Jugular venous flow dynamics during acute weightlessness

During spaceflight, fluids shift headward, causing internal jugular vein (IJV) distension and altered hemodynamics, including stasis and retrograde flow, that may increase the risk of thrombosis. This study's purpose was to determine the effects of acute exposure to weightlessness (0-G) on IJV dimensions and flow dynamics. We used two-dimensional (2-D) ultrasound to measure IJV cross-sectional area (CSA) and Doppler ultrasound to characterize venous blood flow patterns in the right and left IJV in 13 healthy participants (6 females) while 1) seated and supine on the ground, 2) supine during 0-G parabolic flight, and 3) supine during level flight (at 1-G). On Earth, in 1-G, moving from seated to supine posture increased CSA in both left (+62 [95% CI: +42 to 81] mm2, P < 0.0001) and right (+86 [95% CI: +58 to 113] mm2, P < 0.00012) IJV. Entry into 0-G further increased IJV CSA in both left (+27 [95% CI: +5 to 48] mm2, P = 0.02) and right (+30 [95% CI: +0.3 to 61] mm2, P = 0.02) relative to supine in 1-G. We observed stagnant flow in the left IJV of one participant during 0-G parabolic flight that remained during level flight but was not present during any imaging during preflight measures in the seated or supine postures; normal venous flow patterns were observed in the right IJV during all conditions in all participants. Alterations to cerebral outflow dynamics in the left IJV can occur during acute exposure to weightlessness and thus, may increase the risk of venous thrombosis during any duration of spaceflight.NEW & NOTEWORTHY The absence of hydrostatic pressure gradients in the vascular system and loss of tissue weight during weightlessness results in altered flow dynamics in the left internal jugular vein in some astronauts that may contribute to an increased risk of thromboembolism during spaceflight. Here, we report that the internal jugular veins distend bilaterally in healthy participants and that flow stasis can occur in the left internal jugular vein during acute weightlessness produced by parabolic flight.

Renal fluid and acid/base balance during refeeding in restrictive eating disorders

BACKGROUND AND OBJECTIVES

Fluid shifts have been ascribed to central diabetes insipidus in patients with anorexia nervosa hospitalized for refeeding. Recent data, however, suggest that vasopressin production is not dysregulated in this population. Our objective was to describe the trajectory of fluid imbalances in relationship to kidney function, electrolyte disturbances, and acid/base balance during refeeding.

METHODS

A retrospective review of daily fluid balance and biochemical values was performed in 70 sequential unique patients admitted to University of California at Los Angeles Hospital Medical Stabilization Program for Eating Disorders from December 2018 to November 2020.

RESULTS

Participants (2 males/68 females) were between 10 and 24 years of age and with a median body mass index of 16.1 (14.3, 18.1) kg/m² . A severe negative fluid balance (>-900 ml/day) was observed in 80% of patients at some point during hospitalization. Serum sodium concentrations were normal on admission and remained stable during refeeding. Serum bicarbonate concentrations were 25 ± 1 mEq/dl on admission and increased above the normal range in 31% of patients. Metabolic alkalosis was inversely associated with the development of a negative fluid balance. Estimated glomerular filtration rate was impaired in 54% of patients, improved with refeeding, and was not associated with the development of a severe negative fluid balance or metabolic alkalosis.

DISCUSSION

Chronic energy deprivation alters the physiology of renal fluid and bicarbonate handling in ways that are independent of vasopressin and glomerular filtration. Further studies are warranted to understand the renal adaptations that occur during energy restriction and subsequent refeeding.

PUBLIC SIGNIFICANCE

Massive urinary fluid losses occur in patients with restrictive eating disorders hospitalized for refeeding. In addition, many patients have impaired renal bicarbonate excretion. These findings suggest that chronic energy deprivation impairs the kidney's ability to handle the shifts in fluid and acid/base balance that occur when appropriate oral nutrition is re-introduced.

