Ultrafiltration profiling and measurement of relative blood volume as strategies to reduce hemodialysis-related side effects

Haematocrit monitoring and blood volume estimation during continuous renal replacement therapy

BACKGROUND

Continuous haemoglobin, venous blood oxygen saturation, and haematocrit (Hct) monitoring is currently not applied during continuous renal replacement therapy (CRRT). Such Hct monitoring enables estimation of changes in blood volume as percentage change (ΔBV%) from therapy start time and is incorporated into intermittent haemodialysis machines but not CRRT machines despite its potential to optimise fluid management in CRRT patients.

METHODS

To overcome this problem, we used a standalone monitor (CRIT-LINE®IV, Fresenius Medical Care, Concord, USA) with an associated in-line blood chamber (CRIT-LINE®IV Blood Chamber, Fresenius Medical Care, Concord, USA) and designed our own adaptor connection piece (TekMed and Morriset, Melbourne and Brisbane, Australia) to allow these readings at the vascular access outflow and recorded data for estimated Hct and derived ΔBV% during CRRT.

RESULTS

We report on this technique with an illustrative case example and 12 h of CRRT data on the fluid loss rate prescribed, hourly net patient fluid loss (range: 0-308 mL/h), mean arterial pressure, norepinephrine dose (range: 5-14 mcg/min), estimated continuous Hct and ΔBV%, and the otherwise undetected diagnosis of an approximate 15 % decrease in blood volume during the CRRT.

CONCLUSION

We have described a technical CRRT circuit modification that can facilitate a previously unavailable assessment of fluid shifts during CRRT. Further application in clinical trials is now possible.

Prevention of Intradialytic Hypotension in Hemodialysis Patients: Current Challenges and Future Prospects

Intradialytic hypotension, defined as rapid decrease in systolic blood pressure of greater than or equal to 20 mmHg or in mean arterial pressure of greater than or equal to 10 mmHg that results in end-organ ischemia and requires countermeasures such as ultrafiltration reduction or saline infusion to increase blood pressure to improve patient's symptoms, is a known complication of hemodialysis and is associated with several potential adverse outcomes. Its pathogenesis is complex and involves both patient-related factors such as age and comorbidities, as well as factors related to the dialysis prescription itself. Key factors include the need for volume removal during hemodialysis and a suboptimal vascular response which compromises the ability to compensate for acute intravascular volume loss. Inadequate vascular refill, incorrect assessment or unaccounted changes of target weight, acute illnesses and medication interference are further potential contributors. Intradialytic hypotension can lead to compromised tissue perfusion and end-organ damage, both acutely and over time, resulting in repetitive injuries. To address these problems, a careful assessment of subjective symptoms, minimizing interdialytic weight gains, individualizing dialysis prescription and adjusting the dialysis procedure based on patients' risk factors can mitigate negative outcomes.

Why is Intradialytic Hypotension the Commonest Complication of Outpatient Dialysis Treatments?

Intradialytic hypotension (IDH) is the most frequent complication of hemodialysis (HD) treatments with a frequency of 10% to 12% for patients with chronic kidney disease attending for outpatient treatments and is associated with both temporary ischemic stress to vital organs, including the heart and brain, and increased patient mortality. Although there have been many different definitions of IDH over the years, an absolute nadir systolic blood pressure (SBP) has the strongest association with patient outcomes. The unifying pathophysiology is one of reduced effective blood volume, resulting in lower plasma tonicity, and if this cannot be adequately compensated for by activation of neurohumeral systems, then arteriolar tone and blood pressure fall. The risk factors for developing IDH are numerous, ranging from patient-related factors, including age and comorbidity with reduced cardiac reserve, to patient compliance with dietary and lifestyle advice, to reactions with the extracorporeal circuit and medications, choice of dialysate composition and temperature, setting of postdialysis target weight, ultrafiltration rate, and profiling. Advances in dialysis machine technology by providing real time estimates of the effective circulating volume and adjusting dialysate composition to maintain vascular tonicity are being developed, but currently require more sophisticated biofeedback loops to be clinically effective in preventing IDH. While awaiting advances in artificial intelligence, the clinician continues to rely on patient education to limit interdialytic weight gains, frequent assessment of the postdialysis target weight, adjusting dialysate composition and temperature, introducing convective therapies to increase thermal losses, and altering dialysis session duration and frequency to reduce ultrafiltration rate requirements.

Proportional integral feedback control of ultrafiltration rate in hemodialysis

BACKGROUND

Most hemodialysis patients without residual kidney function accumulate fluid between dialysis session that needs to be removed by ultrafiltration. Ultrafiltration usually results in a decline in relative blood volume (RBV). Recent epidemiological research has identified RBV ranges that were associated with significantly better survival. The objective of this work was to develop an ultrafiltration controller to steer a patient's RBV trajectory into these favorable RBV ranges.

METHODS

We designed a proportional-integral feedback ultrafiltration controller that utilizes signals from a device that reports RBV. The control goal is to attain the RBV trajectory associated with improved patient survival. Additional constraints such as upper and lower bounds of ultrafiltration volume and rate were realized. The controller was evaluated in in silico and ex vivo bench experiments, and in a clinical proof-of-concept study in two maintenance dialysis patients.

RESULTS

In all tests, the ultrafiltration controller performed as expected. In the in silico and ex vivo bench experiments, the controller showed robust reaction toward deliberate disruptive interventions (e.g. signal noise; extreme plasma refill rates). No adverse events were observed in the clinical study.

CONCLUSIONS

The ultrafiltration controller can steer RBV trajectories toward desired RBV ranges while obeying to a set of constraints. Prospective studies in hemodialysis patients with diverse clinical characteristics are warranted to further explore the controllers impact on intradialytic hemodynamic stability, quality of life, and long-term outcomes.

The pathophysiology of leg cramping during dialysis and the use of carnitine in its treatment

Leg cramping is a common side effect of hemodialysis, and this is frequently treated by the administration of carnitine, but this is not effective in every patient. Alkalosis is a key component of the etiology of leg cramping during hemodialysis sessions. This is mediated through the binding of calcium ions to serum albumin, which causes hypocalcemia, and an increase in the release of calcium ions from the sarcoplasmic reticulum. Normally the calcium pump on the sarcoplasmic reticulum consumes ATP and quickly reuptakes the released calcium ions, which rapidly stops excessive muscle contractions. Thus, carnitine deficiency results in prolonged muscle contraction because of ATP depletion. However, during ATP production, carnitine is only involved up to the stage of acyl-CoA transport into mitochondria, and for the efficient generation of ATP, the subsequent metabolism of acyl-CoA is also important. For example, β-oxidation and the tricarboxylic acid cycle may be affected by a deficiency of water-soluble vitamins and the electron transport chain requires coenzyme Q10, but statins inhibit its production. The resulting accumulation of excess long-chain acyl-CoA in mitochondria inhibits enzymes involved in energy production. Thus, carnitine administration may be used more effectively if clinicians are aware of its specific physiologic roles.

