Lowering Salt Intake in Chronic Kidney Disease: A Pilot Randomized Crossover Trial
| Status: | Completed |
|---|---|
| Conditions: | Renal Impairment / Chronic Kidney Disease |
| Therapuetic Areas: | Nephrology / Urology |
| Healthy: | No |
| Age Range: | 18 - 85 |
| Updated: | 4/21/2016 |
| Start Date: | May 2009 |
| End Date: | May 2013 |
ABSTRACT
Background:
It is well recognized that excess dietary salt intake plays a major role in the development
of hypertension. Chronic Kidney Disease (CKD) is associated with excess salt and water
retention (excess volume) which is associated with hypertension.
Hypotheses:
Hypothesis 1:
Dietary salt restriction will improve volume status in subjects with CKD stages 3-4 as
assessed by Bioelectrical Impedance Analysis (BIA).
Hypothesis 2:
Dietary salt restriction will result in improved blood pressure control in patients with CKD
stages 3-4.
Hypothesis 3:
Dietary salt restriction will decrease albuminuria in patients with CKD stages 3-4.
Patients and Trial Design: This randomized crossover pilot study is designed to assess the
effect of salt restriction on volume status in patients with CKD stages 3 and 4.
Subjects will be randomized to a treatment order: (1) 4 weeks of salt restriction of <85
mmol sodium per day, a 2 week washout period, and 4 weeks of usual salt diet, OR (2) 4 weeks
of usual diet, 2 weeks washout, and 4 weeks of salt restriction. Patients will receive
dietary counseling in person at each study visit and at weekly intervals by phone calls from
study dieticians. At weeks 0, 4, 6 and 10, patients will undergo assessments for (i)
physical examination with assessments for weight, blood pressure, pulse, anthropometrics and
a standardized clinical assessment of volume status. (ii) volume status using bioelectrical
impedance analysis (BIA) (iii) 24-hour urine testing for, albumin, creatinine and
aldosterone Every 2 weeks throughout the study, a 24-hour urine sodium will be measured for
compliance, and serum electrolytes will be assessed for safety.
Data Analysis: BIA measurements in the low salt group will be compared with the regular diet
group using the standard linear model analysis for 2x2 crossover trials. Additionally,
24-hour ambulatory and static blood pressure and 24-hour urine aldosterone levels will be
compared between the two groups.
Future Implications: A significant reduction in the degree of volume expansion (as assessed
by BIA) and blood pressure as a result of a salt restricted diet would have implications for
renal and cardiovascular protection and would warrant confirmation by a larger randomized
trial.
Background:
It is well recognized that excess dietary salt intake plays a major role in the development
of hypertension. Chronic Kidney Disease (CKD) is associated with excess salt and water
retention (excess volume) which is associated with hypertension.
Hypotheses:
Hypothesis 1:
Dietary salt restriction will improve volume status in subjects with CKD stages 3-4 as
assessed by Bioelectrical Impedance Analysis (BIA).
Hypothesis 2:
Dietary salt restriction will result in improved blood pressure control in patients with CKD
stages 3-4.
Hypothesis 3:
Dietary salt restriction will decrease albuminuria in patients with CKD stages 3-4.
Patients and Trial Design: This randomized crossover pilot study is designed to assess the
effect of salt restriction on volume status in patients with CKD stages 3 and 4.
Subjects will be randomized to a treatment order: (1) 4 weeks of salt restriction of <85
mmol sodium per day, a 2 week washout period, and 4 weeks of usual salt diet, OR (2) 4 weeks
of usual diet, 2 weeks washout, and 4 weeks of salt restriction. Patients will receive
dietary counseling in person at each study visit and at weekly intervals by phone calls from
study dieticians. At weeks 0, 4, 6 and 10, patients will undergo assessments for (i)
physical examination with assessments for weight, blood pressure, pulse, anthropometrics and
a standardized clinical assessment of volume status. (ii) volume status using bioelectrical
impedance analysis (BIA) (iii) 24-hour urine testing for, albumin, creatinine and
aldosterone Every 2 weeks throughout the study, a 24-hour urine sodium will be measured for
compliance, and serum electrolytes will be assessed for safety.
Data Analysis: BIA measurements in the low salt group will be compared with the regular diet
group using the standard linear model analysis for 2x2 crossover trials. Additionally,
24-hour ambulatory and static blood pressure and 24-hour urine aldosterone levels will be
compared between the two groups.
Future Implications: A significant reduction in the degree of volume expansion (as assessed
by BIA) and blood pressure as a result of a salt restricted diet would have implications for
renal and cardiovascular protection and would warrant confirmation by a larger randomized
trial.
Inclusion Criteria:
Individuals eligible to participate in this study must meet all of the following criteria:
- Willing and able to provide written, signed informed consent after the nature of the
study has been explained, and prior to any research-related procedures.
- Age ≥ 18 years and ≤ 85 years.
- Willing and able to comply with all study procedures.
- Patients with eGFR of 20 to 60 ml/min/173m2 by the abbreviated (4-variable) MDRD
equation and a relatively stable clinical course.
- Sitting systolic blood pressure ≥ 100 mmHg prior to study entry (to exclude people at
risk from hypotension from dietary salt reduction).
Exclusion Criteria:
Individuals who meet any of the following exclusion criteria will not be eligible to
participate in the study:
- Recent acute illness (≤1 month). Minor ailments such as a recovered common cold or
allergic rhinitis would not be considered as exclusion criteria but would be left to
the site PI's discretion.
- Recent hospitalization (≤1 month) unless clearly for a minor elective procedure
unlikely to interfere with BIA measurements. The final decision will be left to the
site PI's discretion.
- Any psychological condition (including alcoholism) that could interfere with the
patient's ability to comply with the study protocol.
- Subjects with baseline 24-hour urinary sodium excretion ≤100 mmol/day.
- Amputation of a limb other than fingers or toes.
- Pacemaker, defibrillator, implantable pump, artificial joint, pins, plates or other
types of metal objects in the body (other than dental fillings).
- Coronary stents or metal suture material in the heart.
- Use of any investigational product or investigational medical device within 30 days
prior to screening, or requirement for any investigational agent prior to completion
of all scheduled study assessments.
- Weight over 300 pounds (limitation for examination table).
- Pregnancy or lactation.
- Patients with kidney diseases known to be associated with salt wasting (see above).
- Patients with atrial fibrillation as ambulatory blood pressure measurements may not
be accurate in this setting.
- Any condition that, in the view of the PI, places the subject at high risk of poor
treatment compliance or of not completing the study.
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