A Regional Blood Circulation Alternative to In-series Two Compartment Urea Kinetic Modeling

Schneditz, Daniel; Jc, Van Stone; Jt, Daugirdas

doi:10.1097/00002480-199307000-00086

Cited by 59 publications

(34 citation statements)

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“…Nevertheless, after dialysis the concentration of urea in plasma increases rapidly in an initial period, usually until 60 min postdialysis [62]. This postdialytic urea rebound (PDUR) is a multifactorial event [63, 64]. Vascular access and cardiopulmonary recirculation occurs within the first 2 to 3 min of discontinuing hemodialysis and account for 60 to 70% of total PDUR.…”

Section: Guideline 10: Urea Dialytic Kinetic Dialysis Dose and Protmentioning

confidence: 99%

“…IC versus EC, urea dysequilibrium at the end of the dialysis session and tissue re-equilibration which is usually complete within one hour postdialysis, reaching the equilibrated postdialytic plasma urea concentration. For highly diffusible substances such as urea, distribution in total body water (TBW) seems to be limited by cardiovascular flow rather than diffusion [64]. The apparent IC–EC two-pool model should perhaps be the result of a regional blood flow distribution system in which approximately 80% of TBW (and thereby urea) is located in muscle, bone, and skin, with organs receiving only 20 to 30% of the cardiac output, i.e.…”

Section: Guideline 10: Urea Dialytic Kinetic Dialysis Dose and Protmentioning

confidence: 99%

“…hypovolemia, hypertension, heart failure, hematocrit, alkalosis or acidosis, low-temperature dialysate, can explain PDUR variability. The URR variability could also be explained by vascular resistance changes over the dialysis session, at least for urea [64]. …”

Section: Guideline 10: Urea Dialytic Kinetic Dialysis Dose and Protmentioning

confidence: 99%

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Hemodialysis in children: general practical guidelines

Fischbach¹,

et al. 2005

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Over the past 20 years children have benefited from major improvements in both technology and clinical management of dialysis. Morbidity during dialysis sessions has decreased with seizures being exceptional and hypotensive episodes rare. Pain and discomfort have been reduced with the use of chronic internal jugular venous catheters and anesthetic creams for fistula puncture. Noninvasive technologies to assess patient target dry weight and access flow can significantly reduce patient morbidity and health care costs. The development of urea kinetic modeling enables calculation of the dialysis dose delivery, Kt/V, and an indirect assessment of the intake. Nutritional assessment and support are of major importance for the growing child. Even if the validity of these "urea only" data is questioned, their analysis provides information useful for follow-up. Newer machines provide more precise control of ultrafiltration by volumetric assessment and continuous blood volume monitoring during dialysis sessions. Buffered bicarbonate solutions are now standard and more biocompatible synthetic membranes and specific small size material dialyzers and tubing have been developed for young infants. More recently, the concept of "ultrapure" dialysate, i.e. free from microbiological contamination and endotoxins, has developed. This will enable the use of hemodiafiltration, especially with the on-line option, which has many theoretical advantages and should be considered in the case of maximum/optimum dialysis need. Although the optimum dialysis dose requirement for children remains uncertain, reports of longer duration and/or daily dialysis show they are more effective for phosphate control than conventional hemodialysis and should be considered at least for some high-risk patients with cardiovascular impairment. In children hemodialysis has to be individualized and viewed as an "integrated therapy" considering their longterm exposure to chronic renal failure treatment. Dialysis is seen only as a temporary measure for children compared with renal transplantation because this enables the best chance of rehabilitation in terms of educational and psychosocial functioning. In long term chronic dialysis, however, the highest standards should be applied to these children to preserve their future "cardiovascular life" which might include more dialysis time and on-line hemodiafiltration with synthetic high flux membranes if we are able to improve on the rather restricted concept of small-solute urea dialysis clearance.