Machine Learning Analysis of Time-Dependent Features for Predicting Adverse Events During Hemodialysis Therapy: Model Development and Validation Study

BACKGROUND

Hemodialysis (HD) therapy is an indispensable tool used in critical care management. Patients undergoing HD are at risk for intradialytic adverse events, ranging from muscle cramps to cardiac arrest. So far, there is no effective HD device-integrated algorithm to assist medical staff in response to these adverse events a step earlier during HD.

OBJECTIVE

We aimed to develop machine learning algorithms to predict intradialytic adverse events in an unbiased manner.

METHODS

Three-month dialysis and physiological time-series data were collected from all patients who underwent maintenance HD therapy at a tertiary care referral center. Dialysis data were collected automatically by HD devices, and physiological data were recorded by medical staff. Intradialytic adverse events were documented by medical staff according to patient complaints. Features extracted from the time series data sets by linear and differential analyses were used for machine learning to predict adverse events during HD.

RESULTS

Time series dialysis data were collected during the 4-hour HD session in 108 patients who underwent maintenance HD therapy. There were a total of 4221 HD sessions, 406 of which involved at least one intradialytic adverse event. Models were built by classification algorithms and evaluated by four-fold cross-validation. The developed algorithm predicted overall intradialytic adverse events, with an area under the curve (AUC) of 0.83, sensitivity of 0.53, and specificity of 0.96. The algorithm also predicted muscle cramps, with an AUC of 0.85, and blood pressure elevation, with an AUC of 0.93. In addition, the model built based on ultrafiltration-unrelated features predicted all types of adverse events, with an AUC of 0.81, indicating that ultrafiltration-unrelated factors also contribute to the onset of adverse events.

CONCLUSIONS

Our results demonstrated that algorithms combining linear and differential analyses with two-class classification machine learning can predict intradialytic adverse events in quasi-real time with high AUCs. Such a methodology implemented with local cloud computation and real-time optimization by personalized HD data could warn clinicians to take timely actions in advance.

Sodium and ultrafiltration profiling in hemodialysis: A long-forgotten issue revisited

Sodium and ultrafiltration profiling are method of dialysis in which dialysate sodium concentration and ultrafiltration rate are altered during the course of the dialysis session. Sodium and ultrafiltration profiling have been used, commonly simultaneously, to improve hemodynamic stability during hemodialysis. Sodium profiling is particularly effective in decreasing the incidence of intradialytic hypotension, while ultrafiltration profiling is suggested to decrease subclinical repeated end organ ischemia during dialysis. However, complications such as increased interdialytic weight gain and thirst due to sodium excess have prevented widespread use of sodium profiling. Evidence suggest that different sodium profiling techniques may lead to different clinical results, and preferring sodium balance neutral sodium profiling may mitigate adverse effects related to sodium overload. However, evidence is lacking on the long-term clinical outcomes of different sodium profiling methods. Optimal method of sodium profiling as well as the utility of sodium/ultrafiltration profiling in routine practice await further clinical investigation.

Management of acute intradialytic cardiovascular complications: Updated overview (Review)

An increasing number of patients require renal replacement therapy through dialysis and renal transplantation. Chronic kidney disease (CKD) affects a large percentage of the world's population and has evolved into a major public health concern. Diabetes mellitus, high blood pressure and a family history of kidney failure are all major risk factors for CKD. Patients in advanced stages of CKD have varying degrees of cardiovascular damage. Comorbidities of these patients, include, on the one hand, hypertension, hyperlipidemia, hyperglycemia, hyperuricemia and, on the other hand, the presence of mineral-bone disorders associated with CKD and chronic inflammation, which contribute to cardiovascular involvement. Acute complications occur quite frequently during dialysis. Among these, the most important are cardiovascular complications, which influence the morbidity and mortality rates of this group of patients. Chronic hemodialysis patients manifest acute cardiovascular complications such as intradialytic hypotension, intradialytic hypertension, arrhythmias, acute coronary syndromes and sudden death. Thus, proper management is extremely important.

A Higher Concentration of Dialysate Magnesium to Reduce the Frequency of Muscle Cramps: A Narrative Review

Purpose of review:

Strategies to mitigate muscle cramps are a top research priority for patients receiving hemodialysis. As hypomagnesemia is a possible risk factor for cramping, we reviewed the literature to better understand the physiology of cramping as well as the epidemiology of hypomagnesemia and muscle cramps. We also sought to review the evidence from interventional studies on the effect of oral and dialysate magnesium-based therapies on muscle cramps.

Sources of information:

Peer-reviewed articles.

Methods:

We searched for relevant articles in major bibliographic databases including MEDLINE and EMBASE. The methodological quality of interventional studies was assessed using a modified version of the Downs and Blacks criteria checklist.

Key findings:

The etiology of muscle cramps in patients receiving hemodialysis is poorly understood and there are no clear evidence-based prevention or treatment strategies. Several factors may play a role including a low concentration of serum magnesium. The prevalence of hypomagnesemia (concentration of <0.7 mmol/L) in patients receiving hemodialysis ranges from 10% to 20%. Causes of hypomagnesemia include a low dietary intake of magnesium, use of medications that inhibit magnesium absorption (eg, proton pump inhibitors), increased magnesium excretion (eg, high-dose loop diuretics), and a low concentration of dialysate magnesium. Dialysate magnesium concentrations of ≤0.5 mmol/L may be associated with a decrease in serum magnesium concentration over time. Preliminary evidence from observational and interventional studies suggests a higher dialysate magnesium concentration will raise serum magnesium concentrations and may reduce the frequency and severity of muscle cramps. However, the quality of evidence supporting this benefit is limited, and larger, multicenter clinical trials are needed to further determine if magnesium-based therapy can reduce muscle cramps in patients receiving hemodialysis. In studies conducted to date, increasing the concentration of dialysate magnesium appears to be well-tolerated and is associated with a low risk of symptomatic hypermagnesemia.

Limitations:

Few interventional studies have examined the effect of magnesium-based therapy on muscle cramps in patients receiving hemodialysis and most were nonrandomized, pre-post study designs.

Hemodialysis crossover study using a relative blood volume change-guided ultrafiltration control compared with standard hemodialysis: the BV-UFC study

Background

It has been difficult to sufficiently achieve body-fluid management using blood volume (BV) monitor during hemodialysis (HD) with constant ultrafiltration (UF) rate. Recently, a relative BV change-guided UF control (BV-UFC) system was developed by combining the concepts of an automatic feedback system that could control the UF rate and profile with real- time monitoring of relative changes in BV (%ΔBV). However, this system has limited application in the clinical setting. Therefore, in this study, we aimed to perform the crossover study on HD with BV-UFC compared to standard HD in terms of hemodynamic stability during HD.

Methods

Forty-eight patients entered an 8-week crossover period of standard HD or HD with BV-UFC. Prevalence of intradialytic hypotension (IDH) as a primary outcome and changes in blood pressure (BP), differences in %ΔBV, and achievement of the target ultrafiltration volume as secondary outcomes were compared. IDH was defined as a reduction in systolic BP ≥20 mmHg from the baseline value at 10 min after HD initiation.

