Effect of predialysis eating on measurement of urea reduction ratio and Kt/V

Physicians utilize the measurement of the urea reduction ratio (URR) and Kt/V as surrogates for the adequacy of hemodialysis, as well as to follow the course of patients longitudinally. These measurements are affected by the duration of a dialysis treatment, the type and size of the dialyzer membrane used during the treatment, the blood flow rate during the treatment, and the adequacy of vascular access. We, and others, have noted that eating during dialysis can be associated with decreases in URR and Kt/V. However, there have been no previous studies that have examined the effects of eating before dialysis on these variables. This study examined the effects of eating one-third of a daily diet 2 hours before dialysis as opposed to fasting for a minimum of 3 hours before dialysis on the measured URR and Kt/V as obtained routinely in our dialysis unit. Sixty seven patients gave informed consent for the study, and 42 completed the protocol. No differences were found in URR or Kt/V when dialysis was performed 2 hours after eating compared with performing dialysis after at least a 3-hour fast in the group as a whole or in subgroup analyses of men, women, patients with diabetes, patients in different age groups, or patients who dialyzed on different shifts. Unlike intradialytic food ingestion, moderate predialysis food intake does not affect the measurement of dialysis adequacy as determined by URR and Kt/V.