Purity and stability of online-prepared hemodiafiltration fluid after storage

BACKGROUND/AIMS

Previous studies have suggested that online hemodiafiltration (OL-HDF) fluid can be used as dialysate for continuous renal replacement therapies, and thus HDF costs can be reduced. The aims of this study were to determine the purity of OL-HDF fluid and to verify the stability of the electrolyte composition and acid-base balance during its storage.

METHODS

OL-HDF fluid was collected in 70 individual bags and stored for up to 7 days. The following tests were performed daily in 10 bags: natural visible precipitation (macrocrystallization), sample collection for chemical analysis and fluid culture, limulus amebocyte lysate endotoxin test, standard culture of NALGENE® filters after passing of the fluid, and molecular analysis of bacterial DNA.

RESULTS

The values of pH and pCO(2) showed a significant change starting at 24 h (p < 0.001); after 72 h, their values were beyond the measurable range. Coefficient of variation for pCO(2) was as high as 25.7%. Electrolyte composition (Na(+), K(+), Cl(-), Ca(2+) and glucose) showed a statistically significant difference over time (p < 0.05); however, their coefficients of variation were low (1.7, 1.4, 0.6, 2.3 and 0.9%, respectively), which might not be considered clinically significant. Negative results were obtained at all points by fluid and filter cultures, endotoxin test and molecular analysis. No macrocrystallization was observed at any time point.

CONCLUSIONS

We demonstrate the microbiological purity of OL-HDF fluid stored for up to 7 days. The electrolyte composition was stable, except for a relevant change in pCO(2) and consequently in pH (first noted at 24 h), emphasizing the need to reassess the acid-base balance in multilayer plastic bags in future studies.

Body composition and heart rate variability to achieve dry weight and tolerance

Autonomic dysfunction in patients with end- stage renal disease is associated with poor prognosis. Heart rate variability (HRV), determined by the standard deviation of the normal R- R interval, has been reported to be a useful evaluation of cardiac autonomic modulation. The relationship between HRV and hydration status (HS) can be analyzed by whole body bioimpedance spectroscopy. This allows a classification of patients according the combination of HS with predialysis systolic blood pressure. Differences in HRV can be studied in patients with high over hydration, but normal or low blood pressure, with respect to fluid-overloaded/hypertensive patients and normohydrated/normotensive patients. In conclusion, the assessment of the autonomic nervous system response to the hemodialysis treatment in end- stage renal disease patients, classified according to a reliable and quantitative measurement of their fluid overload, could permit better management of both arterial blood pressure and HS.

[A pilot study comparing pulse high volume hemofiltration (pHVHF) and coupled plasma filtration adsorption (CPFA) in septic shock patients]

High-volume hemofiltration (HVHF) and coupled plasma filtration adsorption (CPFA) have shown potential to improve the treatment of sepsis in animals, but there have been no studies comparing these two treatments in humans. Our aim was to compare the hemodynamic effects of HVHF and CPFA in septic shock patients with acute kidney injury (AKI) undergoing continuous renal replacement therapy (CRRT). We performed a cross-over study enrolling patients with septic shock and AKI who were receiving CRRT. Patients were treated with pulse HVHF and continuous veno-venous hemofiltration (CVV H) on day 1 and CPFA and CVV H on day 2 or vice versa. HVHF was performed for 8-10 hours with a replacement fluid rate of 85 mL/kg/h. CPFA was performed for 8-10 hours with a plasma flow rate of 15%. CVV H was performed for the rest of the day with a replacement fluid rate of 35 mL/kg/h. The primary endpoints were changes in mean arterial pressure, vasopressor requirement (expressed as vasopressor score, VS), and noradrenaline dose after pulse HVHF and CPFA. The two treatments were compared using nonparametric tests. We enrolled 8 patients (median age 70.5 years, SOFA 12.5, SAPS II 69.5). There was a trend towards a reduction in VS with HVHF and CPFA (HVHF p=0.13, CPFA p<0.05). There was no significant difference between the two treatments in terms of percentage change in VS score (p=0.22). The data from this pilot study provide no evidence for a difference in hemodynamic effects between pulse HVHF and CPFA in patients with septic shock already receiving CRRT. A larger sample size is needed to adequately explore this issue.

