Online Clearance Monitoring Research Articles

Use of ionic dialysance to calculate Kt/V in pediatric hemodialysis

Online clearance (OLC) monitor measures conductivity difference between dialysate entering and leaving the dialyser. Derived ionic dialysance (ID) represents effective urea clearance from which Kt/V is calculated, allowing Kt/V monitoring at every treatment without blood sampling. We tested ID accuracy in children and provide recommendations for its use. Using Fresenius machines 2008 K with built-in OLC monitors, we studied 45 hemodialysis (HD) sessions and 168 calculated Kt/V results in 11 patients. Urea distribution volume (V), needed to calculate Kt/V from ID, was estimated using three methods: Mellits and Cheek (MC), KDOQI recommended total body water nomograms (TBWN) and OLC-derived independent from tested HD sessions. Reference spKt/V from pre- and post-HD BUN (Daugirdas) was compared with Kt/V calculated from ID using three different estimated V's. ID was accurate in calculating Kt/V in children when V derived from OLC was used (P = 0.42), with absolute error 0.14 ± 0.12. If TBWN-derived V was used, Kt/V was consistently underestimated by 0.32 ± 0.22. TBWN-derived V can still be recommended for use with OLC for monitoring trend in Kt/V, if underestimation of spKt/V of average 0.3 is accounted for. MC-derived V results in even greater underestimation of spKt/V and therefore cannot be recommended for use with OLC.

Measurement of Vascular Access Flow by Online Clearance Monitor in Online Hemodiafiltration

Background: Measurement of ionic dialysance has been shown to accurately determine urea dialyzer clearance and vascular access flow rate (Qa) in diffusive hemodialysis. Recently, online clearance monitoring (OCM) in an online hemodiafiltration (OL-HDF) machine could accurately measure urea dialyzer clearance. In the present study, OCM was utilized to assess the Qa in OL-HDF. Methods: In 32 stable end-stage renal disease patients undergoing predilution OL-HDF, the values of Qa measured by the OCM technique (Qa_OCMT) in a Fresenius 4008H HDF machine were compared with those determined by the standard ultrasound dilution technique (Qa_UDT). Results: The values of Qa_UDT and Qa_OCMT measured at the beginning of the HDF session were 800.5 ± 910.3 and 794.6 ± 895.4 ml/min (nonsignificant). There was a significant correlation between the two techniques (r = 0.95, p < 0.01). A Bland-Altman plot demonstrated a good agreement. Conclusion: The vascular access flow determined by OCM, which is integrated mostly in the current HDF machine, is highly accurate, easy to perform, and economical and can be used for vascular access surveillance in OL-HDF.

Comparison of Different Methods to Assess Fistula Flow

Background: We compared three access flow (AF) monitoring techniques: blood dilution using ultrasound (US), blood temperature monitoring (BTM), and online clearance monitoring (OCM), and investigated the impact of dialyzer blood flow (Q_B), measurement time point and patient’s position. Methods: US, BTM and OCM were performed in 20 hemodialysis (HD) patients at Q_B300. OCM was unreliable for measuring AF and was therefore further omitted. US and BTM measurements were repeated in 10 patients at Q_B200 ml/min, in 15 patients at the first weekly HD start and end and at the midweek HD start, and switching position during midweek HD. Results: AFs of 1,104 ± 607 (US) and 1,264 ± 664 ml/min (BTM) significantly correlated. No differences were found comparing AF at Q_B300 and Q_B200. AF decreased from HD start to end, while no difference was found changing patient’s position. Conclusion: AFs by BTM and US correlated well and may be measured at Q_B200–300 in all measured positions.

Measuring Kt by ionic dialysance is a useful tool for assessing dialysis dose in critical patients

To evaluate the Kt assessed through ionic dializance (KtOCM) in UCI patients undergoing renal replacement therapy for acute kidney injury, comparing the results with those obtained through the urea removal rate method determined by dialyzate collection (Kturea). 18 adult UCI staying individuals suffering from renal replacement therapy requiring oliguric acute kidney injury were included in this study. RRT consisted in intermittent or extended hemodialysis performed through a Fresenius 4008E dialysis machine equipped with an on-line clearance monitor (OCM Fresenius). The KtOCM results were provided automatically. The Spearman correlation test was used to assess the relationship between the two exploratory methods and the Student s t test to compare the results obtained by the KtOCM and the Kturea. 35 treatments were analyzed. There were not statistically significant differences between the results form the KtOCM and the Kturea (34.9 +/- 10.69 vs 32.78 +/- 11.31, p = NS). A remarkable association was find between both methods (r = 0.87; 95CI, 0.76-0.94; p < 0.001). The assessment of Kt through ionic dialyzance is a simple method to estimate the dose of dialysis in critically ill patients and is and useful tool to monitor and adjust the RRT in real time according to a target dose.