Characteristics of bioimpedance-determined fluid shifts according to intradialytic blood pressure difference

This study was designed to identify the fluid spaces that are most changed during ultrafiltration (UF) according to intradialytic blood pressure (BP) difference. BP data were collected five times (before hemodialysis [HD] and 1–4 h of HD). Intradialytic BP difference was calculated as the highest minus lowest of these BP measurements. Intradialytic systolic BP (SBP) difference over 20 mm Hg and diastolic BP (DBP) difference over 10 mm Hg were defined as wide intradialytic SBP difference (SYS-W) and DBP difference (DIA-W), respectively. We measured the various fluid spaces before HD and 1–4 h of HD, and 30 min after HD using a portable, whole-body bioimpedance spectroscopy (BIS). In this study, 85 prevalent patients aged over 18 years with a fixed dry weight (65.38 ± 12.45 years, 54.18% men, 52.50% patients with diabetes), undergoing HD had participated. 1) Mean relative reduction of extracellular water (ECW) was significantly higher in SYS-W than in narrow intradialytic SBP difference (SYS-N) patients from 1 h to 30 min after HD. 2) Mean relative reduction of intracellular water (ICW) was significantly lower in DIA-W than in narrow intradialytic DBP difference (DIA-N) patients from 1 h to 30 min after HD. 3) ECW of patients with SYS-W was significantly lower than that of patients with SYS-N. Patients with SYS-W have the characteristics of fluid shifts in which reduction of ECW was steeper than patients with SYS-N whereas fluid shifts of ICW were lower in patients with DIA-W than patients with DIA-N.

Overnight Rostral Fluid Shifts Exacerbate Obstructive Sleep Apnea After Stroke

BACKGROUND AND PURPOSE

Overnight shifts of fluid from lower to upper compartments exacerbate obstructive sleep apnea (OSA) in some OSA populations. Given the high prevalence of OSA after stroke, decreased mobility and use of IV fluids among hospitalized patients with stroke, and improvement in OSA in the months after stroke, we hypothesized that overnight fluid shifts occur and are associated with OSA among patients with subacute ischemic stroke.

METHODS

Within a population-based project, we performed overnight sleep apnea tests (ApneaLink Plus) during ischemic stroke hospitalizations. Before sleep that evening, and the following morning before rising from bed, we assessed neck and calf circumference, and leg fluid volume (bioimpedance spectroscopy). The average per subject overnight change in the 3 fluid shift measurements was calculated and compared with zero. Linear regression was used to test the crude association between each of the 3 fluid shift measurements and the respiratory event index (REI).

RESULTS

Among the 292 participants, mean REI was 24 (SD=18). Within individuals, calf circumference decreased on average by 0.66 cm (SD=0.75 cm, P<0.001), leg fluid volume decreased by a mean of 135.6 mL (SD=132.8 mL, P<0.001), and neck circumference increased by 0.20 cm (SD=1.71 cm, P=0.07). In men, when the overnight change of calf circumference was negative, an interquartile range (0.8 cm) decrease in calf circumference overnight was significantly associated with a 25.1% increase in REI (P=0.02); the association was not significant in women. The relationship between overnight change in leg fluid volume and REI was U shaped.

CONCLUSIONS

This population-based, multicenter, cross-sectional study showed that in hospitalized patients with ischemic stroke, nocturnal rostral fluid shifts occurred, and 2 of the 3 measures were associated with greater OSA severity. Interventions that limit overnight fluid shifts should be tested as potential treatments for OSA among patients with subacute ischemic stroke.

Biology of Lymphedema

Simple Summary

Lymphedema is a chronic, debilitating disease of the lymphatic vasculature. Although several reviews focus on the anatomy and physiology of the lymphatic system, this review provides an overview of the lymphatic vasculature and, moreover, of lymphatic system dysfunction and lymphedema. Further, we aim at advancing the knowledge in the area of lymphatic system function and how dysfunction of the lymphatic system—as seen in lymphedema—affects physiological systems, such as the cardiovascular system, and how those might be modulated by lymphedema therapy.

