Merits and limitations of continuous blood volume monitoring during haemodialysis. Summary of the EDTNA/ERCA Journal Club discussion: Winter 2005

The discussion explored and expanded on the issues raised by Dasselaar et al in their review of the measurement of relative blood volume (RBV) changes during dialysis (NDT 2005). Dialysis machines incorporating blood volume monitoring and control are widely available in Europe. The use of continuous blood volume monitoring (CBVM) to help establish dry weight; problems with CBVM due to connection and use of single needle dialysis; the physiological processes that cause RBV changes during eating, exercise and posture changes; and the application of blood volume based biofeedback control were discussed by participants from ten countries. The 'take-home' messages from the discussion were that CBVM can assist in setting target weight, but must be used together with traditional measures and experience. Biofeedback control may help to achieve symptom-free dialysis, but staff should be prepared to monitor patients systematically for several weeks to obtain individualised settings. Users of CBVM should be aware of factors that can alter the central haematocrit leading to apparent changes in RBV. Practical guidelines should be developed to help staff interpret CBVM data effectively.     

Merits and limitations of continuous blood volume monitoring during haemodialysis: Summary of the EDTNA|ERCA Journal Club discussion: winter 2005

The discussion explored and expanded on the issues raised by Dasselaar et al in their review of the measurement of relative blood volume (RBV) changes during dialysis (NDT 2005). Dialysis machines incorporating blood volume monitoring and control are widely available in Europe. The use of continuous blood volume monitoring (CBVM) to help establish dry weight; problems with CBVM due to connection and use of single needle dialysis; the physiological processes that cause RBV changes during eating, exercise and posture changes; and the application of blood volume based biofeedback control were discussed by participants from ten countries. The ‘take‐home’ messages from the discussion were that CBVM can assist in setting target weight, but must be used together with traditional measures and experience. Biofeedback control may help to achieve symptom‐free dialysis, but staff should be prepared to monitor patients systematically for several weeks to obtain individualised settings. Users of CBVM should be aware of factors that can alter the central haematocrit leading to apparent changes in RBV. Practical guidelines should be developed to help staff interpret CBVM data effectively.     

Increase in blood volume during dialysis without ultrafiltration

Combined dialysis and ultrafiltration leads to more frequent episodes of hypotension than isolated ultrafiltration. It has been suggested that decreased plasma volume preservation could be responsible for this phenomenon. The present study evaluates the effects of diffusive dialysis on the changes in relative blood volume (RBV). Six stable hemodialysis patients, without the need of ultrafiltration, were studied during 10 sessions of diffusive dialysis (bicarbonate) lasting 4 h. RBV was monitored continuously by measurement of hematocrit. During the 1st and 2nd h RBV increased by 2.4+/-1.4 and 2.5+/-0.8% respectively, returning to baseline levels at the end of dialysis. No changes in blood pressure or heart rate were noted. We conclude that during diffusive dialysis without ultrafiltration RBV is increased. A decrease in vascular resistance, or changes in regional blood distribution could explain these findings.     

Daily use of the physio dialysis system: Long‐term experience

Background: Hypovolaemia has been implicated as a major causal factor of morbidity during haemodialysis (HD). In order to avoid the appearance of destabilising hypovolaemia a biofeedback control system for intra‐HD blood volume (BV) change modelling has been developed (Hemocontrol?, Hospal Italy). It is based on an adaptive controller incorporated into a HD machine (Integra?, Hospal Italy). The Hemocontrol? biofeedback system (HBS) monitors BV contraction during HD with an optical device; furthermore, HBS modulates BV contraction rates (by adjusting the ultrafiltration rate — UFR) and the refilling rate (by adjusting dialysate conductivity — DC) in order to obtain the desired pre‐determined BV trajectories. Methods: Nineteen patients prone to hypotension (7 males, 12 females, mean age 64.5 ± 3.0 SEM years, on maintenance HD for 80.5 ± 13.2 months) volunteered for the prospective study which aimed to compare the efficacy and safety of bicarbonate HD treatment equipped with HBS, as a whole (HBS), with the gold standard, bicarbonate treatment, equipped with a constant UFR and DC (BD). The study included one period of 6 months of BD always preceding a follow‐up period of HBS treatment ranging from 14 to 30 months (mean 24.0 ± 1.6). Results: The overall occurrence of symptomatic hypotension and muscle cramps was significantly less in HBS treatment. Self‐evaluation of intra‐ and inter‐HD symptoms (the worst score was 0 and the best one 10) did reveal a statistically significant difference, as far as post‐HD fatigue is concerned (6.2 ± 0.2 in HBS vs. 4.3 ± 0.1 in BD treatment, p < 0.0001). No difference between the two treatments was observed when comparing pre‐ and post‐HD lying blood pressure, heart rate, body weights and body weight changes. Conclusions: HBS is an effective treatment. Hypovolaemia‐associated morbidity occurs less in BD treatment than HBS. Furthermore, HBS is a safe treatment in the medium‐term because these results are achieved without potentially harmful changes in blood pressure, body weight and serum sodium concentration.     

