Categorization of the hemodynamic response to hemodialysis: the importance of baroreflex sensitivity

Update on Hemodialysis-Induced Multiorgan Ischemia: Brains and Beyond

Hemodialysis is a life-saving treatment for patients with kidney failure. However, patients requiring hemodialysis have a 10-20 times higher risk of cardiovascular morbidity and mortality than that of the general population. Patients encounter complications such as episodic intradialytic hypotension, abnormal perfusion to critical organs (heart, brain, liver, and kidney), and damage to vulnerable vascular beds. Recurrent conventional hemodialysis exposes patients to multiple episodes of circulatory stress, exacerbating and being aggravated by microvascular endothelial dysfunction. This promulgates progressive injury that leads to irreversible multiorgan injury and the well-documented higher incidence of cardiovascular disease and premature death. This review aims to examine the underlying pathophysiology of hemodialysis-related vascular injury and consider a range of therapeutic approaches to improving outcomes set within this evolved rubric.‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬.

Intradialytic Hypotension and Mortality in Adolescents and Young Adults With Kidney Failure Receiving Maintenance Hemodialysis

Rationale & Objective

Intradialytic hypotension (IDH) is associated with mortality in adults with kidney failure requiring hemodialysis (HD); however, large-scale pediatric studies are lacking. Moreover, there is no evidence-based consensus definition of IDH in pediatric literature. We aimed to examine the association of commonly used definitions of IDH with mortality in adolescents and young adults.

Study Design

This was a retrospective observational cohort study.

Setting & Participants

In total, 1,199 adolescents and young adults (N = 320, aged 10-18 years and N = 879, aged 19-21 years) who initiated HD in a large dialysis organization were included.

Exposures

This study used different definitions of IDH.

Outcome

The study outcome was 2-year all-cause mortality.

Analytical Approach

Several definitions of IDH were selected a priori based on a literature review. Patients were classified as having IDH if it was present in at least 30% of HD treatments during the first 90 days after dialysis initiation. Cox proportional hazards regression was used to test whether IDH associated with 2-year all-cause mortality.

Results

Over a 2-year follow-up period, 54 (4.5%) patients died. Dependent on its definition, IDH was present in 2.9%-61.1% of patients. After the multivariable adjustment for sociodemographic and clinical characteristics, we found no association of IDH with mortality. Results were consistent across subgroups stratified by age (aged <18 and 19-21 years) and predialysis systolic blood pressure (<120, 120-150, and >150 mm Hg). We also examined IDH as occurring in <5%, 5%-29%, 30%-50%, and >50% of baseline treatments, and did not find a dose-response association with mortality (P > 0.05).

Limitations

Owing to low event rates, our current sample size may have been too small to detect a difference in mortality.

Conclusions

Our study found that IDH was not associated with mortality in adolescents and young adults.

Hemodialysis-Related Acute Brain Injury Demonstrated by Application of Intradialytic Magnetic Resonance Imaging and Spectroscopy

SIGNIFICANCE STATEMENT

Hemodialysis (HD) results in reduced brain blood flow, and HD-related circulatory stress and regional ischemia are associated with brain injury over time. However, studies to date have not provided definitive direct evidence of acute brain injury during a HD treatment session. Using intradialytic magnetic resonance imaging (MRI) and spectroscopy to examine HD-associated changes in brain structure and neurochemistry, the authors found that multiple white (WM) tracts had diffusion imaging changes characteristic of cytotoxic edema, a consequence of ischemic insult and a precursor to fixed structural WM injury. Spectroscopy showed decreases in prefrontal N -acetyl aspartate (NAA) and choline concentrations consistent with energy deficit and perfusion anomaly. This suggests that one HD session can cause brain injury and that studies of interventions that mitigate this treatment's effects on the brain are warranted.

BACKGROUND

Hemodialysis (HD) treatment-related hemodynamic stress results in recurrent ischemic injury to organs such as the heart and brain. Short-term reduction in brain blood flow and long-term white matter changes have been reported, but the basis of HD-induced brain injury is neither well-recognized nor understood, although progressive cognitive impairment is common.

METHODS

We used neurocognitive assessments, intradialytic anatomical magnetic resonance imaging, diffusion tensor imaging, and proton magnetic resonance spectroscopy to examine the nature of acute HD-associated brain injury and associated changes in brain structure and neurochemistry relevant to ischemia. Data acquired before HD and during the last 60 minutes of HD (during maximal circulatory stress) were analyzed to assess the acute effects of HD on the brain.

RESULTS

We studied 17 patients (mean age 63±13 years; 58.8% were male, 76.5% were White, 17.6% were Black, and 5.9% were of Indigenous ethnicity). We found intradialytic changes, including the development of multiple regions of white matter exhibiting increased fractional anisotropy with associated decreases in mean diffusivity and radial diffusivity-characteristic features of cytotoxic edema (with increase in global brain volumes). We also observed decreases in proton magnetic resonance spectroscopy-measured N -acetyl aspartate and choline concentrations during HD, indicative of regional ischemia.

CONCLUSIONS

This study demonstrates for the first time that significant intradialytic changes in brain tissue volume, diffusion metrics, and brain metabolite concentrations consistent with ischemic injury occur in a single dialysis session. These findings raise the possibility that HD might have long-term neurological consequences. Further study is needed to establish an association between intradialytic magnetic resonance imaging findings of brain injury and cognitive impairment and to understand the chronic effects of HD-induced brain injury.

CLINICAL TRIALS INFORMATION

NCT03342183 .

Comparison of Heart Autonomic Control between Hemodynamically Stable and Unstable Patients during Hemodialysis Sessions: A Bayesian Approach

Intradialytic hypotension is a common complication during hemodialysis sessions. The analysis of successive RR interval variability using nonlinear methods represents a promising tool for evaluating the cardiovascular response to acute volemic changes. Thus, the present study aims to compare the variability of successive RR intervals between hemodynamically stable (HS) and unstable (HU) patients during a hemodialysis session, through linear and nonlinear methods. Forty-six chronic kidney disease patients volunteered in this study. Successive RR intervals and blood pressures were recorded throughout the hemodialysis session. Hemodynamic stability was defined based on the delta of systolic blood pressure (higher SBP-lower SBP). The cutoff for hemodynamic stability was defined as 30 mm Hg, and patients were stratified as: HS ([n = 21]: ≤29.9 mm Hg) or HU ([n = 25]: ≥30 mm Hg). Linear methods (low-frequency [LFnu] and high-frequency [HFnu] spectra) and nonlinear methods (multiscale entropy [MSE] for Scales 1-20, and fuzzy entropy) were applied. The area under the MSE curve at Scales 1-5 (MSE_1-5), 6-20 (MSE_6-20), and 1-20 (MSE_1-20) were also used as nonlinear parameters. Frequentist and Bayesian inferences were applied to compare HS and HU patients. The HS patients exhibited a significantly higher LFnu and lower HFnu. For MSE parameters, Scales 3-20 were significantly higher, as well as MSE_1-5, MSE_6-20, and MSE_1-20 in HS, when compared to HU patients (p < 0.05). Regarding Bayesian inference, the spectral parameters demonstrated an anecdotal (65.9%) posterior probability favoring the alternative hypothesis, while MSE exhibited moderate to very strong probability (79.4 to 96.3%) at Scales 3-20, and MSE_1-5, MSE_6-20, and MSE_1-20. HS patients exhibited a higher heart-rate complexity than HU patients. In addition, the MSE demonstrated a greater potential than spectral methods to differentiate variability patterns in successive RR intervals.

