Relative Blood Volume Research Articles

Hemoglobin Mass and Blood Volume in Swimming: A Comparison Between Highly Trained, Elite, and World-Class Swimmers.

Total hemoglobin mass (tHbmass) and blood volume (BV) are important determinants of maximal oxygen uptake and endurance capacity. Higher-caliber endurance athletes usually possess higher tHbmass and BV values. This study aimed to compare tHbmass and BV among swimmers of diverse competitive calibers and distances. Thirty swimmers (16 female and 14 male) participated in the study: 3 were tier 5, world class (869 [59] FINA points); 15 were tier 4, elite/international (853 [38] points); and 12 were tier 3, highly trained/national (808 [35] points). They specialized in competition distances ranging from 200m to open-water 10km. Between February 2019 and February 2020, all swimmers had their tHbmass and BV measured by carbon monoxide rebreathing 1 to 6 times and participated in multiple competitions and race events. Relative tHbmass and BV were not different (P > .05) between tiers among women or among men (pooled tHbmass values 14.5 [0.5], 12.5 [1.5], 12.6 [2.3]g/kg for tier 5, tier 4, and tier 3, respectively). No differences were observed in relative tHbmass (P = .215) and BV (P = .458) between pool and open-water swimmers or between 200-, 400-, and 1500-m specialists (P > .05). No significant correlations were found between the highest measured absolute or relative tHbmass and BV and the highest FINA points scored over the follow-up period (R = -.42-.17, P = .256-.833), irrespective of competition distance. tHbmass and BV values did not differ between swimmers of different calibers or among competition distances. Furthermore, these values did not correlate with FINA points, either in males or in females. The present results indicate that hematological characteristics may have a lesser impact on swimming performance than on land-based endurance sports.

Relative Blood Volume Monitoring Using Crit-Line and Hospital Admissions: A Retrospective Analysis of over 25,000 Patients Across 330 Dialysis Clinics

Relative Blood Volume Monitoring Using Crit-Line and Hospital Admissions: A Retrospective Analysis of over 25,000 Patients Across 330 Dialysis Clinics

Estimation of absolute blood volume in hemodialysis patients: A numerical algorithm for assessing blood volume increase after dialysate bolus infusion

ObjectiveA feasible method has recently been proposed for estimating absolute blood volume (ABV) in hemodialysis (HD) patients based on intradialytic infusion of a dialysate bolus and visual assessment of the subsequent increase in relative blood volume (RBV) tracked by the dialysis machine. The aim of this study was to develop a method for more objective determination of such RBV increase to improve the accuracy of ABV estimation. MethodsWe proposed a numerical algorithm consisting of interpolation and polynomial fitting of RBV signals, which we evaluated on data from 64 HD sessions in 48 patients with 240 mL of dialysate infused approximately 1 h into HD. Theestimated ABV values were compared with those from a simple two-point method described previously as well as with the values calculated using the Nadler formula and the Lemmens-Bernstein-Brodsky formula. ResultsCompared to the simple method, the improved method provided higher (more plausible) estimates of ABV (median 4.79 vs 4.53 L, p < 0.001) and specific ABV (median 68.5 vs 66.4 mL/kg, p < 0.001). Theimproved method also provided much lower intra-patient variability of ABV estimated in different sessions of the same week (median spread 180 vs 462 mL, p < 0.001) and showed narrower limits of agreement with both Nadler and Lemmens-Bernstein-Brodsky formulae. ConclusionThe proposed numerical method constitutes a substantial improvement over the simple method by averaging the noise and short-term variability in RBV signals. SignificanceMore accurate estimates of ABV in HD patients could aid in managing their fluid status.

Sidestream dark field imaging and biomarker evaluation reveal minimal significant changes to the microcirculation and glycocalyx in a canine hemorrhagic shock model.

