Potassium Intake in Patients With Chronic Kidney Disease (CKD-K)

Primary Outcome Measures:

• 24-hour ambulatory systolic blood pressure [ Time Frame: At screening, and at the end (4th week) of each intervention period ]
  

Secondary Outcome Measures:

• other measures of peripheral blood pressure (other types of ambulatory blood pressure measurements as well as clinic blood pressure) [ Time Frame: Ambulatory BP: same as primary outcome. Clinic BP: at screening, run-in, and weekly during intervention ]
  
• measures of central blood pressure (pulse wave velocity and augmentation index) [ Time Frame: at screening and at the end (4th week) of each intervention period ]
  
• Serum potassium [ Time Frame: At screening, run-in, and at least 3 times during each intervention period ]
  

In individuals without chronic kidney disease (CKD), potassium (K) lowers blood pressure (BP) and may help prevent cardiovascular disease (CVD) and stroke. In animal models, K prevented kidney injury and decreased kidney inflammation. CKD patients may especially benefit from higher K intake, due to their high prevalence of hypertension, CVD, and stroke, and the possibility that K may retard CKD progression. Despite these potential benefits, there is great uncertainty about the optimal K intake in CKD patients. K is often restricted in these patients due to concerns about elevating serum K. However, renal K excretion does not appear to be substantially impaired until the glomerular filtration rate (GFR) is severely decreased (< 10-20 mL/min/1.73 m2). In this randomized feeding study with a two-period crossover design, the benefits and safety of 4 weeks of 100 mmol versus 40 mmol K/day in 26 non-diabetic adults with stage 3 CKD (estimated GFR 30-59 mL/min/1.73 m2) will be evaluated. After a one-week run-in period, all participants will be randomized to receive either a diet containing either 40 mmol K/day or 100 mmol K/day (within the current K/DOQI recommendations for K intake for stage 3 CKD) during period 1 (they will receive the other during period 2). The primary outcome variable is 24-hour ambulatory systolic BP. Secondary outcomes are other measures of peripheral BP, central BP, inflammatory markers, and serum K. We hope that this study will lead to a larger trial with sufficient power to examine the effects of increased K intake on clinical outcomes such as CKD progression. The ultimate goal of this effort is to develop the scientific basis for guidelines on K intake in CKD.