Results

No significant differences were found in the prevalence of IDH, frequency of intervention for symptomatic IDH, and achievement of the target ultrafiltration volume between the groups. The %ΔBV was significantly fewer (-12.1 ± 4.8% vs. -14.4 ± 5.2%, p <0.001) in the HD with BV-UFC than that in the standard HD.

Conclusions

HD with BV-UFC did not reduce the prevalence of IDH compared with standard HD. The relief of a relative BV reduction at the end of HD may be beneficial in patients undergoing HD with BV-UFC.

Trial Registration

UMIN, UMIN000024670. Registered on December 1, 2016.

Effect of ultrafiltration profiling on outcomes among maintenance hemodialysis patients: a pilot randomized crossover trial

BACKGROUND

More rapid fluid removal during hemodialysis is associated with adverse cardiovascular outcomes and longer dialysis recovery times. The effect of ultrafiltration (UF) profiling, independent of concomitant sodium profiling, on markers of intradialytic hemodynamics and other outcomes has been inadequately studied.

METHODS

Four-phase, blinded crossover trial. Participants (UF rates > 10 mL/h/kg) were assigned in random order to receive hemodialysis with UF profiling (constantly declining UF rate, intervention) vs. hemodialysis with conventional UF (control). Each 3-week 9-treatment period was followed by a 1-week 3-treatment washout period. Participants crossed into each study arm twice (2 phases/arm); 18 treatments per treatment type. The primary outcomes were intradialytic hypotension, pre- to post-dialysis troponin T change, and change from baseline in left ventricular global longitudinal strain. Other outcomes included intradialytic symptoms and blood volume measured-plasma refill (post-dialysis volume status measure), among others. Each participant served as their own control.

RESULTS

On average, the 34 randomized patients (mean age 56 years, 24% female, mean dialysis vintage 6.3 years) had UF rates > 10 mL/h/kg in 56% of treatments during the screening period. All but 2 patients completed the 15-week study (prolonged hospitalization, kidney transplant). There was no significant difference in intradialytic hypotension, troponin T change, or left ventricular strain between hemodialysis with UF profiling and conventional UF. With UF profiling, participants had significantly lower odds of light-headedness and plasma refill compared to hemodialysis with conventional UF.

CONCLUSIONS

Ultrafiltration (UF) profiling did not reduce the odds of treatment-related cardiac stress but did reduce the odds of light-headedness and post-dialysis hypervolemia.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT03301740 (registered October 4, 2017).

Integrated strategies to prevent intradialytic hypotension: research protocol of the DialHypot study, a prospective randomised clinical trial in hypotension-prone haemodialysis patients

INTRODUCTION

In patients on maintenance haemodialysis (HD), intradialytic hypotension (IDH) is a clinical problem that nephrologists and dialysis nurses face daily in their clinical routine. Despite the technological advances in the field of HD, the incidence of hypotensive events occurring during a standard dialytic treatment is still very high. Frequently recurring hypotensive episodes during HD sessions expose patients not only to severe immediate complications but also to a higher mortality risk in the medium term. Various strategies aimed at preventing IDH are currently available, but there is lack of conclusive data on more integrated approaches combining different interventions.

METHODS AND ANALYSIS

This is a prospective, randomised, open-label, crossover trial (each subject will be used as his/her own control) that will be performed in two distinct phases, each of which is divided into several subphases. In the first phase, 27 HD sessions for each patient will be used, and will be aimed at the validation of a new ultrafiltration (UF) profile, designed with an ascending/descending shape, and a standard dialysate sodium concentration. In the second phase, 33 HD sessions for each patient will be used and will be aimed at evaluating the combination of different UF and sodium profiling strategies through individualised dialysate sodium concentration.

ETHICS AND DISSEMINATION

The trial protocol has been reviewed and approved by the local Institutional Ethics Committee (Comitato Etico AVEN, prot. 43391 22.10.19). The results of the trial will be presented at local and international conferences and submitted for publication to a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT03949088).

Blood pressure and volume management in dialysis: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Blood pressure (BP) and volume control are critical components of dialysis care and have substantial impacts on patient symptoms, quality of life, and cardiovascular complications. Yet, developing consensus best practices for BP and volume control have been challenging, given the absence of objective measures of extracellular volume status and the lack of high-quality evidence for many therapeutic interventions. In February of 2019, Kidney Disease: Improving Global Outcomes (KDIGO) held a Controversies Conference titled Blood Pressure and Volume Management in Dialysis to assess the current state of knowledge related to BP and volume management and identify opportunities to improve clinical and patient-reported outcomes among individuals receiving maintenance dialysis. Four major topics were addressed: BP measurement, BP targets, and pharmacologic management of suboptimal BP; dialysis prescriptions as they relate to BP and volume; extracellular volume assessment and management with a focus on technology-based solutions; and volume-related patient symptoms and experiences. The overarching theme resulting from presentations and discussions was that managing BP and volume in dialysis involves weighing multiple clinical factors and risk considerations as well as patient lifestyle and preferences, all within a narrow therapeutic window for avoiding acute or chronic volume-related complications. Striking this challenging balance requires individualizing the dialysis prescription by incorporating comorbid health conditions, treatment hemodynamic patterns, clinical judgment, and patient preferences into decision-making, all within local resource constraints.

Ultrafiltration-profiled hemodialysis to reduce dialysis-related cardiovascular stress: Study protocol for a randomized controlled trial

Rapid fluid removal (ultrafiltration, UF) is associated with higher cardiovascular morbidity and mortality among individuals receiving maintenance hemodialysis (HD). Fluid removal rates that exceed vascular refill rates can result in hemodynamic instability, end-organ damage to the heart, kidneys, gut and brain, among other organs, and patient symptoms. There are no known evidence-based HD treatment strategies to reduce harm from higher UF rates. Ultrafiltration profiling, the practice of varying UF rates to maximize fluid removal during periods of greatest hydration and plasma oncotic pressure, has been proposed as an HD treatment intervention that may reduce UF rate-related complications. This study is a randomized 4-phase cross-over trial in which participants are successively alternated between study arms with intervening washout periods, and treatment order is randomized. After 4-week screening and 6-week baseline periods, participants are randomized to HD with conventional UF or HD with UF profiling for a period of 3 weeks followed by a 1-week washout period before crossing over. Participants cross into conventional UF and UF profiling phases twice (2 phases per arm). The primary outcomes of interest are intradialytic hypotension (nadir intradialytic systolic blood pressure <90 mmHg), pre-to post-HD change in troponin T (expressed as a percentage), change in left ventricular global longitudinal strain (an echocardiographic measure of left ventricular systolic function), and development of intradialytic left ventricular stunning (worsening of contractile function in ≥2 segments). This study will determine the impact of UF profiling on UF rate-related cardiovascular complications in prevalent, maintenance HD patients.

Influence of Hemofiltration on Intradialytic Plasma Volume Decrease

BACKGROUND/AIMS

Compared with hemodialysis (HD), hemodiafiltration (HDF) reduces the frequency of episodes of intradialytic hypotension. Intradialytic plasma volume decrease (IPVD) induced by ultrafiltration is a leading cause of the episodes, and hemofiltration might have a preventive effect on IPVD. This study examined whether online HDF (ol-HDF) prevented IPVD compared with HD.

