Interventions to improve hemodialysis adequacy: protocols based on real-time monitoring of dialysate solute clearance

Interventions to improve hemodialysis adequacy: protocols based on real-time monitoring of... Background: The monitoring of dialysate ultraviolet (UV) absorbance is a validated technology to measure hemodialysis adequacy and allows for continuous and real-time tracking every session as opposed to the typical once-monthly assessments. Clinical care guidelines are needed to interpret the findings so as to troubleshoot problematic absorbance patterns and intervene during an individual treatment as needed. Methods: When paired with highly structured clinical care protocols that allow autonomous nursing actions, this technology has the potential to improve treatment outcomes. These devices measure the UV absorbance of dialysate solutes to calculate and then display the delivered as well as predicted clearance for that session. Various technical factors can affect the course of dialysate absorbance, confound the device’s readout of clearance results and thus lead to challenges for the dialysis unit staff to properly monitor dialysis adequacy. We analyze optimal and problematic patterns to the device’s ‘clearance’ display (e.g. due to thrombosis of hollow fibers, inadequate access blood flow or recirculation) and provide specific interventions to ensure delivery of an adequate dialysis dose. A rigorous algorithm is presented with representative device monitor display profiles from actual hemodialysis sessions. Procedural rationale and interventions are described for each individual scenario. Conclusion: Real-time hemodialysate UV absorbance patterns can be used for protocol-based intradialytic interventions to optimize solute clearance. Key words: dialysis adequacy, Kt/V, recirculation, urea modeling, vascular access Introduction monitoring the effluent for moieties that are urea surrogates by either electrical conductance or ultraviolet (UV) absorption. Real-time monitoring of dialysis adequacy has been made possi- Recent focus has been on validating the effectiveness of current ble by the development and marketing of hemodialysis machines methodologies. Despite concerns that results could be con- that monitor solute clearance. Currently this is accomplished by founded by such problems as interfering substances, inappropri- two different technological approaches, both of which depend on ate urea modeling, solute rebound or errors in calculating urea measuring fluxes of substances from blood into the dialysate: Received: December 9, 2016. Editorial decision: August 28, 2017 Published by Oxford University Press on behalf of ERA-EDTA 2017. This work is written by US Government employees and is in the public domain in the US. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 Interventions to improve hemodialysis adequacy | 395 volume (V), the dialyzer clearance of urea (K), dialysis time (t) and include the component achieved by convective losses through urea reduction ratio (URR) clearance calculations from the differ- ultrafiltration. The calculated Kt/V and URR curves are shown as ent modalities have generally had excellent correlation. predicted (dotted line) and as achieved (solid line). The display Nevertheless, these estimations of dialysate urea ‘appear- also shows the user-set target values for these parameters (red ance’ have not been universally accepted for the purposes of line) over the prescribed treatment time (e.g. 1.4, 75% in 4 h, quality assurance for dialysis adequacy. The efficacy of hemo- respectively). At any point, the user can discern how the dialysis treatments thus still needs to be confirmed by blood achieved clearance varies from the predicted trajectory and tests for urea ‘clearance’. Given the fact that these blood-based whether the patient will reach the adequacy goal. The machine urea clearance tests are preformed infrequently, on the order of can be set so as to alarm and thereby notify the staff when the one per month, there is much practical value from using a real- patient is projected to not reach the clearance target. Patients time device that is available for every treatment. The ability to received their hemodialysis therapy as part of their routine clin- monitor the pattern of intradialytic solute removal, detect prob- ical care as outpatients or inpatients at the University of Florida lems and immediately intervene [1, 2] enhances the provider’s Shands Hospital, Gainesville, FL and the dialysate UV absorbance ability to react to direct therapy variables. Although such a ben- technology was utilized for every patient at every treatment. efit has been proposed, this is the first report of how to use this Hemodialyzers were made of polysulfone [F160, F200 or F16NF technology for protocol-driven changes to impact each dialysis (Fresenius, Worcester, MA, USA) or cap15 or cap 20 (B. Braun, session’s prescription so as to achieve dosing adequacy. Bethlehem, PA, USA)]. This report adheres to the policies of the Since the ionic conductance technology is limited to intermit- University of Florida Institutional Review Board. tent monitoring, typically every 45 min, it is theoretically inferior to the continuous nature of the UV absorbance technique for the Nursing protocol to reach dialysis adequacy goal immediate detection and resolution of problems. Therefore, nursing protocols were developed based on UV absorbance tech- As per physician orders and the dialysis adequacy policy, nurses nology, which are driven by comparing the calculated delivered are empowered to follow the protocol (Figure 1) and react to treat- dialysis dose (Kt/V or URR) profile to that of the ideal trajectory. ment variances to reach the prescribed dose target. Using the Because minute-to-minute changes in treatment efficacy cannot protocol, nursing actions are based on whether the achieved practically be addressed by offsite physicians, nurses would now clearance pattern is above or below the desired trajectory. have a new tool to independently implement physician-driven Variables include the choice of dialyzer (e.g. based on clearance protocols to improve patient care. For example, immediate recog- specifications), blood and dialysis flow rates, treatment time, the nition of low or decreasing clearance can trigger interventions degree of anticoagulation (e.g. dose of heparin), replacement of a that increase dialysis time, alter blood or dialysate flow rate, clotted dialyzer, repositioning of cannulation needles and throm- adjust needle position, improve anticoagulation or replace the bolysis of access catheters. Images of the problematic clearance dialyzer. Additionally, patterns from the continuous device read- curves were obtained during various clinical scenarios when outs suggestive of access recirculation were identified. Patients patients were off trajectory, as well as improved displays of the with patterns suggestive of recirculation underwent verification profiles after remediation by appropriate nursing interventions. by blood-based testing or imaging studies. Real-time continuous monitoring is particularly important for patients using catheters as their primary access, since intermittent erratic flow may oth- Results erwise not be detected. The dialysate UV absorption-based patient care protocol was The goal of this article is to use the findings from the multiple well-accepted by the nursing staff and physicians. When indi- published device-validation studies to describe clearance profiles cated, the efficacy of the protocol-driven changes to the dialysis (calculated from the dialysate UV absorption) that can prompt real- prescription was verified by blood-drawn URR determinations. time changes in the treatment prescription to overcome problems Anecdotally, the nurses, technicians and physicians reported with achieving dialysis adequacy, access function or technical diffi- better patient compliance with staying for their prescribed HD culties involving the extracorporeal circuit. Clinical care guidelines time by showing the patients the underdialysis graphic. The and protocol-driven clearance