Feedback control in hemodialysis

A number of systems of feedback control during dialysis have been developed, which have the shared characteristic of prospectively measuring physiological parameters and then automatically altering dialysis parameters in real time according to a pre-specified dialysis prescription. These include feedback systems aimed at reducing intradialytic hypotension based on relative blood volume monitoring linked to adjustments in ultrafiltration and dialysate conductivity, and blood temperature monitoring linked to alterations in dialysate temperature. Feedback systems also exist that manipulate sodium balance during dialysis by assessing and adjusting dialysate conductivity. In this review article, we discuss the rationale for automated feedback systems during dialysis, describe how the different feedback systems work, and provide a review of the current evidence on their clinical effectiveness

Predictors of post‐hospitalization recovery of renal function among patients with acute kidney injury requiring dialysis

Introduction: Acute kidney injury (AKI) requiring dialysis complicates 1% of all hospital admissions, and up to 30% of survivors will still require dialysis at hospital discharge. There is a paucity of data to describe the postdischarge outcomes or to guide evidence‐based dialysis management of this vulnerable population.Methods: Single‐center, retrospective analysis of 100 consecutive patients with AKI who survived to hospital discharge and required outpatient dialysis. Data collection included baseline characteristics, hospitalization characteristics, and outpatient dialysis treatment variables. Primary outcome was dialysis independence 90 days after discharge.Findings: Overall, 43% of patients recovered adequate renal function to discontinue dialysis, with the majority recovering within 30 days post discharge. Worse baseline renal function was associated with lower likelihood of renal recovery. In the first week postdischarge, patients with subsequent nonrecovery of renal function had greater net fluid removal (5.3 vs. 4.1 L, P = 0.037), higher ultrafiltration rates (6.0 vs. 4.7 mL/kg/h, P = 0.041) and more frequent intradialytic hypotension (24.6% vs. 9.3% with 3 or more episodes, P = 0.049) compared to patients that later recovered.Discussion: A significant proportion of AKI survivors will recover renal function following discharge. Outpatient intradialytic factors may influence subsequent renal function recovery.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141286/1/hdi12545.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141286/2/hdi12545_am.pd

Application of the Lomb-Scargle Periodogram to Investigate Heart Rate Variability during Haemodialysis

Short-term cardiovascular compensatory responses to perturbations in the circulatory system caused by haemodialysis can be investigated by the spectral analysis of heart rate variability, thus providing an important variable for categorising individual patients' response, leading to a more personalised treatment. This is typically accomplished by resampling the irregular heart rate to generate an equidistant time series prior to spectral analysis, but resampling can further distort the data series whose interpretation can already be compromised by the presence of artefacts. The Lomb-Scargle periodogram provides a more direct method of spectral analysis as this method is specifically designed for large, irregularly sampled, and noisy datasets such as those obtained in clinical settings. However, guidelines for preprocessing patient data have been established in combination with equidistant time-series methods and their validity when used in combination with the Lomb-Scargle approach is missing from literature. This paper examines the effect of common preprocessing methods on the Lomb-Scargle power spectral density estimate using both real and synthetic heart rate data and will show that many common techniques for identifying and editing suspect data points, particularly interpolation and replacement, will distort the resulting power spectrum potentially misleading clinical interpretations of the results. Other methods are proposed and evaluated for use with the Lomb-Scargle approach leading to the main finding that suspicious data points should be excluded rather than edited, and where required, denoising of the heart rate signal can be reliably accomplished by empirical mode decomposition. Some additional methods were found to be particularly helpful when used in conjunction with the Lomb-Scargle periodogram, such as the use of a false alarm probability metric to establish whether spectral estimates are valid and help automate the assessment of valid heart rate records, potentially leading to greater use of this powerful technique in a clinical setting.The authors would like to thank Mel Morris and iTrend Medical Research Ltd. for funding the iTrend research programme

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

Characterising Haemodynamic Stress during Haemodialysis Using the Extrema Points Analysis Model.

&lt;b&gt;&lt;i&gt;Background and Aims:&lt;/i&gt;&lt;/b&gt; 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. &lt;b&gt;&lt;i&gt;Methods:&lt;/i&gt;&lt;/b&gt; 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. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; 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 &lt; 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&lt;sup&gt;2&lt;/sup&gt; 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&lt;sup&gt;2&lt;/sup&gt; = 0.19, B = 103.29, 95% CI 38.88-167.70). &lt;b&gt;&lt;i&gt;Conclusion:&lt;/i&gt;&lt;/b&gt; 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.</jats:p

Challenges in Management of Diabetic Patient on Dialysis

Diabetes mellitus is the leading cause of end-stage kidney disease in many countries. The management of diabetic patients who receive dialysis can be challenging. Diabetic dialysis patients have higher rates of cardiovascular events and mortality due to metabolic factors and accelerated vascular calcification. Diabetic haemodialysis patients have high rates of haemodynamic instability which leads to organ ischaemia and end organ damage; autonomic dysfunction seems to play an important role in haemodynamic instability and abnormal organ perfusion during haemodialysis. Poor glycaemic control contributes to fluid overload and worse cardiovascular outcome. Xerostomia and thirst are the main drivers for fluid overload in haemodialysis patients and in peritoneal dialysis a chronic state of hyperhydration that is related to absorption of glucose from the PD fluids, protein loss and malnutrition contributes to fluid overload. Glycaemic control is of great importance and adjustments to diabetic agents are required. In haemodialysis, a reduction in insulin dose is recommended to avoid hypoglycaemia whereas in peritoneal dialysis an increase in insulin dose is often required. Foot ulcers and infection are more common in diabetic dialysis patients compared to non-diabetic dialysis patients or diabetic patients with normal renal function and regular surveillance for early identification is important. Ultimately, a multi-disciplinary approach which includes diabetologist, nephrologist, dietitians, microbiologist, vascular surgeon, interventional radiologist is required to address the complicated aspects of diabetic patient care on dialysis

Randomized Clinical Trial of Dialysate Cooling and Effects on Brain White Matter

Hemodialysis is associated with significant circulatory stress that could produce recurrent and cumulative ischemic insults to multiple organs, such as the brain. We aimed to characterize hemodialysis-induced brain injury by longitudinally studying the effects of hemodialysis on brain white matter microstructure and further examine if the use of cooled dialysate could provide protection against hemodialysis-associated brain injury. In total, 73 patients on incident hemodialysis starting within 6 months were randomized to dialyze with a dialysate temperature of either 37°C or 0.5°C below the core body temperature and followed up for 1 year. Brain white matter microstructure was studied by diffusion tensor magnetic resonance imaging at baseline and follow-up (38 patients available for paired analysis). Intradialytic hemodynamic stress was quantified using the extrema points analysis model. Patients on hemodialysis exhibited a pattern of ischemic brain injury (increased fractional anisotropy and reduced radial diffusivity). Cooled dialysate improved hemodynamic tolerability, and changes in brain white matter were associated with hemodynamic instability (higher mean arterial pressure extrema points frequencies were associated with higher fractional anisotropy [peak r=0.443, P<0.03] and lower radial diffusivity [peak r=−0.439, P<0.02]). Patients who dialyzed at 0.5°C below core body temperature exhibited complete protection against white matter changes at 1 year. Our data suggest that hemodialysis results in significant brain injury and that improvement in hemodynamic tolerability achieved by using cooled dialysate is effective at abrogating these effects. This intervention can be delivered without additional cost and is universally applicable