Baroreflex Sensitivity Assessment Using the Sequence Method with Delayed Signals in End-Stage Renal Disease Patients

Impaired baroreflex sensitivity (BRS) is partially responsible for erratic blood pressure fluctuations in End-Stage Renal Disease (ESRD) patients on chronic hemodialysis (HD), which is related to autonomic nervous dysfunction. The sequence method with delayed signals allows for the measurement of BRS in a non-invasive fashion and the investigation of alterations in this physiological feedback system that maintains BP within healthy limits. Our objective was to evaluate the modified delayed signals in the sequence method for BRS assessment in ESRD patients without pharmacological antihypertensive treatment and compare them with those of healthy subjects. We recruited 22 healthy volunteers and 18 patients with ESRD. We recorded continuous BP to obtain a 15-min time series of systolic blood pressure and interbeat intervals during the supine position (SP) and active standing (AS) position. The time series with delays from 0 to 5 heartbeats were used to calculate the BRS, number of data points, number of sequences, and estimation error. The BRS from the ESRD patients was smaller than in healthy subjects (p < 0.05). The BRS estimation with the delayed sequences also increased the number of data points and sequences and decreased the estimation error compared to the original time series. The modified sequence method with delayed signals may be useful for the measurement of baroreflex sensitivity in ESRD patients with a shorter recording time and maintaining an estimation error below 0.01 in both the supine and active standing positions. With this framework, it was corroborated that baroreflex sensitivity in ESRD is decreased when compared with healthy subjects.

Why and how high volume hemodiafiltration may reduce cardiovascular mortality in stage 5 chronic kidney disease dialysis patients? A comprehensive literature review on mechanisms involved

Online hemodiafiltration (HDF) is an established renal replacement modality for patients with end stage chronic kidney disease that is now gaining rapid clinical acceptance worldwide. Currently, there is a growing body of evidence indicating that treatment with HDF is associated with better outcomes and reduced cardiovascular mortality for dialysis patients. In this comprehensive review, we provide an update on the potential mechanisms which may improve survival in HDF treated patients. The strongest evidence is for better hemodynamic stability and reduced endothelial dysfunction associated with HDF treatments. Clinically, this is marked by a reduced incidence of intradialytic hypotensive episodes, with a better hemodynamic response to ultrafiltration, mediated by an increase in total peripheral vascular resistance and extra-vascular fluid recruitment, most likely driven by the negative thermal balance associated with online HDF therapy. In addition, endothelial function appears to be improved due to a combination of a reduction of the inflammatory and oxidative stress complex syndrome and exposure to circulating cardiovascular uremic toxins. Reports of reversed cardiovascular remodeling effects with HDF may be confounded by volume and blood pressure management, which are strongly linked to center clinical practices. Currently, treatment with HDF appears to improve the survival of dialysis patients predominantly due to a reduction in their cardiovascular burden, and this reduction is linked to the sessional convection volume exchanged.

Incidence and predictors of prolonged hemodynamic depression after carotid artery stenting: Yet another benefit of statins?

OBJECTIVES

We aimed to assess the incidence and predictors of prolonged hemodynamic depression (PHD) after carotid artery stenting (CAS).

METHODS

We retrospectively analyzed data from 216 CAS procedures performed in 207 patients (156 male; median and interquartile range (IQR) of age 68 (62-73) yr) between July 2012 and October 2020. PHD was defined as hypotension (systolic blood pressure ≤ 90 mmHg) and/or bradycardia (heart rate < 60 bpm) lasting >1 h.

RESULTS

The incidence of PHD was 25.9%. At multivariate analysis, asymptomatic lesions (OR: 2.43, 95% CI (1.16-5.06), p: 0.018), the stenosis proximity (<10 mm) to bifurcation (OR: 2.94, 95% CI (1.34-6.43), p: 0.007) and implantation of a Protege stent (OR: 2.93, 95% CI (1.14-7.53), p: 0.025) were independent risk factors, while statin usage (OR: 0.48, 95% CI (0.24-0.95), p: 0.036) was an independent protective factor for PHD after CAS.

CONCLUSIONS

Patients with asymptomatic lesions and stenosis close to the bifurcation are more prone to PHD. The type of the stent selected significantly influences the risk of PHD. Further prospective randomized studies are warranted to investigate the possible protective role of statins against PHD after CAS.

Intradialytic systolic blood pressure variation can predict long-term mortality in patients on maintenance hemodialysis

PURPOSE

It is unclear which time-points of intradialytic blood pressure (BP) best predict prognosis. Thus, it is important to assess the association between different time-points of intradialytic BP and prognosis in clinical practice.

METHODS

We recruited patients who underwent hemodialysis from January 2014 to June 2014. Data about dialysis were collected, including intradialytic BP. Cox regression analysis was performed to examine the association between different time-points of intradialytic BP and clinical events, with a follow-up through December 31, 2019. The primary endpoint was all-cause mortality.

RESULTS

A total of 216 patients were recruited and 62 (30.7%) patients died (6.1 per 100-person year) during the follow-up. Intradialytic SBP varied greatly in fatalities. Univariate and multivariate Cox regression models indicated that the adjusted hazard ratio for death was 1.80 and 5.06 when intradialytic systolic blood pressure (SBP) variation was analyzed in increments of 20 mmHg. Furthermore, we divided intradialytic SBP variation into three categories: < 15 mmHg, 15 ~ 30 mmHg,  ≥ 30 mmHg. Kaplan-Meier analysis indicated that both all-cause mortality and cardiovascular mortality increased significantly for patients with intradialytic SBP variation over 30 mmHg (P = 0.006 and 0.021). Univariate and multivariate Cox regression models indicated that the adjusted hazard ratio for death was 3.78 and 12.62 as intradialytic SBP variation ≥ 30 mmHg vs. intradialytic SBP variation < 15 mmHg.

CONCLUSION

Intradialytic SBP variation, rather than BP of specific intradialytic time-points, has the potential to predict long-term mortality in hemodialysis patients. BP stability is crucial for patients' prognosis.

The renal replacement therapy landscape in 2030: reducing the global cardiovascular burden in dialysis patients

Despite the significant progress made in understanding chronic kidney disease and uraemic pathophysiology, use of advanced technology and implementation of new strategies in renal replacement therapy, the clinical outcomes of chronic kidney disease 5 dialysis patients remain suboptimal. Considering residual suboptimal medical needs of short intermittent dialysis, it is our medical duty to revisit standards of dialysis practice and propose new therapeutic options for improving the overall effectiveness of dialysis sessions and reduce the burden of stress induced by the therapy. Several themes arise to address the modifiable components of the therapy that are aimed at mitigating some of the cardiovascular risks in patients with end-stage kidney disease. Among them, five are of utmost importance and include: (i) enhancement of treatment efficiency and continuous monitoring of dialysis performances; (ii) prevention of dialysis-induced stress; (iii) precise handling of sodium and fluid balance; (iv) moving towards heparin-free dialysis; and (v) customizing electrolyte prescriptions. In summary, haemodialysis treatment in 2030 will be substantially more personalized to the patient, with a clear focus on cardioprotection, volume management, arrhythmia surveillance, avoidance of anticoagulation and the development of more dynamic systems to align the fluid and electrolyte needs of the patient on the day of the treatment to their particular circumstances.

Dialysate temperature reduction for intradialytic hypotension for people with chronic kidney disease requiring haemodialysis

BACKGROUND

Intradialytic hypotension (IDH) is a common complication of haemodialysis (HD), and a risk factor of cardiovascular morbidity and death. Several clinical studies suggested that reduction of dialysate temperature, such as fixed reduction of dialysate temperature or isothermal dialysate using a biofeedback system, might improve the IDH rate.

OBJECTIVES

This review aimed to evaluate the benefits and harms of dialysate temperature reduction for IDH among patients with chronic kidney disease requiring HD, compared with standard dialysate temperature.