interventions based on continuous staff was often able to dissuade the patients from leaving early data allowthe nursingstaff anew opportunitytobenimbleand (staying ‘until the blue line reaches the red line’). Specific clear- empowered so as to provide optimal high-quality dialysis. ance pattern scenarios were identified and are described below. Materials and methods Dialysate-based clearance curve follows predicted trajectory Hemodialysis and online clearance devices Hemodialysis was performed using machines equipped with Dialysate-based clearance pattern on track to meet prescribed dose continuous monitoring of effluent dialysate by UV absorbance Figure 2A demonstrates dialysis sessions in which the dialysate at 280 nm (Adimea device integrated in the Dialog hemodialysis clearance based on UV absorbance follows the anticipated tra- machine, B. Braun, Bethlehem, PA, USA). Clearance is calculated jectory so as to achieve the prescribed dose. In Figure 2A, a Kt/V by analysis of the decrease in the dialysate’s solute absorption goal of 1.4 is reached in a patient weighing 67.8 kg after 4 h using (UVAbs) over time. A logarithmic decline in dialysate moieties is a blood flow (Qb) of 450 mL/min and dialysate flow (Qd) of expected as they are removed from the blood compartment. 500 mL/min. The delivered-dose curve is essentially superim- Characterization of exponentially falling solutes in the effluent posable on the anticipated trajectory. Staff need to stay vigilant yields the dialysis dose expressed as either Kt/V or URR using that there can be concurrent processes with opposite effects on single-pool analysis. While the machine measures absorbance, the displayed curve, although the net effect is unlikely to culmi- it graphically displays the calculated clearance, which increases nate in a tracing that consistently tracks the projected trajectory over time. The software also adjusts the total clearance so as to over the course of the entire dialysis treatment. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 396 | E.A. Ross et al. Enter Treatment Parameters and Dialysis Prescription: Pre Weight & Kt/V (e.g. goal = 1.4) Verify That UV Absorption Device and Alarms are Turned ON Green Light on Display Kt/V On Target* Kt/V Above Target Kt/V Below Target Shallow Slope Steep Slope Verify prescribed Qb (Blood flow) Incrementally increase Qb to maximum per policy Monitor and Consider document every decrease in 15 min HD time Verify Qd (Dialysate Flow): 500 ml/min Increase by 150 ml/min, not to exceed 800 ml/min. Check for recent volume expanders Monitor and document every Evaluate for ilter thrombosis 15 min (e.g. an increasing TMP) Evaluate for access Flush dialyzer with 200 ml Normal saline. recirculaon Evaluate for rapid Assess anticoagulation filter thrombosis Monitor and Lower Qb to test for document every 15 min recirculaon arfact Change ilter if there is indication of dialyzer clotting. Verify adequate Qb (Blood flow) Monitor and Call MD/PA : If need to change in heparin Consider catheter thrombolysis document every dose, dialyzer size or increase treatment me. Increase ancoagulaon and change filter 15 min Fig. 1. Flow diagram of nursing protocol using solute clearance calculated from real-time dialysate UV absorption measurements. Decisions are based on the real-time (measured) clearance curve differing from the projected trajectory. *Signifies the need of the staff to stay vigilant wherein there can be concurrent processes with oppo- site effects on the displayed curve. Fig. 2. (A) Clearance curve (based on UV absorption) for a patient weighing 67.8 kg who can meet the target clearance in the prescribed 4 h. (B) Clearance curve below prescription with gradual clotting of the dialyzer and improved trajectory after increased dialysate flow rate. (C and D) Clearance curves erroneously high due to artifact caused by access recirculation. (E) Clearance curve in a former pediatric patient weighing 54 kg who can reach clearance targets in less than the prescribed 4 h. (F) Clearance curve erroneously high due to artifact caused by rapid volume expansion from intravenous albumin. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 Interventions to improve hemodialysis adequacy | 397 Dialysate-based clearance pattern initially adequate, then falling below fibers due to inadequate anticoagulation. Sudden severe throm- the desired trajectory bosis of the fibers causes a somewhat different pattern. The In Figure 2B, a patient is initially on target for dialysis adequacy rapid decrease in UV absorption by dialysate solutes is incor- and then the trajectory falls below the desired adequacy at 2h rectly attributed to high dialysis clearance (displayed as an due to what was discerned to be gradual clotting of the hollow upward slope in calculated clearance), then the curve flattens fibers. As per the protocol, the Qd was increased to 800 mL/min out (as solute removal remains low). The curve then gradually and the dialysate clearance curve shifted upward to again declines further and further below expectation. match the desired trajectory, achieving the prescribed dose. Discussion Dialysate-based clearance curve higher than predicted The ability to monitor a real-time dialysis dose holds great prom- or prescribed trajectory ise to ensure the delivery of optimal treatments. The first com- Steep upward slope yet actual clearance is inadequate due to access mercially available technology utilized electrical conductance of recirculation effluent dialysate. These devices are based on the premise and Figure 2C and 2D demonstrates two examples of inadequate evidence that sodium fluxes across the dialyzer membrane are clearance due to access recirculation that had not been other- an excellent surrogate for urea dialysance and that they can be wise suspected or detectable during the treatment session. As measured by changes in dialysate conductivity [3, 4]. As currently described below, the greater the recirculation of the extracor- marketed (Fresenius, Waltham, MA, USA), the hemodialysis poreal circuit, the faster the decrease in its concentration of ure- machines intermittently alter dialysate sodium and calculate a mic solutes. This misleading rapid decline in solutes due to the predicted urea clearance (K). Although technically possible to be recirculation phenomenon is erroneously interpreted by the done frequently, with this popular device it is typically done only software as a high dialysis dose; the calculated dialysate clear- every 45 min, or six times over the course of a 4-h treatment. ance curve rises greatly above the machine’s predicted curve. Based on the presumption that those few values are representa- Reversed needles are a potential cause and easily remedied. In tive of the entire session, the device estimates the clearance for Figure 2C, a patient weighing 138 kg with catheter access and a the whole treatment (Kt). However, for determination of the dial- Qb of 300 mL/min was prescribed 5 h at a Qd of 800 mL/min. ysis dose (Kt/V), the urea volume (V)must be established sepa- Recirculation was not clinically detected by the staff and was rately by various empirically derived equations (e.g. using weight, only suspected when the calculated clearance curve was unex- height, gender) or independent technology (e.g. bioimpedance). pectedly greater than anticipated, with a pronounced steep The two major weaknesses of conductance-based dose monitor- slope: this heavyweight patient was erroneously predicted ing are missing the problems that occur between the intermittent to reach a 1.40 Kt/V goal in just over 2 h. Blood sampling con- tests and errors in calculating volume. The latter can be >20%, firmed an 20% access recirculation. Figure 2D demonstrates depending on the methodology chosen for the V estimation [5–8]. how recirculation not only raises the curve but also causes an Monitoring clearance in dialysate effluent can overcome the erroneously high numerical Kt/V to be displayed (3.3 in this deficiencies of conductance-based devices. As any particular example). solute is dialyzed from the blood, the rapid decrease in its plasma