Dialysis hypotension: a hemodynamic analysis

The role of plasma volume and fluid overload in the tolerance to ultrafiltration and hypotension in hemodialysis patients

INTRODUCTION

Ultrafiltration (UF) in hemodialysis (HD) patients is accompanied by irregular falls in plasma volume (PV) and blood pressure (BP).

METHODS

We obtained in 321 patients (large cohort), body weight (BW), BP, samples of blood to determine hemoglobin (Hb) and hematocrit (Ht), Pre and Post HD. We estimated the % variation of the PV and its effect on the BP. In a small cohort of 38/321 patients, arterial blood was drawn Pre and Post HD and at 2, 48, and 72 h to determined Hb and Ht and % variation of the PV. Bio-impedance spectroscopy (BIS) was performed, in the same times, to estimate: dry weight (DW), total body water (TBW), extracellular water (ECW), Fluid overload (FO) and phase angle (PhA).

RESULTS

We divided our large cohort in two groups. The Hypotensive group with a fall equal or more than 20 mmHg (96/321,30%) and Normotensive group with a drop equal or less than 19 mmHg (225/321,70%). The UF was 2.73 ± 0.72 L in the Hypotensive group and 2.53 ± 0.85 L in the Normotensive group (p < 0.0001). The % PV was -11.7 ± 17.8 in the Hypotensive group and -8.53 ± 10.07 in the Normotensive group (p < 0.0001). The systolic blood pressure (SBP) correlated with the % change of the PV (r = -0.232; p < 0.0001). The FO was contrasted with the % of water removed by UF (r = -0.890; p < 0.0001).

CONCLUSION

The SBP drop was secondary to the fall in the PV after UF. The FO was irregular and modulates in part the fall in the SBP.

Current Knowledge of Beta-Blockers in Chronic Hemodialysis Patients

Beta-blockers include a large spectrum of drugs with various specific characteristics, and a well-known cardioprotective efficacy. They are recommended in heart failure, hypertension and arrhythmia. Their use in chronic hemodialysis patients is still controversial, mainly because of the lack of specific randomized clinical trials. Large observational studies and two important clinical trials have reported almost unanimously their efficacy in chronic hemodialysis patients, which seems to be related to their levels of dialyzability and cardioselectivity. A recent meta-analysis suggested that high dialyzable beta-blockers are correlated to a reduced risk of all-cause mortality and cardiovascular complications compared with low dialyzable beta-blockers. Despite their benefits, beta-blockers may have adverse effects, such as intradialytic hypotension with low dialyzability beta-blockers or the risk of sub-therapeutic plasma concentration of high dialyzable ones during dialysis sessions. Both cases are linked to adverse cardiovascular events. A solution for both high and low dialyzable drugs could be their administration after dialysis sessions. Futhermore, the bulk of existing literature seems to favor cardioselective beta-blockers with moderate-to-high dialyzability as the ideal agents in dialysis patients, but further, larger studies are needed. This review aims to analyze beta-blockers' characteristics, indications and evidence-based role in chronic hemodialysis patients.

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.

Circumferential Strain as a Marker of Vessel Reactivity in Patients with Intradialytic Hypotension

Background and Objectives: Intradialytic hypotension (IDH) complicates 4 to 39.9% of hemodialysis (HD) sessions. Vessels' reactivity disturbances may be responsible for this complication. Two-dimensional speckle tracking is used to assess arterial circumferential strain (CS) as a marker of the effectiveness of the cardiovascular response to the reduction of circulating plasma. Materials and Methods: The common carotid artery (CCA) and common iliac artery (CIA) CSs were recorded using ultrasonography in 68 chronically dialyzed patients before and after one HD session. Results: In patients with IDH episodes (n = 26), the CCA-CS was significantly lower both before (6.28 ± 2.34 vs. 4.63 ± 1.74 p = 0.003) and after HD (5.00 (3.53-6.78) vs. 3.79 ± 1.47 p = 0.010) than it was in patients without this complication. No relationship was observed between CIA-CS and IDH. IDH patients had a significantly higher UF rate; however, they did not differ compared to complication-free patients either in anthropometric or laboratory parameters. Conclusions: Patients with IDH were characterized by lower pre- and post-HD circumferential strain of the common carotid artery. The lower CCA-CS showed that impaired vascular reactivity is one of the most important risk factors for this complication's occurrence.

The interstitial compartment as a therapeutic target in heart failure

Congestion is the single most important contributor to heart failure (HF) decompensation. Most of the excess volume in patients with HF resides in the interstitial compartment. Inadequate decongestion implies persistent interstitial congestion and is associated with worse outcomes. Therefore, effective interstitial decongestion represents an unmet need to improve quality of life and reduce clinical events. The key processes that underlie incomplete interstitial decongestion are often ignored. In this review, we provide a summary of the pathophysiology of the interstitial compartment in HF and the factors governing the movement of fluids between the interstitial and vascular compartments. Disruption of the extracellular matrix compaction occurs with edema, such that the interstitium becomes highly compliant, and large changes in volume marginally increase interstitial pressure and allow progressive capillary filtration into the interstitium. Augmentation of lymph flow is required to prevent interstitial edema, and the lymphatic system can increase fluid removal by at least 10-fold. In HF, lymphatic remodeling can become insufficient or maladaptive such that the capacity of the lymphatic system to remove fluid from the interstitium is exceeded. Increased central venous pressure at the site of the thoracic duct outlet also impairs lymphatic drainage. Owing to the kinetics of extracellular fluid, microvascular absorption tends to be transient (as determined by the revised Starling equation). Therefore, effective interstitial decongestion with adequate transcapillary plasma refill requires a substantial reduction in plasma volume and capillary pressure that are prolonged and sustained, which is not always achieved in clinical practice. The critical importance of the interstitium in the congestive state underscores the need to directly decongest the interstitial compartment without relying on the lowering of intracapillary pressure with diuretics. This unmet need may be addressed by novel device therapies in the near future.

Correlation between Angiotensin Serum Levels and Very-Low-Frequency Spectral Power of Heart Rate Variability during Hemodialysis

Cardiovascular regulatory mechanisms that fail to compensate for ultrafiltration and cause hypovolemia during hemodialysis (HD) are not completely understood. This includes the interaction between the autonomic nervous system and the biochemistry that regulates blood pressure and modulates cardiac activity and vascular tone in response to hypovolemia in patients treated with HD. The objective was to evaluate the association of spectral indices of heart rate variability (HRV) with serum levels of angiotensin II, angiotensin 1–7, nitric oxide and total antioxidant capacity during HD. Electrocardiographic records were obtained from 20 patients during HD (3 h), from which HRV data and spectral power data in the very-low-frequency (VLF), low-frequency (LF) and high-frequency (HF) bands were generated. Three blood samples per patient were collected during HD (0.0, 1.5, 3.0 h) to determine the levels of biomarkers involved in the pressor response during HD. Angiotensin II had a positive correlation with VLF (r = 0.390) and with LF/HF (r = 0.359) and a negative correlation with LF (r = −0.262) and HF (r = −0.383). There were no significant correlations between HRV and the other biomarkers. These results suggest that during HD, VLF could reflect the serum levels of angiotensin II, which may be associated with the autonomic response to HD.

