Definitions for the levels of evidence (I–IV) can be found at the end of the "Major Recommendations" field.
Guidelines
No recommendations possible based on Level I or II evidence
Suggestions for Clinical Care
(Suggestions are based on Level III and IV sources)
- Patients with hypertension and progressive chronic kidney disease (CKD) should limit their sodium intake to below 100 mmol per day. (Opinion)
Low sodium diets may be unpalatable initially. Persistence with the diet by both patient, doctor and dietician is usually rewarding. The early use of diuretics (especially loop diuretics) is often required. Thiazide diuretics often fail to have a clinically significant natriuretic or hypotensive effect once there is moderate reduction in the glomerular filtration rate (GFR) (30 to 60 mL/min). In refractory oedema, however, thiazides in combination with loop diuretics may have a synergistic effect. The hypotensive effect of salt restriction is less as the GFR falls with progressive kidney disease.
People with a salt-losing nephropathy may have a high obligatory sodium loss, and sodium restriction may be harmful for them.
The introduction of acidosis correction therapy (e.g., sodium bicarbonate tablets) will increase the daily sodium intake and needs to be accounted for in the dietary advice.
Each 4 g Ural® sachet (Sigma, Clayton, Victoria) contains 28 mmol of sodium. Each sodium bicarbonate tablet contains 10 mmol of sodium/tablet.
1 teaspoon (approximately 5 g) of baking soda in 60 mL of water contains 60 mmol of sodium (see "Acidosis in pre-dialysis patients" guideline for bicarbonate content).
Many salt-substitute compounds contain potassium.
The DASH study looked at varying sodium diet content and hypertension and excluded subjects with renal impairment. There is an abundance of lower salt/sodium diets and improved hypertension control; however, these studies all exclude CKD subjects.
One review article discusses the benefits of sodium restriction in CKD. It summarises the improved control of hypertension in the patient with reduced sodium intake. Salt restriction alone is not adequate to control hypertension in the CKD patient, and anti-hypertensive agents are required (often in combination) to achieve desired levels. In early renal impairment, sodium restriction alone may adequately manage oedema; however, diuretics are needed in oedematous states with more advanced renal failure.
Sodium restriction, in combination with appropriate anti-hypertensive medication, assists in the control of extracellular volume and hypertension in CKD.
Definitions:
Levels of Evidence
Level I: Evidence obtained from a systematic review of all relevant randomized controlled trials (RCTs)
Level II: Evidence obtained from at least one properly designed RCT
Level III: Evidence obtained from well-designed pseudo-randomized controlled trials (alternate allocation or some other method); comparative studies with concurrent controls and allocation not randomized, cohort studies, case-control studies, interrupted time series with a control group; comparative studies with historical control, two or more single arm studies, interrupted time series without a parallel control group
Level IV: Evidence obtained from case series, either post-test or pretest/post-test