The effect of profiled hemodialysis on intradialytic hemodynamics when a proper sodium balance is applied

BACKGROUND: Profiled hemodialysis (HD) has been claimed to ameliorate intradialytic complications such as hypotension. Frequently, these profiles are based on providing the patient with an accumulating sodium load. This increases the risk of interdialytic complications, such as hypertension and increased weight gain. The present study investigated the effect of profiled HD, without an accompanying sodium loading, on intradialytic hemodynamics in stable HD patients. METHODS: In eight stable HD patients a standard hemodialysis (S-HD) was compared to a decreasing Na(+)-profiled hemodialysis (Na-HD), and an ultrafiltration profiled hemodialysis (UF-HD). Care was taken to have the sodium balances similar during these sessions. The patients were monitored non-invasively during dialysis with respect to their cardiac performance by means of electrical impedance cardiography, their variation in blood volume by means of an on-line optical measurement, and their hydration state by means of body impedance analysis. RESULTS: Sodium balance and mean arterial sodium concentrations were similar in the three treatments. Intradialytic hemodynamics during UF-HD were similar to those of S-HD. However, Na-HD improved blood pressure preservation, remarkably without significant blood volume preservation, due to a better stroke volume preservation in the first hour of dialysis. CONCLUSION: Sodium-balanced, Na-profiled HD improves blood pressure preservation in stable HD patients without providing the patients with a sodium load. This effect is due to a better stroke volume preservation early in dialysis, without a significant reduction in blood volume decrease. UF-HD, as mono-therapy, has no beneficial effect on intradialytic hemodynamics in stable patients.     

On-Line Identification of Hemodynamic Variables by Dilution of Ultrapure Dialysate During Hemodialysis

The removal of fluid during hemodialysis (HD) affecting both blood volume and cardiac output (CO) is one of the main causes for intradialytic hypotension. Information on hemodynamic variables obtained during HD may help to detect and to prevent this risk. It was the aim to develop a technique and a model for simple bedside identification of these variables. The 4008H HDF dialysis machine (Fresenius Medical Care, Bad Homburg, Germany) has the capability to inject defined volumes of ultrapure dialysate at correct temperatures into the extracorporeal bloodline at the relatively slow rate of 150 mL/min, which can be used for the purpose of indicator dilution measurements. However, the classic bolus approach to calculate CO fails in the setting of long and slow infusions. Dilution curves were therefore analyzed by a two-compartment model where the exchange between central (V ₁) and peripheral (V ₂) compartments was determined by systemic blood flow (q _sys). A blood volume monitor (BVM, Fresenius Medical Care, Bad Homburg, Germany) was used for on-line measurement of changes in blood water concentration (BWC) caused by the dilution. Extracted dilution curves were then used to fit the two-compartment model to the experimental data. The model produced plausible parameters where q _sys determined in two patients and for repeated measurements (7.6±0.6 L/min) was close to CO obtained by the reference technique (7.1±1.6 L/min). The system has the potential for complete automatization when equipped with appropriate control inputs to the BVM and to the HDF-module of the HD machine.     