To investigate the effects of hemorrhagic shock and fresh whole blood resuscitation on the microcirculation and endothelial glycocalyx using sidestream dark field (SDF) imaging and plasma biomarkers. 8 purpose-bred dogs. Pressure-targeted hemorrhagic shock was induced in anesthetized dogs. SDF measurement of perfused boundary region and microcirculatory variables (RBC flow, total vessel density, and relative and absolute capillary blood volume), biomarker measurement (heparan sulfate, hyaluronan, VE-cadherin, and syndecan-1), mean arterial blood pressure, and cardiac output measurement were performed before anesthesia (TP0), after induction (TP1), after hemorrhagic shock (TP2), and after 50% retransfusion (TP3) and 100% retransfusion (TP4). At TP1, TP2, TP3, and TP4, mean arterial blood pressure was 74.25 ± 7.17 mm Hg, 49.50 ± 13.74 mm Hg, 63.50 ± 13.29 mm Hg, and 71.38 ± 8.77 mm Hg, and cardiac output was 2.57 ± 1.01 L/min, 0.8 ± 0.36 L/min, 1.81 ± 0.57 L/min, and 2.93 ± 1.22 L/min, respectively. Heparan sulfate, hyaluronan, syndecan-1, and VE-cadherin ranges were 24.80 to 77.72 ng/mL, 5.77 to 105.06 ng/mL, below detection to 1,545.69 pg/mL, and 0 to 2.52 ng/mL, respectively. Perfused boundary region, RBC flow, total vessel density, and relative and absolute capillary blood volume ranges were 1.75 to 2.68 µm, 89.6 to 584.5 µm/s, 51.7 to 1,914.3 mm/m2, 0.94 to 1.53 103 μm3, and 1.50 to 94.30 103 μm3, respectively. Heparan sulfate decreased significantly over time (P = .016). No significant differences were found for microcirculatory variables, perfused boundary regions, or other biomarkers. This was the first study to assess microvascular dysfunction and endothelial shedding in a canine hemorrhagic shock model using SDF microscopy (Glycocheck) and plasma biomarkers. Further studies are needed to determine clinical relevance.

A technique for assessing pulmonary perfusion in patients with previously treated COVID-19 pneumonia: clinical controlled non-randomized study

INTRODUCTION: Evaluating pulmonary lung perfusion in patients with previously treated COVID-19 infection may lead to a better understanding of long-term consequences of the disease, as well as may identify the changes determined by their symptoms. Further research is required for optimization of lung perfusion’s design parameters’ methods in order to implement those in clinical practice.OBJECTIVE: To determine the possibilities of an alternative method for evaluation of relative lung perfusion using three-dimensional ultrafast contrast-enhanced MRI on patients with previously treated COVID-19 pneumonia.MATERIALS AND METHODS: We examined 100 patients (28 male and 72 female, aged 22 to 70) who had laboratory-confirmed COVID-19 infection. The research was conducted using the three-dimensional ultrafast dynamic contrast-enhanced MRI based on 3D T1-weighted images. During the postprocessing, we received the values of rPBF (relative pulmonary blood flow), rPBV (relative pulmonary blood volume), and rMTT (relative mean transit time).Statistics. For non-linear dependence modelling we used natural spline transformation for time and interaction effect with a group. Intergroup comparison on integral measures was based on Kruskall-Wallis test (χ2), pair comparisons were based on Conover’s test (Δ). For multiple hypothesis testing correction, we used the false discovery rate (FDR). Comparisons were determined as statistically significant when p&lt;0.05.RESULTS: The differences in obtained values of lung perfusion among patient groups were confirmed both quantitatively (by rMTT, rPBV, rPBF) and qualitatively (by building the curves of contrast agent accumulation). Patients with previously treated COVID-19 demonstrate slower contrast agent transit and increased relative lung blood volume. Their accumulation curves have qualitative differences as well.DISCUSSION: We suggest a new method of evaluation of lung perfusion indicators in patients with previously treated COVID-19. We conducted an intergroup analysis based on the degree of lung damage during the acute phase of COVID-19 (with no infiltrativechanges, with minor lung damage, and major lung damage). The intergroup differences found are more significant for patients with lung damage (both minor and major) than for patients with no infiltrative lung changes during the acute phase of COVID-19.CONCLUSION: This method of evaluation of pulmonary perfusion is able to adequately characterize the functional lung conditions in patients with previously treated COVID-19 pneumonia. The chosen model is the most optimal.

Assessment of microcirculation variables and endothelial glycocalyx using sidestream dark field videomicroscopy in anesthetized dogs undergoing cardiopulmonary bypass.