METHODS

Online HDF of pre-dilution mode (pre-ol-HDF) and post-dilution mode (post-ol-HDF) and HD were performed in 22 patients on maintenance dialysis. In each session, IPVD was calculated by using an intradialytic change in hematocrit, and IPVD in pre-ol-HDF and post-ol-HDF was compared with that in HD in a crossover manner.

RESULTS

While the ratios of intradialytic body weight loss to post-dialysis BW (IBWL/BW) in ol-HDF were generally smaller than those in HD, the levels of IPVD and IPVD/IBWL/BW were generally larger than those in HD; the IPVD levels were 0.108 ± 0.058, 0.113 ± 0.053, and 0.101 ± 0.057 (P = 0.67), and those of IPVD/IWL/BW were 2.21 ± 0.97, 2.32 ± 0.91, and 1.98 ± 1.14 (P = 0.21) in pre-ol-HDF, post-ol-HDF, and HD, respectively.

CONCLUSION

Online mode hemofiltration, in either pre-dilution mode or post-dilution mode, performed in combination with hemodialysis has no preventive effect on IPVD.

Intradialytic hypotension

PURPOSE OF REVIEW

This review focuses on recent advances in our understanding of intradialytic hypotension (IDH) and measures that may reduce its frequency.

RECENT FINDINGS

The frequency and severity of IDH predict the risk for adverse clinical outcomes. The highest mortality risks associated with IDH were observed when the intradialytic systolic blood pressure (SBP) nadirs were <90 and <100 mmHg and the predialysis SBP were ≤159 mmHg or ≥160 mmHg, respectively. Interdialytic weight gain (IDWG) ≥3 kg occurs more frequently among patients with IDH. Prolonged and possibly more frequent dialysis, use of biofeedback devices, dialysate cooling and limiting sodium loading are useful measures to reduce the frequency of IDH.

SUMMARY

Frequent IDH is associated with high IDWGs and a poor prognosis. Studies on prolonged dialysis, biofeedback devices and cooled dialysate have yielded promising results. Intradialytic relative blood volume monitoring devices have been investigated in preventing IDH but results are mixed. Administration of a sodium/hydrogen exchange isoform 3 inhibitor increases stool sodium but has not been shown to decrease IDWG. IDH continues to be a significant dialysis complication deserving of further investigation.

A New Method to Evaluate Patient Characteristic Response to Ultrafiltration during Hemodialysis

Background.

Several factors are involved in the pathogenesis of dialysis discomfort interfering with optimal fluid removal and reducing the efficacy of the treatment; the most important one is a decrease in blood volume caused by an imbalance between ultrafiltration (UF) and plasma refilling (PR) rates.

Objectives.

This study is aimed at devising a method to tailor the dialysis therapy to each individual patient, by analyzing the relationship between PR and UF during the sessions in stable patients and widening the knowledge of fluid exchanges during the treatment.

Methods.

Thirty stable patients undergoing maintenance hemodialysis were enrolled. Three dialysis sessions were monitored for each patient; systemic pressure, blood composition, blood volume % variation, weight loss and conductivity were recorded repeatedly. A Plasma Refilling Index (PRI), defined and calculated by means of parameters measured throughout the dialysis, was introduced as a novel instrument to study plasma refilling phenomena.

Results.

The PRI provides understanding of patient response (in terms of plasma refilling) to the set UF. In the monitored sessions, the PRI trend is found to be characteristic of each patient; a PRI course that is at variance with the characteristic trend is a signal of inadequate or unusual dialysis scheduling. Moreover, statistical analysis highlights two different PRI trends during the first hour and during the rest of the treatment, suggesting the presence of different treatment phases.

Conclusion.

The main advantage of the PRI index is that it is non-invasive peculiar to each patient and easy to compute in a dialysis routine based on online data recorded by the monitor. A deviation from the characteristic trend may be a warning for the clinician. The analysis of the PRI trend also suggests how to modulate UF as a function of interstitial to intravascular fluid removal balance during dialysis.

Reduced Complications during Hemodialysis by Automatic Blood Volume Controlled Ultrafiltration

Background

Intradialytic morbid events (IMEs, mostly hypotension) are frequent complications during hemodialysis (HD). This study investigated whether automatic feedback control via adjustment of the ultrafiltration rate reduces IME frequency.

Methods

In this multi-center cross-over study, 56 hypotension-prone patients were treated both with standard HD (sHD, applying a constant ultrafiltration rate) and HD applying a blood volume controlled ultrafiltration rate (cHD). The relative blood volume (RBV) was continuously monitored. The individual relative blood volume limit (RBVcrit) was determined from the measured RBV during initial sHD. During cHD, the ultrafiltration rate was automatically adjusted to keep the actual RBV above RBVcrit.

Results

In 3,081 HD treatments, slightly fewer IMEs were observed during cHD than during sHD (0.785±0.613 versus 0.695±0.547 per treatment, P=0.144). Less symptomatic events were seen during cHD: -13% for symptomatic hypotension (0.594 versus 0.685 per treatment, P=0.120), and -32% for cramps (0.049 versus 0.072 per treatment, P=0.009). Thirty-one patients with the highest IME rate (IME in at least every second treatment) especially benefited from cHD: 1.185±0.554 versus 0.979±0.543 IME per treatment (P=0.004). The reduction in blood pressure (BP) and the increase in heart rate were lower during the treatments with cHD than with sHD: systolic BP: -18.8±26.7 versus -22.2±28.9 mmHg (P=0.007), diastolic BP: -7.8±14.8 versus -9.1±15.3 mmHg (P=0.064), heart rate: 1.8±10.4 versus 2.3±11.6 per minute (P=0.014). Neither treatment duration nor ultrafiltration volume was significantly different between cHD and sHD.

Conclusion

For cHD, less intradialytic morbid events were observed than for sHD, and pre- to post-dialytic changes in blood pressure and heart rate were less pronounced.

Sodium Prescription in the Prevention of Intradialytic Hypotension: New Insights into an Old Concept

Background: Sodium prescription in patients with intradialytic hypotension remains a challenge for the attending nephrologist, as it increases dialysate conductivity in hypotension-prone patients, thereby adding to dietary sodium levels. Methods: New sodium prescription strategies are now available, including the use of a mathematical model to compute the sodium mass to be removed during dialysis as a physiological controller. Results: This review describes the sodium load of patients with end-stage renal disease on chronic hemodialysis (HD) and discusses 2 strategies to remove excess sodium in patients prone to intradialytic hypotension, namely, Profiled HD and the hemodiafiltration Aequilibrium System. Conclusion: The Profiled HD and Aequilibrium System trial both proved effective in counteracting intradialytic hypotension.

