Urea concentration gradients during conventional hemodialysis

Sombolos, Kostas; Natse, Taïsir; Zoumbaridis, Nikos; Mavromatidis, K.; Karagianni, Anna; Scandalos, J.; Fitili, Christina

doi:10.1016/s0272-6386(96)90102-x

Cited by 8 publications

(3 citation statements)

References 6 publications

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“…HD rats had higher BUN at the beginning of HD, and the BUN reduction rate by HD was smaller (pre-dialysis BUN: 117 mg/dL, post-dialysis BUN: 106 mg/dL) compared to that in a previous clinical report [38]. On the other hand, BUN reduction rate at the inlet and outlet of the dialyzer 1 h after the initiation of HD was similar to that in the clinical report (BUN at the inlet: 111 mg/dL, BUN at outlet: 18 mg/dL) [38]. Therefore, it can be concluded that the miniaturized dialyzer in HD rats showed a performance similar to that in the clinical dialyzer.…”

Section: Plos Onecontrasting

confidence: 69%

In vivo evaluation of drug dialyzability in a rat model of hemodialysis

et al. 2020

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It is important to calculate the drug removal by hemodialysis (HD) for drug dosing regimens in HD patients. However, there are limited and inconsistent information about the dialyzability of drugs by HD. Therefore, the aim of our study is to evaluate drug removal by utilizing a rat model of HD (HD rat) and to extrapolate this result to the drug removal rate in HD patients. HD rats received bilateral nephrectomy and HD for 2 h. The dialysis removal of 6 drugs was evaluated in HD rats. Dialysis efficiency, plasma protein binding rate (PBR) and distribution volume (Vd) of drugs were also measured. Furthermore, we examined the correlation between the dialyzability of drug in HD rats and humans and constructed the prediction formula of the drug dialyzability in HD patients. The clearance of urea and creatinine and normalized dialysis dose in HD rats were 0.83 ± 0.07 mL/min, 0.70 ± 0.08 mL/min, and 0.13 ± 0.06, respectively. The drug dialyzability in HD rats was similar to reported clinical data except for doripenem. A higher correlation was observed between drug dialyzability in reported clinical data and HD rats which were adjusted for PBR (r 2 = 0.936; p < 0.001) compared to unadjusted (r 2 = 0.812; p = 0.009). Therefore, we constructed the prediction formula of the drug dialyzability in HD patients by utilizing the HD rat model and PBR. This study is useful for evaluating the dialyzability of high-risk drugs in a clinical setting and might provide appropriate preclinical dialyzability data for new drug.

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Section: Plos Onecontrasting

confidence: 69%

In vivo evaluation of drug dialyzability in a rat model of hemodialysis

et al. 2020

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“…In fact, urea concentration gradients during HD are reported to be relatively constant [20,21]. By utilizing M Bv and M r , the 2CM can be transformed into a variable-volume one-compartmental model (1CM).…”

Section: Discussionmentioning

confidence: 99%

Analysis of Urea Nitrogen and Creatinine Kinetics in Hemodialysis: Comparison of a Variable-Volume Two-Compartment Model with a Regional Blood Flow Model and Investigation of an Appropriate Solute Kinetics Model for Clinical Application

Yamada¹,

Hiraga²,

Akiba

et al. 2000

Blood Purif

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To investigate an appropriate solute kinetics model for clinical application, we analyzed urea nitrogen (UN) and creatinine (Cr) kinetics by a variable-volume two-compartmental model (2CM) and a regional blood flow model (RBF) in 44 hemodialysis patients with varying proportions of first compartmental volume and regional volume (p₁). Solute kinetics could not be solved in some of the patients with higher p₁ values, and there were more solution failures by the RBF than by the 2CM. The solute generation rate (g) and solute distribution volume in the dry state (V_D) increased with increases in p₁ in both models, but there were some differences between the two models. When g was normalized by V_D, it became relatively constant, irrespective of the p₁ value or model used (0.133 ± 0.029 mg/min/l by the 2CM and 0.132 ± 0.029 mg/min/l by the RBF for UN; 0.0200 ± 0.0049 mg/min/l by the 2CM and 0.0198 ± 0.0048 mg/min/l by the RBF for Cr). The intercompartmental mass transfer coefficient (K_c; liters/min) calculated by the 2CM decreased as p₁ increased (K_c = –1.77·p₁ + 1.16, p < 0.0001, R = 0.999 for UN; K_c = –0.847·p₁ + 0.556, p < 0.0001, R = 1.000 for Cr). The systemic blood flow (Q_sys; liters/min) calculated by the RBF also decreased as p₁ increased (Q_sys = –11.1·p₁ + 6.21, p < 0.0005, R = 1.000 for UN; Q_sys = –5.22·p₁ + 2.90, p < 0.001, R = 0.999 for Cr). Since the RBF more frequently failed to solve the solute kinetics and since there was a difference in its Q_sys values for UN and Cr, the 2CM was considered to be a superior model. When p₁ was extremely low, the 2CM could be transformed into a modified variable-volume one-compartment model (1CM) which presented a similar g/V_D (0.133 ± 0.029 for UN; 0.0200 ± 0.0048 for Cr). This modified 1CM was considered to satisfy appropriate conditions for clinical application, since it is simpler than the 2CM and provides useful information on the dialysis dose.

