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Urea kinetics evaluation of hemodialysis and CAPD patients
S R Acchiardo1, A P Kraus, G LaHatte
1University of Tennessee, Menphis.
Insights
Urea kinetics reveal that continuous ambulatory peritoneal dialysis (CAPD) patients exhibit higher protein catabolic rates (PCR) than hemodialysis patients, despite lower dialysis adequacy (Kt/V). This suggests differences in nutritional status or dialysis efficiency.
Area of Science:
- Nephrology
- Renal Nutrition
- Dialysis Therapy
Background:
- Urea kinetics are established for measuring hemodialysis adequacy.
- The utility of urea kinetics in continuous ambulatory peritoneal dialysis (CAPD) remains less defined.
Purpose of the Study:
- To compare urea kinetics and protein catabolic rate (PCR) between hemodialysis and CAPD patients.
- To investigate the relationship between dialysis adequacy (Kt/V) and nutritional markers in both dialysis modalities.
Main Methods:
- Studied 71 hemodialysis and 71 CAPD patients using urea kinetics.
- Collected 24-hour dialysate and urine samples for urea and creatinine.
- Calculated protein catabolic rate (PCR) from total urea clearance.
Main Results:
- CAPD patients had lower dialysis adequacy (Kt/V = 0.65 +/- 0.1) compared to hemodialysis.
- CAPD patients showed higher PCR at equivalent Kt/V levels than hemodialysis patients.
- Lower BUN, serum albumin, and potassium were observed in CAPD patients.
Conclusions:
- Urea kinetics can be applied to CAPD, revealing higher protein intake/metabolism.
- Differences in nutritional status may be linked to diet, patient selection, or dialysis modality.
- Further research is needed to elucidate factors influencing protein metabolism in CAPD.
Abstract:
Urea kinetics have been used to measure adequacy of hemodialysis. The role of urea kinetics in CAPD has not been clearly established. Using urea kinetics, we studied 71 hemodialysis and 71 CAPD patients. Age was 53 +/- 12 and 45.8 +/- 12 respectively. Urea kinetics in hemodialysis were studied in the standard manner. CAPD patients collected 24 hr, dialysate fluid to measure urea, creatinine, glucose and protein. Urine was collected for 24 hr. to measure urea and creatinine. Protein catabolic rate (pcr) was calculated from the total amount of urea cleared in 24 h. Both groups of patients had similar body weight. Kt/V in CAPD (0.65 +/- 0.1) was at a level considered underdialysis for hemodialysis. In both groups, pcr increased as Kt/V increased. However, CAPD patients had levels of pcr higher than hemodialysis patients at the same level of Kt/V. BUN, serum albumin and serum potassium were significantly lower in CAPD patients. Patients who dialyze more, eat more. Differences in protein intake may be due to a more liberal diet in CAPD, patient selection, removal of middle molecules, or better control of the acidosis.