concentration will be reflected by a similar decrease in its appearance in the used dialysate. The UV absorbance tech- Dialysate-based clearance pattern on trajectory but dialysis dose con- nology continuously measures certain solutes in the effluent, sistently higher than the prescribed goal which will thus exponentially decrease in concentration over As shown in Figure 2E, a lesser weighing former pediatric the treatment time. By mathematically characterizing the loga- patient on multiple dialysis sessions had reached the adequacy rithmic decline in dialysate solute (e.g. curve fitting), the equa- goal more quickly than the 4 h initially prescribed. At 54 kg, a Qb tion yields the Kt/V value using single-pool analysis. For of 400 mL/min and Qd of 500 mL/min, the Kt/V of 1.4 was attain- example, when the natural logarithm of the absorbance is plot- able at just 3 h. This permitted cautious reduction in the dialysis ted against time, the slope of the resultant line is determined by time with verification of adequacy by blood testing. the Kt/V. Hence the advantage of the direct measure approach is that urea volume does not have to be independently deter- Sudden steep upward slope, then curve parallel to predicted trajectory mined; this is the potential major source of error as described This phenomenon is due to sudden hemodilution caused by above. Since treatment efficacy can change over the course of volume expanders such as saline or albumin infusions. The the treatment (e.g. from clotting or changing flow rates), errors diluted blood passing through the dialyzer results in an imme- in curve fitting are overcome by the software performing the diate decrease in uremic solutes appearing in the dialysate analyses every 20 min and not being confounded by alarm con- effluent. The dramatic decrease in dialysate UV absorbance is ditions (e.g. blood leaks, conductivity problems). incorrectly interpreted by the software as being due to a higher The theoretical weakness of using UV methods, however, is dialysis dose, yielding erroneously high Kt/V and URR values. that absorbance at any particular wavelength is not unique for a Figure 2F demonstrates this happening immediately following single substance. Each molecule will not only have an optimal infusion of 50 g of albumin. or peak wavelength but will also absorb over a range of values, and thus the various moieties found in human blood will be Dialysate-based clearance curve lower than predicted expected to have overlapping absorbance spectra. For example, trajectory one study characterized 40 absorption peaks [9]. Thus, choosing Common causes of the achieved dialysate clearance being the wavelength based on the urea molecule (285 nm) would be below the desired trajectory are inadequate prescription (blood nonspecific and has the additional shortcoming that it has rela- or dialysate flows, time, choice of dialyzer) clearance character- tively limited UV absorbance compared with other waste prod- istics in relation to the patient’s size and Kt/V goal, problematic ucts appearing in the dialysate [10]. Wavelengths in the range of access causing low blood flows and gradual clotting the hollow 200–285 nm have been studied in relation to how they Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 398 | E.A. Ross et al. characterize many common solutes [11–13], using the 280 nm could prompt extra dialysis sessions, a change in the dialysate Adimea device. Multiple investigations have established that composition, imaging or revision of the dialysis access. This is small-molecule absorption in that spectral range is an excellent important in that the shape of the displayed Kt/V or URR curve surrogate for urea removal and primarily includes such sub- can thus provide information beyond that of traditional inter- stances as uric acid and creatinine. Small solutes with high mittent adequacy parameters that are calculated using clearance rates account for 95% of UV absorbance [9, 11]. This postdialysis data; the curve can be of particular value for the is analogous to sodium being used as a surrogate for urea in the detection of access recirculation. As long as the intra-access conduction-based technologies. Important for clinical use, there blood flow is more than the extracorporeal pump rate, there is neither negligible confounding from UV absorbance by the would not be any recirculation and the UV absorbance– low concentrations of small and large proteins in the dialysate generated clearance curve would be reliable. Once the pump nor by commonly used medications [9]. The effect of medication flow exceeds the capacity of the malfunctioning access, dia- clearance would be attenuated by their typically having much lyzed blood begins to loop back into the dialyzer. Thus this lower plasma concentrations than that of uremia moieties such ‘clean’ blood from the dialyzer outlet returns to mix with the as urea. A rigorous study across the wide spectrum of pharma- fresh blood (‘recirculates’) and solute concentrations at the dia- ceuticals has not been done. lyzer inlet are lower (and decrease more rapidly) than antici- Theoretically, errors in predicting urea removal could be pated. The recirculation-induced steep decline in the introduced if the various substances have different volumes of extracorporeal circuit’s solutes results in a similar rapidly distribution and different mass transfer coefficients between decreasing pattern in the dialysate (and UV absorption). The soft- the extracellular fluid compartments. As pointed out by ware incorrectly interprets this phenomenon as having been Daugirdas and Tattersall [14], molecules that could confound caused by a high dialysis dose. For example, with substantial absorption calculations tend to be large and have slow removal recirculation the solute concentration can decline so quickly in by hemodialysis and thus UV absorption calculations would be the dialysate that patients can appear to achieve Kt/V values of expected to underestimate urea clearance. Nevertheless, moni- >1.4 in <2 h, which is clearly not physiologically possible. toring of moieties absorbing in this wavelength range has been Properly trained staff can recognize the atypical steep shape of shown to be satisfactory for clinical purposes. Kt/V calcula- the displayed clearance curves, which greatly differ from the urea tions have reportedly been very similar when comparing blood, anticipated (dotted line) trajectory. As long as the access is still conductance and UV absorption techniques, with differences patent and has a minimally acceptable flow rate (e.g. 200 mL/ from 0 to 0.1 [2, 5–7, 15, 16]. UV absorption clearance correlated min), the nurse will be able to decrease the pump rate so as to well with blood testing [17] not just with urea, but also with eliminate the clearance curve’s recirculation artifact. Blood test- potassium and phosphate [1]. Some of the discrepancy may be ing would be needed to verify an adequate URR. We believe that due to deficiencies in the mathematical modeling of single- ver- the ability to detect recirculation as well as other causes of low sus double-pool urea kinetics for the blood-based methodology. clearance has particular clinical importance in the setting of In that, continuous absorbance measurements are preferable to catheters. There have been a number of patients in whom we fewer sampling points and the UV absorbance device can be discerned recirculation from malfunctioning femoral vein cathe- used to more rigorously assess postdialysis rebound, which is ters. The problem was unanticipated from the flow and pressure consistent with two-compartment kinetics [18]. It has also been profiles and would have been missed if not suggested by the UV reported that what has been described as a 7% lower clearance absorption device, confirmed by blood testing and resolved by from the UV methodology is actually due to some overestimation replacement with a new longer catheter. We also fear that cathe- from the two-pool blood-based methodology [2]. ter flow can be so erratic that problems, and thus inadequate Importantly, the potential disadvantages of all