Urea rebound - some disadvantages of urea kinetic modeling

Abstract

PURPOSE: The objectives of the present study are to determine the average urea rebound by examining the urea concentrations immediately after completion of hemodialysis (HD) and comparing these results to urea concentrations taken 30 min after the procedure (equilibrated values), to assess how the delivered dialysis dose changes when URR and Kt/V are calculated using each of these two values and to evaluate the significance of these differences and the reliability of the indicators in use. MATERIAL AND METHODS: The study covered 30 end-stage renal failure (ESRF) patients, 16 males and 14 females on chronic HD at a mean age of 43.90±10.63 years and average duration of dialysis treatment of 6.90±3.75 years. Average urea values were calculated for each patient using data from three consecutive monthly examinations taken immediately and 30 min after HD in order to determine the mean urea rebound percentage. RESULTS: Mean urea values in samples taken immediately and 30 min after HD showed statistically significant differences (p<0.05). Equilibrating urea concentration led to an average increase of 17.7% at the 30 min after HD. There was a statistically significant difference (p<0.05) between the calculated single pool Kt/V (1.23±0.11) and equilibrated Kt/V (1.17±0.18) as well as concerning mean URR values calculated by using non-equilibrated and equilibrated post dialysis urea (65.3±1.18% and 6.67±2.4%, respectively). CONCLUSION: Calculation of URR and single pool model of Kt/V for assessment of dialysis adequacy in ESRF patients on chronic HD results in overestimation of the delivered dialysis dose. These values differ statistically significantly from those when accounting for urea rebound. URR and Kt/Vsp indicators do not possess the necessary reliability as means to evaluate the delivered dialysis dose. Scripta Scientifica Medica 2013; 45(1): 71-74.