SEARCH METHODS

We searched Cochrane Kidney and Transplant's Specialised Register up to 14 May 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

All randomised controlled trials (RCTs), cross-over RCTs, cluster RCTs and quasi-RCTs were included in the review.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted information including participants, interventions, outcomes, methods of the study, and risks of bias. We used a random-effects model to perform quantitative synthesis of the evidence. We assessed the risks of bias for each study using the Cochrane 'Risk of bias' tool. We assessed the certainty of evidence using Grades of Recommendation, Assessment, Development and Evaluation (GRADE).

MAIN RESULTS

We included 25 studies (712 participants). Three studies were parallel RCTs and the others were cross-over RCTs. Nineteen studies compared fixed reduction of dialysate temperature (below 36°C) and standard dialysate temperature (37°C to 37.5°C). Most studies were of unclear or high risk of bias. Compared with standard dialysate, it is uncertain whether fixed reduction of dialysate temperature improves IDH rate (8 studies, 153 participants: rate ratio 0.52, 95% CI 0.34 to 0.80; very low certainty evidence); however, it might increase the discomfort rate compared with standard dialysate (4 studies, 161 participants: rate ratio 8.31, 95% CI 1.86 to 37.12; very low certainty evidence). There were no reported dropouts due to adverse events. No study reported death, acute coronary syndrome or stroke.Three studies compared isothermal dialysate and thermoneutral dialysate. Isothermal dialysate might improve the IDH rate compared with thermoneutral dialysate (2 studies, 133 participants: rate ratio 0.68, 95% CI 0.60 to 0.76; I² = 0%; very low certainty evidence). There were no reports of discomfort rate (1 study) or dropouts due to adverse events (2 studies). No study reported death, acute coronary syndrome or stroke.

AUTHORS' CONCLUSIONS

Reduction of dialysate temperature may prevent IDH, but the conclusion is uncertain. Larger studies that measure important outcomes for HD patients are required to assess the effect of reduction of dialysate temperature. Six ongoing studies may provide much-needed high quality evidence in the future.

Renal Perfusion during Hemodialysis: Intradialytic Blood Flow Decline and Effects of Dialysate Cooling

BACKGROUND

Residual renal function (RRF) confers survival in patients with ESRD but declines after initiating hemodialysis. Previous research shows that dialysate cooling reduces hemodialysis-induced circulatory stress and protects the brain and heart from ischemic injury. Whether hemodialysis-induced circulatory stress affects renal perfusion, and if it can be ameliorated with dialysate cooling to potentially reduce RRF loss, is unknown.

METHODS

We used renal computed tomography perfusion imaging to scan 29 patients undergoing continuous dialysis under standard (36.5°C dialysate temperature) conditions; we also scanned another 15 patients under both standard and cooled (35.0°C) conditions. Imaging was performed immediately before, 3 hours into, and 15 minutes after hemodialysis sessions. We used perfusion maps to quantify renal perfusion. To provide a reference to another organ vulnerable to hemodialysis-induced ischemic injury, we also used echocardiography to assess intradialytic myocardial stunning.

RESULTS

During standard hemodialysis, renal perfusion decreased 18.4% (P<0.005) and correlated with myocardial injury (r=-0.33; P<0.05). During sessions with dialysis cooling, patients experienced a 10.6% decrease in perfusion (not significantly different from the decline with standard hemodialysis), and ten of the 15 patients showed improved or no effect on myocardial stunning.

CONCLUSIONS

This study shows an acute decrease in renal perfusion during hemodialysis, a first step toward pathophysiologic characterization of hemodialysis-mediated RRF decline. Dialysate cooling ameliorated this decline but this effect did not reach statistical significance. Further study is needed to explore the potential of dialysate cooling as a therapeutic approach to slow RRF decline.

Dry-weight reduction improves intradialytic hypertension only in patients with high predialytic blood pressure

BACKGROUND

The aim of this study was to investigate whether additional volume reduction by ultrafiltration can improve blood pressure in patients with intradialytic hypertension (IDH) defined as at least 10 mmHg systolic blood pressure (SBP) rise during hemodialysis.

PATIENTS AND METHODS

This prospective, open-label, single-center study included 11 IDH patients with normal predialytic blood pressure (BP) (group A), 11 IDH patients with high predialytic BP (group B), and 18 patients without IDH as control. Serum angiotensin-II, aldosterone (ALD), angiotensin-converting enzyme, endothelin-1, nitric oxide, and asymmetric dimethylarginine were measured before and after the treatments.

RESULTS

Basic angiotensin-converting enzyme, ALD, endothelin-1, and asymmetric dimethylarginine serum levels were significantly increased in group B compared with control (P < 0.05). On comparing the results from the first and 13th dialysis sessions in group A, the dry weight was reduced by - 0.15 ± 0.16 kg after 12 sessions and the predialytic SBP increased by 3.18 ± 6.25 mmHg before and by 7.37 ± 14.90 mmHg at 4 h during the 13th session. In group B, the dry weight was reduced by 0.67 ± 0.53 kg (P = 0.006 vs. group A) at the 13th session and they had - 12.09 ± 16.20 mmHg less SBP before (P = 0.009 vs. group A) and - 11.82 ± 14.66 mmHg at 4 h of the 13th session. The decrease in dry weight was associated with significantly higher decreases in angiotensin-II and ALD serum levels in group B compared with group A.

CONCLUSION

Reducing fluid overload in IDH patients with high predialytic BP can effectively improve their BP, but had no effect on BP in normal predialytic BP IDH cases.

Impact of intradialytic blood pressure changes on cardiovascular outcomes is independent of the volume status of maintenance hemodialysis patients

Intradialytic systolic blood pressure (SBP) changes are related to the volume status; however, whether SBP change impacts on adverse outcomes depends on the volume status remains uncertain. We retrospectively investigated the relationship among intradialytic changes in SBP, cardiovascular outcomes, and volume status in maintenance hemodialysis patients. We determined SBP changes (ΔSBP) as postdialysis SBP minus predialysis SBP and volume status as the ratio of extracellular water to total body water (ECW/TBW) using bioelectrical impedance analysis. There were 82 (60.3%) with ΔSBP -20 to 10 mm Hg, 21 (15.4%) with ΔSBP ≤ -20 mm Hg, and 33 (24.3%) with ΔSBP ≥ 10 mm Hg, and they were followed up for a median of 34 months. Cardiovascular events more frequently occurred in the patients with ΔSBP ≤ -20 mm Hg and ≥ 10 mm Hg (hazard ratio: 2.3 and 3.0; P = .062 and .006); these associations persisted even after adjusting for postdialysis ECW/TBW (P = .056 and .028). Moreover, ΔSBP ≥ 10 mm Hg was associated with increased cardiovascular mortalities independent of postdialysis ECW/TBW (P = .043). There was an independent association of volume status between considerable SBP decrease or increase during hemodialysis and adverse cardiovascular outcomes. Besides appropriate volume control, other factors related to BP changes during hemodialysis must be investigated.

Blood pressure variation and its correlates among patients undergoing hemodialysis for renal failure in Benin City, Nigeria

Background:

Blood pressure (BP) variation is commonly encountered during hemodialysis (HD) procedure. Both intradialysis hypotension and hypertension have implications for outcome of treatment and overall morbidity and mortality of the patients.

Methodology:

A retrospective study was carried out in the dialysis unit of a tertiary health institution in Benin City among patients who had HD for acute kidney injury (AKI) or chronic kidney disease (CKD) over a 3-year period. Data retrieved included age, gender, type of kidney disease, cause of kidney disease, systolic BP at onset of dialysis and at end of dialysis, and diastolic BP (DBP) at onset of and at end of dialysis.