Ventajas del uso de citrato respecto al acetato como estabilizante en el líquido de hemodiálisis: estudio aleatorizado ABC-treat

Hemodialysis (HD) with bicarbonate dialysis fluid (DF) requires the presence of an acid to prevent the precipitation of calcium and magnesium carbonate. The most used acid is acetic acid, with it several complications have been described. In a previous work, we described the acute changes during an HD session with a DF with citrate instead of acetate. Now, we report the results in the medium term, 16 weeks. It is a prospective, multicenter, crossover and randomized study, where 56 HD patients with bicarbonate three times a week were dialysed for 16 weeks with 3 mmol/L acetate and 16 weeks with 1 mmol/L citrate. Patients older than 18 years with a previous stay on HD of more than 3 months and with a normal functioning arteriovenous fistula were included. Epidemiological data, dialysis, bioimpedance, biochemistry before and after HD, as well as hypotensive episodes, were collected monthly. After 16 weeks of citrate treatment, pre-HD ionic calcium and magnesium were significantly lower and paratiroid hormone (PTH) higher than in the acetate period. No differences were observed in the effectiveness of dialysis. Hypotensive episodes were significantly more frequent with acetate than with citrate: 311 (14.1%) vs 238 (10.8%) sessions. The lean mass index increased by 0.96 ± 2.33 kg/m² when patients switched from DF with acetate to citrate.HD with citrate modifies several parameters of bone mineral metabolism, not only acutely as previously described, but also in the long-term. The substitution of acetate for citrate improves hemodynamic stability, producing less hypotension and can improve nutritional status.     

A Comparative Study of Blood Pressure Control with Short In-Center versus Long Home Hemodialysis

We conducted a randomized crossover trial to establish, within patients, whether long-slow hemodialysis (HD) was associated with better blood pressure (BP) control than standard HD. Nine home HD patients, not on antihypertensive drugs, were dialyzed to the same eKt/V(urea) and target weights for 6-8 h (LD) at home and for 3.5-4.5 h (SD) in the dialysis center 3 times weekly in randomized sequence, with each phase lasting 8 weeks. Ambulatory BP, bioimpedance, neurohormones and autonomic function were measured in each phase. Pre- and postdialysis systolic, ambulatory systolic and diastolic BP were all higher with SD than with LD and intradialysis hypotension was more common. Weight, ECF volume and neurohormones did not differ between treatments. Muscle sympathetic activity was increased in both phases and cardiac sympathetic activity tended higher during SD. These findings suggest that additional factors to ECF volume may contribute to the superior BP control produced by long-slow HD.     

Debate from the 2012 ASH Annual Scientific Sessions: should blood pressure be reduced in hemodialysis patients? con position

The relationship between blood pressure and cardiovascular events in hemodialysis patients is complicated and controversial. The timing of blood pressure measurements (home, before dialysis, after dialysis, during dialysis) provide somewhat different results. Moreover, the use of antihypertensive medications may also confound the relationship between blood pressure and cardiovascular outcome. Most important may be the relationship between central blood volume/pressure and risk for cardiac events, specifically for congestive heart failure and sudden death. Achieving dry-weight during dialysis as opposed to a specific blood pressure level is the optimal strategy for reducing cardiovascular events in the hemodialysis patient.     

L’hypotension diastolique isolée en hémodialyse : facteur de risque de complications cardiovasculaires de novo et de mortalité toute cause

Intra dialytic hypotension is the most common complication in hemodialysis. However, isolated diastolic hypotension (IDH) in hemodialysis is asymptomatic and its detection requires repeated monitoring of blood pressure during dialysis sessions. To study this phenomenon, we conducted a prospective study over a period of 5 years in 45 chronic hemodialysis patients. The IDH, was noted in 42% at inclusion, and in 59,5% of the cases at the end of the study. IDH was associated with advanced age, female gender, high relative critical blood volume, cardiac arrhythmias and diastolic dysfunction of the left ventricle. IDH was also significantly associated with novel cardiovascular complications (P = 0.004) and all-cause mortality (P = 0.038). Isolated diastolic hypotension is a particularly common phenomenon in hemodialysis. Our data encourage in-depth reflection on this subject in hemodialysis. In addition, our study highlights the value of screening for IDH by close monitoring of hemodynamic parameters, and calls for personalized dialysis management based on the analysis of the demonstrated risk factors and on the study of the associated comorbidities.     

Biological effects of oxidant stress in haemodialysis: the possible roles of vitamin E.