A new technique for the detection of dry weight in hemodialysis patients: Estimated pulmonary capillary wedge pressure. A tissue Doppler imaging study

BACKGROUND AND OBJECTIVE

Fluid overload is an important factor of morbidity and mortality in hemodialysis patients. Today correct determination of dry weight (DW) remains an important issue of hemodialysis practice. Within this context, it is subjected to new method searching. The objective of this study was to calculate estimated pulmonary capillary wedge pressure (ePCWP) with Tissue Doppler Imaging (TDI) in hemodialysis patients and to evaluate its correlation with the other volume markers and to evaluate whether it can be a new method for detection of DW.

MATERIALS AND METHODS

Echocardiographic, hemodynamic, and biochemical volume markers of 41 hemodialysis patients were evaluated in the pre- and post-dialysis periods. Patients were divided into two groups based on ePCWP values (Group 1 ePCWP<20mmHg, Group 2 ePCWP>20mmHg).

RESULTS

In the pre-dialysis period; parameters related to volume load including ePCWP, systolic blood pressure, mean arterial pressure, pulse pressure, left atrial diameter, left atrial volume, E/é, ratio and E/V_p ratio were statistically significantly higher in Group2 compared to Group1. On the other hand, strong correlations were found between pre-dialysis ePCWP and systolic blood pressure, mean arterial pressure, pulse pressure, NT-ProBNP, left atrial diameter, E/é ratio and E/V_p ratio.

CONCLUSIONS

Strong correlations found between ePCWP which was calculated with TDI and the other volume markers both in pre-dialysis and post-dialysis periods. These findings can provide a significant contribution to routine evaluating of DW in hemodialysis patients. From this aspect, the prediction of ePCWP with TDI can be a new practical and reproducible method for the determination of DW.

Effect of Beta-Blocker Cardioselectivity on Vascular Refilling in Hemodialysis Patients

BACKGROUND

β-Blockers are the most frequently prescribed cardioprotective drugs in hemodialysis (HD) patients, despite their weak evidence. We sought to evaluate the effects of β-blockers on vascular refilling during HD treatments and examine whether carvedilol, for being noncardioselective and poorly dialyzable, associates more impact than others.

METHODS

The study was performed in a cohort of maintenance HD patients from a tertiary center. All patients had previous β-blocker prescription. We conducted a prospective crossover study and measured vascular refilling volume (Vref) and vascular refilling fraction (Fref) in 2 circumstances: under β-blocker treatment (βb profile) and without β-blocker effect (non-βb profile).

RESULTS

Twenty patients were included, 10 of whom were treated with carvedilol. Predialysis values were comparable between the 2 profiles. Although the βb profile showed lower Vref and higher ABV drop, these differences did not reach statistical significance. Data showed an increase in Fref in the non-βb profile (70.01 ± 6.80% vs. 63.14 ± 11.65%; p = 0.015). The βb profile associated a significantly higher risk of intradialytic hypotension (IDH) (risk ratio 2.40; 95% CI: 1.04-5.55). When analyzing separately the carvedilol group, patients dialyzed under drug effect experienced a significant impairment in Vref, Fref, and refilling rate.

CONCLUSIONS

Administering β-blockers before HD associated a higher risk of IDH and a decrease in Fref. Patients dialyzed under carvedilol effect showed an impaired refilling, probably related to its noncardioselectivity and lower dializability.

Changes in total and segmental extracellular and intracellular volumes with hypotension during hemodialysis measured with bioimpedance spectroscopy

BACKGROUND

Bioelectrical impedance analysis (BIA) devices have been advocated to guide volume management in hemodialysis (HD) patients. We hypothesized that understanding the dynamics of fluid shifts in different body segments may provide additional insight on preventive measures to reduce the risk of intradialytic hypotension.

METHODS

A prospective observational study was conducted among 42 HD patients at risk of hypotension who were admitted as emergencies inpatient.

RESULTS

A total of 191 BIA measurements were made during the 42 HD sessions, and hypotension occurred during 52 measurements (27%). The extracellular water (ECW) to intracellular water ratio (EIR) was measured in different body segments and declined significantly only in the non-access arm with increasing HD session duration (β = -0.04; 95% confidence interval (CI): -0.05 to -0.03, p < 0.01). There was no significant association between EIR and hypotension with respect to the different body segments. Only pre-HD N-terminal-pro b-type natriuretic peptide was significantly associated with hypotension (β = 0.20, 95% CI: 0.04 to 0.89, p = 0.04). There was no association between relative blood volume monitoring change and EIR.

CONCLUSION

In summary, we found that segmental BIA during HD was unable to detect or predict hypotension during dialysis. Although BIA is able to provide information about ECW and guide clinical assessment of volume in HD patients prior to dialysis, our findings did not suggest the use of serial measurements of changes in EIR in different body segments during HD provided sufficient information to predict intradialytic hypotension. Similarly, changes in EIR did not provide information on changes in plasma volume that could potentially trigger interventions to prevent or reduce intra-dialytic hypotension.

A new technique for the detection of dry weight in hemodialysis patients: Estimated pulmonary capillary wedge pressure. A tissue Doppler imaging study

BACKGROUND AND OBJECTIVE

Fluid overload is an important factor of morbidity and mortality in hemodialysis patients. Today correct determination of dry weight (DW) remains an important issue of hemodialysis practice. Within this context, it is subjected to new method searching. The objective of this study was to calculate estimated pulmonary capillary wedge pressure (ePCWP) with Tissue Doppler Imaging (TDI) in hemodialysis patients and to evaluate its correlation with the other volume markers and to evaluate whether it can be a new method for detection of DW.

MATERIALS AND METHODS

Echocardiographic, hemodynamic, and biochemical volume markers of 41 hemodialysis patients were evaluated in the pre- and post-dialysis periods. Patients were divided into two groups based on ePCWP values (Group 1 ePCWP<20mmHg, Group 2 ePCWP>20mmHg).

RESULTS

In the pre-dialysis period; parameters related to volume load including ePCWP, systolic blood pressure, mean arterial pressure, pulse pressure, left atrial diameter, left atrial volume, E/é, ratio and E/Vp ratio were statistically significantly higher in Group2 compared to Group1. On the other hand, strong correlations were found between pre-dialysis ePCWP and systolic blood pressure, mean arterial pressure, pulse pressure, NT-ProBNP, left atrial diameter, E/é ratio and E/Vp ratio.

CONCLUSIONS

Strong correlations found between ePCWP which was calculated with TDI and the other volume markers both in pre-dialysis and post-dialysis periods. These findings can provide a significant contribution to routine evaluating of DW in hemodialysis patients. From this aspect, the prediction of ePCWP with TDI can be a new practical and reproducible method for the determination of DW.

Real-time prediction of intradialytic relative blood volume: a proof-of-concept for integrated cloud computing infrastructure

BACKGROUND

Inadequate refilling from extravascular compartments during hemodialysis can lead to intradialytic symptoms, such as hypotension, nausea, vomiting, and cramping/myalgia. Relative blood volume (RBV) plays an important role in adapting the ultrafiltration rate which in turn has a positive effect on intradialytic symptoms. It has been clinically challenging to identify changes RBV in real time to proactively intervene and reduce potential negative consequences of volume depletion. Leveraging advanced technologies to process large volumes of dialysis and machine data in real time and developing prediction models using machine learning (ML) is critical in identifying these signals.

