Formal Urea Kinetic Modeling Research Articles

Using the Intelligent System to Improve the Delivered Adequacy of Dialysis by Preventing Intradialytic Complications

Acute kidney failure patients while detoxificated by hemodialysis (HD) mostly or continuously faced regular problems such as low blood pressure (hypotension), muscle cramps, nausea, or vomiting. Higher intradialytic symptom leads to low-quality HD treatment. Although more known therapeutic interventions are used to relieve the HD side effects, this study was designed to investigate how intelligent systems can make highly beneficial alterations in dialysis facilities and equipment to ease intradialytic complications and help the staff deliver high-quality treatment. A search was performed among relevant research articles based on nonpharmacological intervention methods considered to prevent adverse effects of renal replacement therapy until 2020 in the PubMed databases using the terms “intradialytic complications,” “intradialytic complication interventions,” “nonpharmacological interventions,” “intradialytic exercises,” and “adequacy calculation methods.” Studies included the prevalence of intradialytic complications, different strategies with the aim of preventing complications, the outcome of intradialytic exercises on dialysis symptoms, and dialysis dose calculation methods. The results showed the incidence of hypotension varying between 5% and 30%, fatigue, muscular cramps, and vomiting as the most common complications during dialysis, which greatly affect the outcome of HD sessions. To prevent hypotension, ultrafiltration profiling, sodium modeling, low dialysate temperature, and changing the position to Trendelenburg are some strategies. Urea reduction ratio (URR), formal urea kinetic modeling (FUKM), formal single-pool urea kinetics, and online clearance monitoring (OCM) are methods for calculating the delivered dose of dialysis in which OCM is a low-cost and accessible way to monitor regularly the quality of dialysis delivered. Integration of the chair and HD machine which is in direct contact with the patient provides an intelligent system that improves the management of the dialysis session to enhance the quality of healthcare service.

Prediction equation for calculating residual kidney urea clearance using urine collections for different hemodialysis treatment frequencies and interdialytic intervals.

The purpose of the study was to explore the precision of an equation designed to estimate residual kidney urea clearance (KRU) from interdialytic urine collection data and pre-hemodialysis (HD) serum urea nitrogen (SUN) in different hemodialysis treatment schedules. The generalizability of the proposed equation was tested in 32 731 HD treatments where urine was collected prior to a dialysis session, mostly for 24 h but sometimes longer, in patients being dialyzed 1-4 times/week. The residual kidney urea clearance estimating equation predicted a KRU that matched the one computed by formal modeling within 5% in >98% of sessions analyzed. The errors in estimated versus modeled KRU for interdialytic intervals (IDIs) of 2, 3, 4 and 7 days, were 1.6 ± 1.5%, -0.4 ± 1.6%, 0.9 ± 1.6%, and 1.5 ± 1.2%, respectively. Percent errors were similar for schedules of 1-4/week with the exception of urine collection during the 2-day interval of a 2:5-day twice-weekly schedule; here error averaged 5.0 ± 1.2%. Use of the average of the SUN values at the start and end of the collection period overestimated modeled KRU by 11.3 ± 4.5%, whereas an equation suggested by others underestimated modeled KRU by -9.9 ± 3.4%. The equation tested predicts values for KRU that are similar to those obtained from formal urea kinetic modeling, with percent errors that only rarely exceed 5%. It gives relatively precise results for a wide range of HD treatment schedules, IDIs and urine collection periods. chronic hemodialysis, clearance, guidelines, hemodialysis, predialysis.

Energy metabolism, body composition, and urea generation rate in hemodialysis patients

Hemodialysis (HD) adequacy is currently assessed using normalized urea clearance (Kt/V), although scaling based on Watson volume (V) may disadvantage women and men with low body weight. Alternative scaling factors such as resting energy expenditure and high metabolic rate organ mass have been suggested. The relationship between such factors and uremic toxin generation has not been established. We aimed to study the relationship between body size, energy metabolism, and urea generation rate. A cross-sectional cohort of 166 HD patients was studied. Anthropometric measurements were carried on all. Resting energy expenditure was measured by indirect calorimetry, fat-free mass by bio-impedance and total energy expenditure by combining resting energy expenditure with a questionnaire-derived physical activity data. High metabolic rate organ mass was calculated using a published equation and urea generation rate using formal urea kinetic modeling. Metabolic factors including resting energy expenditure, total energy expenditure and fat-free mass correlated better with urea generation rate than did Watson volume. Total energy expenditure and fat-free mass (but not Watson Volume) were independent predictors of urea generation rate, the model explaining 42% of its variation. Small women (<mean V) had a significantly higher urea generation rate per kg than women with higher V. Similarly urea generation rate normalized to fat-free mass was significantly greater in small women than in all others (significant only in comparison to larger men). Exercise-related energy expenditure correlated significantly with urea generation rate. Energy metabolism, body composition and physical activity play important roles in small solute uremic toxin generation in HD patients and hence may impact on minimum dialysis requirements. Small women generate relatively more small solute toxins than other groups and thus may have a higher relative need for dialysis.

CHAPTER 1

CHAPTER 1

Indices for assessment of hemodialysis adequacy: A comparison of different formulae

Of the various indices used in the assessment of dialysis adequacy, fractional urea clearance controlled for volume of distribution "Kt/V" remains the most widely used. Its determination is best performed by formal urea kinetic modeling (UKM), which is laborious and cumbersome, and the computational softwares are largely unavailable, particularly in developing countries. Consequently, different equations have been developed that approximate the formal UKM determination. Of the available formulae, that from second-generation logarithmic equation have been found to approximate values derived from formal UKM closely. We set out to determine the clinical utility of percent reduction of urea and Kt/V formulae derived from it, using the logarithmic equation as the standard.

