory tests and inspection items were done in Southern Hospital.Medical data were collected from patient medical records.All subjects were prospectively observed for 12 months and followed up every 3 months.The examinations were completed as above and clinical data were recorded in detail.Definition:cardio-cerebrovascular events:include the following,coronary artery disease,congestive heart failure,stroke,and peripheral vascular disease.(1)Coronary artery disease diagnosed by clinical and electrocardiographic or laboratory tests,typical angina pectoris and/or coronary angiography,coronary artery bypass surgery,or percutaneous transluminal vascular Angioplasty,clinically diagnosed acute coronary syndrome and sudden cardiac death;(2)congestive heart failure:echocardiographic examination shows that the ejection fraction is less than 50%or according to the New York Heart Association standard NYHA classification based on clinical and cardiac function Cardiovascular Function Class Ⅲ-Ⅳ;(3)Cerebrovascular Events:Clinical and cranial computed tomography(CT)or cranial magnetic resonance imaging(MRI)tests confirmed the presence of acute cerebral hemorrhage,acute cerebral embolism,cerebral thrombosis,ischemic stroke,obsolescence Cerebral Infarction;(4)Peripheral Artery Stenosis:Clinical or vascular color Doppler or computed tomography angiography(CTA)examination has demonstrated the presence of stenosis or occlusion of the aorta other than the coronary artery and its branch arteries.Hypertension:meets one of the following(1)the patient had the history of hypertension;(2)the patient was taking any antihypertensive drugs;(3)Three measurements of blood pressure systolic blood pressure≥140 mmHg(1 mmHg=0.133 kPa)and/or diastolic blood pressure≥90 mmHg on different days.DM:meets one of the following(1)the patient had the history of diabetes;(2)the patient was using any antidiabetic agents;(3)Fasting blood glucose≥7.0mmol/L or two-hour postprandial blood glucose≥11.1mmol/L.Statistical Analysis:Variables are exqpressed in a standard way.Continuous variables are expressed as means ± standard deviation,categorical variables as numbers with percentages,and the continuous variables with skewed distribution are ejqjressed by the median and quartile.Baseline characteristics were compared using independent t-test between two groups and one-way ANOVA among three groups for continuous variables and the chi square test for categorical variables,non-parametric Mann-Whitney test for continuous variables with skewed distribution.When the baseline and endpoint values are compared,the continuous distribution of the normal distribution uses the paired t-test and the continuous distribution of the skewed distribution uses the Wilcoxon rank sum test Pearson’s correlation was performed to elucidate the relationship between the sodium intake and output.In addition,risk factors assumed to be associated with the morbidity of CVD and the decline of residual renal function were evaluated using multivariate regression analysis.A p-values of<0.05 was considered statistically significant.Statistical analyses were performed using the SPSS software package(version 23.0).Results(1)According to the salt intake for adult CKD patients recommended in the 2012 KDIGO guidelines(<5g/d),patients are divided into three groups:① extremely low salt intake group:salt intake≤3g/d.② low salt intake group:salt intake is more than 3g/d but less than or equal to 5g/d.③ high salt group:salt intake>5g/d.(2)The total sodium intake in PD patients was positively correlated with the total sodium removal(r=0.52,P<0.05),especially with the total amount of sodium cleared through peritoneal dialysis(r=0.90,p<0.05).This can be used to estimate the patients sodium salt intake through the amount of sodium cleared in the dialysate.There was no significant correlation between total sodium intake and urinary sodium clearance.(3)During the study(12-month observation period),There was a statistically significant difference in the decreased of residual renal function between the low salt intake group(salt intake ≤5g/d)and high salt intake group(salt intake>5g/d)(18.02±11.22 vs 32.59±19.30 L/(w·1.73m2),p=0.04).There was a statistically significant difference between the high and low salt intake group(32.59±19.30 vs 16.39±11.33 L/(w·1.73m2),p=0.04),high and the very low salt intake group(32.59±19.30 vs 19.56±11.40 L/(w·1.73m2),p=0.01).There was no statistical difference between the very low and the low salt intake group(19.56±11.40 vs 16.39±11.33 L/(w·1.73m2),p>0.05).There is a correlation between the decrease of residual renal function and salt intake(r=0.39,P=0.02),and multivariate regression analysis shows that salt intake is an independent factor in the decline of residual renal function(p=14.65,95%CI:7.43-21.87,P<0.001).(4)The current results have not yet shown the correlation between salt intake and new cardio-cerebrovascular events in patients undergoing peritoneal dialysis.(HR=1.41,95%CI 0.26-7.74,P>0.05).Conclusions(1)Total sodium intake in PD patients was correlated with the total sodium removal and the total amount of sodium cleared through peritoneal dialysis,so this can be used to estimate the patients sodium salt intake through the amount of sodium cleared in the dialysate or the total amount.There was no significant correlation between total sodium intake and urinary sodium clearance.(2)The decline of residual renal function was related to the amount of salt intake in PD patients.Taking more salt(salt intake>5g/d)can result in a faster decline in residual renal function,and extremely limited salt may not be conducive to protecting residual kidney function.(3)The current results have not yet shown the correlation between salt intake and new cardio-cerebrovascular events in patients undergoing peritoneal dialysis. |
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