Effect of Viscous Fiber on Postprandial Kalemic Response in Hemodialysis Patients

Overview

High blood potassium levels (hyperkalemia) is a major problem for people with kidney failure undergoing hemodialysis treatment. In order to reduce the risk of hyperkalemia, people with kidney failure are advised to limit or avoid high-potassium foods. However, high-potassium foods comprise many healthy food choices, including commonly consumed fruits and vegetables that are key sources of dietary fiber, and other important nutrients. Risk of hyperkalemia from dietary potassium intake is most notable in the first few hours after a meal when ingested potassium enters the bloodstream. In general, dietary potassium is very well absorbed. However, dietary fiber has been shown to increase the proportion of dietary potassium that is excreted in stool. Based on these findings, it has been proposed that fiber may help to lower the risk of hyperkalemia in people with kidney disease. It remains unclear whether dietary fiber increases potassium excretion in stool by reducing the absorption of dietary potassium, or by drawing body potassium into the bowels by increasing stool bulk. The distinction may be important, as reducing potassium absorption would be expected to be of greater benefit in preventing hyperkalemia caused by eating high-potassium foods. In this study, the investigators will assess whether a fiber supplement can reduce the effect of dietary potassium from orange juice on blood potassium levels in people with kidney disease undergoing maintenance hemodialysis treatment.

The source population for this study will be adults (18-89 years old) with kidney failure undergoing thrice weekly maintenance hemodialysis (HD) treatment. Participants will include 10 patients without diabetes mellitus, and 10 patients with type 2 diabetes mellitus (T2D) that is being managed with lifestyle with or without long-acting insulin. Patients with a moderate hyperkalemia (\>6.5 mEq/L) in the last 6-months, taking potassium-lowering medications, having gastrointestinal (GI) disorders that may alter potassium digestion and absorption, and low hemoglobin concentrations (\<10.0 g/dL) will be excluded. In addition, participants who are deemed inappropriate for the intervention by the study Nephrologist based on cognition, prognosis or pending treatments will be excluded. Once enrolled, participants will be asked to complete questionnaires on demographics, dietary intake, GI symptoms, and urine output. In addition, baseline data on anthropometrics, physical function, medical history and blood parameters will be obtained by physical exam and review of medical records. Treatment measurement visits will be conducted on the same non-dialysis treatment days at the University of Nevada, Reno Clinical Research Center with participants in a fasted state. Serial blood samples will be collected before, and 60, 120 and 180 minutes after ingesting orange juice providing 0.35 mEq/kg dose of potassium alone, or with 0.15 g/kg of psyllium-based fiber. The sequence of treatments (1) orange juice or 2) orange juice + fiber) will be randomly assigned with equal allocation by T2D status. If a participant's body weight exceeds 120% of ideal body weight (IBW), then the dose of orange juice and fiber will be based on adjusted body weight. Blood tests at times 0 and 60-minutes post-treatment will be analyzed for the basic metabolic panel plus insulin, and the 120- and 180-minutes blood samples will be analyzed for potassium concentrations. The kalemic response to study treatments will assessed based on: 1) peak change in plasma potassium concentrations, and 2) total area under the curve for plasma potassium until 180-minutes. These parameters will be compared across treatment conditions using paired t-test. If non-normally distributed, values will be log-transformed prior to analyses.