To evaluate microcirculation and endothelial glycocalyx (eGC) variables using sidestream darkfield (SDF) videomicroscopy in canine cardiopulmonary bypass (CPB). Dogs undergoing CPB for surgical correction of naturally-occurring cardiac disease were prospectively included. Variables collected included patient demographics, underlying cardiac disease, red blood cell flow (Flow), 4-25 μm vessel density (Density), absolute capillary blood volume (CBVabs), relative capillary blood volume (CBVrel) and eGC width assessed by perfused boundary region (PBR). Anesthetized healthy dogs were used as control. Microcirculation and eGC variables were compared at baseline under anesthesia (T0), on CPB prior to cross clamping (T1), after cross clamp removal following surgical correction (T2) and at surgical closure (T3). Twelve dogs were enrolled, including 10 with a complete dataset. Median Flow was 233.9, 79.9, 164.3, and 136.1 μm/s at T0, T1, T2, and T3, respectively, (p = 1.00). Median Density was 173.3, 118.4, 121.0 and 155.4 mm/mm2 at T0, T1, T2, and T3, respectively, (p = 1.00). Median CBVabs decreased over time: 7.4, 6.6, 4.8 and 4.7 103μm3 at T0, T1, T2, and T3, respectively, (p < 0.01). Median CBVrel increased over time: 1.1, 1.5,1.1, and 1.3 103μm3 at T0, T1, T2, and T3, respectively, (p < 0.001). Median PBR increased over time: 1.8, 2.1, 2.4, 2.1 μm at T0, T1, T2, and T3, respectively, (p < 0.001). Compared to control dogs (n = 8), CPB dogs had lower CBVabs at T0. Alterations in eGC thickness and microvascular occur in dogs undergoing CPB for naturally-occurring cardiac disease.

Delivery of recombinant sestrin2 ameliorates oxidative stress, mitochondrial damage and renal dysfunction in contrast-induced acute kidney injury

Although the use of iodinated contrast agents is sometimes unavoidable for accurate diagnosis, contrast-induced acute kidney injury (CI-AKI) is a possible complication of its administration. The pathogenesis of CI-AKI has not been fully elucidated, but oxidative stress is thought to be a major factor. Sestrin2 plays an important role in cellular and mitochondrial homeostasis by regulating oxidative stress. In this study, we aimed to investigate whether recombinant adenovirus containing sestrin2 (RS) can attenuate CI-AKI by reducing oxidative stress in a CI-AKI mice model. Our results showed that RS decreases oxidative stress, pro-inflammatory cytokines (TNF-α, IL-1α, IL-1β and IL-6) and apoptosis (Bax/Bcl2 and cleaved caspase-3) in the CI-AKI model. Additionally, RS alleviated mitochondrial damage, as evidenced by morphological changes, are restored ATP synthesis. Furthermore, RS administration resulted in a decrease in mitochondrial fission marker (Drp1) that was increased in the CI-AKI model, while the mitochondrial fusion marker (Mfn2) increased, indicating a restoration of mitochondrial dynamics. Decreased relative blood volume, as evaluated on computed tomography (CT), significantly increased compared to the CI-AKI group after RS administration. Finally, renal injury markers such as Kim-1, Ngal, IL-18 also decreased and kidney function was preserved with RS. These results suggested that RS can mitigate the deterioration of renal function in CI-AKI model.

#5859 A NEW ULTRAFILTRATION RATE FEEDBACK CONTROLLER FOR ATTAINMENT OF RELATIVE BLOOD VOLUME TARGETS DURING HEMODIALYSIS

Abstract Background and Aims Preciado et al. (NDT, 2019) have identified half-hourly relative blood volume (RBV) targets during hemodialysis (HD) that are associated with significantly improved patient survival. Attainment of these RBV targets would necessitate incessant adjustments to the ultrafiltration rate (UFR) by the dialysis nurse, which is logistically not feasible. We developed a proportional-integral controller (Casper et al., Int J Artif Organs, 2022) that takes RBV data from the commercially available CLiC® device as an input and provides UFR suggestions to guide the RBV curve into the desired targets. The clinician pre-specifies the desired UF goal and the maximum allowed upward/downward deviation from this goal. The Controller then optimizes the RBV trajectory within the limits allowed by the clinician's prescription. The present study aimed to characterize the performance of this feedback controller. Methods We conducted a single-arm, prospective, interventional pilot study in subjects on chronic HD at three Avantus Renal Therapy dialysis centers in New York City. Subjects were treated with Fresenius 2008T HD machines. RBV was measured with the CLiC® device. CLiC® and HD machine data were fed into a research laptop running the UFR Feedback Controller software. The UFR recommendations (generated every 10 minutes) were evaluated by dialysis nurses, who then either implemented or disregarded them as they deemed clinically appropriate. The nurses were instructed to only override Controller recommendations if medically indicated, but not in an attempt to manage the subjects’ RBV trajectories themselves. RBV target range attainment with the UFR Feedback Controller was compared to standard of care treatments (data obtained retrospectively) in the same subjects. Results Fifteen subjects (58.9 ± 15.3 years, dialysis vintage 4.1 ± 2.4 years, baseline interdialytic weight gain 2.6 ± 0.8 L, treatment time 222 ± 28 min) were studied prospectively with the UFR Feedback Controller (63 study visits, 4.2 ± 1.9 visits per subject). Nine subjects contributed at least two complete treatments to each study period (Controller and standard of care, respectively) and were included in this analysis. The probabilities of achieving an RBV within the desired target range for each timepoint, stratified by study period (standard of care versus UFR Feedback Controller), are shown in the Figure. Use of the Controller was associated with a higher rate of RBV target range attainment for every timepoint. We confirmed these results with generalized linear mixed-effects models: Across all RBV target timepoints, use of the Controller was a significant predictor of better RBV target range attainment (P &amp;lt; 0.0001). Use of the UFR Feedback Controller was a significant predictor of RBV target range attainment for timepoints 60, 90, 120, and 150 minutes, and a borderline significant predictor for timepoints 30 and 180 minutes. Conclusion Use of this UFR Feedback Controller was associated with a significant and clinically meaningful increase in RBV target range attainment. This technology individualizes the UFR to the patient's plasma refill kinetics during the HD treatment and may assist clinicians with optimizing fluid management in their patients.