Results:

Complete data were available for 217 patients. One hundred and seven patients (49.3%) had no significant change in BP; 30.9% had intradialytic hypertension (IDHT) while 19.8% had intradialytic hypotension (IDH). IDH was more prevalent among patients with diabetic kidney disease while IDHT was more common among patients with hypertensive nephropathy (P = 0.002). Female patients had higher mean BP parameters compared to male patients pre- and post-dialysis, but only changes in DBP were statistically significant (P = 0.029). Patients with CKD had higher mean BP parameters pre- and post-dialysis compared to patients with acute AKI and the differences were statistically significant.

Conclusion:

Females had higher mean BP parameters than males. Patients with CKD had higher mean BP parameters compared with AKI patients. IDHT is a significant problem among patients on HD in our center. Measures to curtail this trend should be instituted with the goal of reducing morbidity and mortality.

A brief review of intradialytic hypotension with a focus on survival

Intradialytic hypotension (IDH), a common complication of ultrafiltration during hemodialysis therapy, is associated with high mortality and morbidity. IDH, defined as a nadir systolic blood pressure of less than 90 mm Hg on more than 30% of treatments, is a relevant definition and is correlated with mortality. Risk factors for IDH include patient demographics, anti-hypertensive medication use, larger interdialytic weight gain, and dialysis prescription features as dialysate sodium, high ultrafiltration rate, and dialysate temperature. A high frequency of IDH events carries a substantial death risk. An ultrafiltration rate >10 mL/h/kg, and even more so >13 mL/h/kg, is highly predictive of cardiovascular and all-cause mortality. Evidence suggests that IDH causes acute reversible segmental myocardial hypoperfusion and contractile dysfunction (myocardial stunning), which can result in long-term loss of myocardial contractility, leading to premature death. IDH also has negative end-organ effects on the brain and gut, contributing to mortality through stroke, and endotoxin translocation with associated inflammation and protein-energy wasting. Given strong association of IDH and dialysis mortality, a paradigm shift to its approach is urgently needed. Randomized controlled trials are required to prospectively test drugs and monitoring devices which may reduce IDH.

Intradialytic Central Venous Oxygen Saturation is Associated with Clinical Outcomes in Hemodialysis Patients

Central venous oxygen saturation (ScvO₂) in the superior vena cava is predominantly determined by cardiac output, arterial oxygen content, and oxygen consumption by the upper body. While abnormal ScvO₂ levels are associated with morbidity and mortality in non-uremic populations, ScvO₂ has received little attention in hemodialysis patients. From 1/2012 to 8/2015, 232 chronic hemodialysis patients with central venous catheters as vascular access had their ScvO₂ monitored during a 6-month baseline period and followed for up to 36 months. Patients were stratified into upper and lower two tertiles by a ScvO₂ of 61.1%. Survival analysis employed Kaplan-Meier curves and adjusted Cox proportional hazards models. Patients in the lower tertiles of ScvO₂ were older, had longer hemodialysis vintage, lower systolic blood pressure, lower ultrafiltration rates, higher leukocyte counts and neutrophil-to-lymphocyte ratios. Kaplan-Meier analysis indicated a shorter survival time in the lower tertiles of ScvO₂ (P = 0.005, log-rank test). In adjusted Cox analysis, a 1 percent point decrease in mean ScvO₂ was associated with a 4% increase in mortality (HR 1.04 [95% CI 1.01-1.08], P = 0.044), indicating that low ScvO₂ is associated with poor outcomes. Research on the relative contributions of cardiac output and other factors is warranted to further elucidate the pathophysiology underlying this novel finding.

Comparison of stroke volume measurements during hemodialysis using bioimpedance cardiography and echocardiography

BACKGROUND

Fluid management remains a major challenge of hemodialysis (HD) care, with serious implications for morbidity and mortality. Intradialytic fluid management is typically guided by blood pressure, an indirect resultant of hemodynamics status. Direct measurements of hemodynamic parameters may improve cardiovascular outcomes by providing rational bases for intervention. We compare stroke volume (SV) measurements using a noninvasive, regional biompedance cardiography device (NiCaS) with Doppler echocardiography (Echo) in HD setting.

METHODS

Stroke volumes were simultaneously measured using the devices in 17 patients receiving maintenance HD. Measurements were made during 2 weekly HD treatments, and twice within each HD treatment during the first and last hour of each treatment, for a total of 64 SV measurements. Agreement between devices was assessed using linear regression, a Pearson's correlation coefficient, and a Bland-Altman plot all adjusted for repeated measures within patients.

RESULTS

Echo and NiCaS SV mean and 95% CIs were 58.0 (50.1, 65.8) and 56.7 (49.4, 64.0) mL, respectively. NiCaS SV correlated strongly with Echo SV during the first and last hours of treatments (r = 0.93, P < 0.001 and r = 0.92, P < 0.001, respectively). Linear regression of NiCaS on Echo showed a slope of 0.97, 95% CI (0.91, 1.02) which did not differ from 1, P = 0.20. A Bland-Altman plot and 4-Quadrant plot confirmed that the 2 methods produced comparable measurements.

CONCLUSION

NiCaS SV measurements are similar to and strongly correlated with Echo SV measurements. This suggests that noninvasive NiCaS technology may be a practical method for measuring SV during HD.

Faster rate of blood volume change in pediatric hemodialysis patients impairs cardiac index

BACKGROUND

Intradialytic hypotension and myocardial stunning are proposed as contributing to the pathogenesis of increased cardiovascular disease burden and death in patients receiving maintenance hemodialysis (HD). Noninvasive cardiac output measurements provide a dynamic, real-time assessment of hemodynamic parameters. We investigated intradialytic changes in hemodynamic parameters in pediatric outpatients receiving chronic HD and determined patient and treatment risk factors associated with such intradialytic changes.

METHODS

Hemodialysis was performed using linear fluid removal over 4 h with polysulfone dialyzers. Continuous wave Doppler ultrasound was used to measure hemodynamic parameters prior, 2 h into, and after the mid-week HD treatment session. Pulse wave tonometry was performed at the same time. The percentage change in blood volume was measured by noninvasive hematocrit monitoring during HD.

RESULTS

Twenty-two patients fit the inclusion criteria, of whom 16 (73 %) were male. The mean age of the patients was 17 ± 3.8 years, and the dialysis vintage was 47.8 ± 33.7 months. The cardiac index decreased significantly midway through the HD treatment session and remained low until the end of treatment. A significant decline in cardiac index without hypotension occurred in 12 (54 %) patients. Expected increase in systemic vascular resistance index to preserve the cardiac index was not observed. Weight, percentage fluid overload, dialysis vintage, and adequacy did not correlate with the observed decline in the cardiac index. The decrease in blood volume at the 2 h (R = 0.43, p = 0.045) and 4 h (R = 0.56, p = 0.007) time points was the only factor associated with cardiac index decline.

CONCLUSION

The cardiac index and stroke volume decreased significantly during the HD session. Patients with larger blood volume changes during the first 2 h of HD and at 4 h showed a significant decrease in cardiac index that did not recover at the completion of the HD treatment. Rate of fluid removal was the only significant risk factor for compromised cardiac index during HD. Conventional methods currently used for assisting fluid removal in HD are inadequate to assess hemodynamic changes.

Cardiovascular impact in patients undergoing maintenance hemodialysis: Clinical management considerations

Patients undergoing maintenance hemodialysis develop both structural and functional cardiovascular abnormalities. Despite improvement of dialysis technology, cardiovascular mortality of this population remains high. The pathophysiological mechanisms of these changes are complex and not well understood. It has been postulated that several non-traditional, uremic-related risk factors, especially the long-term uremic state, which may affect the cardiovascular system. There are many cardiovascular changes that occur in chronic kidney disease including left ventricular hypertrophy, myocardial fibrosis, microvascular disease, accelerated atherosclerosis and arteriosclerosis. These structural and functional changes in patients receiving chronic dialysis make them more susceptible to myocardial ischemia. Hemodialysis itself may adversely affect the cardiovascular system due to non-physiologic fluid removal, leading to hemodynamic instability and initiation of systemic inflammation. In the past decade there has been growing awareness that pathophysiological mechanisms cause cardiovascular dysfunction in patients on chronic dialysis, and there are now pharmacological and non-pharmacological therapies that may improve the poor quality of life and high mortality rate that these patients experience.