of these devi- dialysis, could be missed by the intermittent nature of the ces that use urea surrogates for curve-fitting clearance calcula- conduction-based devices. tions could be overcome by technology that would precisely It is important for the staff to also appreciate how sequential measure urea concentration in dialysate. Highly sensitive and remedies to abnormal dialysate absorption-based clearance selective urea assays would also permit mass clearance calcula- curves can reveal more than one problem in a dialysis treat- tions, but those machines are complex, require calibration and ment. For example, an abnormal curve may persist after replac- have not been practical or economically feasible for mass mar- ing a dialyzer and could thus unmask a second problem. From a keting. For example, results from using the Biostat 1000 device practical standpoint, this would be a circumstance in which this (Baxter Healthcare, McGaw Park, IL, USA) supported the use of technology could make it difficult to discern access recircula- dialysate measurements for determinations of adequacy [19, tion. Users thus need to be cognizant of the possibility that 20], but the machine was not made commercially available. simultaneous unrelated problems could have opposite effects In this article we have demonstrated the usefulness of con- on the displayed curve, wherein one could increase the dis- tinuous real-time monitoring of dialysis clearance for maintain- played curve (e.g. recirculation) while a second malfunction ing and achieving adequacy goals. While it remains imperative decreases it (e.g. partial clotting). We believe it would be theo- to verify these estimations with blood-based urea determina- retically possible, but rare, for these combined effects to culmi- tions, those measurements cannot be performed instantane- nate in a resultant curve precisely following the trajectory over ously and thus real-time UV absorbance technology can guide the full course of many hours of treatment; deviations would nimble intradialytic changes to the prescription: adjusting blood provide the opportunity for a trained operator to detect both or dialysate flow, prolonging dialysis time, repositioning nee- problems. Another example of complications with opposing dles, checking for access recirculation, optimizing anticoagula- effects on the dialysate absorption curve would be an tion of the extracorporeal circuit and replacing dialyzers ultrafiltration-associated decrease in cardiac output and an impaired by thrombosed fibers. Clearance curves (calculated increase in cardiopulmonary recirculation and hemoconcentra- from the dialysate UV absorption measurements) that unex- tion. The limitations of both absorbance- and ionic conductance- pectedly deviate from the predicted trajectories can also prompt based technologies emphasize that they cannot replace tradi- unscheduled postdialysis laboratory testing, which in turn tional measures of clearance and dialysis adequacy. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 Interventions to improve hemodialysis adequacy | 399 6. Sternby J. Whole body Kt/V from dialysate urea measure- Lastly, the behavioral benefits of using real-time clearance monitoring are not to be underestimated. Anecdotally, many ments during hemodialysis. J Am Soc Nephrol 1998; 9: patients have been convinced to not sign off dialysis early by 2118–2123 showing them their clearance curves. This educational tool has 7. Castellarnau A, Werner M, Gu¨ nthner R et al. Real-time Kt/V led some recalcitrant patients to stay on treatment until the determination by ultraviolet absorbance in spent dialysate: ‘blue line hits the red line’; however, this is only a partial solu- technique validation. Kidney Int 2010; 78: 920–925 8. Moret K, Beerenhout CH, van den Wall Bake AW et al. Ionic tion to the nonadherence wherein ultrafiltration goals may still not be met. High fluid removal volumes will also increase solute dialysance and the assessment of Kt/V: the influence of dif- removal by convection, so that the adequacy predictions that ferent estimates of V on method agreement. Nephrol Dial do not incorporate ultrafiltration will underestimate actual total Transplant 2007; 22: 2276–2282 9. Schoots AC, Homan HR, Gladdines MM et al. Screening of clearance. The ability of the staff to detect problems in real time, troubleshoot, intervene and thus improve dialysis has UV-absorbing solutes in uremic serum by reversed phase important implications for nursing care. Not only is the quality HPLC–change of blood levels in different therapies. Clin Chim of dialysis care improved, but we believe there is a morale and Acta 1985; 146: 37–51 10. Filutowicz Z, Lukaszewski K, Pieszynski K. Remarks on career satisfaction benefit from enhancing nursing autonomy related to improved clinical outcomes. spectra-photometric monitoring of urea in dialysate. J Med Informat Technol 2004; 8: 105–110 In conclusion, continuous dialysate UV absorption–based monitoring of hemodialysis clearance is a very promising tech- 11. Arund J, Tanner R, Uhlin F et al. Do only small uremic toxins, nology to achieve and maintain treatment adequacy goals. chromophores, contribute to the online dialysis dose moni- Real-time intradialysis quality assurance for every session is far toring by UV absorbance? Toxins (Basel) 2012; 4: 849–861 12. Lindley EJ, Tattersall J, De Vos JY et al. On line UV-absorbance superior to the typical monthly assessments. Protocol-driven modifications to treatment parameters are valuable nursing measurements. J Renal Care 2007; 33: 41–48 tools for optimizing patient therapy outcomes. 13. Fridolin I, Lindberg L-G. On-line monitoring of solutes in dialysate using wavelength-dependent absorption of ultra- violet radiation. Med Biol Eng Comput 2003; 41: 263–270 14. Daugirdas JT, Tattersall JE. Automated monitoring of hemo- Conflict of interest statement dialysis adequacy by dialysis machines: potential benefits to patients and cost savings. Kidney Int 2010; 78: 833–835 None declared. 15. Uhlin F, Fridolin I, Lindberg LG et al. Estimation of delivered dialysis dose by on-line monitoring of the ultraviolet absorb- References ance in the spent dialysate. Am J Kidney Dis 2003; 41: 1026–1036 1. Fridolin I, Magnusson M, Lindberg LG. On-line monitoring of solutes in dialysate using absorption of ultraviolet radiation: 16. Di Filippo S, Andrulli S, Manzoni C et al. On-line assessment of delivered dialysis dose. Kidney Int 1998; 54: 263–267 technique description. Int J Artif Organs 2002; 25: 748–761 17. Ficheux A, Gayrard N, Szwarc I et al. Use of spent dialysate 2. Uhlin F, Fridolin I, Magnusson M et al. Dialysis dose (Kt/V) and analysis to estimate blood levels of uraemic solutes without clearance variation sensitivity using measurement of ultraviolet-absorbance (on-line), blood urea, dialysate urea and blood sampling: urea. Nephrol Dial Transplant 2010; 25: 873–879 ionic dialysance. NephrolDialTransplant 2006; 21: 2225–2231 3. Polaschegg HD. Automatic, noninvasive intradialytic clear- 18. Tomson R, Uhlin F, Fridolin I. Urea rebound assessment based on UV absorbance in spent dialysate. ASAIO J 2014; 60: ance measurement. Int J Artif Organs 1993; 16: 185–191 459–465 4. Kuhlmann U, Goldau R, Samadi N et al. Accuracy and safety 19. Canaud B, Bosc JY, Leblanc M et al. Evaluation of high-flux of online clearance monitoring based on conductivity varia- tion. Nephrol Dial Transplant 2001; 16: 1053–1058 hemodiafiltration efficiency using an on-line urea monitor. Am J Kidney Dis 1998; 31: 74–80 5. Manzoni C, Di Filippo S, Corti M et al. Ionic dialysance as a 20. Depner TA, Keshaviah PR, Ebben JP et al. Multicenter clinical method for the on-line monitoring of delivered dialysis validation of an on-line monitor of dialysis adequacy. JAm without blood sampling. Nephrol Dial Transplant 1996; 11: 2023–2030 Soc Nephrol 1996; 7: 464–471 Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Clinical Kidney Journal Oxford University Press

Interventions to improve hemodialysis adequacy: protocols based on real-time monitoring of dialysate solute clearance

Free
6 pages

Loading next page...