Oxidative stress has been proposed to play a role in many disease states, including cardiovascular and infectious diseases, cancer, diabetes and neurodegenerative pathologies. The fact that these diseases have an increased incidence in uremia, and particularly in dialysis patients, suggests an increased exposure to oxidative stress in this condition. In haemodialysis (HD), the absence of a complete correction of the uremic toxicity together with the untoward effects of the dialysis, malnutrition and the progressive worsening of the clinical condition, can lead to a high susceptibility to oxidative stress by an abnormal production of oxidants - including reactive oxygen species (ROS) and uremic toxins with prooxidant function - and defective antioxidant protection. One of the most investigated biological effects of the oxidative stress in the HD patients is lipid peroxidation in plasma and blood cell membranes. Moreover, we have recently described how abnormal apoptosis in peripheral blood leukocytes is associated with cell oxidative stress (intracellular thiol depletion). Vitamin E, in both in vitro and in vivo conditions, has been proposed to partially correct these effects. In this review we evaluated some features of two new dialysis strategies using an antioxidant approach to the protection against the oxidant stress in HD. Their rationale is based on the emerging role of vitamin E in counteracting some biological effects associated with oxidant stress namely lipid peroxidation and apoptosis. These techniques use: 1) the recirculation of the dialysate through a suspension of vitamin E-enriched liposomes combined with the supplementation by the dialysate with ascorbic acid, this method has been called hemolipodialysis; 2) the coating of the dialysis membrane with vitamin E (vitamin E- modified dialysis membranes). These unconventional approaches to the antioxidant therapy in HD open a widely unexplored and promising field in the evolution of the biomaterials and dialysis quality.     

China collaborative study on dialysis: a multi-centers cohort study on cardiovascular diseases in patients on maintenance dialysis

ABSTRACT: BACKGROUND: Cardiovascular disease (CVD) is the main cause of death in patients on chronic dialysis. The question whether dialysis modality impacts cardiovascular risk remains to be addressed. China Collaborative Study on Dialysis, a multi-centers cohort study, was performed to evaluate cardiovascular morbidity during maintenance hemodialysis (HD) and peritoneal dialysis (PD). Result The cohort consisted of chronic dialysis patients from the database of 9 of the largest dialysis facilities around China. The inclusion period was between January 1, 2005, and December 1, 2010. Cardiovascular morbidity was defined as the presence of clinically diagnosed ischemic heart disease, heart failure, peripheral vascular disease, and/or stroke. The patients who had cardiovascular morbidity before initiation of dialysis were excluded. Data collection was based on review of medical record. A total of 2,388 adult patients (1,775 on HD and 613 on PD) were enrolled. Cardiovascular morbidity affected 57% patients and was comparable between HD and PD patients. However, clinically diagnosed ischemic heart disease and stroke was more prevalent in PD than HD patients. When the patients were stratified by age or dialysis vintage, the cardiovascular morbidity was significantly higher in PD than HD among those aged 50 years or older, or those receiving dialysis over 36 months. Multivariate analysis revealed that the risk factors for cardiovascular morbidity had different pattern in PD and HD patients. Hyperglycemia was the strongest risk factor for cardiovascular morbidity in PD, but not in HD patients. Hypertriglyceridemia and hypoalbuminemia were independently associated with CVD only in PD patients. CONCLUSIONS: Cardiovascular morbidity during chronic dialysis was more prevalent in PD than HD patients among those with old age and long-term dialysis. Metabolic disturbance-related risk factors were independently associated with CVD only in PD patients. Better understanding the impact of dialysis modality on CVD would be an important step for prevention and treatment.     

Excessive Fall of Blood Pressure During Maintenance Hemodialysis in Patients With Chronic Renal Failure Is Induced by Vascular Malfunction and Imbalance of Autonomic Nervous Activity