The Mathematical Basis, Clinical Application and Limitations of Ionic Dialysance

Morbidity and mortality in hemodialysis patients are closely related to dialysis adequacy. Unfortunately, in real life, the dialysis dose that is delivered during each hemodialysis session, for various reasons, may not even be close to that prescribed. It would be ideal if one could assess and verify the dialysis dose delivered in every dialysis treatment. Formal urea kinetic modeling (Kt/V) has been used widely to quantify the dialysis dosage. Recently, ionic dialysance is becoming more popular as a method to assess the delivered Kt/V of dialysis treatment. Its mathematical basis is reviewed, and its pitfalls, limitations and clinical relevance are briefly described.

Natural logarithmic estimates of Kt/V in the pediatric hemodialysis population.

The natural logarithm formula for Kt/V proposed by Daugirdas is recognized as a valid and simple alternative to formal urea kinetic modeling (UKM) in adults receiving hemodialysis. No data have been published to validate the use of this formula in infants, children, and adolescents. We compared Kt/V derived by formal UKM with the natural logarithmic formula for 103 treatments in 21 pediatric end-stage renal disease patients receiving chronic hemodialysis. Values for Kt/V derived by formal UKM ranged from 0.65 to 2.06. Patients ranged in age from 1.8 to 22.5 years and in dry weight from 10.2 to 82.5 kg. The largest percent error between the two methods for any data point was less than 6%. The total error (absolute value percent error + 2 SD) was less than 6% across the entire range of dry weights. Our data show excellent agreement between formal UKM and the natural logarithm formula for Kt/V in pediatric hemodialysis patients, even those weighing less than 30 kg. These results support the use of the natural logarithm formula as a valid alternative to formal UKM in children. The simplicity of this formula should allow for the use of Kt/V as the best measure to study the relationship between delivered dialysis dose and outcomes in children.

Kt/V by Urea Kinetic Modeling: Variability in Calculated V

One of the main reasons for doing formal urea kinetic modeling is to determine V (the urea distribution volume). However, V seems to vary quite widely in individual patients even if “equilibrated” postdialysis blood urea nitrogen (BUN) values are used. Why?

Accuracy of the urea reduction ratio in predicting dialysis delivery

Since the mechanistic analysis of the National Cooperative Dialysis Study data [1], measurement of the KtIV urea has increasingly been recognized as a valuable adjunct in the care of chronic hemodialysis patients. Formal urea kinetic modeling (UKM) has been criticized, however, as being too difficult and unnecessaiy [2]. Easier to perform estimations of Kt/V which incorporate the urea reduction ratio (URR) have come into widespread use [2—5]. Use of the URR itself has also been recommended as an acceptable means of quantifying delivered dialysis [6], a suggestion that has been endorsed by a U.S. governmental agency [7] and a national organization of nephrologists [8]. Theoretical considerations suggest that the actual KtIV for any given URR may vary over a considerable range [9, 10]. We sought to determine the extent of this range in Kt/V (as determined by formal UKM) for differing URR values in a large multicenter, prospective study.

The Effect of Dialyzer Reuse on Dialysis Delivery

It is well documented that the reprocessing of dialyzers may reduce their solute clearance capabilities. However, the effect of dialyzer reuse has never been assessed in an uncontrolled clinical practice setting. We addressed this issue in a prospective 436-patient, 34-center study. All patients underwent formal urea kinetic modeling monthly, usually for 3 sequential months. Dialyzers were reprocessed and reused in the usual manner for each unit. As a result, urea kinetic modeling was performed in individual patients using dialyzers with differing numbers of prior uses. For each patient, Kt/V urea for the treatment using the dialyzer with the most reuses (mean, 13.8) was compared with that with the treatment using the dialyzer with the fewest reuses (mean, 3.8). The mean Kt/V delivered for high reuse treatments was significantly lower than that for low reuse treatments (1.05 v 1.10, P = 0.002). Prescribed Kt/V in high and low reuse treatments was identical. Individual centers appeared to differ substantially (P = 0.06) in the effect of reuse on delivered Kt/V. Of the 23 centers using formalin-based reprocessing, an average difference of > or = 0.12 (mean, 0.17) in Kt/V between high and low reuse treatments was seen in 10 centers. Dialyzer reprocessing significantly impairs dialysis delivery, an effect that may be related to the methods and procedures in individual dialysis centers.

A Model's Just a Model: Formal Urea Kinetic Modeling Is Not a Necessity

Seminars in DialysisVolume 6, Issue 3 p. 156-159 A Model's Just a Model: Formal Urea Kinetic Modeling Is Not a Necessity Robert H. Barth, Corresponding Author Robert H. Barth Department of Veterans Affairs Medical Center and the State University of NY Health Science Center, Brooklyn, New YorkAddress correspondence to: Robert H. Barth, MD, Chief, Hemodialysis, DVA Medical Center, 800 Poly Place, Brooklyn, NY 11209.Search for more papers by this author Robert H. Barth, Corresponding Author Robert H. Barth Department of Veterans Affairs Medical Center and the State University of NY Health Science Center, Brooklyn, New YorkAddress correspondence to: Robert H. Barth, MD, Chief, Hemodialysis, DVA Medical Center, 800 Poly Place, Brooklyn, NY 11209.Search for more papers by this author First published: May 1993 https://doi.org/10.1111/j.1525-139X.1993.tb00285.xCitations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume6, Issue3May 1993Pages 156-159 RelatedInformation

Formal Urea Kinetic Modeling Is Necessary with Current Dialytic Therapy

Formal Urea Kinetic Modeling Is Necessary with Current Dialytic Therapy