 
/lp/ou_press/interventions-to-improve-hemodialysis-adequacy-protocols-based-on-real-6qWMn4qOvA
Publisher
Oxford University Press
Copyright
Published by Oxford University Press on behalf of ERA-EDTA 2017.
ISSN
2048-8505
eISSN
2048-8513
D.O.I.
10.1093/ckj/sfx110
Publisher site
See Article on Publisher Site

Abstract

Background: The monitoring of dialysate ultraviolet (UV) absorbance is a validated technology to measure hemodialysis adequacy and allows for continuous and real-time tracking every session as opposed to the typical once-monthly assessments. Clinical care guidelines are needed to interpret the findings so as to troubleshoot problematic absorbance patterns and intervene during an individual treatment as needed. Methods: When paired with highly structured clinical care protocols that allow autonomous nursing actions, this technology has the potential to improve treatment outcomes. These devices measure the UV absorbance of dialysate solutes to calculate and then display the delivered as well as predicted clearance for that session. Various technical factors can affect the course of dialysate absorbance, confound the device’s readout of clearance results and thus lead to challenges for the dialysis unit staff to properly monitor dialysis adequacy. We analyze optimal and problematic patterns to the device’s ‘clearance’ display (e.g. due to thrombosis of hollow fibers, inadequate access blood flow or recirculation) and provide specific interventions to ensure delivery of an adequate dialysis dose. A rigorous algorithm is presented with representative device monitor display profiles from actual hemodialysis sessions. Procedural rationale and interventions are described for each individual scenario. Conclusion: Real-time hemodialysate UV absorbance patterns can be used for protocol-based intradialytic interventions to optimize solute clearance. Key words: dialysis adequacy, Kt/V, recirculation, urea modeling, vascular access Introduction monitoring the effluent for moieties that are urea surrogates by either electrical conductance or ultraviolet (UV) absorption. Real-time monitoring of dialysis adequacy has been made possi- Recent focus has been on validating the effectiveness of current ble by the development and marketing of hemodialysis machines methodologies. Despite concerns that results could be con- that monitor solute clearance. Currently this is accomplished by founded by such problems as interfering substances, inappropri- two different technological approaches, both of which depend on ate urea modeling, solute rebound or errors in calculating urea measuring fluxes of substances from blood into the dialysate: Received: December 9, 2016. Editorial decision: August 28, 2017 Published by Oxford University Press on behalf of ERA-EDTA 2017. This work is written by US Government employees and is in the public domain in the US. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 Interventions to improve hemodialysis adequacy | 395 volume (V), the dialyzer clearance of urea (K), dialysis time (t) and include the component achieved by convective losses through urea reduction ratio (URR) clearance calculations from the differ- ultrafiltration. The calculated Kt/V and URR curves are shown as ent modalities have generally had excellent correlation. predicted (dotted line) and as achieved (solid line). The display Nevertheless, these estimations of dialysate urea ‘appear- also shows the user-set target values for these parameters (red ance’ have not been universally accepted for the purposes of line) over the prescribed treatment time (e.g. 1.4, 75% in 4 h, quality assurance for dialysis adequacy. The efficacy of hemo- respectively). At any point, the user can discern how the dialysis treatments thus still needs to be confirmed by blood achieved clearance varies from the predicted trajectory and tests for urea ‘clearance’. Given the fact that these blood-based whether the patient will reach the adequacy goal. The machine urea clearance tests are preformed infrequently, on the order of can be set so as to alarm and thereby notify the staff when the one per month, there is much practical value from using a real- patient is projected to not reach the clearance target. Patients time device that is available for every treatment. The ability to received their hemodialysis therapy as part of their routine clin- monitor the pattern of intradialytic solute removal, detect prob- ical care as outpatients or inpatients at the University of Florida lems and immediately intervene [1, 2] enhances the provider’s Shands Hospital, Gainesville, FL and the dialysate UV absorbance ability to react to direct therapy variables. Although such a ben- technology was utilized for every patient at every treatment. efit has been proposed, this is the first report of how to use this Hemodialyzers were made of polysulfone [F160, F200 or F16NF technology for protocol-driven changes to impact each dialysis (Fresenius, Worcester, MA, USA) or cap15 or cap 20 (B. Braun, session’s prescription so as to achieve dosing adequacy. Bethlehem, PA, USA)]. This report adheres to the policies of the Since the ionic conductance technology is limited to intermit- University of Florida Institutional Review Board. tent monitoring, typically every 45 min, it is theoretically inferior to the continuous nature of the UV absorbance technique for the Nursing protocol to reach dialysis adequacy goal immediate detection and resolution of problems. Therefore, nursing protocols were developed based on UV absorbance tech- As per physician orders and the dialysis adequacy policy, nurses nology, which are driven by comparing the calculated delivered are empowered to follow the protocol (Figure 1) and react to treat- dialysis dose (Kt/V or URR) profile to that of the ideal trajectory. ment variances to reach the prescribed dose target. Using the Because minute-to-minute changes in treatment efficacy cannot protocol, nursing actions are based on whether the achieved practically be addressed by offsite physicians, nurses would now clearance pattern is above or below the desired trajectory. have a new tool to independently implement physician-driven Variables include the choice of dialyzer (e.g. based on clearance protocols to improve patient care. For example, immediate recog- specifications), blood and dialysis flow rates, treatment time, the nition of low or decreasing clearance can trigger interventions degree of anticoagulation (e.g. dose of heparin), replacement of a that increase dialysis time, alter blood or dialysate flow rate, clotted dialyzer, repositioning of cannulation needles and throm- adjust needle position, improve anticoagulation or replace the bolysis of access catheters. Images of the problematic clearance dialyzer. Additionally, patterns from the continuous device read- curves were obtained during various clinical scenarios when outs suggestive of access recirculation were identified. Patients patients were off trajectory, as well as improved displays of the with patterns suggestive of recirculation underwent verification profiles after remediation by appropriate nursing interventions. by blood-based testing or imaging studies. Real-time continuous monitoring is particularly important for patients using catheters as their primary access, since intermittent erratic flow may oth- Results erwise not be detected. The dialysate UV absorption-based patient care protocol was The goal of this article is to use the findings from the multiple well-accepted by the nursing staff and physicians. When indi- published device-validation studies to describe clearance profiles cated, the efficacy of the protocol-driven changes to the dialysis (calculated from the dialysate UV absorption) that can prompt real- prescription was verified by blood-drawn URR determinations. time changes in the treatment prescription to overcome problems Anecdotally, the nurses, technicians and physicians reported with achieving dialysis adequacy, access function or technical diffi- better patient compliance with staying for their prescribed HD culties involving the extracorporeal circuit. Clinical care guidelines time by showing