Ralf Wojke

On-line haemodiafiltration versus haemodialysis: stable haematocrit with less erythropoietin and improvement of other relevant blood parameters.

Background: Controlled randomised studies to prove improved cardiovascular stability and improved anaemia management during on-line haemodiafiltration (oHDF) are scarce. Methods: 70 patients were treated with both haemodialysis (HD) and oHDF in a cross-over design during 2 × 24 weeks at a dialysis dose of eKt/V≧1.2. Patients randomised into group A started on HD and switched over to oHDF, whereas patients in group B began with oHDF and were treated with HD afterwards. Intradialytic morbid events (IME), such as symptomatic hypotension or muscle cramps, were noted in case of appearance. Blood parameters reflecting anaemic status, phosphate status, lipid metabolism, oxidative stress, and accumulation of advanced glycation end products were recorded either monthly or at the end of each study phase. Results: The mean incidence of IME was 0.15 IME per treatment, and there was no statistical difference between oHDF and HD. A higher haematocrit (oHDF 31.5% vs. HD 30.5%, p < 0.01) at a lower erythropoietin dose (oHDF 4,913 vs. HD 5,492 IU/week, p = 0.02) was found during oHDF, when the sequence of HD and oHDF had not been taken into account. For the study groups, the results were less distinct: in group A, a higher haematocrit (HD 30.4% vs. oHDF 32.0%, p < 0.01) at a comparable erythropoietin dose (HD 5,421 vs. oHDF 5,187 IU/week, ns) was observed during oHDF, whereas in group B an identical haematocrit (oHDF 30.8% vs. HD 30.7%, ns) was achieved at a reduced erythropoietin dose (oHDF 4,622 vs. HD 5,568 IU/week, p < 0.01). During oHDF, lower levels of free and protein-bound pentosidine and of serum phosphate were found. Conclusion: In contrast to other studies, no benefit regarding cardiovascular stability for oHDF was found, but oHDF could well offer a potential benefit regarding anaemia correction, inflammation, oxidative stress, lipid profiles, and calcium-phosphate product.

Observation of microbubbles during standard dialysis treatments

Background The infusion of microbubbles as a side effect of haemodialysis was repeatedly demonstrated in recent publications, but the knowledge on the source of microbubbles and on microbubble formation is scarce. Methods Microbubbles in the range of 10–500 µm were measured by a non-invasive bubble counter based on a pulsed ultrasonic Doppler system in a non-interventional study of a single centre. Totally, 29 measurements were performed in standard treatments covering a broad range of patient and treatment conditions (types of blood access, treatment modes, blood flow rates and arterial pressures). Results Several possible sources of microbubbles could be identified such as an arterial luer lock connector at negative pressure and remnant bubbles from insufficient priming, but some sources of microbubbles remain unknown. Microbubbles were found in all treatments, haemodialysis (HD) and online haemodiafiltration. The lowest average microbubble rates (17 ± 16 microbubbles per minute) were observed in patients treated by online haemodiafiltration at medium blood flow rates and moderate arterial pressures and the highest average microbubble rates (117 ± 63 microbubbles per minute) at high blood flow rates (550 mL/min) and low arterial pressures (−210 mmHg). Generally, the microbubble rate correlated to both blood flow rate (correlation coefficient r = 0.45) and negative arterial pressure (r = 0.67). Conclusions Microbubbles are a general side effect of HD; origin and pathophysiologic consequences of this phenomenon are not well understood, and deserve further study.

Determination of dialysis dose: a clinical comparison of methods.