Abstract

This narrative review portrays the lymphatic system, a poorly understood but important physiological system. While several reviews have been published that are related to the biology of the lymphatic system and lymphedema, the physiological alternations, which arise due to disturbances of this system, and during lymphedema therapy, are poorly understood and, consequently, not widely reported. We present an inclusive collection of evidence from the scientific literature reflecting important developments in lymphedema research over the last few decades. This review aims at advancing the knowledge on the area of lymphatic system function as well as how system dysfunction, as seen in lymphedema, affects physiological systems and how lymphedema therapy modulates these mechanisms. We propose that future studies should aim at investigating, in-detail, aspects that are related to fluid regulation, hemodynamic responses, and endothelial and/or vascular changes due to lymphedema and lymphedema therapy.

Muscle swelling following blood flow-restricted exercise does not differ between cuff widths in the proximal or distal portions of the upper leg

The purpose was to understand how wider cuffs, covering larger portions of the limb, may affect acute muscle swelling when used during low-load knee extension exercise with blood flow restriction. A total of 96 individuals (53 females and 43 males) completed two visits, with visit one used for measuring maximal strength and arterial occlusion pressure (AOP), and visit two to compare between a narrow (5 cm) and a wide (12 cm) cuff for acute changes in muscle thickness and echo intensity following exercise. Ultrasound measurements were completed at a proximal and distal site within both legs, with the proximal site located beneath the cuff within the leg exercising using the wide cuff. Study findings indicate that the difference in acute changes for muscle thickness [median difference (95% credible interval) of 0.009 (-0.03, 0.05) cm] and echo intensity [median difference (95% credible interval) of 0.79 (-0.28, 1.89) AU] between cuff widths did not differ between proximal and distal sites. Additionally, acute changes in muscle thickness did not differ between cuff widths, sexes or participants who had AOP measured and those who were estimated. Lastly, acute changes in echo intensity did not differ between cuff widths and those who had AOP measured and those who were estimated. However, there was evidence showing how there might be greater reductions in echo intensity for females at the distal site. The previously observed attenuation of muscle growth under the cuff is unlikely to be related to differences in the acute muscle swelling response.

A Nomogram for the Rapid Prediction of Hematocrit Following Blood Loss and Fluid Shifts in Neonates, Infants, and Adults

Introduction

There is often a need for a simple means of predicting hematocrit (Hct) following blood loss, administration of intravenous fluids, or fluid shifts. The aim of this study is to introduce a nomogram for the rapid prediction of blood volume and packed red cell volume appropriate for a given patient's body weight and Hct in both the pediatric and adult populations.

Methods

A nomogram for prediction of Hct was created using the following variables: 1) blood volume determined from bodyweight, 2) estimated blood loss, and 3) initial Hct.

Results

Hct was calculated after blood loss, administration of intravenous fluids, or fluid shifts using the pediatric and adult nomograms. Alternatively, the nomograms can be used to back-calculate blood or fluid loss if Hct is known. The nomogram allows for adjustment for measured and insensible fluid losses and fluid administration.

Conclusions 

The nomogram helps to predict the Hct and fluid requirements in neonates, children, and adults with blood loss, fluid administration, and rehydration following dehydration. It allows for the calculation of Hct after fluid shifts in a simple, fast, and portable manner. We believe it can be a useful adjunct to monitor the fluid balance in all patients, especially in resource-limited settings where laboratory equipment may not be available.

Long-term effects of cardiac rehabilitation on sleep apnea severity in patients with coronary artery disease

STUDY OBJECTIVES

Sleep apnea (SA) is prevalent among patients with coronary artery disease (CAD) and increases cardiovascular risk. A previous study showed that 1 month of cardiac rehabilitation (CR) reduced severity of SA in patients with CAD by reducing fluid accumulation in the legs during the day and the amount of fluid shifting rostrally into the neck overnight. The aim of this study was to evaluate whether CR will lead to longer-term attenuation of SA in patients with CAD.