Acute kidney injury in cancer patients and impedance cardiography-assisted renal replacement therapy: Experience from the onconephrology unit of a Chinese tertiary hospital

Acute kidney injury (AKI) in cancer patients may disrupt anticarcinogenic treatment and greatly increase associated mortality rates. The present study reported on the management of cancer patients with AKI and, from the nephrologic viewpoint, on the significance of fine volume control during the continuous renal replacement therapy (CRRT). The records of 117 cancer patients with AKI treated over three years were reviewed and their data were compared with those of 120 healthy controls. AKI was defined according to the Kidney Disease: Improving Global Outcomes criteria with serum creatinine levels determined on initial admission and for the diagnosis of AKI. CRRT with concomitant impedance cardiography (ICG) monitoring was performed in 79 patients. On average, AKI manifested as a 1.68±0.38-fold increase in serum creatinine within 10.2±5.7 days. The causes of AKI were diverse, with the major ones being nephrotoxic agents, hypotension and obstructive nephropathy. Renal biopsy confirmed two cases of thrombotic microangiopathy, due to the use of interfon-α and sunitinib malate, respectively, and a third case of cast nephropathy caused by immunoglobulin D multiple myeloma. The patients were generally marantic and had compromised cardiac function compared with the healthy controls. The CRRT prescription was discriminatingly optimized by the ICG parameters effecting discreet fluid balance, as the thoracic fluid content was significantly correlated with the ultrafiltration rate. By considering the causative mechanisms and applying subtle ICG-assisted volume control, the present study may thus help to improve the safety and efficacy of CRRT in cancer patients with AKI. In addition, it provided information to bring advances in onconephrology, a novel nephrological subspecialty field.

Intra-dialytic blood oxygen saturation (SO2): association with dialysis hypotension (the SOGLIA Study)

BACKGROUND

Intradialytic hypotension (IDH) has a dramatic impact on the main outcomes of dialysis patients. Early warning of hemodynamic worsening during dialysis would enable preventive measures to be taken. Blood oxygen saturation (SO₂) is used for hemodynamic monitoring in the critical care setting and may provide useful information about IDH onset.

AIM

To evaluate whether short- and medium-term variations in the SO₂ signal (ST-SO_2var, MT-SO_2var,) during dialysis are a predictor of IDH.

METHODS

In this 3-month observational cohort study, 51 hypotension-prone chronic hemodialysis (HD) patients, with vascular access by arteriovenous fistula (AVF) or central venous catheter (CVC), were enrolled. Continuous non-invasive blood SO₂ was monitored (fc = 0.2 Hz) by an optical sensor on the arterial line of the extracorporeal circulation; blood pressure (every 30 min), symptoms and their time of appearance were noted. Predictive power of IDH was expressed by the area under curve (AUC) sensitivity and specificity based on intradialytic variations in SO₂.

RESULTS

A total of 1290 HD sessions were analyzed. Overall, off-line ST-SO_2var analysis proved able to correctly predict IDH in 67 % of the sessions where IDH occurred. The best predictive performance was found in the presence of highly arterialized AVF (SO₂ > 95 %) (75 % sensitivity; AUC 0.825; p < 0.05). On the contrary, in sessions with CVC, IDH prediction proved more efficient by MT-SO_2var (AUC 0.575; p = 0.01).

CONCLUSIONS

Intradialytic SO₂ variability could be a valid parameter to detect in advance the hemodynamic worsening that precedes IDH. Appropriate timely intervention could help prevent IDH onset.

Concordance of absolute and relative plasma volume changes and stability of Fcells in routine hemodialysis

Central hematocrit (H) measurements are currently used to track the degree of ultrafiltration-induced hemoconcentration with the aim to detect and prevent excessive intravascular fluid depletion during hemodialysis (HD). Failure to maintain hemodynamic stability is commonly attributed to the misinterpretation of H caused by an unaccountable increase in Fcells , the ratio of whole-body hematocrit to H. It was the aim to examine Fcells under everyday conditions in a group of stable HD patients. Absolute plasma volume (Vp ) and H were concomitantly measured during routine HD in the extracorporeal system in hourly intervals by noninvasive and continuous technology (CritLine-Instrument-III) and indocyanine green dye dilution to derive relative plasma volumes from Vp and H (RPVp , RPVH ), respectively, and to calculate Fcells . Thirteen patients were studied during two midweek treatments (n = 26). Both absolute Vp (P < 0.05) and relative plasma volumes RPVH (P < 0.001) decreased during HD. Vp at any time point was positively correlated to RPVH (r = 0.52). Moreover, relative plasma volumes RPVH and RPVp determined by independent techniques were identical and showed negligible bias (-0.2%) but considerable limits of agreement (-15.6% to +15.3%). Fcells was stable and in the range of 0.9 ± 0.05 throughout HD and not different from the value assumed at the beginning of HD. Although Fcells remains constant in patients on routine dialysis and relative plasma volumes (RPVH and RPVp ) determined by independent techniques are therefore comparable, the variability of experimental conditions during dialysis and the limited accuracy of absolute volume measurements using available technology continues to complicate the ultrafiltration control problem.

Vasopressin and prevention of hypotension during hemodialysis

CONTEXT

The occurrence of intradialytic hypotension (IDH) during hemodialysis (HD) continues to be a main problem in patients with ESRD (end-stage kidney disease). It also negatively affects health-related quality of life. We aimed to determine vasopressin effect in decreasing IDH.

EVIDENCE ACQUISITION

We reviewed clinical and experimental literature in a variety of sources, including PubMed, Current Content, Scopus, Embase, and Iranmedex regarding the possible effect of vasopressin administration in prevention of hypotension during HD to clarify its mechanism, efficacy, and safety.

RESULTS

Although arginine vasopressin is widely recognized for its anti-diuretic properties, it is also a well-recognized vasoconstrictor. It has been shown that the vasopressin release (as it would normally be expected) does not increase in the majority of HD patients with recurrent dialysis hypotension. In addition, it has also been reported that vasopressin secretion (due to the osmotic stimulation) is the most important mechanism in blood pressure control in ESRD patients receiving hypertonic solution for IDH. Therefore, it is suggested that vasopressin administration may improve hemodynamic stability among ESRD patients during HD. There are few clinical trials about this issue, suggesting that administration of exogenous vasopressin may be significantly associated with a decreased incidence of IDH as well as cardiovascular stability in ESRD patients in need of volume removal during HD.

CONCLUSIONS

Vasopressin insufficiency may have an important role in the pathogenesis of hemodynamic instability during HD and administration of exogenous vasopressin is significantly associated with a lower incidence of IDH.

Blood pressure and blood volume: acute and chronic considerations in hemodialysis

Hypertension is highly prevalent yet poorly controlled in the majority of dialysis patients and represents a significant burden of disease, with rates of morbidity and mortality greater than those in the general population. In dialysis, blood volume plays a critical role in the pathogenesis of hypertension, with expansion of extracellular volume increasingly recognized as an independent risk factor for morbidity and mortality. Within the current paradigm of dialysis prescription the majority of patients remain chronically volume expanded. However, management of blood pressure and volume state is difficult for clinicians with a paucity of randomized evidence adding to the complexity of nonlinear morbidity and mortality associations. With dialysis itself as a significant cardiac stressor, control of volume state is critical to minimize intradialytic hemodynamic instability, aid in preservation of cardiac anatomy and prevent progression to cardiovascular morbidity and mortality. This review explores the relationship of blood volume to blood pressure and potential targets for management in this at risk population.