Brain-kidney cross-talk: Definition and emerging evidence

Cross-talk is broadly defined as endogenous homeostatic signaling between vital organs such as the heart, kidneys and brain. Kidney-brain cross-talk remains an area with excitingly few publications despite its purported clinical relevance in the management of currently undertreated conditions such as resistant hypertension. Therefore, this review aims to establish an organ-specific definition for kidney-brain cross-talk and review the available and forthcoming literature on this topic.

Potential role of endurance training in altering renal sympathetic nerve activity in CKD?

Chronic kidney disease (CKD), is characterized by a progressive loss of renal function and increase in cardiovascular risk. In this review paper, we discuss the pathophysiology of increased sympathetic nerve activity in CKD patients and raise the possibility of endurance exercise being an effective countermeasure to address this problem. We specifically focus on the potential role of endurance training in altering renal sympathetic nerve activity as increased renal sympathetic nerve activity negatively impacts kidney function as well indirectly effects multiple other systems and organs. Recent technological advances in device based therapy have highlighted the detrimental effect of elevated renal sympathetic nerve activity in CKD patients, with kidney function and blood pressure being improved post renal artery nerve denervation in selected patients. These developments provide optimism for the development of alternative and/or complementary strategies to lower renal sympathetic nerve activity. However, appropriately designed studies are required to confirm preliminary observations, as the widespread use of the renal denervation approach to lower sympathetic activity presently has limited feasibility. Endurance training may be one alternative strategy to reduce renal sympathetic nerve activity. Here we review the role of endurance training as a potential alternative or adjunctive to current therapy in CKD patients. We also provide recommendations for future research to assist in establishing an evidence base for the use of endurance training to lower renal sympathetic activity in CKD patients.

The Cerebrovascular-Chronic Kidney Disease Connection: Perspectives and Mechanisms

Chronic kidney disease (CKD) is an independent risk factor for the development of cerebrovascular disease, particularly small vessel disease which can manifest in a variety of phenotypes ranging from lacunes to microbleeds. Small vessel disease likely contributes to cognitive dysfunction in the CKD population. Non-traditional risk factors for vascular injury in uremia include loss of calcification inhibitors, hyperphosphatemia, increased blood pressure variability, elastinolysis, platelet dysfunction, and chronic inflammation. In this review, we discuss the putative pathways by which these mechanisms may promote cerebrovascular disease and thus increase risk of future stroke in CKD patients.

Hemodialysis-induced regional left ventricular systolic dysfunction

Introduction Hemodialysis (HD) patients are under observably elevated cardiovascular mortality. Cardiac dysfunction is closely related to death caused by cardiovascular diseases (CVD). In the general population, repetitive myocardial ischemia induced left ventricular (LV) dysfunction may progress to irreversible loss of contraction step by step, and finally lead to cardiac death. In HD patients, to remove water and solute accumulated from 48 or 72 hours of interdialysis period in a 4-hour HD session will induce myocardial ischemia. In this study, we evaluated the prevalence and potential risk factors associated with HD-induced LV systolic dysfunction and provide some evidences for clinical strategies. Methods We recruited 31 standard HD patients for this study from Fudan University Zhongshan hospital. Echocardiography was performed predialysis, at peak stress during HD (15 minutes prior to the end of dialysis), and 30 minutes after HD. Auto functional imaging (AFI) was used to assess the incidence and persistence of HD-induced regional wall motion abnormalities (RWMAs). Blood samples were drawn to measure biochemical variables. Findings Among totally 527 segments of 31 patients, 93.54% (29/31) patients and 51.40% (276/527) segments were diagnosed as RWMAs. Higher cTnT (0.060 ± 0.030 vs. 0.048 ± 0.015 ng/mL, P = 0.023), phosphate (2.07 ± 0.50 vs. 1.49 ± 0.96 mmol/L, P = 0.001), UFR (11.00 ± 3.89 vs. 8.30 ± 2.66 mL/Kg/h, P = 0.039) and lower albumin (37.83 ± 4.48 vs. 38.38 ± 2.53 g/L, P = 0.050) were found in patients with severe RWMAs (RWMAs in more than 50% segments). After univariate and multivariate analysis, interdialytic weight gain (IDWG) was found as independent risk factor of severe RWMAs (OR = 1.047, 95%CI 1.155-4.732, P = 0.038). Discussion LV systolic dysfunction induced by HD is prevalent in conventional HD patients and should be paid attention to. Patients would benefit from better weight control during interdialytic period to reduce ultrafiltration rate.

Intradialytic Hypoxemia in Chronic Hemodialysis Patients

When kidney failure occurs, patients are at risk for fluid overload states, which can cause pulmonary edema, pleural effusions, and upper airway obstruction. Kidney disease is also associated with impaired respiratory function, as in central sleep apnea or chronic obstructive pulmonary disease. Hence, respiratory and renal diseases are frequently coexisting. Hypoxemia is the terminal pathway of a multitude of respiratory pathologies. The measurement of oxygen saturation (SO2) is a basic and commonly used tool in clinical practice. Both arterial oxygen saturation (SaO2) and central venous oxygen saturation (ScvO2) can be easily obtained in hemodialysis (HD) patients, SaO2 from an arteriovenous access and ScvO2 from a central catheter. Here, we give a brief overview of the anatomy and physiology of the respiratory system, and the different technologies that are currently available to measure oxygen status in dialysis patients. We then focus on literature regarding intradialytic SaO2 and ScvO2. Lastly, we present clinical vignettes of intradialytic drops in SaO2 and ScvO2 in association with different symptoms and clinical scenarios with an emphasis on the pathophysiology of these cases. Given the fact that in the general population hypoxemia is associated with adverse outcomes, including increased mortality, cardiac arrhythmias and cardiovascular events, we posit that intradialytic SO2 may serve as a potential marker to identify HD patients at increased risk for morbidity and mortality.

Cardiovascular Autonomic Dysfunction in Chronic Kidney Disease: a Comprehensive Review

Cardiovascular autonomic dysfunction is a major complication of chronic kidney disease (CKD), likely contributing to the high incidence of cardiovascular mortality in this patient population. In addition to adrenergic overdrive in affected individuals, clinical and experimental evidence now strongly indicates the presence of impaired reflex control of both sympathetic and parasympathetic outflow to the heart and vasculature. Although the principal underlying mechanisms are not completely understood, potential involvements of altered baroreceptor, cardiopulmonary, and chemoreceptor reflex function, along with factors including but not limited to increased renin-angiotensin-aldosterone system activity, activation of the renal afferents and cardiovascular structural remodeling have been suggested. This review therefore analyzes potential mechanisms underpinning autonomic imbalance in CKD, covers results accumulated thus far on cardiovascular autonomic function studies in clinical and experimental renal failure, discusses the role of current interventional and therapeutic strategies in ameliorating autonomic deficits associated with chronic renal dysfunction, and identifies gaps in our knowledge of neural mechanisms driving cardiovascular disease in CKD.

Baroreflex dysfunction in chronic kidney disease

Chronic kidney disease (CKD) patients have high cardiovascular mortality and morbidity. The presence of traditional and CKD related risk factors results in exaggerated vascular calcification in these patients. Vascular calcification is associated with reduced large arterial compliance and thus impaired baroreflex sensitivity (BRS) resulting in augmented blood pressure (BP) variability and hampered BP regulation. Baroreflex plays a vital role in short term regulation of BP. This review discusses the normal baroreflex physiology, methods to assess baroreflex function, its determinants along with the prognostic significance of assessing BRS in CKD patients, available literature on BRS in CKD patients and the probable patho-physiology of baroreflex dysfunction in CKD.