METHODS

Fifteen patients with CAD and SA who had participated in a 1-month randomized trial of the effects of exercise training on SA were followed up until they completed 6 months of CR (age: 65 ± 10 years; body mass index: 27.0 ± 3.9 kg/m²; apnea-hypopnea index [AHI]: 39.0 ± 16.7). The AHI was evaluated at baseline by polysomnography and then at 6 months by portable monitoring at home. Cardiorespiratory fitness (VO_2peak) was evaluated via a graded cardiopulmonary exercise test at baseline and 6 months later. The 6-month CR program included once weekly, 90-minute, in-facility exercise sessions, and 4 days per week at-home exercise sessions.

RESULTS

After 6 months of CR, there was a 54% reduction in the AHI (30.5 ± 15.2 to 14.1 ± 7.5, P < .001). Body mass index remained unchanged, but VO_2peak increased by 27% (20.0 ± 6.1 to 26.0 ± 8.9 mL/kg/min, P = .04).

CONCLUSIONS

Participation in CR is associated with a significant long-term decrease in the severity of SA. This finding suggests that attenuation of SA by exercise could be a mechanism underlying reduced mortality following participation in CR in patients with CAD and SA.

CLINICAL TRIAL REGISTRATION

This study is registered at www.controlled-trials.com with identifier number ISRCTN50108373.

Population-based volume kinetics of Ringer's lactate solution in patients undergoing open gastrectomy

In order to maintain stable blood pressure and heart rate during surgery, anesthesiologists need to administer the appropriate amount of fluid with appropriate fluid type to the patient, then quantifying how fluid is distributed and eliminated from the body is useful for establishing a fluid administration strategy. In this study we characterized the volume kinetics of Ringer's lactate solution in patients undergoing open gastrectomy. When propofol and remifentanil reached a pseudosteady state at the target concentration and blood pressure was stabilized following surgical stimulation, enrolled patients were administered 1000 mL of Ringer's lactate solution for 20 min, followed by continuous infusion at a rate of 6 mL/kg/h until the time of the last blood collection for volume kinetic analysis. Arterial blood samples were collected to measure the hemoglobin concentration at different time points. The change in hemoglobin-derived plasma dilution induced by the administration of Ringer's lactate solution was evaluated by nonlinear mixed effects modeling. Three hundred and twenty-three plasma dilution data points from 27 patients were used to determine the pharmacokinetic characteristics of Ringer's lactate solution. A two-volume model best described the pharmacokinetics of Ringer's lactate solution. The mean arterial pressure (MAP) and body weight (WT) were significant covariates for the elimination clearance (k_r) and central volume of distribution at baseline (V_c0), respectively. The parameter estimates were as follows: k_r (mL/min) = 124 + (MAP/70)^14.2, V_c0 (mL) = 0.95 + 3440 × (WT/63), V_t0 (mL) = 2730, and k_t (mL/min) = 181. A higher MAP was associated with a greater elimination clearance and, consequently, less water accumulation in the interstitium. As body weight increases, volume expansion in the blood vessels increases.

The influence of biological sex and cuff width on muscle swelling, echo intensity, and the fatigue response to blood flow restricted exercise

The purpose was to determine if the muscle swelling, echo intensity, and fatigue responses to blood flow restriction differs based on cuff width (Experiment 1), applied pressure (Experiment 2), and sex. Ultrasound of muscle was taken before and after exercise. In Experiment 1 (n = 96), men swelled more than women and more with a narrow cuff than a wide cuff (0.60 cm vs. 0.52 cm). Expressed as a percentage change, there were no longer differences between cuffs (Narrow: 15% vs. Wide: 14%) or sex (Men: 14% vs. Women: 15%). Echo intensity remained unchanged. Women required more repetitions to reach task failure in sets 2, 3, and 4. In Experiment 2 (n = 87), men swelled more than women (Men: 0.46 cm vs. Women: 0.31 cm). Expressed as a percentage change, there were no differences. Echo intensity decreased in both conditions and to a greater extent with a higher applied pressure. If the acute muscle swelling response is important for initiating long term adaptation, then our results indicate that neither cuff width, sex, nor applied pressure will differentially impact the adaptation observed via this mechanism. Changes in echo intensity were inconsistent and the utility of this measurement may need to be reconsidered.