Intradialytic hypotension

Intradialytic hypotension (IDH) is common in children during conventional, 4 hour haemodialysis (HD) sessions. The declining blood pressure (BP) was originally believed to be caused by ultrafiltration (UF) and priming of the HD circuit, however emerging data now supports a multifactorial aetiology. Therefore strategies to improve haemodynamic stability need to be diverse and address specific patient requirements or risks. In the treatment of IDH immediate action is required to stop or reduce the severity of symptoms that may precede or follow. Typically UF is slowed or stopped, a fluid bolus is given and in resistant cases the HD session is prematurely discontinued. Patients complete their treatment under-dialysed and volume expanded. Chronically, repeated episodes of IDH cause devastating, multi-system morbidity with an increased risk of mortality. This had provided the impetus for more haemodynamically friendly dialysis prescriptions that attenuate the risk of IDH. During pediatric HD several preventative strategies have been tested but with variable success. Of these, dialysate sodium profiling, UF guided by relative blood volume (RBV) algorithms, cooling and intradialytic mannitol appear to be the most effective. However in refractory cases one may be left with no option but to switch dialysis modality to haemodiafiltration (HDF) or more frequent or prolonged HD regimens.

Intra-dialytic hypotension and blood volume and blood temperature monitoring

Intra-dialytic hypotension (IDH) is a common problem affecting haemodialysis patients. Its aetiology is complex and influenced by multiple patient and dialysis factors. IDH occurs when the normal cardiovascular response cannot compensate for volume loss associated with ultrafiltration, and is exacerbated by a myriad of factors including intra-dialytic fluid gains, cardiovascular disease, antihypertensive medications and the physiological demands placed on patients by conventional haemodialysis. The use of blood volume monitoring and blood temperature monitoring technologies is advocated as a tool to predict and therefore prevent episodes of IDH. We review the clinical utility of these technologies and summarize the current evidence of their effect on reducing the incidence of IDH in haemodialysis population.

Review: modelling the dialysate

Dialysate prescription is evolving as new technology allows greater opportunity to alter dialysate constituents throughout dialysis, providing scope for tailored prescription for an individual patient. The intention of modelling or profiling is to improve the tolerability of dialysis and long-term patient outcomes. This approach can be applied to both electrolytes and water. Despite these advances in technology, benefits of modelling have not been demonstrated consistently. This review examines the use of individual prescription and modelling of dialysate sodium, ultrafiltrate, potassium, calcium, magnesium, bicarbonate and phosphate.

The value of sequential dialysis, mannitol and midodrine in managing children prone to dialysis failure

The uremic state impairs compensatory responses to ultrafiltration (UF). Intradialytic symptoms and hypotension can result and lead to premature discontinuation of treatment and sub-optimal dialysis. We report the benefits of mannitol, sequential dialysis and midodrine in reducing dialysis failures in those children prone to intradialytic hypotension. Prophylactic mannitol halved the odds of intradialytic symptoms and hypotension and increased UF volumes. Sequential dialysis halved the odds of symptoms but hypotension persisted. In one patient with refractory hypotension, only intradialytic midodrine consistently maintained acceptable intradialytic blood pressures, reduced intradialytic symptoms and increased the UF potential.

Evaluating methods for improving ultrafiltration in pediatric hemodialysis

Adequate ultrafiltration (UF) is necessary for good health, but it can be hindered by the development of intradialytic symptoms and hypotension. To determine whether sodium ramping, UF profiles and mannitol could improve UF in children, we instituted a standardized prescription for chronic hemodialysis in our unit. We prospectively analyzed 506 treatments from ten patients. Ultrafiltration volumes up to 9.7% of dry weight were obtained with an overall mean of 5.4%. Mannitol reduced the risk of intradialytic symptoms by 64% (p < 0.05) with a mean UF volume of 6.2%. Step sodium ramping from 148-138 mmol/l reduced the odds of intradialytic symptoms (p = 0.1) and hypotension (p < 0.05) with no difference in the mean UF compared with linear profiles. All UF profiles were associated with an increased risk of intradialytic symptoms, but the effect was only statistically significant with profile 2 (stepwise UF reduction). Overall intradialytic morbidity occurred in 10% of the treatments. Notwithstanding the study limitations, UF volumes higher than traditional recommendations of 5% of the dry weight were achieved with the use of mannitol and 148-138 mmol/l sodium ramping. Despite this, the desired dry weight was not achieved in 66% of our treatments. No clear benefit was seen with UF profiles.

Impact of hemocontrol on hypertension, nursing interventions, and quality of life: a randomized, controlled trial

BACKGROUND

Volume overload contributes to the pathogenesis of hypertension in hemodialysis (HD) patients.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

The Hemocontrol (HC) system (Gambro), which automatically adjusts ultrafiltration rate and dialysate conductivity during dialysis, has been suggested to improve hemodynamic tolerance and thereby facilitate fluid removal. A 6-mo randomized, controlled trial was performed to test the hypothesis that the addition of the HC system to a systematic BP management protocol may lower home BP in comparison with standard HD as primary end point. Secondary end points were the number of nursing interventions during dialysis and health-related quality of life.

RESULTS

Complete BP data were available for 36 of the 44 patients who completed the trial. There was a statistically significant overall decrease in systolic BP during the study period (P = 0.005). However, the difference between the HC group and the standard HD group was NS (HC: from 147.8 +/- 21.7 to 139.8 +/- 16.2 mmHg; standard HD: from 141.9 +/- 19.2 to 135.2 +/- 9.9 mmHg). The number of HD sessions that required nursing interventions decreased in the HC group, whereas it increased in the standard HD group (HC: 42.9% reduction; standard HD: 35.7% increase; P = 0.04). There was also a significant improvement in health-related quality of life in the HC group but not in the standard HD group.

CONCLUSIONS

These results suggest that the addition of the HC system to a systematic BP management protocol provides no additional benefit with regard to BP reduction. However, the HC system may improve the patient tolerability to dialysis.

Longer treatment time and slower ultrafiltration in hemodialysis: Associations with reduced mortality in the DOPPS

Longer treatment time (TT) and slower ultrafiltration rate (UFR) are considered advantageous for hemodialysis (HD) patients. The study included 22,000 HD patients from seven countries in the Dialysis Outcomes and Practice Patterns Study (DOPPS). Logistic regression was used to study predictors of TT > 240 min and UFR > 10 ml/h/kg bodyweight. Cox regression was used for survival analyses. Statistical adjustments were made for patient demographics, comorbidities, dose of dialysis (Kt/V), and body size. Europe and Japan had significantly longer (P < 0.0001) average TT than the US (232 and 244 min vs 211 in DOPPS I; 235 and 240 min vs 221 in DOPPS II). Kt/V increased concomitantly with TT in all three regions with the largest absolute difference observed in Japan. TT > 240 min was independently associated with significantly lower relative risk (RR) of mortality (RR = 0.81; P = 0.0005). Every 30 min longer on HD was associated with a 7% lower RR of mortality (RR = 0.93; P < 0.0001). The RR reduction with longer TT was greatest in Japan. A synergistic interaction occurred between Kt/V and TT (P = 0.007) toward mortality reduction. UFR > 10 ml/h/kg was associated with higher odds of intradialytic hypotension (odds ratio = 1.30; P = 0.045) and a higher risk of mortality (RR = 1.09; P = 0.02). Longer TT and higher Kt/V were independently as well as synergistically associated with lower mortality. Rapid UFR during HD was also associated with higher mortality risk. These results warrant a randomized clinical trial of longer dialysis sessions in thrice-weekly HD.