the patients the underdialysis graphic. The and protocol-driven clearance interventions based on continuous staff was often able to dissuade the patients from leaving early data allowthe nursingstaff anew opportunitytobenimbleand (staying ‘until the blue line reaches the red line’). Specific clear- empowered so as to provide optimal high-quality dialysis. ance pattern scenarios were identified and are described below. Materials and methods Dialysate-based clearance curve follows predicted trajectory Hemodialysis and online clearance devices Hemodialysis was performed using machines equipped with Dialysate-based clearance pattern on track to meet prescribed dose continuous monitoring of effluent dialysate by UV absorbance Figure 2A demonstrates dialysis sessions in which the dialysate at 280 nm (Adimea device integrated in the Dialog hemodialysis clearance based on UV absorbance follows the anticipated tra- machine, B. Braun, Bethlehem, PA, USA). Clearance is calculated jectory so as to achieve the prescribed dose. In Figure 2A, a Kt/V by analysis of the decrease in the dialysate’s solute absorption goal of 1.4 is reached in a patient weighing 67.8 kg after 4 h using (UVAbs) over time. A logarithmic decline in dialysate moieties is a blood flow (Qb) of 450 mL/min and dialysate flow (Qd) of expected as they are removed from the blood compartment. 500 mL/min. The delivered-dose curve is essentially superim- Characterization of exponentially falling solutes in the effluent posable on the anticipated trajectory. Staff need to stay vigilant yields the dialysis dose expressed as either Kt/V or URR using that there can be concurrent processes with opposite effects on single-pool analysis. While the machine measures absorbance, the displayed curve, although the net effect is unlikely to culmi- it graphically displays the calculated clearance, which increases nate in a tracing that consistently tracks the projected trajectory over time. The software also adjusts the total clearance so as to over the course of the entire dialysis treatment. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 396 | E.A. Ross et al. Enter Treatment Parameters and Dialysis Prescription: Pre Weight & Kt/V (e.g. goal = 1.4) Verify That UV Absorption Device and Alarms are Turned ON Green Light on Display Kt/V On Target* Kt/V Above Target Kt/V Below Target Shallow Slope Steep Slope Verify prescribed Qb (Blood flow) Incrementally increase Qb to maximum per policy Monitor and Consider document every decrease in 15 min HD time Verify Qd (Dialysate Flow): 500 ml/min Increase by 150 ml/min, not to exceed 800 ml/min. Check for recent volume expanders Monitor and document every Evaluate for ilter thrombosis 15 min (e.g. an increasing TMP) Evaluate for access Flush dialyzer with 200 ml Normal saline. recirculaon Evaluate for rapid Assess anticoagulation filter thrombosis Monitor and Lower Qb to test for document every 15 min recirculaon arfact Change ilter if there is indication of dialyzer clotting. Verify adequate Qb (Blood flow) Monitor and Call MD/PA : If need to change in heparin Consider catheter thrombolysis document every dose, dialyzer size or increase treatment me. Increase ancoagulaon and change filter 15 min Fig. 1. Flow diagram of nursing protocol using solute clearance calculated from real-time dialysate UV absorption measurements. Decisions are based on the real-time (measured) clearance curve differing from the projected trajectory. *Signifies the need of the staff to stay vigilant wherein there can be concurrent processes with oppo- site effects on the displayed curve. Fig. 2. (A) Clearance curve (based on UV absorption) for a patient weighing 67.8 kg who can meet the target clearance in the prescribed 4 h. (B) Clearance curve below prescription with gradual clotting of the dialyzer and improved trajectory after increased dialysate flow rate. (C and D) Clearance curves erroneously high due to artifact caused by access recirculation. (E) Clearance curve in a former pediatric patient weighing 54 kg who can reach clearance targets in less than the prescribed 4 h. (F) Clearance curve erroneously high due to artifact caused by rapid volume expansion from intravenous albumin. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 Interventions to improve hemodialysis adequacy | 397 Dialysate-based clearance pattern initially adequate, then falling below fibers due to inadequate anticoagulation. Sudden severe throm- the desired trajectory bosis of the fibers causes a somewhat different pattern. The In Figure 2B, a patient is initially on target for dialysis adequacy rapid decrease in UV absorption by dialysate solutes is incor- and then the trajectory falls below the desired adequacy at 2h rectly attributed to high dialysis clearance (displayed as an due to what was discerned to be gradual clotting of the hollow upward slope in calculated clearance), then the curve flattens fibers. As per the protocol, the Qd was increased to 800 mL/min out (as solute removal remains low). The curve then gradually and the dialysate clearance curve shifted upward to again declines further and further below expectation. match the desired trajectory, achieving the prescribed dose. Discussion Dialysate-based clearance curve higher than predicted The ability to monitor a real-time dialysis dose holds great prom- or prescribed trajectory ise to ensure the delivery of optimal treatments. The first com- Steep upward slope yet actual clearance is inadequate due to access mercially available technology utilized electrical conductance of recirculation effluent dialysate. These devices are based on the premise and Figure 2C and 2D demonstrates two examples of inadequate evidence that sodium fluxes across the dialyzer membrane are clearance due to access recirculation that had not been other- an excellent surrogate for urea dialysance and that they can be wise suspected or detectable during the treatment session. As measured by changes in dialysate conductivity [3, 4]. As currently described below, the greater the recirculation of the extracor- marketed (Fresenius, Waltham, MA, USA), the hemodialysis poreal circuit, the faster the decrease in its concentration of ure- machines intermittently alter dialysate sodium and calculate a mic solutes. This misleading rapid decline in solutes due to the predicted urea clearance (K). Although technically possible to be recirculation phenomenon is erroneously interpreted by the done frequently, with this popular device it is typically done only software as a high dialysis dose; the calculated dialysate clear- every 45 min, or six times over the course of a 4-h treatment. ance curve rises greatly above the machine’s predicted curve. Based on the presumption that those few values are representa- Reversed needles are a potential cause and easily remedied. In tive of the entire session, the device estimates the clearance for Figure 2C, a patient weighing 138 kg with catheter access and a the whole treatment (Kt). However, for determination of the dial- Qb of 300 mL/min was prescribed 5 h at a Qd of 800 mL/min. ysis dose (Kt/V), the urea volume (V)must be established sepa- Recirculation was not clinically detected by the staff and was rately by various empirically derived equations (e.g. using weight, only suspected when the calculated clearance curve was unex- height, gender) or independent technology (e.g. bioimpedance). pectedly greater than anticipated, with a pronounced steep The two major weaknesses of conductance-based dose monitor- slope: this heavyweight patient was erroneously predicted ing are missing the problems that occur between the intermittent to reach a 1.40 Kt/V goal in just over 2 h. Blood sampling con- tests and errors in calculating volume. The latter can be >20%, firmed an 20% access recirculation. Figure 2D demonstrates depending on the methodology chosen for the V estimation [5–8]. how recirculation not only raises the curve but also causes an Monitoring clearance in dialysate effluent can overcome the erroneously high numerical Kt/V to be displayed (3.3 in this deficiencies of conductance-based devices. As any particular example). solute is dialyzed