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“…The measurement of recirculation using urea basedmethods has been fraught with difficulty, largely a resultof problems in obtaining the “systemic” sample ofblood necessary for making this measurement (13, 18). Itis now well accepted that use of peripheral venous bloodfor the systemic sample overestimates recirculationsubstantially because the BUN from this site exceeds thatin arterial blood as a result of arteriovenousdisequilibrium (due to cardiopulmonary recirculation) (19–22) and venovenousdisequilibrium (due toregional blood flow inequalities) (23–26). Two needle methods in which thesystemic sample is drawn from the arterial line have the potential advantage ofeliminating both ofthese causes of a falsely high BUN while also eliminating an unnecessaryvenipuncture.…”

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confidence: 99%

Recognition of the Failing Vascular Access: A Current Perspective

Sherman

Besarab

Schwab

et al. 1997

Seminars in Dialysis

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SJS) and the Austin Diagnostic Clinic, Austin, Texas (G.A.B.)Recognizing and treating the failed and failing vascular access is a subject of growing interest and concern among nephrologists. Even though a large percentage of vascular access problems are handled in the outpatient setting, access complications still account for 21% of all hospitalizations for chroinc dialysis patients and are a growing source of morbidity and cost (1-4). The increasing use of tunneled superior vena cava catheters (4, 5) and more recently, inferior vena cava catheters (6,7,8) as well as the attention being paid to construction of exotic tertiary access (9) all attest to the increasing difficulty of maintaining vascular access patency in an aging population. Lost of all vascular access sites, while still relatively rare, is a feared and devastating complication, particularly for the patient unable to receive peritoneal dialysis.The current thrust of investigative efforts in this area is aimed at prolonging the functional life of vascular accesses (10). Long term, there may be clinically important progress in areas such as the development of direct inhibitors of the stenotic process. Up to this point, however, the most useful clinical technique has been to use post-dialyzer venous drip chamber pressures (''venous pressure'') and recirculation measurements to screen patients for functionally significant stenotic lesions (11-15) which then can be treated by surgery or angioplasty to decrease the risk of clotting and loss of the access site (16).The measurement of recirculation using urea based methods has been fraught with difficulty, largely a result of problems in obtaining the ''systemic'' sample of blood necessary for making this measurement (13, 18). It is now well accepted that use of peripheral venous blood for the systemic sample overestimates recirculation substantially because the BUN from this site exceeds that in arterial blood as a result of arteriovenous disequilibrium (due to cardiopulmonary recirculation) (19-22) and venovenous disequilibrium (due to regional blood flow inequalities) (23-26). Two needle methods in which the systemic sample is drawn from the arterial line have the potential advantage of eliminating both of these causes of a falsely high BUN while also eliminating an unnecessary venipuncture.Recent advances in measuring recirculation using non urea based methods have shown that recirculation is absent (0%) in a properly cannulated, well functioning access (27-32). However, two needle methods have typically yielded results significantly greater than 0% in most patients. This is partially explained by the normal laboratory variability in urea measurement (33) but, probably of greater consequence, is the typical 30 second (or more) delay in sampling after slowing or stopping the blood pump (15). It now appears that the BUN in arterial line blood will begin to rebound within about 15 seconds of slowing or stopping dialysis, an interval shorter than previously appreciated (34). As a result, many of the two need...

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Urea concentration gradients during conventional hemodialysis

Cited by 8 publications

References 6 publications

In vivo evaluation of drug dialyzability in a rat model of hemodialysis

In vivo evaluation of drug dialyzability in a rat model of hemodialysis

Analysis of Urea Nitrogen and Creatinine Kinetics in Hemodialysis: Comparison of a Variable-Volume Two-Compartment Model with a Regional Blood Flow Model and Investigation of an Appropriate Solute Kinetics Model for Clinical Application

Recognition of the Failing Vascular Access: A Current Perspective

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