Effect of sodium balance and the combination of ultrafiltration profile during sodium profiling hemodialysis on the maintenance of the quality of dialysis and sodium and fluid balances

Excessive sodium gain is a major hindrance of sodium profiling hemodialysis (HD) that offsets the benefit in reducing intradialytic hypotension-related discomforts (IHD). Patients who showed frequent IHD (>30% of the sessions; n = 11) were enrolled in a prospective study that consisted of two phases. In the phase 1 study, eight treatment modalities were evaluated: Conventional HD (control), sodium balance-positive step-down sodium profiling HD (PS), sodium balance-neutral step-down sodium profiling HD (NS), sodium balance-neutral alternating sodium profiling HD (NA) without ultrafiltration (UF) profile, and all those with UF profile (UF only, PS+U, NS+U, and NA+U). The incidences of "dialysis failure," defined as the occurrence of one or more of (1) session failure (discontinuation of session <75% of planned time), (2) UF failure (%UF achieved <70%), and (3) delivery failure (Kt/V <1.1), were 48.5, 21.2, 42.4, 39.4, 45.5, 18.2, 21.2, and 18.2% in control, PS, NS, NA, UF only, PS+U, NS+U, and NA+U, respectively. Four treatments, PS, PS+U, NS+U, and NA+U, reduced the incidence of dialysis failure significantly as compared with control (P < 0.05) and were evaluated in the phase 2 study, a randomized controlled 6-wk crossover study. Parameters were measured in the steady state after a 6-wk maintenance of each treatment. Diffusive sodium gain (DeltaNa) was significantly increased with sodium balance-positive profiles with or without UF profile, PS and PS+U (PS 1.9 +/- 1.1, PS+U 1.7 +/- 1.0 mEq/L; both P < 0.05 to control -0.1 +/- 0.2, NS+U 0.5 +/- 0.4, NA+U 0.4 +/- 0.2 mEq/L). They also increased the interdialytic weight gain (PS 3.8 +/- 0.6, PS+U 4.0 +/- 0.6 kg; both P < 0.05 to control 2.7 +/- 0.6, NS+U 3.3 +/- 0.6 kg; both P = NS to NA+U 3.5 +/- 0.6 kg). Predialysis weight and the required amount of UF also increased significantly with these sodium balance-positive profiles. Although the absolute amount of UF was larger with PS and PS+U, %UF achieved targeting dry weight was higher with sodium balance-neutral profiles with UF profiles, NS+U and NA+U (NS+U 92.7 +/- 3.8, NA+U 93.7 +/- 6.8%; both P < 0.05 to control 72.6 +/- 14.0, PS 88.3 +/- 6.6, PS+U 88.2 +/- 8.2%). Postdialysis weight was closest to dry weight with these treatments showing Delta (postdialysis weight - dry weight) of 0.3 +/- 0.1 and 0.3 +/- 0.2 kg in NS+U and NA+U (both P < 0.05 to control 1.0 +/- 0.6 kg; both P = NS to PS 0.5 +/- 0.3, PS+U 0.5 +/- 0.4 kg). Incidence of excessive weight gain and subjective discomforts during the interdialytic period increased significantly with PS. In conclusion, continuous use of sodium balance-positive sodium profiles resulted in an undesirable steady state with sodium and fluid expansion offsetting their hemodynamic benefit. Sodium balance-neutral sodium profiles in combination with UF profile were associated with less sodium and weight gains, better UF performance with postdialysis weight closest to dry weight, and fewer interdialytic problems with the equivalent hemodynamic benefit. Therefore, it is proposed that sodium balance-neutral sodium profiling HD with UF profile is a better choice, ensuring the dialysis of quality without sodium gain-related complications.

Hemodialysis-Induced Hypotension: Impact of Technologic Advances

Hemodialysis-induced hypotension is one of the most serious complications in renal replacement therapy. The main cause of intradialytic hypotension is hypovolemia due to an imbalance between the amount of fluid removed and the refilling capacity of the intravascular compartment. Hypotension occurs when compensatory mechanisms for hypovolemia are overwhelmed by excessive fluid removal. As long as renal replacement therapy is limited to only a few hours per week, intradialytic hypotension will continue to be a relevant problem. Research has mainly focused on enlarging the compensatory capacity for ultrafiltration-induced hypovolemia. This article critically discusses the technical approaches that have been introduced into therapy in recent years with the promise of reducing dialysis-induced hypotensive episodes.

Optimal dialysis for the end-stage renal disease patient with cardiovascular disease

The increasing incidence and prevalence of end-stage renal disease (ESRD) that requires renal replacement therapy has placed a focus on the dialysis procedure itself with respect to its hemodynamic and cardiovascular complications. More than 50% of patients with ESRD will die of cardiovascular disease (CVD). A considerable contribution to cardiovascular events occurs with the dialysis procedure itself. This paper explores the intradialytic complications of hemodialysis as they relate to the cardiovascular system and highlights opportunities for research and improved quality of care.

Inter-dialytic variations in blood volume and total body water in uraemic patients treated by dialysis

BACKGROUND

An optimal balance of sodium and water is one of the most important goals of haemodialysis (HD) therapy. However, while inter-dialytic variations in blood volume (BV) have been well described, very little is known about the dynamics of fluid accumulation and distribution in body compartments during the inter-dialysis period.

METHODS

We studied inter-dialysis variations in BV, measured as percent variation of plasma haemoglobin (Hb) concentrations (% triangle up BV) and percent variation of total body water (% triangle up TBW), in 24 uraemic patients treated by standard bicarbonate dialysis. These parameters were determined at the end of the last weekly dialysis (T0), after 24 h (T1), 48 h (T2), and at the beginning of the following dialysis session (T3). At each time point we measured Hb, haematocrit (Hct), serum albumin (sAlb), plasma sodium (Na), plasma potassium (K), blood urea nitrogen (BUN), plasma osmolality (Osm), body weight (BW), systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). All patients were clinically stable and had no evidence of acute blood loss in the 3 weeks before the study.

RESULTS

During the inter-dialysis period, there were increases in BUN, K and Osm, but Na did not change. SBP and DBP also did not change. HR tended to decrease, and showed a significant reduction between T0 and T3. TBW increased in a linear fashion whereas BV increased exponentially, showing a slow rise during the first 24 h followed by a greater increase in the following time intervals. This was confirmed by concomitant but opposite percent variations in Hct and sAlb concentrations.

