Imprecision of the hemodialysis dose when measured directly from urea removal

被引:30
作者
Depner, TA
Greene, T
Gotch, FA
Daugirdas, JT
Keshaviah, PR
Star, RA
机构
[1] Univ Calif Davis, Div Nephrol, Sacramento, CA 95817 USA
[2] Cleveland Clin Fdn, Dept Biostat & Epidemiol, Cleveland, OH 44195 USA
[3] Univ Calif San Francisco, Dept Nephrol, San Francisco, CA 94143 USA
[4] Vet Adm Med Ctr, Dept Res, Chicago, IL USA
[5] Baxter Clin Engn Lab, Minneapolis, MN USA
[6] Univ Texas, SW Med Ctr, Dept Internal Med, Dallas, TX USA
关键词
direct dialysate quantification; urea kinetic modeling; error analysis; dialysate-side modeling; hemodialysis adequacy;
D O I
10.1046/j.1523-1755.1999.00269.x
中图分类号
R5 [内科学]; R69 [泌尿科学(泌尿生殖系疾病)];
学科分类号
1002 ; 100201 ;
摘要
Background. The postdialysis blood urea nitrogen (BUN; C-t) is a pivotal parameter for assessing hemodialysis adequacy by conventional blood-side methods, but C-t is relatively unstable because of hemodialysis-induced disequilibrium. The uncertainty associated with this method is potentially reduced or eliminated by measuring urea removed on the dialysate side, a more direct approach that can determine adequacy from the fraction of urea removed and by substituting an estimate of the equilibrated postdialysis BUN (C-eq) for C-t. For a patient with a known urea volume (V), C-eq, the equilibrated Kt/V (eKt/V), and the solute removal index (SRI) can be calculated from the predialysis BUN (C-0), total urea nitrogen removed (A), and V from simple mass balance calculations (dialysate/volume method). However, a theoretical error analysis showed that relatively small errors in A, C-0, or V are magnified when SRI or eKt/V is calculated using this method, especially at higher eKt/V values (for example, if eKt/V = 1.4 per dialysis, a 7% dialysate collection error causes a 20% error in eKt/V). Methods. During three to four baseline dialyses in each of 39 patients enrolled in the pilot phase of the HEMO Study, "A" was measured using an instrument that sampled dialysate frequently (Biostat(R)), and V was calculated from A, Co, and C-eq (median CV for V = 5.6%). The mean V was then applied to the dialysate/volume method to estimate eKt/V and SRI during two to five subsequent dialyses per patient (comparison dialyses). The accuracy and precision of these estimates were assessed by comparing them with eKt/V and SRI derived from a direct measurement of C-eq drawn 30 minutes after dialysis (reference method), from mathematical curve-fitting of sequential dialysate urea concentrations (dialysate curve-fit method), and from another blood-side method that estimates eKt/V from single pool Kt/V and the fractional rate of solute removal (rate method): eKt/V = spKt/V - 0.6 K/V + 0.03. Results. During: 125 comparison dialyses, median absolute errors for calculated eKt/V compared with the reference method were 0.169, 0.061, and 0.071 for the dialysate/volume method, the rate method, and the dialysate curve-fitting method, respectively. The corresponding correlation coefficients were 0.47, 0.88, and 0.81. For SRI, median absolute errors were 0.044, 0.018, and 0.027, and the correlation coefficients were 0.54, 0.85, and 0.74 for the three methods. Conclusions. The precision of eKt/V and SRI measurements was significantly lower for the dialysate/volume method compared with the blood-side methods. Inclusion of the dialysate curve analysis provided by the Biostat(R) restored precision to the dialysate method to a level comparable to that of the blood-side methods. New techniques employing dialysate urea analysis should include a concentration profile to avoid these inherent methodological errors and assure the accuracy of eKt/V and SRI.
引用
收藏
页码:635 / 647
页数:13
相关论文
共 32 条
  • [1] [Anonymous], CONTEMP DIAL NEPHROL
  • [2] Precise quantification of dialysis using continuous sampling of spent dialysate and total dialysate volume measurement
    Argiles, A
    Ficheux, A
    Thomas, M
    Bosc, JY
    Kerr, PG
    Lorho, R
    Flavier, JL
    Stec, F
    Adele, C
    Leblanc, M
    Garred, LJ
    Canaud, B
    Mion, H
    Mion, CM
    [J]. KIDNEY INTERNATIONAL, 1997, 52 (02) : 530 - 537
  • [3] ESTIMATION OF THE COEFFICIENT OF VARIATION FROM LABORATORY ANALYSIS OF SPLIT SPECIMENS FOR QUALITY-CONTROL IN CLINICAL-TRIALS
    CONNETT, JE
    LEE, WW
    [J]. CONTROLLED CLINICAL TRIALS, 1990, 11 (01): : 24 - 36
  • [4] Daugirdas J T, 1995, Adv Ren Replace Ther, V2, P295
  • [5] DAUGIRDAS JT, 1995, ASAIO J, V41, pM719, DOI 10.1097/00002480-199507000-00107
  • [6] Depner T.A., 1991, PRESCRIBING HEMODIAL, P91
  • [7] REFINING THE MODEL OF UREA KINETICS - COMPARTMENT EFFECTS
    DEPNER, TA
    [J]. SEMINARS IN DIALYSIS, 1992, 5 (02) : 147 - 154
  • [8] Depner TA, 1996, J AM SOC NEPHROL, V7, P464
  • [9] PITFALLS IN QUANTITATING HEMODIALYSIS
    DEPNER, TA
    [J]. SEMINARS IN DIALYSIS, 1993, 6 (02) : 127 - 133
  • [10] Quantifying hemodialysis
    Depner, TA
    [J]. AMERICAN JOURNAL OF NEPHROLOGY, 1996, 16 (01) : 17 - 28