METHOD

We conducted a proof-of-concept analysis to retrospectively assess near real-time dialysis treatment data from in-center patients in six clinics using Optical Sensing Device (OSD), during December 2018 to August 2019. The goal of this analysis was to use real-time OSD data to predict if a patient's relative blood volume (RBV) decreases at a rate of at least - 6.5 % per hour within the next 15 min during a dialysis treatment, based on 10-second windows of data in the previous 15 min. A dashboard application was constructed to demonstrate how reporting structures may be developed to alert clinicians in real time of at-risk cases. Data was derived from three sources: (1) OSDs, (2) hemodialysis machines, and (3) patient electronic health records.

RESULTS

Treatment data from 616 in-center dialysis patients in the six clinics was curated into a big data store and fed into a Machine Learning (ML) model developed and deployed within the cloud. The threshold for classifying observations as positive or negative was set at 0.08. Precision for the model at this threshold was 0.33 and recall was 0.94. The area under the receiver operating curve (AUROC) for the ML model was 0.89 using test data.

CONCLUSIONS

The findings from our proof-of concept analysis demonstrate the design of a cloud-based framework that can be used for making real-time predictions of events during dialysis treatments. Making real-time predictions has the potential to assist clinicians at the point of care during hemodialysis.

Clinical Epidemiology of Systolic and Diastolic Orthostatic Hypotension in Patients on Peritoneal Dialysis

Blood pressure changes upon standing reflect a hemodynamic response, which depends on the baroreflex system and euvolemia. Dysautonomia and fluctuations in blood volume are hallmarks in kidney failure requiring replacement therapy. Orthostatic hypotension has been associated with mortality in hemodialysis patients, but neither this relationship nor the impact of changes in blood pressure has been tested in patients on peritoneal dialysis. We investigated both these relationships in a cohort of 137 PD patients. The response to orthostasis was assessed according to a standardized protocol. Twenty-five patients (18%) had systolic orthostatic hypotension, and 17 patients (12%) had diastolic hypotension. The magnitude of systolic and diastolic BP changes was inversely related to the value of the corresponding supine BP component (r = -0.16, p = 0.056 (systolic) and r = -0.25, p = 0.003 (diastolic), respectively). Orthostatic changes in diastolic, but not in systolic, BP were linearly related to the death risk (HR (1 mmHg reduction): 1.04, 95% CI 1.01-1.07, p = 0.006), and this was also true for CV death (HR: 1.08, 95% CI 1.03-1.12, p = 0.001). The strength of this association was not affected by further data adjustment (p ≤ 0.05). These findings suggest that independent of the formal diagnosis of orthostatic hypotension, even minor orthostatic reductions in diastolic BP bear an excess death risk in this population.

Impact of dialysate sodium concentration on vascular refilling

BACKGROUND

Although relationship between dialysate sodium concentration and hemodynamic stability has been well studied over the years, outcomes of absolute blood volume (ABV) maintenance and vascular refilling volume (V_ref ) modifications were not included, as its analysis has not been easily accessible to direct investigation. However, recent studies report a simple and feasible methodology to assess ABV and V_ref during hemodialysis (HD) treatments. It is the aim of this study to analyze whether sodium concentration in dialysate modifies ABV drop and V_ref .

METHODS

The study was performed in 19 patients under HD. During three different sessions, sodium concentration in dialysate was randomized to three different profiles: low sodium concentration (LNa, 138 mEq/L), neutral sodium concentration (NNa, 140 mEq/L), and high sodium concentration (HNa, 143 mEq/L). ABV and V_ref were calculated using Kron et al methodology.

RESULTS

Predialysis values of the measured parameters showed similar results for the three profiles. Sodium concentration showed an effect on ABV drop, V_ref, and vascular refilling fraction (F_ref ). Pair-wise comparison revealed mean ABV decreased 0.21 L less when using HNa profile versus LNa profile (p = 0.027), a mean V_ref increase of 0.39 L (p = 0.038), and a mean F_ref increase of 9.94% (p = 0.048).

CONCLUSIONS

This study shows that the use of HNa profiles increases V_ref and F_ref and reduces ABV drop during dialysis treatments when compared to LNa profiles.

Epidemiology of nursing home dialysis patients-A hidden population

Introduction

Dialysis patients are often discharged from hospitals to skilled nursing facilities (SNFs), but little has been published about their natural history.

Methods

Using electronic medical record data, we conducted a retrospective cohort study of nursing home patients treated with in‐SNF hemodialysis from January 1, 2018 through June 20, 2020 within a dialysis organization across eight states. A dialytic episode began with the first in‐SNF dialysis and was ended by hospitalization, death, transfer, or cessation of treatment. The clinical characteristics and natural history of these patients and their dialytic episodes are described.

Findings

Four thousand five hundred and ten patients experienced 9274 dialytic episodes. Dialytic episodes had a median duration of 18 days (IQR: 8–38) and were terminated by a hospitalization n = 5747 (62%), transfer n = 2638 (28%), death n = 568 (6%), dialysis withdrawal n = 129 (1.4%), recovered function n = 2 (0.02%), or other cause n = 6 (0.06%). Increased patient mortality was associated with advancing age, low serum creatinine, albumin, or sodium, and low pre‐dialytic systolic blood pressure (sBP). U‐shaped relationships to mortality were observed for intradialytic hypotension frequency and for post‐ > pre‐hemodialysis sBP frequency. Prescription of dialysis five times weekly in the first 2 weeks was associated with better survival in the first 90 days (HR 0.77, CI 0.62–0.96; p < 0.02).

Discussion

Provision of in‐SNF dialysis by an external dialysis organization enables discharge from the acute care setting for appropriate treatment with increased nursing contact time in an otherwise under‐resourced environment. SNF ESRD patient clinical characteristics and outcomes are extensively characterized for the first time.

Absolute blood volume variations during hemodialysis: Does dialysate temperature play a role?

BACKGROUND

Vascular refilling occurs to preserve hemodynamic stability during hemodialysis (HD). Recent studies report a feasible and noninvasive method to determine absolute blood volume (ABV), and estimate vascular refilling during HD. The objective of this study is to analyze if lowering dialysate temperature modifies variations in ABV during HD.

METHODS

The study was performed in 50 patients under HD. During two different sessions, relative blood volume was assessed using dialysate temperatures of 35.5°C (cool dialysate) and 36.5°C (neutral dialysate). ABV and vascular refilling were calculated using Kron et al methodology.

RESULTS

Thirty-nine intradialytic morbid events (IMEs) were observed in 30 patients, 14 under cool dialysate and 25 during neutral dialysate. We did not found statistically differences in ABV or in refilling volume between cool and neutral temperature. When analyzing apart only those patients who presented IME, we observed lower drop in ABV in the 35.5°C dialysate treatments (0.57 L) versus 36.5°C dialysate treatments (0.71 L). When cool dialysate was used, the vascular refilling fraction tended to be higher, but data did not turn statistically significant.

CONCLUSIONS

In selected groups of patients the use of cool dialysate induces lower ABV variations that could improve hemodynamic stability during HD treatments.