Reliability analysis of the heart autonomic control parameters during hemodialysis sessions

The study of heart autonomic control (HAC) in patients with chronic kidney disease (CKD) undergoing dialysis treatment has been carried out, however, there are no studies reporting the reliability of measurements of HAC parameters involving the mentioned samples and conditions. The reliability of many HAC parameters was evaluated from patients with CKD during two sessions of hemodialysis. The successive R-R intervals were recorded during two sessions of hemodialysis from 14 CKD patients that were undergoing dialysis for at least 6 months and with no history of recurrent hypotensive events. HAC parameters were obtained with time and frequency domain analysis, as well as with nonlinear methods. The reliability was measured with the intraclass correlation coefficient (ICC). The results showed excellent reliability (ICC=0.90–0.98) for most heart rate variability (HRV) parameters, especially the parameters obtained in the time domain [square root of the mean squared differences between successive R-R intervals (RMSSD), percentage of adjacent R-R intervals that differ by more than 50 ms (pNN50), mean of the 5-min standard deviations of R-R intervals (SDNNi), and triangular index] and with non-linear methods [standard deviation of the instantaneous variability beat-to-beat (SD1), standard deviation in long-term continuous R-R intervals (SD2), detrended fluctuation analysis (DFA) α1 and α2, approximate and sample entropies, and correlation dimension (D2): ICC=0.86–0.96]. Among the parameters obtained in the frequency domain (normalized magnitude from the spectrum of low-frequency components (LFnu), normalized magnitude from the spectrum of high-frequency components (HFnu), and LF/HF ratio), the LF/HF ratio showed better reliability (ICC=0.96 vs. ICC=0.70). Measurements of HAC parameters have excellent test-retest reliability for the studied samples and conditions.

Intradialytic Blood Pressure Abnormalities: The Highs, The Lows and All That Lies Between

BACKGROUND

Frequent blood pressure (BP) measurements are necessary to ensure patient safety during hemodialysis treatments. Intradialytic BPs are not optimal tools for hypertension diagnosis and cardiovascular risk stratification, but they do have critical clinical and prognostic significance. We present evidence associating intradialytic BP phenomena including fall, rise and variability with adverse clinical outcomes and review related pathophysiologic mechanisms and potential management strategies.

SUMMARY

Observational studies demonstrate associations between intradialytic hypotension, hypertension and BP variability and mortality. Lack of consensus regarding diagnostic criteria has hampered data synthesis, and prospective studies investigating optimal management strategies for BP phenomena are lacking. Mechanistic data suggest that cardiac, gut, kidney and brain ischemia may lie on the causal pathway between intradialytic hypotension and mortality, and endothelial cell dysfunction, among other factors, may be an important mediator of intradialytic hypertension and adverse outcomes. These plausible pathophysiologic links present potential therapeutic targets for future inquiry. The phenomenon of intradialytic BP variability has not been adequately studied, and practical clinical measures and treatment strategies are lacking.

KEY MESSAGES

Intradialytic BP phenomena have important prognostic bearing. Clinical practice guidelines for both intradialytic hypotension and hypertension exist, but their underlying evidence is weak overall. Further research is needed to develop consensus diagnostic criteria for intradialytic hypotension, hypertension and BP variability and to elucidate optimal treatment and prevention strategies for each BP manifestation.

Impact of extracorporeal blood flow rate on blood pressure, pulse rate and cardiac output during haemodialysis

BACKGROUND

If blood pressure (BP) falls during haemodialysis (HD) [intradialytic hypotension (IDH)] a common clinical practice is to reduce the extracorporeal blood flow rate (EBFR). Consequently the efficacy of the HD (Kt/V) is reduced. However, only very limited knowledge on the effect of reducing EBFR on BP exists and data are conflicting. The aim of this study was to evaluate the effect and the potential mechanism(s) involved by investigating the impact of changes in EBFR on BP, pulse rate (PR) and cardiac output (CO) in HD patients with arteriovenous-fistulas (AV-fistulas).

METHODS

We performed a randomized, crossover trial in 22 haemodynamically stable HD patients with AV-fistula. After a conventional HD session each patient was examined during EBFR of 200, 300 and 400 mL/min in random order. After 15 min when steady state was achieved CO, BP and PR were measured at each EFBR, respectively.

RESULTS

Mean (SD) age was 71 (11) years. Systolic BP was significantly higher at an EBFR of 200 mL/min as compared with 300 mL/min [133 (23) versus 128 (24) mmHg; P < 0.05], but not as compared with 400 mL/min [133 (23) versus 130 (19) mmHg; P = 0.20]. At EBFR of 200, 300 and 400 mL/min diastolic BP, mean arterial pressure, PR and CO remained unchanged.

CONCLUSION

Our study does not show any consistent trend in BP changes by a reduction in EBFR. Reduction in EBFR if BP falls during IDH is thus not supported. However, none of the patients experienced IDH. Further studies are required to evaluate the impact of changes in EBFR on BP during IDH.

Ischemic brain injury in hemodialysis patients: which is more dangerous, hypertension or intradialytic hypotension?

Abnormalities of cognitive function and high levels of depression incidence are characteristic of hemodialysis patients. Although previously attributed to the humoral effects of uremia, it is becoming increasingly appreciated that many elements of the overall disease state in CKD patients contribute to functional disturbances and physical brain injury. These factors range from those associated with the underlying primary diseases (cardiovascular, diabetes etc.) to those specifically associated with the requirement for dialysis (including consequences of the hemodialysis process itself). They are, however, predominantly ischemic threats to the integrity of brain tissue. These evolving insights are starting to allow nephrologists to appreciate the potential biological basis of dependency and depression in our patients, as well as develop and test new therapeutic approaches to this increasingly prevalent and important issue. This review aims to summarize the current understanding of brain injury in this setting, as well as examine recent advances being made in the modification of dialysis-associated brain injury.

Effect of dialysate sodium concentration on sodium gradient and hemodialysis parameters

This retrospective study was performed to determine the ranges of the sodium gradient (SG) between the dialysate sodium concentration (DNa) and serum sodium concentration (SNa) in hemodialysis (HD) patients and to examine the relationships between HD parameters over a 1 year period. Fifty-five clinically stable HD patients, who had been on HD >2 years were enrolled. Monthly HD [ultrafiltration (UF) amount, systolic blood pressure (SBP), frequency of intradialytic hypotension (IDH)] and laboratory data were collected and 12-month means were subjected to analysis. The SG was calculated by subtracting SNa from prescribed DNa. Mean SG values were 1.5±3.3 (range -5.6~9.1). SG was positively related to DNa and the frequency of IDH. A higher SG was associated with larger UF amounts and SBP reduction during HD. The percentages of patients with a SG ≥3mEq/L increased as DNa increased. On the other hand, SG was not found to be associated with SNa or pre-HD SBP. DNa appears to cause a significant increase in SG, and this seems to be related to HD parameters, such as, UF amount and IDH.

Hemodialysis-associated cardiomyopathy: a newly defined disease entity

Cardiovascular disease is the most common cause of the greatly elevated rates of mortality characteristic of patients undergoing maintenance hemodialysis. This article is an attempt to describe the complex and evolving features of cardiac disease routinely encountered in HD patients. Furthermore, by trying to appreciate the pathophysiological drivers, and the crucial interaction with the HD treatment itself, this article seeks to define cardiac disease in this setting (HD-associated cardiomyopathy) as a unique and complex entity. By understanding the phenotype and basis of HD-associated cardiomyopathy, we can develop an evolved understanding of the dominant processes involved in its development and offer up dialysis-based interventions specifically designed to mitigate the cumulative ischemic insults consequent to conventional HD treatment. This article explores the justification of this approach and recent evidence of its efficacy.