CONCLUSIONS

Despite the limitations of the current methodology, our data show that the increase in TBW is redistributed during the long inter-dialysis period and this may prevent the effects of a too premature expansion of the intra-vascular compartment. This is especially evident during the first 24 h after HD, during which % triangle up BV is lowest, indicating a preferential distribution of the fluid load towards the extra-vascular space. During the following time intervals, the extra-vascular compartment refills in conjunction with an exponential expansion of BV that reaches its maximum in the last 24 h before HD.

Characteristics of hypotension-prone haemodialysis patients: is there a critical relative blood volume?

BACKGROUND

Intradialytic morbid events (IME, mostly hypotension) mainly due to ultrafiltration-induced hypovolaemia still are the most frequent complication during haemodialysis (HD). This study was performed to test the hypothesis that there is an individual critical relative blood volume (RBV(crit)) in IME-prone HD patients.

METHODS

In this prospective international multicentre study, 60 IME-prone patients from nine dialysis centres were observed during up to 21 standard HD sessions without trial-specific intervention. The RBV was monitored continuously by an ultrasonic method (BVM; blood volume monitor). Also, the ultrafiltration rate was registered continuously. Blood pressure was measured at regular intervals, and more frequently during IME. All IME and specific therapeutic interventions were noted.

RESULTS

In total, 537 IME, some with more than one symptom, were documented during 585 HD sessions. The occurrence of IME increased up to 10-fold from the start to the end of the HD session. RBV(crit) showed a wide inter-individual range, varying from 71 to 98%. However, the intra-individual RBV limit was relatively stable, with an SD of <5% in three-quarters of the patients. In patients with congestive heart failure, cardiac arrhythmia, advanced age, low ultrafiltration volume and low diastolic blood pressure, higher values of RBV(crit) were observed. While all correlations between RBV(crit) and patient characteristics alone were found to be of weak or medium strength, the combination of diastolic blood pressure, ultrafiltration volume and age resulted in a strong correlation with RBV(crit): the linear equation with these parameters allows an estimation of RBV(crit) in patients not yet monitored with a BVM.

CONCLUSIONS

An individual RBV limit exists for nearly all patients. In most IME-prone patients, these RBV values were stable with only narrow variability, thus making it a useful indicator to mark the individual window of haemodynamic instabilities.

Rheopheresis for age-related macular degeneration: a novel indication for therapeutic apheresis in ophthalmology

Age-related macular degeneration (AMD) is the leading cause of visual impairment and blindness in the elderly. Successful therapy is not yet available for the majority of patients, especially not for patients with dry AMD. AMD at cellular and molecular levels is at least in part a microcirculatory disorder of the retina. Rheopheresis is a safe and effective modality of therapeutic apheresis to treat microcirculatory disorders and represents a novel treatment option for patients with dry AMD. Elimination of a defined spectrum of high molecular weight proteins from human plasma including pathophysiologically relevant risk factors for AMD such as fibrinogen, cholesterol, von Willebrand factor, and alpha 2-macroglobulin results in the reduction of blood and plasma viscosity as well as erythrocyte and thrombocyte aggregation. Pulses of lowering blood and plasma viscosity performed as a series of Rheopheresis treatments lead to rapid changes of blood flow, subsequently inducing sustained improvement of microcirculation and recovery of retinal function. Two controlled randomized clinical trials demonstrated the safety and efficacy of Rheopheresis for the treatment of AMD patients, especially for those with the dry form. Recently the interim analysis of the sham-controlled, double blind, randomized multicenter Multicenter Investigation of Rheopheresis for AMD (MIRA-I) trial confirmed these results. The framework of completed and still ongoing controlled clinical trials in combination with postcertification studies including the RheoNet registry represents a comprehensive quality management approach for this novel interdisciplinary therapy for AMD. The development and continuous update of guidelines for the precise indication of Rheopheresis for AMD follows the requirements of evidence-based medicine.

Modifying the dialysis prescription to reduce intradialytic hypotension

The dialysis prescription can have a substantial impact on the frequency of intradialytic hypotension (IDH). Plasma volume will decline to a greater extent when the ultrafiltration (UF) rate is rapid (high interdialytic weight gains and/or short treatment time), favoring IDH. The relationship of the target weight to the euvolemic weight determines the size of the interstitial fluid compartment, which is a major determinant of the rate of plasma refilling during UF. The higher the dialysate sodium, the smaller the decline in plasma volume for any given amount of UF. Use of a dialysate temperature that prevents a positive thermal balance during dialysis will allow peripheral vascular resistance to be maintained and minimize IDH. A higher ionized calcium during treatment facilitates an increase in cardiac output, a benefit that may be particularly notable in patients with depressed cardiac ejection fraction. Low dialysate magnesium, potassium, and bicarbonate may all favor IDH, although insufficient data are available for definitive conclusions. The choice of antihypertensive medication and the treatment schedule must be carefully considered in patients with IDH. The future integration of technology to monitor blood pressure, plasma volume, and thermal and sodium balance into a computer-based biofeedback system will very likely go a long way toward reducing the frequency of IDH.

Clinical case-based approach to understanding intradialytic hypotension

The approach to end-stage renal disease (ESRD) patients who develop intradialytic hypotension (IDH) encompasses an understanding of the pathophysiology, appropriate dialysis prescription modification, application of newer pharmacologic therapies, and development of strategies for prevention. Patients should have a "minimal data set" as part of their predialysis assessment. This information is critical to prescription modifications that may help decrease the risk for IDH. Individuals at "high risk" for IDH should be kept to a "safe zone" for dialysis ultrafiltration (</=3% of body weight). Specific maneuvers that may decrease the risk for IDH include adjustment of the dialysate sodium or calcium concentration and dialysate temperature. The first priority for patients developing IDH should be the stabilization of the blood pressure and improvement in the patient's symptomology. Pharmacologic intervention should be considered for patients who require repeat interventions for IDH. "At-risk" patients with a strong cardiac history should undergo an assessment of their cardiovascular status if IDH episodes occur. The use of pharmacologic therapy, ie, midodrine, alone or in combination with prescription modification, can be helpful in decreasing interventions required for IDH. Noncompliance and high interdialytic weight gain in the setting of left ventricular hypertrophy (LVH) and diastolic dysfunction can increase the risk of IDH. Assessment of antihypertensive medications should be performed on a regular basis to determine the correct dosing schedule for patients with hypertension who develop IDH. Coronary flow reserve may be compromised in patients with LVH, adding to the risk for perfusion injury with low blood pressure. Increasing the dialysate calcium concentration may decrease the incidence of arrhythmogenicity in certain patients. Patients with low body temperature may benefit most from cool dialysate. Unit personnel should be aware of the potential link between hypotension and the increased relative risk for death in ESRD patients. Clinical training sessions on IDH risk recognition and appropriate treatment should be implemented within the dialysis unit. Because repeated bouts of IDH can be disruptive to the smooth efficiency of unit operations, attention to prevention as well as acute intervention of IDH is important. Preventive strategies can be developed in each unit to decrease the number of future IDH events. Considering the importance of hypotension in overall patient survival, attention to identifying the percentage of patients in each unit who experience IDH and/or who present with low blood pressure (systolic <110 mm Hg) should be tracked as a quality assurance initiative.