Low-Intensity Intradialytic Exercise Attenuates the Relative Blood Volume Drop Due to Intravascular Volume Loss during Hemodiafiltration

INTRODUCTION

Patients in hemodiafiltration (HDF) eliminate volume overload by ultrafiltration. Vascular volume loss is among the main mechanisms contributing to adverse events such as intradialytic hypotension. Here, we hypothesize that the intradialytic exercise (IDEX) is an intervention that could improve the acute response of physiological mechanisms involved during vascular volume loss. To test this hypothesis, we evaluated the hemodynamic response to mild aerobic exercise during HDF.

METHODS

Nineteen end-stage renal disease (ESRD) patients (11 women: 40 ± 10.8 years old, and 8 men: 42 ± 21 years old) receiving HDF thrice a week, with 6 months of previous physical conditioning, participated in this study. Three HDF sessions were scheduled for each patient: 1 resting in supine position, 1 resting in sitting position, and 1 doing aerobic exercise. The first 2 sessions were taken as control. The ultrafiltration rate was set to 800 mL/h in each session. The hemodynamic response was monitored through the relative blood volume (RBV), and cardiovascular variables measured noninvasively by photoplethysmography. Adequacy variables such as Kt/V and percentage reduction of urate, urea, creatinine (Cr), and phosphate were also monitored.

FINDINGS

The decrease rate of the RBV was smaller in the session with IDEX compared to the sessions with no exercise. No differences were found neither in the cardiovascular variables nor in the adequacy variables among the 3 sessions. There were no hypotension events during the session with exercise, and 8 events during the sessions without exercise (p = 0.002).

DISCUSSION

Mild exercise during HDF decreased the RBV drop and was associated with less hypotension events. The lack of differences in the hemodynamic variables suggests an adequate acute response of cardiovascular compensation variables to intradialytic hypovolemia.

Comparative Analysis on Machine Learning and Deep Learning to Predict Post-Induction Hypotension

Hypotensive events in the initial stage of anesthesia can cause serious complications in the patients after surgery, which could be fatal. In this study, we intended to predict hypotension after tracheal intubation using machine learning and deep learning techniques after intubation one minute in advance. Meta learning models, such as random forest, extreme gradient boosting (Xgboost), and deep learning models, especially the convolutional neural network (CNN) model and the deep neural network (DNN), were trained to predict hypotension occurring between tracheal intubation and incision, using data from four minutes to one minute before tracheal intubation. Vital records and electronic health records (EHR) for 282 of 319 patients who underwent laparoscopic cholecystectomy from October 2018 to July 2019 were collected. Among the 282 patients, 151 developed post-induction hypotension. Our experiments had two scenarios: using raw vital records and feature engineering on vital records. The experiments on raw data showed that CNN had the best accuracy of 72.63%, followed by random forest (70.32%) and Xgboost (64.6%). The experiments on feature engineering showed that random forest combined with feature selection had the best accuracy of 74.89%, while CNN had a lower accuracy of 68.95% than that of the experiment on raw data. Our study is an extension of previous studies to detect hypotension before intubation with a one-minute advance. To improve accuracy, we built a model using state-of-art algorithms. We found that CNN had a good performance, but that random forest had a better performance when combined with feature selection. In addition, we found that the examination period (data period) is also important.

All-cause mortality in relation to changes in relative blood volume during hemodialysis

Background

Relative blood volume (RBV) monitoring is widely used in hemodialysis (HD) patients, yet the association between intradialytic RBV and mortality is unknown.

Methods

Intradialytic RBV was recorded once/min during a 6-month baseline period; all-cause mortality was noted during follow-up. RBV at 1, 2 and 3 h into HD served as a predictor of all-cause mortality during follow-up. We employed Kaplan–Meier analysis, univariate and adjusted Cox proportional hazards models for survival analysis.

Results

We studied 842 patients. During follow-up (median 30.8 months), 249 patients (29.6%) died. The following hourly RBV ranges were associated with improved survival: first hour, 93–96% [hazard ratio (HR) 0.58 (95% confidence interval (CI) 0.42–0.79)]; second hour, 89–94% [HR 0.54 (95% CI 0.39–0.75)]; third hour, 86–92% [HR 0.46 (95% CI 0.33–0.65)]. In about one-third of patients the RBV was within these ranges and in two-thirds it was above. Subgroup analysis by median age (≤/> 61 years), sex, race (white/nonwhite), predialysis systolic blood pressure (SBP; ≤/> 130 mmHg) and median interdialytic weight gain (≤/> 2.3 kg) showed comparable favorable RBV ranges. Patients with a 3-h RBV between 86 and 92% were younger, had higher ultrafiltration volumes and rates, similar intradialytic average and nadir SBPs and hypotension rates, lower postdialysis SBP and a lower prevalence of congestive heart failure when compared with patients with an RBV >92%. In the multivariate Cox analysis, RBV ranges remained independent and significant outcome predictors.

Conclusion

Specific hourly intradialytic RBV ranges are associated with lower all-cause mortality in chronic HD patients.

Adequacy of Fluid/Sodium Balance and Blood Pressure Control

Hypotension and orthostatic hypotension are frequently observed in CAPD patients. In the present paper the possible causes of these complications were reviewed, and the roles of sodium and water were pointed out.

In addition, we reported our experience using different sodium concentrations in CAPD dialysis fluid. In 38 CAPD patients sodium concentration in the dialysate was changed from 132 to 137 mEq/L. At first, arterial blood pressure increased in 4 patients (10%), and they were switched to 132 mEq/L sodium. Of the other 34 patients, 3 required larger doses of antihypertensive agents, while 9 reduced the number and/or dose of antihypertensive drugs. Thirst, body weight, residual renal function, 24-hour ultrafiltration, and biochemical examinations did not change using 137 mEq/L sodium concentrations for 6 months. In the 21 patients who did not change their antihypertensive treatment, upright blood pressure tended to increase, but the difference was not statistically significant.

In 3 hypotensive patients sodium concentration was increased to 142 mEq/L. Thirst increased in 2 of the 3, one observed a transient increase in 24-hour ultrafiltration, and none showed changes in plasma sodium level. One patient developed reversible hypertension, one became normotensive, and the third had no changes in blood pressure.

Effective Continuous Ambulatory Peritoneal Dialysis following Abdominal Aortic Aneurysm Repair

+ Objective

To review a single center's experience with the initiation and maintenance of continuous ambulatory peritoneal dialysis (CAPD) in 8 patients with a history of abdominal aortic aneurysm repair (AAAR).

+ Design

Retrospective case review with long-term follow-up.

+Patients (or Participants)

Eight patients with multiple medical problems including a history of abdominal aortic aneurysm repair and end-stage renal failure who received peritoneal dialysis catheters between December 1986 and July 1991.

+ Main Outcome Measures

Success of catheter implantation and maintenance of continuous ambulatory peritoneal dialysis; incidence of peritoneal infection and long-term complications; overall clinical course.

+ Results

Over five years 8 patients with a history of reconstructed abdominal aortic aneurysm received peritoneal dialysis catheters without complication and dialyzed successfully for 88 patient-months in total. Three patients had a total of five episodes of peritonitis, at an incidence of 0.68 episodes per patient per year, a rate not significantly different from that of our overall CAPD patient population (1.09) and that reported by other groups.