Different hemoglobin levels on the clearance rate of urea

Objective Online clearance monitoring explore different hemoglobin level of maintenance hemodialysis patients the effects of urea clearance rate.Methods 29 cases of patients will be randomized according to hemoglobin level divided into two groups,A group:Hb:100～130 g/L B group:Hb:50～99 g/L The use of online urea clearance rate monitor(OCM) observate the changes of area clearance rate(KT/V).Results A group:KT/V:1.22±0.8 Bgroup:KT/V:1.54 ±1.0 Between the two groups were significantly different(P＜0.05).Conclusion For maintenance hemodialysis patients,High levels of hemoglobin,the value of KT/V is lower;Low levels of hemoglobin,the value of KT/V is higher. Key words: Hemoglobin; Urea clearance rate; Online clearance monitoring

A comparison of methods for determining urea distribution volume for routine use in on-line monitoring of haemodialysis adequacy

The availability of haemodialysis machines equipped with on-line clearance monitoring (OCM) allows frequent assessment of dialysis efficiency and adequacy without the need for blood samples. Accurate estimation of the urea distribution volume 'V' is required for Kt/V calculated from OCM to be consistent with conventional blood sample-based methods. Ten stable HD patients were monitored monthly for 6 months. Time-averaged OCM clearance (K(OCM)) and pre- and post-dialysis blood samples were collected at each monitored session. The second generation Daugirdas formula was used to calculate the single-pool variable volume Kt/V, (Kt/V)(D). Values of V to allow comparison between OCM and blood-based Kt/V were determined from Watson's formula (V(Watson)), bioimpedance spectroscopy (V(BIS)), classical urea kinetic modelling (V(UKM_C)) and a simple computation of V (V(UKM_S)) from the blood-based Kt/V and K(OCM)t. Comparison of K(OCM)t/V with (Kt/V)(D) shows that using V(Watson) leads to significant systematic underestimation of dialysis dose. K(OCM)t/V(BIS) agrees with (Kt/V)(D) to within +/- 10%. K(OCM)t/V(UKM_S) is, by definition, identical to (Kt/V)(D) when initially calculated. However, if a historical value of V is used, agreement between K(OCM)t/V and (Kt/V)(D) over 6 months varies by 5% for V(BIS) and 10% for V(UKM_S). When investigating the effect of different treatment strategies on dialysis efficiency, any estimate of V can be used provided it is constant, as K is the relevant parameter. When frequent supervision of actual dialysis dose is required, the greatest consistency between K(OCM)t/V and the reference, Kt/V(D), over time is achieved with V(BIS).

ON LINE UV‐ABSORBANCE MEASUREMENTS: Summary of the EDTNA|ERCA Journal Club discussion Summer 2006

The discussion was initiated by a paper comparing the measurement of dialysis dose (Kt/V) and solute clearance using on-line ultra-violet absorbance, blood and dialysate urea and ionic dialysance by Uhlin et al (NDT 2006). Participants from 14 countries discussed the theory behind the UV absorbance technique and the potential for its use in routine practice, the correlation between Kt/V measured using different methods, the use of ionic dialysance and the optimisation of dose monitoring. The 'take-home' messages from the discussion were that UV-absorbance could help ensure the delivery of dialysis dose as it provides real time feedback on the effect interventions such as repositioning of needles. The technology is relatively inexpensive and requires no consumables but changes in the dialysis machine settings could lead to misleading measurements if not communicated to the UV monitor. Session-to-session variation in dialysis dose can be measured using on-line clearance monitoring. If it is already on the machine and costs nothing, why not use it? Alternatively, regular access recirculation checks and a record of the total blood volume processed at each session allow problems with delivered dialysis dose to be picked up between routine blood tests.

