Urea peritoneal transfer evaluated using plasma water urea concentrations.
OBJECTIVE
To quantify differences in evaluation of urea peritoneal transport parameters according to the expression of urea concentration in whole plasma and plasma water.


METHODS
Prospective study in which the dialysate samples for urea determinations were taken at short dwell times (2.5-45 minutes) during three consecutive exchanges of intermittent peritoneal dialysis (IPD). Blood samples were drawn at the beginning and at the end of the study period. Urea peritoneal transport parameters were calculated using urea concentration in whole plasma and plasma water. The results were then compared.


METHODS
Peritoneal dialysis unit of a nephrology department.


METHODS
Ten stable patients on IPD.


METHODS
Dialysate and blood sample collections.


METHODS
Dialysate-to-plasma ratios (D/P), peritoneal clearances (Cp), and diffusive mass transport coefficients (KBD) of urea.


RESULTS
At short dwell times, uncorrected (whole plasma) D/P and Cp of urea values were higher than the corrected (plasma water) values by 5.7%-5.9%. Uncorrected urea KBD, calculated using the simplified two-sample model of Garred et al., yielded an overestimation that significantly increased with prolongation of dwell (8.5 +/- 0.5% at 2.5 minutes vs 13.0 +/- 0.8% at 45 minutes). Urea KBD, assessed by the linear regression model of Garred and Spencer, was 9.4 +/- 0.3% higher for uncorrected values.


CONCLUSIONS
The expression of urea concentration in whole plasma instead of plasma water overestimates urea peritoneal transfer parameters. The percent overestimation (y) of urea KBD, calculated using the simplified model of Garred et al., can be predicted with the equation y = 0.131x + 7.563, where x is the dwell time (in minutes.
Grzegorzewska
A E
AE
Department of Nephrology, Karol Marcinkowski University of Medical Sciences, Poznan, Poland.
D000328:Adult; D001692:Biological Transport; D015314:Dialysis Solutions / Q000737:chemistry; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000628:therapy; D008297:Male; D010530:Peritoneal Dialysis; D010537:Peritoneum / Q000378:metabolism*; D010949:Plasma / Q000737:chemistry; D011446:Prospective Studies; D014508:Urea / Q000032:analysis / Q000378:metabolism*
D015314:Dialysis Solutions; D014508:Urea