OBJECTIVE: To study whether or not continuous peritoneal dialysis (CPD) can provide acceptable levels of normalized urea and creatinine clearance in heavyweight individuals. DESIGN: Retrospective analysis of urea and creatinine clearance studies. SETTING: CPD patients followed in four dialysis units in Albuquerque, two dialysis units in Thessaloniki, and two dialysis units in Athens. PARTICIPANTS: One hundred and ninety-nine patients on CPD with 266 clearance determinations between 1991 and 1995. INTERVENTIONS: The heavyweight group consisted of 22 patients (24 clearance studies) weighing 100 kg or more (109 +/- 8.7 kg) at the time of the clearance study. All subjects were obese. The reference group consisted of 177 CPD subjects (242 clearance studies) of normal weight (68.7 +/- 12.2 kg). Urea fractional clearance (KT/V) and normalized creatinine clearance (Ccr) were compared between the heavyweight and the reference groups. MAIN OUTCOME MEASURES: The lowest acceptable weekly levels were set at 1.70 for KT/V and 54.4 L/1.73 m2 for Ccr. RESULTS: Weekly KT/V was 1.75 +/- 0.41 in the heavyweight group and 1.94 +/- 0.52 in the reference group (p = 0.047). Corresponding weekly Ccr levels were 64.0 +/- 24.3 and 77.6 +/- 40.3 L/1.73 m2, respectively (p = 0.021). In the heavyweight group, 13 studies (54.2%) had acceptable KT/V values compared to 160 studies (66.1%) in the reference group (NS). Corresponding values for acceptable Ccr were 17 (70.8%) and 165 (68.2%), respectively (NS). Drain volume was 12.96 +/- 4.40 L/24 hours in the heavyweight group and 9.63 +/- 2.58 L/24 hours in the reference group (p = 0.001). High daily exchange volume was delivered by a combination of daily continuous ambulatory peritoneal dialysis (CAPD) and nocturnal automated peritoneal dialysis (APD) in 13/16 heavyweight studies. This combination was tolerated better than any other method of delivering a large daily exchange volume. CONCLUSION: Although normalized urea and creatinine clearances are lower in obese, heavyweight individuals than in lean CPD subjects with lower weight, approximately equal percentages of these two groups achieve acceptable clearance levels. However, heavyweight individuals require larger-than-usual daily exchange volumes. The preferred way to deliver these large dialysate volumes is a combination of daily CAPD and nocturnal APD.

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