Dialysis dose (Kt/V) and clearance variation sensitivity using measurement of ultraviolet-absorbance (on-line), blood urea, dialysate urea and ionic dialysance

An on-line monitoring system for dialysis dose calculations could make it possible to provide an adequate dialysis dose that is consistently given to haemodialysis (HD) patients. The aim of this study was to compare dialysis dose (Kt/V) using four different methods and their sensitiveness to a reduction in clearance. Six patients were monitored on-line with ultraviolet (UV)-absorbance at a wavelength of 297 nm in three consecutive dialysis sessions during 1 week. During the last treatment, the clearance was reduced by approximately 25% by decreasing the blood flow. For the determination of UV-absorbance, a spectrophotometer was connected to the fluid outlet of the dialysis machine with all spent dialysate passing through a flow cuvette. The equilibrated Kt/V (eKt/V) estimated by UV-absorbance was compared with eKt/V from the ionic dialysance method using the on-line clearance monitor (OCM) and the appurtenant software dose-calculation tool DCTool (Fresenius Medical Care, Germany), eKt/V calculated from the dialysate-urea slope and with eKt/V from pre- and post-dialysis blood-urea samples as reference. The study demonstrates that the sensitiveness to clearance reduction is similar in the four methods compared for eKt/V. When the different methods were compared, the mean eKt/V of UV-absorbance was 1.21 +/- 0.20, blood 1.30 +/- 0.21, dialysate 1.32 +/- 0.21 and OCM (using the DCTool) 1.31 +/- 0.21. The standard deviation was of the same magnitude. The UV-method gives a similar response to clearance reduction compared with the other methods when comparing dialysis dose. The high sampling rate by continuous monitoring of UV-absorbance allows evaluation of the clearance process during dialysis and gives immediate feedback to on-line adjustments.

Determination of the delivered hemodialysis dose using standard methods and on-line clearance monitoring

Delivered dialysis dose has a cumulative effect and significant influence upon the adequacy of dialysis, quality of life and development of co-morbidity at patients on dialysis. Thus, a great attention is given to the optimization of dialysis treatment. On-line Clearance Monitoring (OCM) allows a precise and continuous measurement of the delivered dialysis dose. Kt/V index (K = dialyzer clearence of urea; t = dialysis time; V = patient's total body water), measured in real time is used as a unit for expressing the dialysis dose. The aim of this research was to perform a comparative assessment of the delivered dialysis dose by the application of the standard measurement methods and a module for continuous clearance monitoring. The study encompassed 105 patients who had been on the chronic hemodialysis program for more than three months, three times a week. By random choice, one treatment per each controlled patient was taken. All the treatments understood bicarbonate dialysis. The delivered dialysis dose was determined by the calculation of mathematical models: Urea Reduction Ratio (URR) single-pool index Kt/V (spKt/V) and by the application of OCM. Urea Reduction Ratio was the most sensitive parameter for the assessment and, at the same time, it was in the strongest correlation with the other two, spKt/V indexes and OCM. The values pointed out an adequate dialysis dose. The URR values were significantly higher in women than in men, p < 0.05. The other applied model for the delivered dialysis dose measurement was Kt/V index. The obtained values showed that the dialysis dose was adequate, and that, according to this parameter, the women had significantly better dialysis, then the men p < 0.05. According to the OCM, the average value was slightly lower than the adequate one. The women had a satisfactory dialysis according to this index as well, while the delivered dialysis dose was insufficient in men. The difference between the women and the men was significant. The application of OCM has shown that it is the most rigorous parameter for the assessment of adequacy and that its regular use would contribute to increasing of the delivered dialysis dose and improvement of the treatment quality.

ON‐LINE CLEARANCE MONITORING FOR BLOOD ACCESS MANAGEMENT

On-line Clearance Monitoring (OCM) provides frequent and precise information about urea clearance values during haemodialysis. In the case of blood access recirculation, it is presumed that urea clearance values on OCM would be lower and suspect to blood access malfunction. In order to check the relation between significantly lower urea clearance values and blood access recirculation, the Kt value (Clearance x time/min) for fifteen patients on OCM, including the patients with a low Kt/V in spite of their small urea distribution volume (V) was observed. Average urea clearance was calculated indirectly using Kt value (Kt/time in minutes = average clearance ml/min) and blood access recirculation tests performed using slow/stop flow two-needle, three samples method (urea method). After comparison of the recirculation percentage to clearance value, positive correlation between high recirculation and clearance reduction was noted. OCM alongside detection of haemodialysis inefficiency is also a practical instrument for blood access management between regular monitoring. Lower OCM urea clearance values demonstrate a possible blood access problem that can be confirmed with another method. When an OCM urea clearance reading is decreased by more than 25%, undiscovered access recirculation can be suspected.

