Urea Concentration and Haemodialysis Dose

Abstract

Background. Dialysis dose is commonly defined as a clearance scaled to some measure of body size, but the toxicity of uraemic solutes is probably associated more to their concentrations than to their clearance. Methods. 619 dialysis sessions of 35 patients were modified by computer simulations targeting a constant urea clearance or a constant urea concentration. Results. Urea generation rate G varied widely in dialysis patients, rather independently of body size. Dialysing to eKt/V 1.2 in an unselected patient population resulted in great variations in time-averaged concentration (TAC) and average predialysis concentration (PAC) of urea (5.9–40.2 and 8.6–55.8 mmol/L, resp.). Dialysing to equal clearance targets scaled to urea distribution volume resulted in higher concentrations in women. Dialysing to the mean HEMO-equivalent TAC or PAC (17.7 and 25.4 mmol/L) required extremely short or long treatment times in about half of the sessions. Conclusions. The relation between G and V varies greatly and seems to be different in women and men. Dialysing to a constant urea concentration may result in unexpected concentrations of other uraemic toxins and is not recommended, but high concentrations may justify increasing the dose despite adequate eKt/V, std EKR, or std K/V.

Settings The Role of Methylglyoxal Accumulation on Cognitive Function Impairment of Chronic Hemodialysis Patients: an Observational Study

“…22 Cognitive impairment consists of dysfunction in at least two components of cognitive function. 22 Based on MMSE score, the severity of cognitive impairment is divided into three groups: mild (20)(21)(22)(23)(24), moderate (13)(14)(15)(16)(17)(18)(19)(20), and severe (<12). 23 Tests on the MMSE questionnaire include orientation tests, to assess awareness and memory, and registration test to assess working memory.…”

“…9,10 Multiple mechanisms have been suggested to be the cause of this impairment, such as vascular abnormalities and accumulation of uremic toxins in CKD. 11,12,13 In 2013, the European Uremic Toxin Work Group found over 90 uremic toxin groups in dialysis patients, one of them is methylglyoxal (MG). 11,12 MG has been associated with cognitive decline in studies involving diabetic rats, for it will react to lysine and arginine, forming advanced glycation end products (AGE) that can cause neuronal apoptosis.…”

Automatic hemodialysis prescriptions by urea kinetic modeling

“…The model creates a prescription that meets or exceeds both regardless how they are determined and related to each other. The concentration limits provide extra safety and modify the prescription if urea generation rate is high . Kt/V targets cannot be used due to varying frequency.…”

Adjusting Hemodialysis Dose for Protein Catabolic Rate

“…In a recent study, women had higher urea concentrations than men when simulating dialysis with equal eKt/V, stdEKR or stdK/V [5]. Dialyzing to an equal concentration would deliver more Kt/V to women.…”

“…In an unselected hemodialysis population, the variation of predialysis urea concentrations was 6.1-fold [5]. …”