[Methylobacterium radiotolerans bacteremia in hemodialysis patients]

Central venous catheters (CVCs) play an important role in replacement therapy for patients with acute and chronic renal failure. Secondary infections due to central venous access are responsible for 48-73% of bacteremia in hemodialysis patients and are an important cause of morbidity and increased health costs for these patients. Episodes of unexplained fever were noted in hemodialysis patients in our center starting in October 2006. An investigation for causative microorganisms was conducted from October 2006 to April 2007. Bacterial DNA was extracted and amplified using universal primers for bacterial 16S. Amplification by multiple PCR was performed on the samples and the subsequent sequencing led to the identification of the microorganism of interest as belonging to Methylobacterium radiotolerans. We report the largest cluster of dialysis catheter-related bloodstream infections caused by M. radiotolerans, and describe the difficulties in the prompt and correct identification of these bacteria. Thirty-seven patients had positive cultures for M. radiotolerans from blood (2.7%) or CVC (29.7%) or both (67.6%). After removal and replacement of CVCs and antibiotic therapy and the strict application of an infection management protocol, there were no more fever episodes or cultures positive for M. radiotolerans.

Sequential convective therapies (SCT): a prospective study on feasibility, safety, adequacy and tolerance of on-line hemofiltration and hemodiafiltration in sequence

Sequential dialysis techniques (i.e pure ultrafiltration followed by dialysis) have been used in the past, due to their capability to remove large volumes of fluids without inducing hemodynamic instability. The disadvantages of inadequate efficiency and lack of technology lead to the decline of such methods. Hemofiltration (HF) and hemodiafiltration (HDF) are recently being utilized in a greater proportion thanks to on-line fluid preparation systems. Each process (HF and HDF) has its own benefits in the removal of small, medium and high-molecular weight substances and in hemodynamic stability. Sequential convective therapies (SCT) such as hemofiltration-hemodiafiltration in sequence (HF-HDF) may combine the benefits and eliminate the disadvantages of each method and should be studied in order to explore their potential application in modern dialysis. Furthermore they can be easily applied nowadays, due to the development of new sophisticated dialysis machines. In order to evaluate the feasibility, safety, efficiency and tolerance of different SCT methods we studied 3 schedules: SCT1: 1h pre-dilution HF followed by 3h of post-dilution HDF (in the HF mode we lost 25% of the total fluid that had to be removed). SCT2: 1h pre-dilution HF followed by 3h of post-dilution HDF (in the HF mode we lost 50% of the total fluid that had to be removed). SCT3: 2h pre-dilution HF followed by 2h of post-dilution HDF (in the HF mode we lost 50% of the total fluid that had to be removed). We studied 6 chronic hemodialysis patients using the same machine (AK200 ULTRA), with on-line fluid preparation system and the same type of dialyzer (Polyflux 210). SCT schedules were compared to on-line HF, on-line HDF and high flux dialysis performed with the same dialyzers. The treatments resulted safe, easy, feasible and well tolerated with an improved hemodynamic response to high volume convective therapies. Adequacy of treatment was satisfactory in all SCT schedules while middle molecular weight solute clearance and removal resulted higher in treatments with higher convective component. SCT might represent an interesting option for the future especially in patients with hemodynamic instability and requirements for interventions during treatment.

Sequential hemofiltration-hemodiafiltration technique: all in one?