Characterising haemodynamic stress during haemodialysis using the extrema points analysis model

BACKGROUND AND AIMS

It is becoming recognised that the process of haemodialysis (HD) itself induces circulatory stress that could be implicated in the observed higher rate of end-organ damage. We aimed to study the haemodynamic performance during HD using the extrema points (EP) analysis model, and to examine the determinants of the model and its relation to circulatory stress.

METHODS

63 incident HD patients were studied. Mean arterial blood pressure (MAP) EP frequencies and baroreflex sensitivity during HD were computed for continuous non-invasive haemodynamic monitoring. Pulse-wave velocity as a measure of arterial stiffness was performed. High-sensitivity troponin-T was also measured.

RESULTS

The time of each dialysis session was divided into four quarters. Repeated measures ANOVA of the MAP EP frequencies for all subjects during HD demonstrated a gradual significant increase reaching peak levels at the third quarter of dialysis time and remaining at that peak during the fourth quarter (F(3,171228) = 392.06, p < 0.001). In multivariate regression, lower baroreflex sensitivity was the only independent predictor of higher MAP EP frequencies (β = -0.642, p = 0.001, adjusted R(2) for the whole model = 0.385). In linear regression analysis, higher MAP EP frequencies were associated with higher troponin-T levels (β = 0.442, p = 0.002, R(2) = 0.19, B = 103.29, 95% CI 38.88-167.70).

CONCLUSION

The EP analysis model using MAP is a novel functional haemodynamic measure that can represent and quantify circulatory stress during HD. This measure seems to be determined by the integrity of the autonomic function in HD and could represent the link between circulatory stress and end-organ damage in HD patients.

Are serum to dialysate sodium gradient and segmental bioimpedance volumes associated with the fall in blood pressure with hemodialysis?

INTRODUCTION

A fall in blood pressure is the most common complication of outpatient hemodialysis. Several factors have been implicated, including serum sodium to dialysate gradient, ultrafiltration rate, and the amount of fluid to be removed during dialysis.

METHODS

We prospectively audited 400 adult patients attending for their routine midweek hemodialysis session, and recorded changes in mean arterial blood pressure (MAP).

RESULTS

Mean age 58.4 ± 16.6 years, 60.9% male, 30.7% diabetic, 36.8% Caucasoid, single pool Kt/V 1.57 ± 0.4, and median percentage change in MAP -6.7% (-14.1 to + 2.8). The percentage fall in MAP was greatest for those starting with higher MAPs (β 0.448 , F 67.5, p<0.001), greater serum sodium to dialysate sodium gradient (β 0.676, F 5.59, p = 0.019), and age (β 0.163, F 5.15, p = 0.024). In addition, the percentage fall in MAP was greater in those with the lowest segmental extracellular water/total body water (ECW/TBW) ratios in the right arm prior to dialysis (β -477.5, F 7.11, p = 0.008).

CONCLUSIONS

Falls in blood pressure are common during dialysis, and greater for those starting dialysis with the highest systolic pressures, greater dialysate to serum sodium concentration gradient, and also those with the least ECW in the arm. As such, segmental bioimpedance may be useful in highlighting patients at greatest risk for a fall in blood pressure with dialysis.

Renal transplantation normalizes baroreflex sensitivity through improvement in central arterial stiffness

BACKGROUND

In end-stage renal disease (ESRD) patients, the most common cause of mortality and morbidity are cardiovascular events. This could be attributed to the impaired baroreflex function observed in this group of patients. The effect of renal transplantation (RT) on the baroreflex sensitivity (BRS) in ESRD patients has been inadequately addressed. Therefore, we investigated baroreflex function and its relation to arterial stiffness indices and cardiovascular variability parameters (heart rate and blood pressure variability--HRV and BPV) in ESRD patients before and after transplantation to decipher the underlying mechanism of attenuated BRS in ESRD patients.

METHODS

We studied 23 ESRD patients (mean age; 36 years) prospectively before and at 3 and 6 months after RT. Baroreflex function was determined by spontaneous method (sequence and spectral indices). Short-term HRV and BPV were assessed using power spectrum analysis of RR intervals and systolic blood pressure by frequency domain analysis. Arterial stiffness indices were assessed by carotid-femoral pulse-wave velocity (PWV), augmentation index (AI) and central pulse pressure using Sphygmocor Vx device (AtCor Medical, Australia).

RESULTS

RT was associated with the normalization of BRS by 6 months. Arterial stiffness indices, such as AI and central pulse pressure, showed a significant reduction as early as 3 months after RT. PWV and frequency domain measures of HRV after RT did not show statistically significant changes except the LF/HF ratio which had a significant increase at 6 months when compared with baseline. Systolic BPV total power showed a significant reduction by 3 months after RT.

CONCLUSIONS

Our data suggest that RT normalizes BRS in ESRD patients by 6 months which follows the improvement in the AI and central pulse pressure.

Exploring haemodynamics of haemodialysis using extrema points analysis model

Background

Haemodialysis is a form of renal replacement therapy used to treat patients with end stage renal failure. It is becoming more appreciated that haemodialysis patients exhibit higher rates of multiple end organ damage compared to the general population. There is also a strong emerging evidence that haemodialysis itself causes circulatory stress. We aimed at examining haemodynamic patterns during haemodialysis using a new model and test that model against a normal control.

Methods

We hypothesised that blood pressures generated by each heart beat constantly vary between local peaks and troughs (local extrema), the frequency and amplitude of which is regulated to maintain optimal organ perfusion. We also hypothesised that such model could reveal multiple haemodynamic aberrations during HD. Using a non-invasive cardiac output monitoring device (Finometer®) we compared various haemodynamic parameters using the above model between a haemodialysis patient during a dialysis session and an exercised normal control after comparison at rest.

Results

Measurements yielded 29,751 data points for each haemodynamic parameter. Extrema points frequency of mean arterial blood pressure was higher in the HD subject compared to the normal control (0.761Hz IQR 0.5-0.818 vs 0.468Hz IQR 0.223-0.872, P < 0.0001). Similarly, extrema points frequency of systolic blood pressure was significantly higher in haemodialysis compared to normal. In contrary, the frequency of extrema points for TPR was higher in the normal control compared to HD (0.947 IQR 0.520-1.512 vs 0.845 IQR 0.730-1.569, P < 0.0001) with significantly higher amplitudes.

Conclusion

Haemodialysis patients potentially exhibit an aberrant haemodynamic behaviour characterised by higher extrema frequencies of mean arterial blood pressure and lower extrema frequencies of total peripheral resistance. This, in theory, could lead to higher variation in organ perfusion and may be detrimental to vulnerable vascular beds.

Noninvasive techniques for prevention of intradialytic hypotension

Episodes of hypotension during hemodialysis treatment constitutes an important clinical problem which has received considerable attention in recent years. Despite the fact that numerous approaches to reducing the frequency of intradialytic hypotension (IDH) have been proposed and evaluated, the problem has not yet found a definitive solution--an observation which, in particular, applies to episodes of acute, symptomatic hypotension. This overview covers recent advances in methodology for predicting and preventing IDH. Following a brief overview of well-established hypotension-related variables, including blood pressure, blood temperature, relative blood volume, and bioimpedance, special attention is given to electrocardiographic and photoplethysmographic (PPG) variables and their significance for IDH prediction. It is concluded that cardiovascular variables which reflect heart rate variability, heart rate turbulence, and baroreflex sensitivity are important to explore in feedback control hemodialysis systems so as to improve their performance. The analysis of hemodialysis-related changes in PPG pulse wave properties hold considerable promise for improving prediction.