from the blood, the rapid decrease in its plasma concentration will be reflected by a similar decrease in its appearance in the used dialysate. The UV absorbance tech- Dialysate-based clearance pattern on trajectory but dialysis dose con- nology continuously measures certain solutes in the effluent, sistently higher than the prescribed goal which will thus exponentially decrease in concentration over As shown in Figure 2E, a lesser weighing former pediatric the treatment time. By mathematically characterizing the loga- patient on multiple dialysis sessions had reached the adequacy rithmic decline in dialysate solute (e.g. curve fitting), the equa- goal more quickly than the 4 h initially prescribed. At 54 kg, a Qb tion yields the Kt/V value using single-pool analysis. For of 400 mL/min and Qd of 500 mL/min, the Kt/V of 1.4 was attain- example, when the natural logarithm of the absorbance is plot- able at just 3 h. This permitted cautious reduction in the dialysis ted against time, the slope of the resultant line is determined by time with verification of adequacy by blood testing. the Kt/V. Hence the advantage of the direct measure approach is that urea volume does not have to be independently deter- Sudden steep upward slope, then curve parallel to predicted trajectory mined; this is the potential major source of error as described This phenomenon is due to sudden hemodilution caused by above. Since treatment efficacy can change over the course of volume expanders such as saline or albumin infusions. The the treatment (e.g. from clotting or changing flow rates), errors diluted blood passing through the dialyzer results in an imme- in curve fitting are overcome by the software performing the diate decrease in uremic solutes appearing in the dialysate analyses every 20 min and not being confounded by alarm con- effluent. The dramatic decrease in dialysate UV absorbance is ditions (e.g. blood leaks, conductivity problems). incorrectly interpreted by the software as being due to a higher The theoretical weakness of using UV methods, however, is dialysis dose, yielding erroneously high Kt/V and URR values. that absorbance at any particular wavelength is not unique for a Figure 2F demonstrates this happening immediately following single substance. Each molecule will not only have an optimal infusion of 50 g of albumin. or peak wavelength but will also absorb over a range of values, and thus the various moieties found in human blood will be Dialysate-based clearance curve lower than predicted expected to have overlapping absorbance spectra. For example, trajectory one study characterized 40 absorption peaks [9]. Thus, choosing Common causes of the achieved dialysate clearance being the wavelength based on the urea molecule (285 nm) would be below the desired trajectory are inadequate prescription (blood nonspecific and has the additional shortcoming that it has rela- or dialysate flows, time, choice of dialyzer) clearance character- tively limited UV absorbance compared with other waste prod- istics in relation to the patient’s size and Kt/V goal, problematic ucts appearing in the dialysate [10]. Wavelengths in the range of access causing low blood flows and gradual clotting the hollow 200–285 nm have been studied in relation to how they Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 398 | E.A. Ross et al. characterize many common solutes [11–13], using the 280 nm could prompt extra dialysis sessions, a change in the dialysate Adimea device. Multiple investigations have established that composition, imaging or revision of the dialysis access. This is small-molecule absorption in that spectral range is an excellent important in that the shape of the displayed Kt/V or URR curve surrogate for urea removal and primarily includes such sub- can thus provide information beyond that of traditional inter- stances as uric acid and creatinine. Small solutes with high mittent adequacy parameters that are calculated using clearance rates account for 95% of UV absorbance [9, 11]. This postdialysis data; the curve can be of particular value for the is analogous to sodium being used as a surrogate for urea in the detection of access recirculation. As long as the intra-access conduction-based technologies. Important for clinical use, there blood flow is more than the extracorporeal pump rate, there is neither negligible confounding from UV absorbance by the would not be any recirculation and the UV absorbance– low concentrations of small and large proteins in the dialysate generated clearance curve would be reliable. Once the pump nor by commonly used medications [9]. The effect of medication flow exceeds the capacity of the malfunctioning access, dia- clearance would be attenuated by their typically having much lyzed blood begins to loop back into the dialyzer. Thus this lower plasma concentrations than that of uremia moieties such ‘clean’ blood from the dialyzer outlet returns to mix with the as urea. A rigorous study across the wide spectrum of pharma- fresh blood (‘recirculates’) and solute concentrations at the dia- ceuticals has not been done. lyzer inlet are lower (and decrease more rapidly) than antici- Theoretically, errors in predicting urea removal could be pated. The recirculation-induced steep decline in the introduced if the various substances have different volumes of extracorporeal circuit’s solutes results in a similar rapidly distribution and different mass transfer coefficients between decreasing pattern in the dialysate (and UV absorption). The soft- the extracellular fluid compartments. As pointed out by ware incorrectly interprets this phenomenon as having been Daugirdas and Tattersall [14], molecules that could confound caused by a high dialysis dose. For example, with substantial absorption calculations tend to be large and have slow removal recirculation the solute concentration can decline so quickly in by hemodialysis and thus UV absorption calculations would be the dialysate that patients can appear to achieve Kt/V values of expected to underestimate urea clearance. Nevertheless, moni- >1.4 in <2 h, which is clearly not physiologically possible. toring of moieties absorbing in this wavelength range has been Properly trained staff can recognize the atypical steep shape of shown to be satisfactory for clinical purposes. Kt/V calcula- the displayed clearance curves, which greatly differ from the urea tions have reportedly been very similar when comparing blood, anticipated (dotted line) trajectory. As long as the access is still conductance and UV absorption techniques, with differences patent and has a minimally acceptable flow rate (e.g. 200 mL/ from 0 to 0.1 [2, 5–7, 15, 16]. UV absorption clearance correlated min), the nurse will be able to decrease the pump rate so as to well with blood testing [17] not just with urea, but also with eliminate the clearance curve’s recirculation artifact. Blood test- potassium and phosphate [1]. Some of the discrepancy may be ing would be needed to verify an adequate URR. We believe that due to deficiencies in the mathematical modeling of single- ver- the ability to detect recirculation as well as other causes of low sus double-pool urea kinetics for the blood-based methodology. clearance has particular clinical importance in the setting of In that, continuous absorbance measurements are preferable to catheters. There have been a number of patients in whom we fewer sampling points and the UV absorbance device can be discerned recirculation from malfunctioning femoral vein cathe- used to more rigorously assess postdialysis rebound, which is ters. The problem was unanticipated from the flow and pressure consistent with two-compartment kinetics [18]. It has also been profiles and would have been missed if not suggested by the UV reported that what has been described as a 7% lower clearance absorption device, confirmed by blood testing and resolved by from the UV methodology is actually due to some overestimation replacement with a new longer catheter. We also fear that cathe- from the two-pool blood-based methodology [2]. ter flow can be so erratic that problems, and thus inadequate Importantly, the