The method used for volume estimation significantly influences KprT/V results in peritoneal dialysis patients.
We studied 51 patients (age 50 +/- 15 years; weight 75 +/- 17 kg; blood urea nitrogen 62 +/- 20 mg/dL), 61% of whom were obese. The volume of distribution of urea was estimated by anthropometric formulas (Watson and Hume) and as 58% of actual and ideal body weight. Volumes derived from use of 58% of actual body weight were highest (43.4 +/- 10.0 kg; p = 0.0005); no differences were noted between Watson and Hume volumes and those obtained using 58% of ideal body weight (38.5 +/- 8.0, 39.4 +/- 7.5, and 37.0 +/- 5.6 kg, respectively). Normalized daily urea clearance (KprT/V) was lowest and highest when using 58% of actual and ideal body weight, respectively (0.251 +/- 0.081 and 0.290 +/- 0.091; p < 0.0001). KprT/V values derived using the Watson and Hume methods were similar (0.279 +/- 0.081 and 0.274 +/- 0.083, respectively), but significantly lower than those obtained using actual body weight (p < 0.0001). Differences were magnified in obese patients. A subset of patients underwent hemodialysis for urea volume measurement by urea kinetic modeling. Volume estimates using bioelectrical impedance showed the least bias when compared to values calculated during a hemodialysis treatment. We conclude that KprT/V is very dependent on body habitus and the method used for volume determination. Standardization of the volume parameter is essential to defining therapeutic guidelines and for meaningful comparisons between centers.
Department of Medicine, William Beaumont Hospital, Royal Oak, Michigan, USA.
F
F
Dumler
C
C
Cruz
D001823:Body Composition; D001835:Body Weight; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis / Q000379:methods*; D014508:Urea / Q000378:metabolism
D014508:Urea