Sequential dialysis techniques (i.e. pure ultrafiltration followed by dialysis) have been used in the past, due to their capability to remove large volumes of fluids without inducing hemodynamic instability. The disadvantages of the inadequate dialysis and the lack of technology lead to the decline such methods. Hemofiltration (HF) and hemodiafiltration (HDF) are recently being utilized in a greater proportion thanks to the on line fluid preparation systems. Each process (HF and HDF) has its own benefits in the removal of small, medium and high-molecular weight substances and in the hemodynamic stability. Sequential hemofiltration/ hemodiafiltration (SHF/HDF), may combine the benefits and eliminate the disadvantages of each method. Furthermore they can be easily applied nowadays, due to the development of new high technological hemodialysis machines. In order to evaluate the feasibility and the effects of SHF/HDF we studied 7 chronic hemodialysis patients (6 months of treatment with SHF/HDF switched to 6 months of SHDF/HF), using the same machine (AK200 ULTRA), with on line fluid preparation system and the same type of dialyzer (Polyflux 210). The feasibility of such techniques (SHF/HDF or vice versa) resulted excellent. All sessions left the patients in a condition of well-being making fulltime work. No difference was observed between the different period of treatment, but a reduction in pre value was observed in calcium-phosphorous product, C-reactive protein and beta2-microglobulin, at the end of the sequential techniques. SHF/HDF therapy is a very promising technique. Further studies are needed to better explore the potential of such a therapeutic approach in the quality of life, the hemodialysis adequacy and the hemodynamic stability of our patients.

[Rationale for the use of extracorporeal treatments for sepsis]

Sepsis is the leading cause of disability and mortality among critical patients; moreover, it causes high economic expenditures. Although very much is known about the pathophysiology of this condition and its mediators despite great investments directed to its control, mortality rates remain high. Recent treatment manuals emphasize the value of early goal-oriented therapy and also point to the high efficacy of activated protein C. Extracorporeal blood clearance may potentially become a new approach to treating this condition. There are reports on its positive clinical results that are likely associated with the effective removal of septic mediators. Human and animal studies, few and rather alike as they are, have yielded promising results. It is evident that the use of these procedures is justified; however, their efficiency in sepsis requires large-scale, correctly conducted studies.

Pulse high volume hemofiltration

The sepsis syndrome is the most common cause of acute renal failure and multiple organ dysfunction in critically ill subjects and continues to have an alarmingly high mortality. Normal immune homeostasis is interrupted by a complex storm of inflammatory mediators responsible for the deleterious effects. Extracorporeal blood purification techniques can confer benefits in sepsis by proven non-specific removal of these mediators (pro- or anti-inflammatory), and provide a logical and adequate approach to treat this syndrome. High volume hemofiltration (HVHF) has had the most dramatic effect conferring benefits in hemodynamics, reduction in vasopressor doses and improvement in survival. "Pulse HVHF" is the latest approach which may offer the most efficient results: a daily schedule of 6-8 hours followed by standard CVVH. This paper describes the rationale and potential of this technique. Reliability and tolerance of this technique and biological effects are described.

Continuous renal replacement technology: from adaptive devices to flexible multipurpose machines

OBJECTIVE

To review the evolution of technologies in the development of renal replacement therapies.

DATA SOURCES

Articles and published reviews on renal replacement therapies.

SUMMARY OF REVIEW

Continuous arterio-venous haemofiltration (CAVH) was the first continuous renal replacement technique capable of overcoming the traditional haemodialysis-related side effects, making possible the treatment of critically ill patients safely and with less physiological instability. The evolution of technology and the progress experienced in intensive care units (ICUs) has made it possible to start renal replacement therapy programs in the absence of a chronic dialysis facility or a trained nephrological team. Initial limitations and draw-backs of CAVH, stimulated the ICU staff to explore new avenues for better therapy. Extracorporeal therapies are today a routine experience in the ICUs: continuous renal replacement therapies are a broadly accepted treatment for acute renal failure. Furthermore, alternative indications for extracorporeal blood circulation (e.g. sepsis, liver failure, congestive heart failure, drug intoxications, hyperthermia, immuno-mediated syndromes) are becoming more and more popular. The ideal machine has yet to be completed, but progress has occurred and has opened a new era for critical care nephrology and the further expansion of blood purification technology in the ICU.

CONCLUSIONS

Technical advances in renal replacement therapies have increased their functionality (i.e. used in hepatic failure, sepsis, cardiac failure and immuno-mediated syndromes), are easier to operate and have less side-effects compared with their standard extracorporeal counterparts. Further improvements may see them become a routine part in the management of the critically ill patient.