+ Conclusion

Our experience suggests that historical AAAR poses no significant risk to and should not preclude the implementation of continuous ambulatory peritoneal dialysis. Indeed, CAPD offers a safe and optimal dialytic alternative for patients with historical abdominal aortic aneurysm repair in whom compromised cardiovascular hemodynamics may significantly influence morbidity and survival.

Intradialytic Hypotension: Mechanisms and Outcome

Intradialytic hypotension (IDH) occurs in approximately 10-12% of treatments. Whereas several definitions for IDH are available, a nadir systolic blood pressure carries the strongest relation with outcome. Whereas the relation between IDH may partly be based on patient characteristics, it is likely that also impaired organ perfusion leading to permanent damage, plays a role in this relationship. The pathogenesis of IDH is multifactorial and is based on a combination of a decline in blood volume (BV) and impaired vascular resistance at a background of a reduced cardiovascular reserve. Measurements of absolute BV based on an on-line dilution method appear more promising than relative BV measurements in the prediction of IDH. Also, feedback treatments in which ultrafiltration rate is automatically adjusted based on changes in relative BV have not yet resulted in improvement. Frequent assessment of dry weight, attempting to reduce interdialytic weight gain and prescribing more frequent or longer dialysis treatments may aid in preventing IDH. The impaired vascular response can be improved using isothermic or cool dialysis treatment which has also been associated with a reduction in end organ damage, although their effect on mortality has not yet been assessed. For the future, identification of vulnerable patients based on artificial intelligence and on-line assessment of markers of organ perfusion may aid in individualizing treatment prescription, which will always remain dependent on the clinical context of the patient.

Ultrafiltration Rate, Residual Kidney Function, and Survival Among Patients Treated With Reduced-Frequency Hemodialysis

RATIONALE & OBJECTIVE

Patients receiving twice-weekly or less-frequent hemodialysis (HD) may need to undergo higher ultrafiltration rates (UFRs) to maintain acceptable fluid balance. We hypothesized that higher UFRs are associated with faster decline in residual kidney function (RKF) and a higher rate of mortality.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

1,524 patients with kidney failure who initiated maintenance HD at a frequency of twice or less per week for at least 6 consecutive weeks at some time between 2007 and 2011 and for whom baseline data for UFR and renal urea clearance were available.

PREDICTOR

Average UFR during the first patient-quarter during less-frequent HD (<6, 6-<10, 10-<13, and≥13mL/h/kg).

OUTCOME

Time to all-cause and cardiovascular death, slope of decline in RKF during the first year after initiation of less-frequent HD (with slopes above the median categorized as rapid decline).

ANALYTICAL APPROACH

Cox proportional hazards regression for time to death and logistic regression for the analysis of rapid decline in RKF.

RESULTS

Among 1,524 patients, higher UFR was associated with higher all-cause mortality; HRs were 1.43 (95% CI, 1.09-1.88), 1.51 (95% CI, 1.08-2.10), and 1.76 (95% CI, 1.23-2.53) for UFR of 6 to<10, 10 to<13, and≥13mL/h/kg, respectively (reference: UFR < 6mL/h/kg). Higher UFR was also associated with higher cardiovascular mortality. Baseline RKF modified the association between UFR and mortality; the association was attenuated among patients with renal urea clearance≥5mL/min/1.73m². Higher UFR had a graded association with rapid decline in RKF; ORs were 1.73 (95% CI, 1.18-2.55), 1.89 (95% CI, 1.12-3.17), and 2.75 (95% CI, 1.46-5.18) at UFRs of 6 to<10, 10 to<13, and≥13mL/h/kg, respectively (reference: UFR < 6mL/h/kg).

LIMITATIONS

Residual confounding from unobserved differences across exposure categories.

CONCLUSIONS

Higher UFR was associated with worse outcomes, including shorter survival and more rapid loss of RKF, among patients receiving regular HD treatments at a frequency of twice or less per week.

Effects of sertraline in the prevention of low blood pressure in patients undergoing hemodialysis

INTRODUCTION

Intradialytic hypotension (IDH) is a major complication of hemodialysis, with a prevalence of about 25% during hemodialysis sessions, causing increased morbidity and mortality.

OBJECTIVE

To study the effects of sertraline to prevent IDH in hemodialysis patients.

METHODS

This was a double-blind, crossover clinical trial comparing the use of sertraline versus placebo to reduce intradialytic hypotension.

RESULTS

Sixteen patients completed the two phases of the study during a 12-week period. The IDH prevalence was 32%. A comparison between intradialytic interventions, intradialytic symptoms, and IDH episodes revealed no statistical difference in the reduction of IDH episodes (p = 0.207) between the two intervention groups. However, the risk of IDH interventions was 60% higher in the placebo group compared to the sertraline group, and the risk of IDH symptoms was 40% higher in the placebo group compared to the sertraline group. Survival analysis using Kaplan-Meier estimator supported the results of this study. Sertraline presented a number needed to treat (NNT) of 16.3 patients to prevent an episode from IDH intervention and 14.2 patients to prevent an episode from intradialytic symptoms.

CONCLUSION

This study suggests that the use of sertraline may be beneficial to reduce the number of symptoms and ID interventions, although there was no statistically significant difference in the blood pressure levels.

Recurrent reversible neurologic deficits during hemodialysis

Acute neurologic complications in patients receiving dialysis may be secondary to either underlying comorbid diseases, or to the dialysis procedure itself. An incident hemodialysis patient suffered recurrent consecutive episodes of transient ischemic attacks (TIA) that occurred only during hemodialysis and resolved upon discontinuation of the procedure. Eventual work-up demonstrated an almost complete occlusion of left internal carotid artery. It is likely that the decrease in cerebral blood flow that occurs during hemodialysis, in conjunction with the severely stenotic internal carotid artery, explained the patient's symptoms. The stenotic lesion was deemed inoperable. The patient was transferred to peritoneal dialysis and had no further TIA events.

Hypertonic Mannitol for the Prevention of Intradialytic Hypotension: A Randomized Controlled Trial

RATIONALE & OBJECTIVE

Intradialytic hypotension (IDH) is a common complication at the initiation of hemodialysis (HD) therapy, is associated with greater mortality, and may be related to relatively rapid shifts in plasma osmolality. This study sought to evaluate the effect of an intervention to minimize intradialytic changes in plasma osmolality on the occurrence of IDH.

STUDY DESIGN

Double-blind, single-center, randomized, controlled trial.

SETTING & PARTICIPANTS

Individuals requiring initiation of HD for acute or chronic kidney disease.

INTERVENTION

Mannitol, 0.25g/kg/h, versus a similar volume of 0.9% saline solution during the first 3 HD sessions.

OUTCOMES

The primary end point was average decline in systolic blood pressure (SBP). The secondary end point was the proportion of total sessions complicated by IDH (defined as a decrease ≥ 20mm Hg from the pre-HD SBP). Exploratory end points included biomarkers of cardiac and kidney injury.