Acute hypotension during maintenance hemodialysis (HD) is not only a critical complication, but also an independent risk factor for mortality in patients with chronic renal failure (CRF). This study was designed to clarify the mechanisms underlying excessive fall of blood pressure during HD. Fifty‐six CRF patients with HD thrice a week were divided into two groups according to the intradialytic hypotension episodes after 4 weeks of the observation period; the hypotension group, showing four or more episodes of intradialytic hypotension, and the non‐hypotension group, showing three episodes of intradialytic hypotension or less. The intradialytic hypotension was defined as a fall of ≥30 mm Hg in the systolic blood pressure during HD. The brachial‐ankle pulse wave velocity (ba‐PWV), serum high‐sensitivity (hs)‐CRP, reactive oxygen species (ROS) generation, and serum malondialdehyde‐modified LDL (MDA‐LDL) were measured before HD. The high‐ frequency (HF) and low‐frequency components (LF) of the heart rate variability and entropy were analyzed by the maximal entropy method. The ba‐PWV, hs‐CRP, ROS generation, and MDA‐LDL were significantly higher in the hypotension group than in the non‐hypotension group. HF, LF/HF, and entropy during HD increased significantly in the non‐hypotension group, while entropy during HD decreased significantly in the hypotension group as compared with the baseline. LF/HF and entropy during HD were significantly lower in the hypotension group than in the non‐hypotension group. These findings suggest that the major factors causing excessive fall of blood pressure during HD in patients with CRF might be vascular malfunction and imbalance of autonomic nervous activity.     

Acute Intradialytic Cardiac Function and Inflammatory Cytokine Changes During High‐Efficiency Online Hemodiafiltration With Acetate‐Free and Standard Dialysis Solutions

Acetate in standard acetate‐containing bicarbonate (AC) dialysis fluid could induce peripheral vasodilatation, suppression of myocardial function, and inflammatory cytokine production, resulting in intradialytic hypotension in conventional hemodialysis (HD) patients. Online hemodiafiltration (HDF) provides superior hemodynamic stability over HD. The potentially additive hemodynamic benefits of the novel acetate‐free bicarbonate (AF) dialysis fluid in online HDF have never been explored before. The present randomized, double‐blind, crossover study was conducted in 22 online HDF patients to investigate the impact of AF dialysis fluid on hemodynamic and cytokine changes compared with AC dialysis fluid in online HDF. The results demonstrated the comparable changes of arterial pressure between AF and AC online HDF. During the study periods, the incidences of composite intradialytic hypotension and other adverse events were not different. The baseline and hourly changes of cardiac index, cardiac output, and peripheral vascular resistance during dialysis were comparable (P = 0.534, 0.199, and 0.641, respectively). The percent reductions of NT‐proBNP and cTnT were not significantly different (72.6 ± 12.3 vs. 72.6 ± 12.8%, P = 0.99 and 35.2 ± 12.8 vs. 36.7 ± 12.0%, P = 0.51). The changes of all pro‐inflammatory cytokines (IL‐2β, IL‐6, IL‐8, and TNF‐α) and anti‐inflammatory cytokine (IL‐10) during dialysis were comparable between both groups. In conclusion, AF dialysis solution does not offer additional hemodynamic benefit for stable online HDF patients. The hemodynamic stability provided by online HDF might protect the adverse effects of acetate.     

ULTRA VIOLET ABSORBANCE ON‐LINE MEASUREMENT UTILIZED TO MONITOR CLINICAL EVENTS DURING HAEMODIALYSIS

Background — On‐line monitoring systems of spent dialysate, used to estimate dialysis dose, have been developed with different instrumentation during the last two decades. The routine use of an on‐line monitoring system has been suggested to provide an adequate dialysis dose to the haemodialysis (HD) patient. The aim of this study was to show that monitoring the spent dialysate using UV‐absorbance might bring new information about the clearance process. Methods — 108 HD treatments distributed among 16 clinical stable patients were monitored on‐line using ultra violet (UV) absorbance. For the measurement of UV‐absorbance a spectrophotometer was connected to the fluid outlet of the dialysis machine with all spent dialysate passing through a flow cuvette. The UV‐absorbance curves were examined in combination with the recorded observations of events that occurred during the studied treatments. Results — The study demonstrates that UV‐absorbance visualizes different kinds of events such as hypotension, conductivity alarms and restricted flow in artery needle blood pump stops that often occur during dialysis treatment. Conclusion — An on‐line UV‐monitoring system with a high sampling rate makes it possible to identify variations in dialysis clearance of different origin and gives feedback after performing interventions during a dialysis session.     