Caspase-3 and -8 activation and cytokine removal with a novel cellulose triacetate super-permeable membrane in an in vitro sepsis model

Pro-apoptotic molecules are generated during sepsis which may be responsible for alteration of organ function in sepsis. Removal of systemic apoptotic activity may affect recovery from sepsis. Current high flux membranes might not be sufficiently permeable to eliminate pro-apoptotic factors. We evaluated the elimination of pro-apoptotic factors induced by LPS in human whole blood by a super-permeable cellulose triacetate membrane (SUREFLUX FH 150, Nipro, Osaka, Japan) in comparison to a standard high flux cellulose triacetate membrane (UT 700, Nipro, Osaka, Japan) and a polyethersulfone plasmafilter (Bellco, Mirandola Italy) in an in vitro blood circulation. We spiked human whole blood with lipopolysaccharide from Escherichia coli (Serotype 026-86, 10 mg/ml), incubated it for 3 hours to allow cytokine generation and recirculated it at 300 ml/min for 3 hours. The UF line was first returned to the blood module at 10 min. After this, the UF was drained from 10 to 60 min at a rate of 1000 ml/h. Zero balance was obtained by re-infusion of bicarbonate buffered hemofiltration fluid. Apoptosis was assessed on U937 monocytes (incubated with plasma or ultrafiltrate) by fluorescence microscopy dyes (Hoechst 33342, propidium iodide) and annexin V flow cytometry. Caspase-3 and Caspase-8 activity was assessed on the recirculated blood monocytes by spectrophotometric methods. IL-2, IL-10 and TNFalpha were determined by commercially available ELISAs. Sieving coefficients and clearances were determined for the different cytokines. Caspase-3 and Caspase-8 were activated by LPS and remained either stable or increased during in vitro circulation. Apoptosis activity of U937 cells, when incubated with the ultrafiltrate, increased in parallel with arterial plasma values (for Uf: UT700 = 23.1%; Sureflux FH150 = 42.5%). However, by 60 min the apoptotic activity recorded with the ultrafiltrate was reduced to the levels of arterial plasma (for Uf: UT700 = 19.8%; Sureflux FH150 = 11.2%). Sieving coefficients in the super-permeable membrane were significantly higher for all measured cytokines in comparison to the standard high flux membrane (e.g. TNFalpha 0.72 vs 0.03 p < 0.001) and close to the values observed for the plasmafiltration membrane. Nevertheless protein losses measured by albumin leakage were much lower with the Sureflux filter in comparison to the plasmafilter. In conclusion, pro-apoptotic factors can be eliminated by dialytic membranes with the removal rate maximized by using super high flux dialysers which may represent a compromise between hemofiltration and plasmafiltration membranes.

Iron management in hemodialysis patients: optimizing outcomes in Vicenza, Italy

The management of anemia in uremic patients undergoing hemodialysis requires the appropriate combination of erythropoietin treatment, iron supplementation, and on occasion androgen therapy. Identifying and correcting functional iron deficiency is crucial to optimizing erythropoietin efficiency. Recently, however, the trend to administer maintenance iron with resultant high serum ferritin and high transferrin saturation has led to an increase in reports of iron overload. Oral iron supplementation is inexpensive and safe, but poor patient compliance and reduced intestinal absorption may limit its efficacy. Intravenous iron, on the other hand, is effective, and its safety is related to the iron salt used. Currently available data suggest that iron saccharate may be the safest iron salt available for intravenous administration, although iron gluconate is safer than the dextran forms of intravenous iron. It should be kept in mind, however, that all forms of intravenous iron may have the potential of inducing iron overload. At this time, the levels of ferritin that define iron overload are not clearly established. The side effects of iron overload are well recognized (infections, malignancies, vascular diseases); however, no guidelines exist for safe practice. There are many markers of iron deficiency, with serum ferritin and hypochromic red cell percentage currently the best markers available in clinical practice.