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Section: Guideline 10: Urea Dialytic Kinetic Dialysis Dose and Protmentioning

confidence: 99%

Section: Guideline 10: Urea Dialytic Kinetic Dialysis Dose and Protmentioning

confidence: 99%

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Hemodialysis in children: general practical guidelines

Fischbach¹,

et al. 2005

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“…Schneditz and Daugirdas proposed an alternative to this diffusion-based model, identifying the site of urea sequestration as organs which are relatively poorly perfused, such as skin and muscle [49,50]. The two models are mathematically equivalent, with K ei playing the same role as Q l , the fraction of cardiac output destined for the low-perfusion compartment [51].…”

Section: The Mechanics Of Measuring Dialysis Dosementioning

confidence: 99%

Reassessing hemodialysis adequacy in children: the case for more

Sharma

2001

Pediatric Nephrology

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Several lines of evidence support an upward revision in pediatric hemodialysis dose guidelines: Although current recommendations are derived largely from studies of dialysis mortality and morbidity in adults, recent reports of improved growth and pubertal development with more intensive dialysis highlight the need for appropriate pediatric outcome measures in the assessment of dialysis adequacy, particularly in prepubertal patients. Even if adult studies can be extrapolated directly to younger patients, reappraisal of these data would appear to justify an increase in recommended dialysis clearances, based on higher dietary protein intake and accumulating evidence that adults, too, benefit from more intensive therapy. Suboptimal dialysis may also occur when dialysis dose is overestimated by urea kinetic models that fail to account for compartment effects and post-treatment urea rebound. Studies comparing the available models in pediatric patients have appeared recently, and a few models have been developed specifically for pediatric applications. These should permit more reliable estimates of solute clearance for a much-needed multicenter trial to clarify optimal dialysis therapy for growing children.

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“…Based on this physiological disproportion of CO distribution, Schneditz et al . proposed the regional blood flow (RBF) model and explained the post-dialytic rebound phenomena for urea and creatinine [26,27], Smye et al . first employed this RBF model for explaining the effect of intra-dialytic exercise with the assumption of increased CO [28].…”

Section: Introductionmentioning

confidence: 99%

Comparison of toxin removal outcomes in online hemodiafiltration and intra-dialytic exercise in high-flux hemodialysis: A prospective randomized open-label clinical study protocol

et al. 2012

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BackgroundMaintenance hemodialysis (HD) patients universally suffer from excess toxin load. Hemodiafiltration (HDF) has shown its potential in better removal of small as well as large sized toxins, but its efficacy is restricted by inter-compartmental clearance. Intra-dialytic exercise on the other hand is also found to be effective for removal of toxins; the augmented removal is apparently obtained by better perfusion of skeletal muscles and decreased inter-compartmental resistance. The aim of this trial is to compare the toxin removal outcome associated with intra-dialytic exercise in HD and with post-dilution HDF.Methods/designThe main hypothesis of this study is that intra-dialytic exercise enhances toxin removal by decreasing the inter-compartmental resistance, a major impediment for toxin removal. To compare the HDF and HD with exercise, the toxin rebound for urea, creatinine, phosphate, and β2-microglobulin will be calculated after 2 hours of dialysis. Spent dialysate will also be collected to calculate the removed toxin mass. To quantify the decrease in inter-compartmental resistance, the recently developed regional blood flow model will be employed. The study will be single center, randomized, self-control, open-label prospective clinical research where 15 study subjects will undergo three dialysis protocols (a) high flux HD, (b) post-dilution HDF, (c) high flux HD with exercise. Multiple blood samples during each study session will be collected to estimate the unknown model parameters.DiscussionThis will be the first study to investigate the exercise induced physiological change(s) responsible for enhanced toxin removal, and compare the toxin removal outcome both for small and middle sized toxins in HD with exercise and HDF. Successful completion of this clinical research will give important insights into exercise effect on factors responsible for enhanced toxin removal. The knowledge will give confidence for implementing, sustaining, and optimizing the exercise in routine dialysis care. We anticipate that toxin removal outcomes from intra-dialytic exercise session will be comparable to that obtained by standalone HDF. These results will encourage clinicians to combine HDF with intra-dialytic exercise for significantly enhanced toxin removal.Trial registrationClinicalTrials.gov number, NCT01674153

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A Regional Blood Circulation Alternative to In-series Two Compartment Urea Kinetic Modeling

Cited by 59 publications

References 0 publications

Hemodialysis in children: general practical guidelines

Hemodialysis in children: general practical guidelines

Reassessing hemodialysis adequacy in children: the case for more

Comparison of toxin removal outcomes in online hemodiafiltration and intra-dialytic exercise in high-flux hemodialysis: A prospective randomized open-label clinical study protocol

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