RESULTS

52 patients were randomly assigned and contributed to 156 study visits. There were no significant differences in average SBP decline between the mannitol and placebo groups (15±11 vs 19±16mm Hg; P = 0.3). The proportion of total sessions complicated by IDH was lower in the mannitol group compared to placebo (25% vs 43%), with a nominally lower risk for developing an episode of IDH (OR, 0.38; 95% CI, 0.14-1.00), though this finding was of borderline statistical significance (P = 0.05). There were no consistent differences in cardiac and kidney injury biomarker levels between treatment groups.

LIMITATIONS

Modest sample size and number of events.

CONCLUSIONS

In this pilot randomized controlled trial studying patients requiring initiation of HD, we found no difference in absolute SBP decline between those who received mannitol and those who received saline solution. However, there were fewer overall IDH events and a nominally lower risk for dialysis sessions being complicated by IDH in the mannitol group. A larger multicenter randomized controlled trial is warranted.

FUNDING

Government funding to an author (Dr Mc Causland is supported by National Institute of Diabetes and Digestive and Kidney Diseases grant K23DK102511).

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT01520207.

Intradialytic hypotension and splanchnic shifting: Integrating an overlooked mechanism with the detection of ischemia-related signals during hemodialysis

In the most simple analysis, a patient's hematocrit during hemodialysis will rise when the rate of ultrafiltration exceeds the rate at which the fluid is mobilized from extravascular spaces; the greater the rise in hematocrit, the lower blood volume is and the more likely intradialytic hypotension (IDH) is to occur. A secondary mechanism of IDH may be due to sudden shift of blood volume away from the heart under conditions of borderline cardiac filling. A substantial portion of blood volume resides in the splanchnic venous system. During the early part of dialysis, a centripetal shift of red cells from this anatomical region to the central circulation has been documented to occur. The magnitude of this shift is unpredictable, and it may depend on the level of splanchnic vasoconstriction predialysis. The amount of splanchnic shift may also be reduced in patients with autonomic dysfunction. Once this central shift in blood volume has occurred, it can be reversed during further ultrafiltration due to ischemia-induced release of vasodilatory molecules that cause dilation of upstream splanchnic arterioles; this causes increased transmission of arterial pressure to the splanchnic veins, acutely increasing their capacity. The increased splanchnic venous capacity may cause a sudden shift of blood away from the central circulation to fill these veins under conditions where cardiac filling has already been reduced. The result can be severe IDH due to insufficient cardiac filling and cardiac output. One fruitful preventive approach might be to continuously monitor the blood or dialysate for the sudden appearance of such ischemia-related molecules or other signals which may herald not only dialysis hypotension but tissue stunning, warning that the fluid removal rate should be immediately reduced.

Use of vasopressor for dialysis-related hypotension is a risk factor for death in hemodialysis patients: Nationwide cohort study

Because hypotension during hemodialysis (HD) makes continuation of HD difficult and is associated with mortality, pressor approaches are necessary for patients with hypotension. However, the relationships between the pressor approaches and the risk of death have not been clarified yet. We analyzed data from a nationwide prospective cohort study of the Japanese Society for Dialysis Therapy Renal Data Registry (n = 29,309). The outcome was all-cause one-year death. The association between the use of pressor approaches and the outcome was examined using Cox proportional hazards models adjusted for baseline characteristics, propensity score matched analysis and Bayesian networks. The background features of the patients were as follows: male, 59.6%; average age, 64.5 ± 12.5 years; and patients with diabetes mellitus, 31.5%. The pressor group showed a higher risk of the outcome than the control group [adjusted hazard ratio (aHR) 1.33 (95% CI: 1.21, 1.47), p = 0.0001]. Propensity score matched analysis also showed that the matched-pressor group had a higher risk of the outcome than the matched-control group [aHR 1.30 (95% CI: 1.17, 1.45), p = 0.0001]. Moreover, the Bayesian network showed a direct causal relationship from the use of pressor approaches to the outcome. The use of oral vasopressors [aHR 1.20 (95% CI: 1.07, 1.35), p = 0.0018], intravenous injection of vasopressors [aHR 1.54 (95% CI: 1.32, 1.79), p = 0.0001] and normal saline [aHR 1.18 (95% CI: 1.05, 1.33), p = 0.0066] were associated with a high risk of the outcome. In conclusion, this study showed that the use of pressor approaches during HD may be an independent risk factor for death.

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.

Individualized Hemodialysis Treatment: A Perspective on Residual Kidney Function and Precision Medicine in Nephrology

Background: Residual kidney function (RKF) is often expected to inevitably and rapidly decline among hemodialysis patients and, hence, has been inadvertently ignored in clinical practice. The importance of RKF has been revisited in some recent studies. Given that patients with end-stage renal disease now tend to initiate maintenance hemodialysis therapy with higher RKF levels, there seem to be important opportunities for incremental hemo­dialysis by individualizing the dose and frequency according to their RKF levels. This approach is realigned with precision medicine and patient-centeredness. Summary: In this article, we first review the available methods to estimate RKF among hemodialysis patients. We then discuss the importance of maintaining and monitoring RKF levels based on a variety of clinical aspects, including volume overload, blood pressure control, mineral and bone metabolism, nutrition, and patient survival. We also review several potential measures to protect RKF: the use of high-flux and biocompatible membranes, the use of ultrapure dialysate, the incorporation of hemodiafiltration, incremental hemodialysis, and a low-protein diet, as well as general care such as avoiding nephrotoxic events, maintaining appropriate blood pressure, and better control of mineral and bone disorder parameters. Key Message: Individualized hemodialysis regimens may maintain RKF, lead to a better quality of life without compromising long-term survival, and ensure precision medicine and patient-centeredness in nephrology practice.

Intradialytic hypotension, blood pressure changes and mortality risk in incident hemodialysis patients

Background

Intradialytic hypotension (IDH) occurs frequently in maintenance hemodialysis (HD) patients and may be associated with higher mortality. We hypothesize that nadir intradialytic systolic blood pressure (niSBP) is inversely related to death risk while iSBP change (Δ) and IDH frequency are incrementally associated with all-cause mortality.

Methods

In a US-based cohort of 112 013 incident HD patients over a 5-year period (2007-11), using niSBP, ΔiSBP (pre-HD SBP minus niSBP) and IDH frequency (proportion of HD treatments with niSBP <90 mmHg) within the first 91 days of HD, we examined mortality-predictability at 1, 2 and 5 years using Cox models and restricted cubic splines adjusted for case-mix, comorbidities and laboratory covariates.

Results

We observed that niSBP of <90 and ≥140 mmHg had a 5-year mortality hazard ratio (HR) (95% confidence interval) of 1.57 (1.47-1.67) and 1.25 (1.18-1.33), respectively, compared with niSBP 110 to <120 mmHg. ΔiSBP of <15 and ≥50 compared with 21-30 mmHg had mortality HR of 1.31 (1.26-1.37) and 1.32 (1.24-1.39), respectively. Among patients with >40% IDH frequency, we observed a mortality HR of 1.49 (1.42-1.57) compared with 0% IDH frequency in fully adjusted models. These associations were robust at 1 and 2 years of follow-up.

Conclusion

In conclusion, we observed a U-shaped association between niSBP and ΔiSBP and mortality and a direct linear relationship between IDH frequency and mortality. Our findings lend some prognostic insight of HD blood pressure and hemodynamics, and have the potential to guide blood pressure management strategies among the HD population.