CONVENTIONAL BLOOD SAMPLING VERSUS ON‐LINE CLEARANCE MONITORING

On-line Clearance Monitoring (OCM) calculates the Kt/V during a dialysis session using a module incorporated into the Fresenius 4008 H/S haemodialysis machine (1). The method is based on repeated increments in dialysate sodium concentrations followed by measuring the change of dialysate sodium concentration after the dialysate has passed through the kidney. OCM is a patient friendly, non-invasive and easy method for measuring Kt/V. Kt/V calculated on single-pool urea kinetics according to Daugirdas was compared to Kt/V measured by OCM in thirty stable patients on chronic haemodialysis. Patients were dialysed using a dialyser with either a high-flux polysulfone or a haemophane membrane. In four patients OCM was measured in ten consecutive sessions to assess the intra-individual variation in OCM. The calculated Kt/V was compared to Kt/Vocm in three patients at five consecutive dialysis sessions to measure the intra-individual correlation. A linear correlation was present between Kt/Vocal and Kt/Vac for both the polysulfone and haemophane membrane. Intra-individual Kt/Vocm showed very stable values with an average variation of less than 5%. Intra-individual correlation between calculated Kt/V and Kt/Vocm was high.

Experience with the Gambro Phoenix Hemodialysis Machine using Diascan and Exalis in a Pediatric Hemodialysis Unit

Introduction: In 2001 our Renal Dialysis Unit underwent a major renovation to five stations. The new space and funding allowed for acquisition of new state‐of‐the‐art hemodialysis machines. We describe our experience with the Gambro Phoenix with Diascan and Exalis. Prior to the move an evaluation was undertaken. Criteria for selection with a scoring tool were utilized to rate machine performance for use in children. The decision for the Gambro Phoenix machine was based on: the performance rated highly due to ease of set up; large viewing touch screen; compatibility with existing equipment; benefits of online clearance monitoring (Diascan); network data management system (Exalis) and the future availability of blood volume monitoring (Hemoscan). Our program was the first center to dialyze a pediatric patient on the Phoenix machine in Canada.Patients and results: 13 patients (age 2–23 years) were hemodialyzed between May 2002 and September 2003 for periods of 2 week to 16 months, greater than 5000 h of dialysis time. The move was not uneventful. During the first months of operation issues such as inadequate electrical supply for the new machines, reverse osmosis (RO) pump failure, leaks, and no emergency power to the RO were prevalent. The new software also exposed glitches. Subsequent Phoenix use proceeded uneventfully. Staff were able to problem solve easily with clinical and technical support from Gambro Canada. Education for the online clearance monitoring, Diascan and Exalis, was necessary. No major problems with dialysis were encountered. The benefits and reliability of Diascan have been previously described (Lindsay RM, Sternby J, Semin Dial. 2001; 14:300). Diascan readings provided real‐time measurement of sodium (Na), which correlated well with laboratory values. Automatic readouts of Kt/V allowed for monitoring of dialysis adequacy which was consistent with calculated percent reduction in urea (PRU). At this point, use of the Phoenix has been demonstrated to work well in a pediatric facility.

Accuracy and safety of online clearance monitoring based on conductivity variation

Haemodialysis dose has been shown to have a distinct impact upon the morbidity and mortality rate in patients on regular dialysis therapy. Accordingly, the adequacy of dialysis treatment should be guaranteed. In 200 dialysis sessions two or three +/-10% dialysate conductivity variations were applied to test patient compliance and the accuracy of an electrolyte based online clearance measurement (OCM) reflecting the total clearance of urea. Using a step profile the electrolytic clearance showed highly significant correlation with the reference data in the blood side (n=118, r=0.867, P<0.001) and dialysate side (n=118, r=0.820, P<0.001) if only reference values were taken into account for which the error in mass balance did not exceed 5%. Kt/V according to the single pool model (n=35, r=0.940, P<0.001), the equilibrated single pool variable volume kinetic model (n=36, r=0.982, P<0.001), Daugirdas formula (n=34, r=0.951, P<0.001) and direct quantification of dialysance via spent dialysate (n=26, r=0.900, P<0.001) showed outstanding correlations with electrolyte-based Kt/V at mass balance error below 5%. No adverse clinical effect of OCM was reported. Serum sodium, body weight, heart rate and breathing rate at rest, arterial pO(2) and pCO(2) and blood pressure before haemodialysis remained unaffected in OCM measurements in comparison with baseline parameters. A small influx of sodium (1.53+/-7.62 mmol) into the patient was seen following the impulse, but no signs associated with fluid overload were observed during the study period of 10 consecutive dialysis sessions. The OCM option of the haemodialysis machine provides a safe and accurate tool for continuous online monitoring of total urea clearance.