Effects of the Kv7 voltage-activated potassium channel inhibitor linopirdine in rat models of haemorrhagic shock

Recently, we demonstrated that Kv7 voltage-activated potassium channel inhibitors reduce fluid resuscitation requirements in short-term rat models of haemorrhagic shock. The aim of the present study was to further delineate the therapeutic potential and side effect profile of the Kv7 channel blocker linopirdine in various rat models of severe haemorrhagic shock over clinically relevant time periods. Intravenous administration of linopirdine, either before (1 or 3 mg/kg) or after (3 mg/kg) a 40% blood volume haemorrhage, did not affect blood pressure and survival in lethal haemorrhage models without fluid resuscitation. A single bolus of linopirdine (3 mg/kg) at the beginning of fluid resuscitation after haemorrhagic shock transiently reduced early fluid requirements in spontaneously breathing animals that were resuscitated for 3.5 hours. When mechanically ventilated rats were resuscitated after haemorrhagic shock with normal saline (NS) or with linopirdine-supplemented (10, 25 or 50 μg/mL) NS for 4.5 hours, linopirdine significantly and dose-dependently reduced fluid requirements by 14%, 45% and 55%, respectively. Lung and colon wet/dry weight ratios were reduced with linopirdine (25/50 μg/mL). There was no evidence for toxicity or adverse effects based on measurements of routine laboratory parameters and inflammation markers in plasma and tissue homogenates. Our findings support the concept that linopirdine-supplementation of resuscitation fluids is a safe and effective approach to reduce fluid requirements and tissue oedema formation during resuscitation from haemorrhagic shock.

Quantitative model of hematologic and plasma volume responses after ascent and acclimation to moderate to high altitudes

Despite decades of research, the magnitude and time course of hematologic and plasma volume (PV) changes following rapid ascent and acclimation to various altitudes are not precisely described. To develop a quantitative model, we utilized a comprehensive database and general linear mixed models to analyze 1,055 hemoglobin ([Hb]) and hematocrit (Hct) measurements collected at sea level and repeated time points at various altitudes in 393 unacclimatized men (n = 270) and women (n = 123) who spent between 2 h and 7 days at 2,500-4,500 m under well-controlled and standardized experimental conditions. The PV change (ΔPV) was calculated from [Hb] and Hct measurements during a time period when erythrocyte volume is stable. The results are 1) ΔPV decreases rapidly (~6%) after the 1st day at 2,500 m and [Hb] and Hct values increase by 0.5 g/dl and 1.5 points, respectively; 2) ΔPV decreases an additional 1%, and [Hb] and Hct increase an additional 0.1 g/dl and 0.2 points every 500-m increase in elevation above 2,500 m after the 1st day; 3) ΔPV continues to decrease over time at altitude, but the magnitude of this decrease and subsequent increase in [Hb] and Hct levels is dependent on elevation and sex; and 4) individuals with high initial levels of [Hb] and Hct and older individuals hemoconcentrate less at higher elevations. This study provides the first quantitative delineation of ΔPV and hematological responses during the first week of exposure over a wide range of altitudes and demonstrates that absolute altitude and time at altitude, as well as initial hematologic status, sex, and age impact the response.