Hemodynamic Effects of the Light Stabilizer Tinuvin 770 in Dogs In Vivo

Introduction

Tinuvin 770 [bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, Ciba-Geigy, Basel, Switzerland] is a UV light stabilizer that is a component of many plastic materials used world-wide in the medical and food industries. We report on the acute hemodynamic effects of Tinuvin 770 examined in dogs.

Materials and Methods

Tinuvin 770 was dissolved in a mixture of saline and ethanol (1:1 v/v) and was administered to 12 intravenously narcotized and respirated dogs in increasing doses (T1-T7: 1, 3.3, 6.6, 10, 33.3, 66.6 and 100 mg, respectively). The doses were given as bolus injections over a three minute period, and the effects were recorded for 12 minutes. The vehicle was used as a control. Hemodynamic parameters (heart rate, blood pressure, end-diastolic pressure, dp/dt, cardiac output) and ECG were monitored continously.

Results

At doses T1-T4, systolic and diastolic blood pressures, mean pressure and ventricular contractility were significantly decreased without significant changes in cardiac output, heart rate, or PQ interval. At doses T5 and T6, declines in blood pressure and myocardial contractility were observed. At doses T6 and T7, heart rate and PQ interval decreased substantially. Irreversible circulatory failure occured in one dog after administering dose T6 and in 8 dogs following dose T7.

Conclusion

Tinuvin 770 induces acute hemodynamic alterations. In lower doses, it causes peripheral vasodilatation, however at higher doses acute cardiac failure occured. Plastics containing Tinuvin 770 should be used with care in medical practice and the laboratory.

Mechanisms, Clinical Implications, and Treatment of Intradialytic Hypotension

Individuals with ESKD requiring maintenance hemodialysis face a unique hemodynamic challenge, typically on a thrice-weekly basis. In an effort to achieve some degree of euvolemia, ultrafiltration goals often involve removal of the equivalent of an entire plasma volume. Maintenance of adequate end-organ perfusion in this setting is dependent on the institution of a variety of complex compensatory mechanisms. Unfortunately, secondary to a myriad of patient- and dialysis-related factors, this compensation often falls short and results in intradialytic hypotension. Physicians and patients have developed a greater appreciation for the breadth of adverse outcomes associated with intradialytic hypotension, including higher cardiovascular and all-cause mortality. In this review, we summarize the evidence for adverse outcomes associated with intradialytic hypotension, explore the underlying pathophysiology, and use this as a basis to introduce potential strategies for its prevention and treatment.

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.

Vasoactive Agents and Blood Pressure Regulation in Sequential Ultrafiltration and Hemodialysis

Hypotension is a common and sometimes dangerous side effect of hemodialysis. Its etiology is multifactorial and largely unknown. Earlier studies on the role of endogenous blood pressure regulating agents such as catecholamines and renin have rendered conflicting results. We studied the influence of ultrafiltration and isovolemic hemodialysis separately on the plasma concentrations of the following blood pressure regulating agents: adrenaline, noradrenaline, dopamine, neuropeptide Y, calcitonin gene-related peptide (CGRP), renin (PRA), angiotensin II, vasopressin, aldosterone and Cortisol. During isolated ultrafiltration, plasma levels of two strong vasoconstrictors (noradrenaline and angiotensin II) and one strong vasodilator (calcitonin gene-related peptide, CGRP) increased significantly (noradrenaline 3.24 ± 0.60 nM to 4.31 ± 0.55 nM; p = 0.032, angiotensin II 19.74 ± 3.46 pmol/l to 28.49 ± 7.24 pmol/l; p= 0.047) No symptomatic hypotension occurred. At the end of isovolemic hemodialysis, plasma levels of all the vasoconstricting agents had decreased to pretreatment values, but those of CGRP had continued to rise (from 85.3 ± 17.6 pmol/l to 114.5 ± 25.3 pmol/l, p=0.031). During isovolemic hemodialysis, blood pressure fell to symptomatic levels, but was restored at the end of treatment. The study shows that hemodialysis patients respond to fluid removal by ultrafiltration with an increase in plasma levels of CGRP, noradrenaline and angiotensin II. The net effect is an appropriate vasoconstriction and adequate blood pressure is maintained during isolated ultrafiltration. During hemodialysis, the patients’ blood volumes remained unchanged as evident by a stable hematocrit, the vasoconstrictor hormones returned to normal levels, but in several patients there was a continuous release of vasodilating CGRP. Hypotension, then occurred in these patients due to the imbalance between vasoconstricting and vasodilating factors.

The Influence of Different Glucose Concentrations in Haemodialysis Solutions on Metabolism and Blood Pressure Stability in Diabetic Patients

In recent years the percentage of diabetic patients on haemodialysis has increased. Considering the high frequency of intradialytic hypotensive and hypoglycaemic episodes experienced by these patients, it was the aim of the present study to evaluate the influence of different dialysate glucose concentrations (5.5 mmol/L or 11 mmol/L) on blood pressure and glycaemic regulation, using special dialysis equipment - the GENIUS® System.

This cross-over, prospective and randomised study, total duration 14 weeks, included 20 diabetic patients on maintenance haemodialysis. Group 1: 9 patients dialysed using dialysate with a glucose concentration of 5.5 mmol/L and after 7 weeks switched to dialysate with a glucose concentration of 11 mmol/L. Group 2: vice versa.

Results show a statistically higher number of patients with hypoglycaemic and hypotensive episodes using dialysate with a 5.5 mmol/L glucose concentration. Also, mean serum glucose values were higher during haemodialysis sessions with a glucose dialysate concentration of 11 mmol/L. There were no statistical differences between the groups in laboratory values, HbA1C, insulin doses or in anthropometric parameters.

Our results suggest that fewer diabetic patients undergoing haemodialysis using a higher dialysate glucose concentration of 11 mmol/L have hypoglycaemic and hypotensive episodes. Since this dialysate glucose concentration had no influence on lipid or hepatic metabolism, anthropometric parameters and especially HbA1C values in this short-term study, the long term examination of its effects is warranted.

Conductivity: On-Line Monitoring of Dialysis Adequacy

Cardiovascular disease and the inadequacy of delivered dialysis are the main factors determining morbidity and mortality in dialysis patients. We have already demonstrated that a conductivity kinetic model makes it possible to match interdialytic sodium loading and intradialytic sodium removal (the main factor determining cardiovascular morbidity) without the need for blood samples and, thus, in routine clinical practice.

The aim of the present study was to test the possibility of using the conductivity method also to determine Kt/v without blood or dialysate sampling.

In 18 steady-state patients, the urea distribution volume (V) was kinetically determined once using ionic dialysance (D) values instead of those of effective urea clearance. One month later, the Kt/V was determined by using the current D and T values and the predetermined V (Dt/V), then compared with the equilibrated Kt/V computed by means of the SPVV kinetic model (eqKt/V). The mean value of Dt/V was 1.18 ± 0.15; while of eqKt/V it was 1.18 ± 0.16, with a mean difference of 0.00 ± 0.07.

The conductivity method therefore seems to be very promising not only for monitoring the sodium balance, but also for quantifying delivered dialysis. Since its simplicity and low-cost make it suitable for use at each dialysis session, the conductivity method could therefore lead to significant progress in dialytic practice by contributing to the elimination of the two main causes of morbidity and mortality in dialysis patients.