Baroreflex sensitivity estimation by the sequence method with delayed signals

OBJECTIVE

To evaluate a modified sequence method with delayed time series for baroreflex sensitivity (BRS) estimation during supine position and orthostatism in healthy human beings.

METHODS

Nineteen clinically healthy volunteers (12 men, age 28.4 ± 6.2 years old) were included. Blood pressure recordings were obtained during supine position and orthostatism (15 min each) with a Finometer. Systolic blood pressure (SBP) and inter beat intervals (IBI) measured from all heartbeats were used to estimate BRS in both positive and negative sequences, with SBP delayed between 0 and 5 heartbeats. BRS estimations were compared by ANOVA, p < 0.05 was considered significant. Optimal recording time based on fixed BRS error estimation was calculated for each time series.

RESULTS

BRS estimation was similar between positive and negative sequences in all conditions (BRS = 12.0 ± 2.0 ms/mmHg in supine position, delay 0). BRS with no delay was similar to BRS with delays between 1 and 5 heartbeats. Compared to supine position, BRS was smaller in orthostatism in all delays (BRS = 8.0 ± 2.0 ms/mmHg with delay 0). The shortest optimal recording time with delayed time series was similar in supine position and orthostatism (4.3 ± 1.7 vs. 3.74 ± 0.07 min, respectively). Estimation error was linearly correlated to IBI, regardless of the delay.

CONCLUSION

BRS estimation with sequence method improves with delayed time series, during supine position and orthostatism. Reduced BRS estimation error and recording time from this method could benefit studies with large populations or patients with low tolerance to orthostatism.

Troponin T for the detection of dialysis-induced myocardial stunning in hemodialysis patients

BACKGROUND AND OBJECTIVES

Circulating troponin T levels are frequently elevated in patients undergoing long-term dialysis. The pathophysiology underlying these elevations is controversial.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In 70 prevalent hemodialysis (HD) patients, HD-induced myocardial stunning was assessed echocardiographically at baseline and after 12 months. Nineteen patients were not available for the follow-up analysis. The extent to which predialysis troponin T was associated with the occurrence of HD-induced myocardial stunning was assessed as the primary endpoint.

RESULTS

The median troponin T level in this hemodialysis cohort was 0.06 ng/ml (interquartile range, 0.02-0.10). At baseline, 64% of patients experienced myocardial stunning. These patients showed significantly higher troponin T levels than patients without stunning (0.08 ng/ml [0.05-0.12] versus 0.02 ng/ml [0.01-0.05]). Troponin T levels were significantly correlated to measures of myocardial stunning severity (number of affected segments: r=0.42; change in ejection fraction from beginning of dialysis to end of dialysis: r=-0.45). In receiver-operating characteristic analyses, predialytic troponin T achieved an area under the curve of 0.82 for the detection of myocardial stunning. In multivariable analysis, only ultrafiltration volume (odds ratio, 4.38 for every additional liter) and troponin T (odds ratio, 9.33 for every additional 0.1 ng/ml) were independently associated with myocardial stunning. After 12 months, nine patients had newly developed myocardial stunning and showed a significant increase in troponin T over baseline (0.03 ng/ml at baseline versus 0.05 ng/ml at year 1).

CONCLUSIONS

Troponin T levels in HD patients are associated with the presence and severity of HD-induced myocardial stunning.

Rationale and design of a multi-centre randomised controlled trial of individualised cooled dialysate to prevent left ventricular systolic dysfunction in haemodialysis patients

Background

The main hypothesis of this study is that patients having regular conventional haemodialysis (HD) will have a smaller decline in cardiac systolic function by using cooler dialysate. Cooler dialysate may also be beneficial for brain function.

Methods/Design

The trial is a multicentre, prospective, randomised, un-blinded, controlled trial. Patients will be randomised 1:1 to use a dialysate temperature of 37°C for 12 months or an individualised cooled dialysate. The latter will be set at 0.5°C less than the patient’s own temperature, determined from the mean of 6 prior treatment sessions with a tympanic thermometer, up to a maximum of 36°C. Protocol adherence will be regularly checked. Inclusion criteria are incident adult HD patients within 180 days of commencing in-centre treatment 3 times per week with capacity to consent for the trial and without contra-indications for magnetic resonance imaging. Exclusion criteria include not meeting inclusion criteria, inability to tolerate magnetic resonance imaging and New York Heart Association Grade IV heart failure. During the study period, resting cardiac and cerebral magnetic resonance imaging will be performed at baseline and 12 months on an inter-dialytic day. Cardiovascular performance during HD will also be assessed by continuous cardiac output monitors, intra-dialytic echocardiography and biomarkers at baseline and 12 months. The primary outcome measure is a 5% between-group difference in left ventricular ejection fraction measured by cardiac magnetic resonance imaging at 12 months compared to baseline. Analysis will be by intention-to-treat. Secondary outcome measures will include changes in cerebral microstructure and changes in cardiovascular performance during HD. A total of 73 patients have been recruited into the trial from four UK centres. The trial is funded by a Research for Patient Benefit Grant from the National Institute of Healthcare Research. AO is funded by a British Heart Foundation Clinical Research Training Fellowship Grant. The funders had no role in the design of the study.

Discussion

This investigator-initiated study has been designed to provide evidence to help nephrologists determine the optimal dialysate temperature for preserving cardiac and cerebral function in HD patients.

Trial registration

ISRCTN00206012 and UKCRN ID 7422

How should we manage adverse intradialytic blood pressure changes?

Variations in intradialytic blood pressure (BP) are a common and predictable occurrence in ESRD patients. These are caused by a decrease in blood volume provoked by ultrafiltration, lack of normal compensatory responses to fluid removal, underlying cardiac disease, and electrolyte changes that may adversely affect cardiovascular function. Intradialytic hypotension is the most frequent complication of the hemodialysis (HD) procedure and is fundamentally a consequence of an ultrafiltration rate that surpasses mechanisms activated to avert a decline in BP. Intradialytic hypertension is a less well-understood problem that has been recently associated with increased mortality. Fundamental patient characteristics and components of the HD procedure are involved in the pathophysiology of intradialytic hypotension and intradialytic hypertension. Correction of patient factors, modulation of HD prescription, and management of pharmacologic agents are the strategies to deal with adverse intradialytic BP changes.

Are there neurological consequences of recurrent intradialytic hypotension?

Structural abnormalities of the brain are common in hemodialysis (HD) patients, as are a wide range of severe functional deficiencies of cerebral function. Both depression and increasing dependency are highly prevalent in HD patients and worsen severely within the first 12 months of dialysis initiation. HD, as it is commonly practiced, is associated with significant recurrent episodes of circulatory stress. This results in acute injury to the heart, skin, kidney and gut, and drives longer term end-organ chronic injury. This article aims to explore the hypothesis that the cerebral microcirculation is also sensitive to dialysis-based circulatory stress (and other multiorgan consequences of recurrent dialysis-induced ischemia), and that this may drive specific patterns of brain injury with resultant psychiatric and functional consequences.

Prognostic indicators of cardiovascular risk in renal disease

Although the annual mortality rate for end-stage renal disease (ESRD) is decreasing, likely due to an increase in kidney transplantation rate, the survival probability for ESRD patients from day one of dialysis has not changed, and is still poor with a 5-year survival rate of approximately 34%. This is contributed to by a high prevalence of cardiovascular disease, which is the leading cause of death in ESRD patients. In order to improve survival outcomes, patients at high risk of cardiovascular related mortality need to be identified. Heart rate variability (HRV), baroreceptor sensitivity, and baroreceptor reflex effectiveness index can be used to assess heart rate control and may predict cardiovascular mortality. This paper will discuss how HRV, baroreceptor sensitivity, and baroreceptor reflex effectiveness index are altered in renal disease and the utility of these indices as markers of cardiac risk in this patient population.