A Lumped-Parameter Subject-Specific Model of Blood Volume Response to Fluid Infusion

This paper presents a lumped-parameter model that can reproduce blood volume response to fluid infusion. The model represents the fluid shift between the intravascular and interstitial compartments as the output of a hypothetical feedback controller that regulates the ratio between the volume changes in the intravascular and interstitial fluid at a target value (called "target volume ratio"). The model is characterized by only three parameters: the target volume ratio, feedback gain (specifying the speed of fluid shift), and initial blood volume. This model can obviate the need to incorporate complex mechanisms involved in the fluid shift in reproducing blood volume response to fluid infusion. The ability of the model to reproduce real-world blood volume response to fluid infusion was evaluated by fitting it to a series of data reported in the literature. The model reproduced the data accurately with average error and root-mean-squared error (RMSE) of 0.6 and 9.5% across crystalloid and colloid fluids when normalized by the underlying responses. Further, the parameters derived for the model showed physiologically plausible behaviors. It was concluded that this simple model may accurately reproduce a variety of blood volume responses to fluid infusion throughout different physiological states by fitting three parameters to a given dataset. This offers a tool that can quantify the fluid shift in a dataset given the measured fractional blood volumes.

The source of net ultrafiltration during hemodialysis is mostly the extracellular space regardless of hydration status

Fluid shifts are common in patients undergoing chronic hemodialysis (HD) during the intradialytic periods, as several liters of fluid are removed during ultrafiltration (UF). Some patients have experienced frequent intradialytic hypotension (IDH). However, the characteristics of fluid shifts and which fluid space is affected remain controversial. Therefore, we designed this study to evaluate the fluid spaces most affected by UF and to determine whether hydration status influences the fluid shifts during HD. This was a prospective cohort study of 40 patients undergoing HD. We measured the patient's fluid spaces using a whole-body bioimpedance apparatus to evaluate the changes in the fluid spaces before HD and 1-4 hours of HD and 30 minutes after HD. UF achieved during HD by the 40 patients (age, 60.0 ± 5.2 years; 50% men; 50% of patients with diabetes; body weight, 61.3 ± 10.5 kg) was 2.18 ± 0.78 L (measured fluid overload, 2.15 ± 1.24 L). 1) Mean relative reduction of total body water and extracellular water was reduced from the start to the end of HD. 2) However, mean relative reduction of intracellular water was not reduced from the start to the end of HD. 3) No significant differences in fluid shifts were observed according to hydration status. The source of net UF during HD is mostly the extracellular space regardless of hydration status. Thus, IDH may be related to differences in the interstitial fluid shift to the vascular space.

Regular exercise improves weight stability in patients with advanced heart failure

OBJECTIVES

The purpose of this study was to determine if a progressive, prescribed home-based aerobic exercise program would alter the natural physiological processes that maintain fluid balance stability in patients with New York Heart Association (NYHA) class III/IV heart failure after medical optimization (titration of oral medical therapy with or without the infusion of an intravenous inotrope).

METHODS

A total of 56 men and women from a large tertiary trauma I hospital were enrolled with 56 subjects contributing to baseline analysis and 42 subjects at 24 weeks. Subjects were diagnosed with heart failure via NYHA classification IV or III for at least 6 months and were hospitalized for a current acute decompensation exacerbation in which they were being medically optimized. The exercise intervention was a home-based, prescribed, progressive aerobic exercise program lasting for 24 weeks. The exercise participants had weekly phone calls to gather data and progress the exercise program and one 12-week follow up. The usual care participants received random phone calls to collect data and had one 12-week follow up visit to attain physical assessment values.

RESULTS

Subjects were primarily female (59%), nonwhite (54%), and NYHA class IV (52%) versus class III (48%). The mean age was 58 years (±11.8 years). The subjects had a mean ejection fraction of 17.7 % (±7%) and mean maximal oxygen consumption of 12.1 (±3.4). Using a hierarchical multiple regression model, it was demonstrated that an exercise prescription (intensity, frequency, duration) significantly predicted 24 h weight fluctuations within a NYHA class III/IV heart failure population after medical optimization (R(2) linear = 0.713, F = 3.224, p = 0.015).

CONCLUSION

This study demonstrated that exercise is a successful adjunctive therapy to managing the daily weight variability or fluid status instability of patients with NYHA class III/IV heart failure that is often a debilitating aspect of the syndrome.