potential disadvantages of all of these devi- dialysis, could be missed by the intermittent nature of the ces that use urea surrogates for curve-fitting clearance calcula- conduction-based devices. tions could be overcome by technology that would precisely It is important for the staff to also appreciate how sequential measure urea concentration in dialysate. Highly sensitive and remedies to abnormal dialysate absorption-based clearance selective urea assays would also permit mass clearance calcula- curves can reveal more than one problem in a dialysis treat- tions, but those machines are complex, require calibration and ment. For example, an abnormal curve may persist after replac- have not been practical or economically feasible for mass mar- ing a dialyzer and could thus unmask a second problem. From a keting. For example, results from using the Biostat 1000 device practical standpoint, this would be a circumstance in which this (Baxter Healthcare, McGaw Park, IL, USA) supported the use of technology could make it difficult to discern access recircula- dialysate measurements for determinations of adequacy [19, tion. Users thus need to be cognizant of the possibility that 20], but the machine was not made commercially available. simultaneous unrelated problems could have opposite effects In this article we have demonstrated the usefulness of con- on the displayed curve, wherein one could increase the dis- tinuous real-time monitoring of dialysis clearance for maintain- played curve (e.g. recirculation) while a second malfunction ing and achieving adequacy goals. While it remains imperative decreases it (e.g. partial clotting). We believe it would be theo- to verify these estimations with blood-based urea determina- retically possible, but rare, for these combined effects to culmi- tions, those measurements cannot be performed instantane- nate in a resultant curve precisely following the trajectory over ously and thus real-time UV absorbance technology can guide the full course of many hours of treatment; deviations would nimble intradialytic changes to the prescription: adjusting blood provide the opportunity for a trained operator to detect both or dialysate flow, prolonging dialysis time, repositioning nee- problems. Another example of complications with opposing dles, checking for access recirculation, optimizing anticoagula- effects on the dialysate absorption curve would be an tion of the extracorporeal circuit and replacing dialyzers ultrafiltration-associated decrease in cardiac output and an impaired by thrombosed fibers. Clearance curves (calculated increase in cardiopulmonary recirculation and hemoconcentra- from the dialysate UV absorption measurements) that unex- tion. The limitations of both absorbance- and ionic conductance- pectedly deviate from the predicted trajectories can also prompt based technologies emphasize that they cannot replace tradi- unscheduled postdialysis laboratory testing, which in turn tional measures of clearance and dialysis adequacy. Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018 Interventions to improve hemodialysis adequacy | 399 6. Sternby J. Whole body Kt/V from dialysate urea measure- Lastly, the behavioral benefits of using real-time clearance monitoring are not to be underestimated. Anecdotally, many ments during hemodialysis. J Am Soc Nephrol 1998; 9: patients have been convinced to not sign off dialysis early by 2118–2123 showing them their clearance curves. This educational tool has 7. Castellarnau A, Werner M, Gu¨ nthner R et al. Real-time Kt/V led some recalcitrant patients to stay on treatment until the determination by ultraviolet absorbance in spent dialysate: ‘blue line hits the red line’; however, this is only a partial solu- technique validation. Kidney Int 2010; 78: 920–925 8. Moret K, Beerenhout CH, van den Wall Bake AW et al. Ionic tion to the nonadherence wherein ultrafiltration goals may still not be met. High fluid removal volumes will also increase solute dialysance and the assessment of Kt/V: the influence of dif- removal by convection, so that the adequacy predictions that ferent estimates of V on method agreement. Nephrol Dial do not incorporate ultrafiltration will underestimate actual total Transplant 2007; 22: 2276–2282 9. Schoots AC, Homan HR, Gladdines MM et al. Screening of clearance. The ability of the staff to detect problems in real time, troubleshoot, intervene and thus improve dialysis has UV-absorbing solutes in uremic serum by reversed phase important implications for nursing care. Not only is the quality HPLC–change of blood levels in different therapies. Clin Chim of dialysis care improved, but we believe there is a morale and Acta 1985; 146: 37–51 10. Filutowicz Z, Lukaszewski K, Pieszynski K. Remarks on career satisfaction benefit from enhancing nursing autonomy related to improved clinical outcomes. spectra-photometric monitoring of urea in dialysate. J Med Informat Technol 2004; 8: 105–110 In conclusion, continuous dialysate UV absorption–based monitoring of hemodialysis clearance is a very promising tech- 11. Arund J, Tanner R, Uhlin F et al. Do only small uremic toxins, nology to achieve and maintain treatment adequacy goals. chromophores, contribute to the online dialysis dose moni- Real-time intradialysis quality assurance for every session is far toring by UV absorbance? Toxins (Basel) 2012; 4: 849–861 12. Lindley EJ, Tattersall J, De Vos JY et al. On line UV-absorbance superior to the typical monthly assessments. Protocol-driven modifications to treatment parameters are valuable nursing measurements. J Renal Care 2007; 33: 41–48 tools for optimizing patient therapy outcomes. 13. Fridolin I, Lindberg L-G. On-line monitoring of solutes in dialysate using wavelength-dependent absorption of ultra- violet radiation. Med Biol Eng Comput 2003; 41: 263–270 14. Daugirdas JT, Tattersall JE. Automated monitoring of hemo- Conflict of interest statement dialysis adequacy by dialysis machines: potential benefits to patients and cost savings. Kidney Int 2010; 78: 833–835 None declared. 15. Uhlin F, Fridolin I, Lindberg LG et al. Estimation of delivered dialysis dose by on-line monitoring of the ultraviolet absorb- References ance in the spent dialysate. Am J Kidney Dis 2003; 41: 1026–1036 1. Fridolin I, Magnusson M, Lindberg LG. On-line monitoring of solutes in dialysate using absorption of ultraviolet radiation: 16. Di Filippo S, Andrulli S, Manzoni C et al. On-line assessment of delivered dialysis dose. Kidney Int 1998; 54: 263–267 technique description. Int J Artif Organs 2002; 25: 748–761 17. Ficheux A, Gayrard N, Szwarc I et al. Use of spent dialysate 2. Uhlin F, Fridolin I, Magnusson M et al. Dialysis dose (Kt/V) and analysis to estimate blood levels of uraemic solutes without clearance variation sensitivity using measurement of ultraviolet-absorbance (on-line), blood urea, dialysate urea and blood sampling: urea. Nephrol Dial Transplant 2010; 25: 873–879 ionic dialysance. NephrolDialTransplant 2006; 21: 2225–2231 3. Polaschegg HD. Automatic, noninvasive intradialytic clear- 18. Tomson R, Uhlin F, Fridolin I. Urea rebound assessment based on UV absorbance in spent dialysate. ASAIO J 2014; 60: ance measurement. Int J Artif Organs 1993; 16: 185–191 459–465 4. Kuhlmann U, Goldau R, Samadi N et al. Accuracy and safety 19. Canaud B, Bosc JY, Leblanc M et al. Evaluation of high-flux of online clearance monitoring based on conductivity varia- tion. Nephrol Dial Transplant 2001; 16: 1053–1058 hemodiafiltration efficiency using an on-line urea monitor. Am J Kidney Dis 1998; 31: 74–80 5. Manzoni C, Di Filippo S, Corti M et al. Ionic dialysance as a 20. Depner TA, Keshaviah PR, Ebben JP et al. Multicenter clinical method for the on-line monitoring of delivered dialysis validation of an on-line monitor of dialysis adequacy. JAm without blood sampling. Nephrol Dial Transplant 1996; 11: 2023–2030 Soc Nephrol 1996; 7: 464–471 Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/394/4565559 by Ed 'DeepDyve' Gillespie user on 20 June 2018

Journal

Clinical Kidney JournalOxford University Press

Published: Oct 25, 2017

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off