Effects of Postdialysis Urea Rebound on Dialysis Adequacy in Hemodialysis Patients

Kwon, Kun Ho; Lee, Seoung Woo; Kim, Moon Jae

Abstract

Urea reduction ratio (URR) and Kt/Vurea are objective parameters of dialysis delivery in hemodialysis patients and correlate with nutritional status and patient outcome. URR and Kt/Vurea depend on postdialysis blood urea nitrogen (BUN). In patients with severe postdialysis urea rebound (PDUR), these parameters do not accurately reflect dialysis adequacy. We measured PDUR 30 minutes after dialysis in 26 chronic stable hemodialysis patients. The impact of PDUR on dialysis delivery assessed by URR and Kt/Vurea and the independent factors affecting on PDUR were evaluated. All patients had been dialyzed for 4 hours thrice a week using hemophan membrane. 1) The mean age of patients was 48.6+/-14.8 years and sex ratio was 1:2.3. The mean duration of hemodialysis was 42.7+/-45.0 months. Primary renal diseases were chronic glomerulonephritis 11 (42.3%), diabetic nephropathy 7 (26.9%), and hypertension 4 (15.4%). 2) The mean blood flow was 209.2+/-17.4ml/min. URR, Kt/Vurea, and nPCR using immediate postdialysis BUN were 60+/-7%, 1.13+/-0.21, 1.09+/-0.28g/kg/ day, respectively. The mean recirculation rate was 4.4+/-2.3%. 3)The mean PDUR was 12.2+/-4.6% (range:6-22 %). URR, Kt/Vurea, and nPCR using BUN 30 minutes after dialysis were 55+/-7%, 0.99+/-0.18, and 1.02+/-0.25 g/kg/day, respectively and were significantly lower than those using immediate postdialysis BUN (P<0.05). 4) When the patients were divided according to the degree of PDUR (low PDUR group:<12%, high PDUR group: > or = 12%), high PDUR group was significantly higher than low PDUR group in hematocrit (27.0+/-2.6 vs. 23.5+/-3.6%, P=0.008), URR (64.3+/-5.4 vs. 55.8+/-6.8%, P=0.002), Kt/Vurea (1.26+/-0.17 vs. 1.03+/-0.18, P=0.002), and total recirculation rate (5.6+/-2.7 vs. 3.6+/-1.7%, P=0.05). There were no differences in age, sex, postdialysis body weight, ultrafiltration rate, blood flow, serum albumin, predialysis BUN, creatinine, and nPCR. 5) In multiple regression analysis, the independent factors affecting on PDUR were Kt/Vurea (beta=0.546, P<0.001), recirculation rate (beta=0.422, P<0.001), and hematocrit (beta=0.366, P=0.0017). In conclusion, we think that PDUR should be considered in hemodialysis patients when estimating dialysis delivery, especially if they had high Kt/ Vurea, recirculation rate, and hematocrit.