A New Approach to Blood Pressure and Blood Volume Modulation during Hemodialysis: An Adaptive Fuzzy Control Module

The paper proposes a fuzzy logic based procedure able to control as far as possible the behaviour of the blood pressure of a patient during a dialysis session, allowing him to reach the foreseen dry weight. A PI discrete-time fuzzy control is used in order to compare the controlled variables concerning the (blood pressure and blood volume) to the reference values. Two different reference tables, concerning the pressure and volume errors and rates are introduced, then the proposed control actions are mixed in order to obtain the final value (net ultrafiltration rate). A smooth function of volemia acts on the second control variable, Na concentration in the dialysate. The adaptive control system was simulated on an IBM-PC, rules and terms were expressed by linguistic judgements like: IF “situation”, THEN “action”. A pre-processor converts the rules into the numerical values of the reference tables. The obtained simulation results are satisfactory, the introduction of the Na control allows reaching the target dry weight of the patient with a stable blood pressure.

Monitoring Sodium Removal and Delivered Dialysis by Conductivity

As cardiovascular stability and the delivery of the prescribed dialysis “dose” seem to be the main factors in determining the morbidity and mortality of hemodialyzer patients today, it is of paramount importance to match hydro-sodium removal with interdialytic load and to verify the delivered dialysis at each session. A specially designed Biofeedback Module (BM - COT Hospal) allows the automatic determination of plasma water conductivity and effective ionic dialysance with no need for blood samples. Using BM, we evaluated the validity of “conductivity kinetic modelling” (CKM) and the possibility that this may substitute “sodium kinetic modelling”. Moreover, we evaluated the “in vivo” relationship between ionic dialysance and effective urea clearance. Our results demonstrate that: 1) CKM makes it possible to obtain programmed end-dialysis plasma water conductivity with an error of less than ± 0.14 mS/cm, roughly equivalent to a sodium concentration of ± 1.4 mEq/L. 2). Ionic dialysance and effective urea clearance are not equivalent but, as the interrelationship between these is known, the BM allows the routine monitoring of delivered dialysis.

Regulation of Base Balance in Bicarbonate Hemofiltration

The purpose of this study was to investigate the feasibility of bicarbonate as a substitute for acetate or lactate in hemofiltration solutions using a new bag for the bicarbonate substitution fluid. We analysed 24 hemofiltration sessions with different HCO3– concentrations (30, 35 and 40 mEq/L) in the substitution fluid. The increase in the HCO3– concentration in the substitution fluid resulted in a more positive HCO3– balance. The Net Base Gains (NBG) were, respectively, 73.7 ± 92 with 30, 138.2 ± 97 with 35 (p < 0.05 vs 30) and finally 201 ± 65.9 with 40 mEq/L (p < 0.001 vs 30). The physical separation between the base losses and gains could facilitate the modelling approach in hemofiltration. By means of a stepwise regression analysis, we studied a series of variables that could influence end-treatment HCO3–, which was significantly and directly dependent (F = 6.003, r = 0.747, p = 0.0027) on the HCO3– concentration in the substitution fluid and the apparent HCO3– space. HCO3– values predicted by the statistical model correlated well with those actually measured (r = 0.757; p < 0.001). This mathematical modelling approach allowed us to predict the quantities and concentrations of HCO3– to be infused in order to obtain an ideal acidosis correction, tailored to individual patient needs.

Hemodialysis Ultrafiltration Rate Targets Should Be Scaled to Body Surface Area Rather than to Body Weight

The association between higher ultrafiltration rates and poor outcomes in hemodialysis patients has received increased attention, to the point that various regulatory entities are considering adding ultrafiltration rate as a quality measure to be monitored and controlled. Most of the discussion to date has focused on ultrafiltration rate scaled to body weight, or more correctly, body mass (ml/hour per kg). One outcome study suggests that ultrafiltration rate might best be not scaled at all to body size, as modestly higher ultrafiltration rate in very small-size patients may be associated with some survival benefit, probably via increased dietary intake. Outcomes studies also suggest that the risk of exceeding a weight-scaled ultrafiltration target may be magnified in very large patients, and that body weight-scaled ultrafiltration targets in such patients should be set a lower level. Here, we present an analysis, based on physiological hemodynamic arguments, that it would be better to scale ultrafiltration rate to body surface area rather than to body mass. Whatever ultrafiltration rate is scaled to, attempts to restrict ultrafiltration rate by limiting interdialytic weight gain in small, possibly malnourished patients, should be done cautiously, to prevent an inadvertent lowering of intake of calories and dietary protein.

A Bayesian approach for the identification of patient-specific parameters in a dialysis kinetic model

Hemodialysis is the most common therapy to treat renal insufficiency. However, notwithstanding the recent improvements, hemodialysis is still associated with a non-negligible rate of comorbidities, which could be reduced by customizing the treatment. Many differential compartment models have been developed to describe the mass balance of blood electrolytes and catabolites during hemodialysis, with the goal of improving and controlling hemodialysis sessions. However, these models often refer to an average uremic patient, while on the contrary the clinical need for customization requires patient-specific models. In this work, we assume that the customization can be obtained by means of patient-specific model parameters. We propose and validate a Bayesian approach to estimate the patient-specific parameters of a multi-compartment model, and to predict the single patient's response to the treatment, in order to prevent intra-dialysis complications. The likelihood function is obtained by means of a discretized version of the multi-compartment model, where the discretization is in terms of a Runge-Kutta method to guarantee convergence, and the posterior densities of model parameters are obtained through Markov Chain Monte Carlo simulation. Results show fair estimations and the applicability in the clinical practice.

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.

Central venous pressure and ultrasonographic measurement correlation and their associations with intradialytic adverse events in hospitalized patients: A prospective observational study

PURPOSE

To investigate correlation of central venous pressure (CVP) with ultrasonographic measurement of central veins, along with association between these variables and occurrence of intradialytic adverse events in hospitalized patients.

MATERIALS AND METHODS

Patients requiring hemodialysis via dialysis catheter were prospectively enrolled. CVP measurements through catheter, internal jugular vein aspect ratio, subclavian vein collapsibility, inferior vena cava (IVC) maximal diameter, and IVC collapsibility were recorded before and after hemodialysis. Predictive accuracy of ultrasonographic measurements in discriminating high versus low CVP and their association with intradialytic adverse events were evaluated. Area under receiver operating characteristic curves (AUCs) were calculated.

RESULTS

Fifty-nine patients were enrolled. Median (interquartile range) pre- and post-dialysis CVPs were 8 (4-13)mmHg and 6 (3-10)mmHg, respectively (P<0.01). In pre-dialysis, IVC collapsibility had the highest AUC (0.79, P<0.01) to predict CVP >8mmHg. In post-dialysis, IVC maximal diameter had the highest AUC (0.86, P<0.01) to predict CVP ≤4mmHg. Fifteen patients (25%) had adverse events. Neither pre-dialytic CVP nor ultrasonographic variables were associated with occurrence of adverse events.

CONCLUSIONS

Highest accuracy in predicting low and high CVP was observed with ultrasonographic assessment of IVC diameter and collapsibility. Adverse events were not predicted by pre-dialytic CVP or ultrasonographic measurements.

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.