Fluid distribution kinetics during cardiopulmonary bypass

OBJECTIVE

The purpose of this study was to examine the isovolumetric distribution kinetics of crystalloid fluid during cardiopulmonary bypass.

METHODS

Ten patients undergoing coronary artery bypass grafting participated in this prospective observational study. The blood hemoglobin and the serum albumin and sodium concentrations were measured repeatedly during the distribution of priming solution (Ringer's acetate 1470 ml and mannitol 15% 200 ml) and initial cardioplegia. The rate of crystalloid fluid distribution was calculated based on 3-min Hb changes. The preoperative blood volume was extrapolated from the marked hemodilution occurring during the onset of cardiopulmonary bypass. Clinicaltrials.gov: NCT01115166.

RESULTS

The distribution half-time of Ringer's acetate averaged 8 minutes, corresponding to a transcapillary escape rate of 0.38 ml/kg/min. The intravascular albumin mass increased by 5.4% according to mass balance calculations. The preoperative blood volume, as extrapolated from the drop in hemoglobin concentration by 32% (mean) at the beginning of cardiopulmonary bypass, was 0.6-1.2 L less than that estimated by anthropometric methods (p<0.02). The mass balance of sodium indicated a translocation from the intracellular to the extracellular fluid space in 8 of the 10 patients, with a median volume of 236 ml.

CONCLUSIONS

The distribution half-time of Ringer's solution during isovolumetric cardiopulmonary bypass was 8 minutes, which is the same as for crystalloid fluid infusions in healthy subjects. The intravascular albumin mass increased. Most patients were hypovolemic prior to the start of anesthesia. Intracellular edema did not occur.

Blood volume-monitored regulation of ultrafiltration in fluid-overloaded hemodialysis patients: study protocol for a randomized controlled trial

BACKGROUND

Data generated with the body composition monitor (BCM, Fresenius) show, based on bioimpedance technology, that chronic fluid overload in hemodialysis patients is associated with poor survival. However, removing excess fluid by lowering dry weight can be accompanied by intradialytic and postdialytic complications. Here, we aim at testing the hypothesis that, in comparison to conventional hemodialysis, blood volume-monitored regulation of ultrafiltration and dialysate conductivity (UCR) and/or regulation of ultrafiltration and temperature (UTR) will decrease complications when ultrafiltration volumes are systematically increased in fluid-overloaded hemodialysis patients.

METHODS/DESIGN

BCM measurements yield results on fluid overload (in liters), relative to extracellular water (ECW). In this prospective, multicenter, triple-arm, parallel-group, crossover, randomized, controlled clinical trial, we use BCM measurements, routinely introduced in our three maintenance hemodialysis centers shortly prior to the start of the study, to recruit sixty hemodialysis patients with fluid overload (defined as ≥15% ECW). Patients are randomized 1:1:1 into UCR, UTR and conventional hemodialysis groups. BCM-determined, 'final' dry weight is set to normohydration weight -7% of ECW postdialysis, and reached by reducing the previous dry weight, in steps of 0.1 kg per 10 kg body weight, during 12 hemodialysis sessions (one study phase). In case of intradialytic complications, dry weight reduction is decreased, according to a prespecified algorithm. A comparison of intra- and post-dialytic complications among study groups constitutes the primary endpoint. In addition, we will assess relative weight reduction, changes in residual renal function, quality of life measures, and predialysis levels of various laboratory parameters including C-reactive protein, troponin T, and N-terminal pro-B-type natriuretic peptide, before and after the first study phase (secondary outcome parameters).

DISCUSSION

Patients are not requested to revert to their initial degree of fluid overload after each study phase. Therefore, the crossover design of the present study merely serves the purpose of secondary endpoint evaluation, for example to determine patient choice of treatment modality. Previous studies on blood volume monitoring have yielded inconsistent results. Since we include only patients with BCM-determined fluid overload, we expect a benefit for all study participants, due to strict fluid management, which decreases the mortality risk of hemodialysis patients.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01416753.