Background: Guidelines recommend regular measurements of the delivered hemodialysis dose Kt/V. Nowadays, automatic non-invasive online measurements are available as alternatives to the conventional method with blood sampling, laboratory analysis, and calculation. Methods:In a prospective clinical trial, three different methods determining dialysis dose were simultaneously applied: Kt/V_Dau (conventional method with Daugirdas’ formula), Kt/V_OCM [online clearance measurement (OCM) with urea distribution volume V based on anthropometric estimate], and Kt/V_BCM [OCM measurement with V measured by bioimpedance analysis (Body Composition Monitor)]. Results:1,076 hemodialysis patients were analyzed. The dialysis dose was measured as Kt/V_Dau = 1.74 ± 0.45, Kt/V_OCM = 1.47 ± 0.34, and Kt/V_BCM = 1.65 ± 0.42. The difference between Kt/V_OCM and Kt/V_BCM was due to the difference between anthropometric estimated V_Watson and measured V_BCM. Compared to Kt/V_Dau, Kt/V_OCM was 15% lower and Kt/V_BCM 5% lower. Kt/V_Dau was incidentally prone to falsely high values due to operative errors, whereas in these cases OCM-based measurements Kt/V_OCM and Kt/V_BCM delivered realistic values. Conclusions:The automated OCM Kt/V_OCM with anthropometric estimation of urea distribution volume was the easiest method to use, but Kt/V_BCM with measured urea distribution volume was closer to the conventional method.

Dialysate saving by automated control of flow rates: Comparison between individualized online hemodiafiltration and standard hemodialysis

Cost reduction and quality improvement seem to be conflicting issues. However, online hemodiafiltration (oHDF) with new automatic functions offers a cost‐efficient therapy compared to hemodialysis (HD). Seven dialysis centers conducted a randomized clinical trial with cross‐over design: high‐flux HD vs. postdilutional oHDF with functions coupling both dialysate and substitution flow rates to blood flow rates. During the 6 weeks of the study, all treatment parameters remained unchanged for HD and oHDF, apart from dialysate and substitution flow rate. Treatment data were recorded during each treatment, and predialytic and postdialytic concentrations of urea were recorded at the end of each study phase. The analysis involved 956 treatments of 54 patients. The mean dialysate consumption was 123.2 ± 6.4 l for HD and 113.4 ± 14.9 l for oHDF (p < 0.0001), the mean dialysis dose was 1.42 ± 0.23 for HD and 1.47 ± 0.26 for oHDF (p < 0.0001); oHDF resulted in a lower dialysate consumption (8.0% less) and a slightly increased dialysis dose (Kt/V 3.5% higher) compared to HD. oHDF with the investigated automatic functions offers substantial savings in dialysate consumption without decreasing dialysis dose.

Simultaneous blood temperature control and blood volume control reduces intradialytic symptoms

Purpose Intra-dialytic morbid events (IME; e.g. hypotension, cramps, headaches) are frequent complications during hemodialysis (HD), known to be associated with ultrafiltration-induced hypovolemia and body temperature changes. Feedback control of blood volume adjusts the ultrafiltration rate in order to keep the blood volume above the patients individual limit; feedback control of blood temperature maintains the mean arterial blood temperature at the individual pre-dialytic level. Each of these methods reduces the frequency of IME. Methods In a randomized clinical trial the simultaneous application of both feedback controls was investigated for the first time. In 15 weeks, each patient went through 3 study phases: an observational screening phase, a standard phase (STD), and a blood temperature- and blood volume-control phase (CTL). Patients with at least 5 sessions with IME out of 15 sessions in the screening phase were eligible for the study and randomized either into sequence STD-CTL or CTL-STD. Results 26 patients completed the study according to protocol, and 778 HD treatments were analyzed. The general treatment parameters were similar in both study phases: treatment duration (STD: 244 min, CTL: 243 min, NS), pre-dialytic weight (STD: 72.3 kg, CTL: 72.2 kg, NS), and weight loss due to ultrafiltration (STD: 3.26 kg, CTL: 3.15 kg, NS). The proportion of HD treatments with IME was 32.8% during STD and 18.0% during CTL (p=0.024). Conclusions The frequency of HD sessions with IME was significantly reduced by 45% compared to standard HD in this randomized clinical trial by use of individualized HD treatments with simultaneous feedback control of blood volume and blood temperature.