Reduction of carbamylated albumin by extended hemodialysis

Abstract

Introduction Among conventional hemodialysis (CHD) patients, carbamylated serum albumin (C-Alb) correlates with urea and amino acid deficiencies and is associated with mortality. We postulated that reduction of C-Alb by intensive HD may correlate with improvements in protein metabolism and cardiac function. Methods One-year observational study of in-center nocturnal extended hemodialysis (EHD) patients and CHD control subjects. Thirty-three patients receiving 4-hour CHD who converted to 8-hour EHD were enrolled, along with 20 controls on CHD. Serum C-Alb, biochemistries, and cardiac MRI parameters were measured before and after 12 months of EHD. Findings EHD was associated with reduction of C-Alb (average EHD change -3.20 mmol/mol [95% CI -4.23, -2.17] compared to +0.21 [95% CI -1.11, 1.54] change in CHD controls, P < 0.001). EHD was also associated with increases in average essential amino acids (in standardized units) compared to CHD (+0.38 [0.08, 0.68 95%CI]) vs. -0.12 [-0.50, 0.27, 95% CI], P = 0.047). Subjects who reduced C-Alb more than 25% were found to have reduced left ventricular mass, increased urea reduction ratio, and increased serum albumin compared to nonresponders, and % change in C-Alb significantly correlated with % change in left ventricular mass. Discussion EHD was associated with reduction of C-Alb as compared to CHD, and reduction of C-Alb by EHD correlates with reduction of urea. Additional studies are needed to test whether reduction of C-Alb by EHD also correlates with improved clinical outcomes.

Keywords: Carbamylated albumin; carbamylation; cardiac hypertrophy; extended duration hemodialysis; nocturnal hemodialysis; uremia.

Figure 1

Change in carbamylated albumin by treatment group. Figure shows unadjusted mean baseline and end of study (1 year) carbamylated albumin levels±stand errors in EHD patients (closed circle) and controls (open circle); mean values did not differ significantly between treatment groups at baseline (P=0.26). Values listed in figure are mean 12-month change in carbamylated albumin by treatment group and associated P value.

Figure 2

EHD reduces C-Alb in proportion to baseline C-Alb values. Figure shows association between change in carbamylated albumin over the 1-year study period and baseline C-Alb values. EHD patients are represented with closed circle and controls with open circles. Line shows linear association amongst EHD-treated subjects (r=0.74, P<0.001).

Figure 3

Correlation between change in carbamylated albumin and change in left ventricular mass. Figure shows correlation (r=0.47, P<0.001) between percent change carbamylated albumin and percent change left ventricular mass over the 1-year study period. EHD patients are represented with closed circle and controls with open circles. After adjusting for treatment group this correlation was attenuated but remained statistically significant (r=0.32, P=0.02).