Midodrine improves chronic hypotension in hemodialysis patients

BACKGROUND: The effects of midodrine on chronic hypotension in hemodialysis (HD) patients have not been well investigated. METHODS: We evaluated midodrine's effect on autonomic function and hemodynamics in 12 HD patients who had chronic systolic blood pressure less than 100 mm Hg. Midodrine (5.0 mg) twice a day was given for 4 weeks. Another 12 age- and sex-matched HD patients with normotension were selected as a control group. Autonomic function tests included the heart-rate responses to the Valsalva maneuver and 30:15 ratio as well as supine and standing blood pressure (BP) and sustained hand-grip test. Hemodynamic changes included 24-hour blood pressure, cardiac output, total peripheral resistance (TPR), and plasma renin and aldosterone concentrations. RESULTS: Compared with the control subjects, HD patients with chronic hypotension had more severe autonomic dysfunction and significantly lower TPR. After 4 weeks of midodrine therapy, sympathetic function (orthostatic and hand-grip tests) improved in conjunction with significant increases in mean arterial pressure (MAP) (79.5 +/- 4.9 to 85.0 +/- 5.1 mm Hg, P < 0.05) and TPR (768 +/- 37 versus 1097 +/- 72 dyne/sec/cm-5, P < 0.01) despite no significant change in Valsalva ratio, 30:15 ratio, and cardiac output. MAP changes were positively correlated with TPR changes (r = 0.82, P < 0.001). Supine plasma renin activity was significantly increased. In addition, MAP during HD was also significantly increased during midodrine therapy. CONCLUSIONS: Midodrine improves chronic hypotension in HD patients by modulating autonomic function and its direct effects on peripheral vessels.     

Choice of renal replacement therapy in patients with diabetic end stage renal disease

Diabetic nephropathy is becoming the leading cause of end-stage renal disease (ESRD) worldwide. Although the prognosis of patients with diabetes and ESRD receiving Renal Replacement Therapy (RRT) has improved greatly, the presence of pre-existing cardiovascular disease means that the survival and medical rehabilitation of diabetics continue to be inferior to that of non-diabetics. RRT should be initiated earlier in patients with diabetes than in non-diabetics and the main choices of modalities are: 1) haemodialysis (HD), 2) Peritoneal dialysis (PD), 3) Kidney transplantation alone (KTA) or 4) simultaneous kidney and pancreas transplantation (SPKT). The most common modality of RRT utilised in the diabetic patient remains HD but this method is associated with many clinical problems, in particular the managment of vascular access and frequent intradialytic hypotension. There is accumulating evidence demonstrating that both survival and medical rehabilitation of patients with diabetes and ESRD is superior after renal transplantation with or without pancreas transplantation.     

Changes in Volumetric Hemodynamic Parameters Induced by Fluid Removal on Hemodialysis in Critically Ill Patients

Management of volume status is difficult in critically ill patients with renal failure. Volumetric hemodynamic indices are increasingly being used to guide fluid therapy in the intensive care unit (ICU), but are not established to monitor hemodialysis‐induced fluid removal in critically ill patients. Using volumetric hemodynamic monitoring, changes in extravascular lung water index (EVLWI) and intrathoracic blood volume index (ITBVI) were measured immediately before and after hemodialysis sessions in 35 ICU patients. Additional hemodynamic and oxygenation related parameters were recorded at the same time, and online relative blood volume (RBV) monitoring was performed during hemodialysis. EVLWI decreased significantly with fluid removal (median 10.0 vs. 9.6 mL/kg, P = 0.001), whereas ITBVI remained stable (median 1012 vs. 1029 mL/m², P = 0.402). Significant changes were also observed in stroke volume variation (median 12.0 vs. 13.0 %, P = 0.012), cardiac index (median 4.2 vs. 3.5 mL/min/m², P = 0.003), mean arterial pressure (median 77 vs. 85.5 mmHg, P = 0.006), norepinephrine dose (median 0.092 vs. 0.114 μg/kg per min, P = 0.043), and hemoglobin values (median 9.5 vs. 10.4 gm/dL, P = 0.036). RBV decreased by 7.8% (median); there was no correlation with either the volumetric measurements or the other hemodynamic parameters recorded. EVLWI reduction with dialysis reflects the removal of excess body fluid, whereas preservation of cardiac preload is indicated by ITBVI stability. Volumetric hemodynamic measurements provide additional information concerning fluid status and are thus potentially useful to guide fluid removal on hemodialysis in critically ill patients.