Defining Peritoneal Dialysis Adequacy: Kt/Vurea Revisited

Background. Although adequate peritoneal dialysis is not well defined, Kt/Vurea has been used as an index, and various values have been proposed. However, conflicting evidence existed regarding the appropriateness of using Kt/Vurea to define dialysis adequacy and its optimal value. Therefore, the present study performed a theoretical analysis on whether we should use Kt/Vurea to define peritoneal dialysis adequacy and what the optimal value should be. Methods. The three-pore model was applied to evaluate the transport patterns of different molecular weight solutes and fluid. Optimal Kt/Vurea value was estimated based on urea kinetics and nitrogen balance. Results. The removal pattern of small solute, middle and large molecules, and fluid and sodium are quite different. Depending on the dwell time, higher urea removal does not necessarily mean higher sodium, fluid, and other molecular weight solute removals. To reach nitrogen balance, the dialysis doses and therefore Kt/Vurea values varied with different dietary protein intakes in a patient with a given weight and residual renal function. Conclusion. This study shows that Kt/Vurea in peritoneal dialysis cannot represent the removal of other solutes and fluid, indicating that Kt/Vurea alone should not be used as a sole indicator of peritoneal dialysis adequacy. The results also show that optimal Kt/Vurea cannot be a fixed value, but varies according to individual dietary protein intake and tolerable blood urea level.     

腹部手术对腹膜透析的影响

目的 :探讨先前腹部手术对CAPD效能和并发症的影响。方法 :将 81例肾衰竭患者分成两组 :A组4 7例 ,无腹部手术史 ;B组 34例 ,有腹部手术史。随访置管CAPD后第 1、第 7个月腹膜肌酐清除率和生化指标。结果 :两组在开始CAPD后第 1、第 7个月腹膜肌酐清除率均无显著性差异 (P >0 .0 5 ) ,但B组术后血性透出液发生率(17.6 % )高于A组 (2 .1% ) (P <0 .0 5 )。经过半年随访 ,各组内腹膜肌酐清除率保持稳定。随访过程中无疝气、腹壁水肿和胸积液等并发症发生。结论 :既往中小腹部手术一般不影响腹膜透析顺利进行 ,但行腹膜透析置管术时应谨慎 ,术后注意监测腹膜溶质清除能力。     

Continuous Ambulatory Peritoneal Dialysis (CAPD) Adequacy Influences Serum Free Carnitine Level

Objective: An evaluation of serum free carnitine level in CAPD patients in relation to dietary intake, nutritional status and CAPD adequacy and duration. Study design: Food diaries, nutritional (total body mass, lean body mass, serum level of proteins, carnitine, cholesterol) and adequacy (Kt/V, PCR, tCcr, EN) parameters were obtained in 23 CAPD patients. Results: Normal carnitine level (41.8±6.7 µmol/l) was found in 17 patients being on CAPD through 11.1±9.6 months, whereas in 6 persons treated with CAPD through 9.7±4.1 months carnitine level was 25.4±5.7 µmol/l. Significant differences between low and normal carnitine groups were in tCcr (82.7±16.7 v. 65.9±13.2 l/wk/1.73 m² BSA), effluent volume (10.9±0.8 v. 9.9±1.5 l/day), effluent glucose concentration (729=167 v. 530±220 mg/dl) and serum globulin level (22.6±6.4 v. 29.3±4.4 g/l). Significant correlation coefficients (for n=23) were found between serum carnitine level and effluent volume (r=–0.509) or plasma globulin level (r=+0.522). Conclusion: Patients with higher CAPD adequacy show lower serum free carnitine levels and this is related to higher effluent volumes.     

We Use Kt/V Urea as a Measure of Adequacy of Peritoneal Dialysis

In the early days of chronic dialysis therapy, there was recognition that patients on continuous peritoneal dialysis enjoyed improvement in symptoms and signs of kidney failure similar to those receiving hemodialysis, despite slower removal rates of small solutes such as urea and creatinine. It was suggested that removal of toxic middle molecular weight solutes by the peritoneal membrane compensated for this difference. The publication of the National Cooperative Dialysis Study then focused attention on urea clearance as a significant predictor of hospitalization in hemodialysis patients. The peritoneal dialysis community made a mistake in adopting urea kinetics to the peritoneal dialysis process, while ignoring the benefits incumbent in continuous dialysis therapy and middle molecular weight solute removal. Sadly, to this day, despite the publication of many studies that have been unable to find an association between peritoneal small solute kinetics and outcome, Kt/V urea is employed as a marker of adequacy in these patients.