#4200 INTERACTIONS BETWEEN INTRADIALYTIC CENTRAL VENOUS OXYGEN SATURATION, RELATIVE BLOOD VOLUME, AND ALL-CAUSE MORTALITY IN HEMODIALYSIS PATIENTS

Abstract Background and Aims In maintenance hemodialysis patients, low central venous oxygen saturation (ScvO2) and small decline in relative blood volume (RBV) have been associated with adverse outcomes [1,2]. Here we explore the interactions between ScvO2 and RBV change in relation to all-cause mortality. Method We conducted a retrospective study in maintenance hemodialysis patients with central venous catheters as vascular access. During a 6-month baseline period, Crit-Line (Fresenius Medical Care, Waltham, MA) was used to measure continuously intradialytic ScvO2 and hematocrit-based RBV. We defined four groups per median change of RBV and median ScvO2. Patients with ScvO2 above median and RBV change below median were defined as reference. The follow up period was 3-years. We constructed a Cox proportional hazards model with adjustment for age, diabetes, and dialysis vintage to assess the association between ScvO2 and RBV and all-cause mortality during follow-up. Results Baseline comprised 5,231 dialysis sessions in 216 patients. The median RBV change was –5.5% and median ScvO2 was 58.8%. During follow-up, 44 patients (20.4%) died. Kaplan-Meier analysis is shown in Figure 1. In the adjusted model, all-cause mortality was highest in patients with ScvO2 below median and RBV change above median (HR 6.32; 95% confidence interval [CI] 1.37 to 29.06), followed by patients with ScvO2 below median and RBV change below median (HR 5.04; 95% CI 1.14 to 22.35) and ScvO2 above median and RBV change above median (HR 4.52; 95% CI 0.95 to 21.36). Conclusion Concurrent combined monitoring of intradialytic ScvO2 and RBV change may provide additional insights into a patient's circulatory status. Patients with low ScvO2 and small changes in RBV may represent a specifically vulnerable group of patients at particularly high risk for adverse outcomes, possibly related to poor cardiac reserve and fluid overload.

#4261 RELATIONSHIP BETWEEN FLUID OVERLOAD AND AVERAGE PLASMA REFILL RATE IN HEMODIALYSIS PATIENTS

Abstract Background and Aims Attaining the optimal balance between achieving adequate volume removal while preserving organ perfusion remains challenging in patients on maintenance hemodialysis (HD). Quantification of fluid status using bioimpedance spectroscopy (BIS) has become routine in many countries. Inadequate vascular space refill from the interstitial tissue (plasma refill rate, PRR) is the main contributing factor of hemodynamic instability during HD. We aimed to explore the association between fluid overload (FO) and plasma refill rate (PRR) in chronic HD patients. Method Pre-HD FO [l] was assessed once per subject by BIS (Body Composition Monitor; Fresenius Medical Care) in four urban HD dialysis clinics in the U.S. For each treatment within 30 days before and after the BIS measurement, we calculated the respective pre-HD FO by assuming that differences in pre-HD body weight were equivalent to differences in FO. We then used intradialytic hematocrit (measured with the Crit-Line® Monitor, Fresenius Medical Care) and ultrafiltration data to quantify the average PRR, normalized by body weight (Wang et al. Kidney360, 2023): To calculate the starting blood volume (BV), we first calculated the ending BV using the Nadler equation, followed by back-calculating the starting BV based on the cumulative change in relative BV. Plasma refill volume was calculated as the sum of the changes in blood volume and ultrafiltration volume; plasma refill volume was then divided by treatment time and estimated clinical dry weight to calculate the PRR [ml/kg/hr]. Results We analyzed 746 HD sessions from 79 patients (age 61 ± 15 years; 52 (66%) males; 41 (52%) black and 33 (42%) white). Across all HD sessions, PRR was positively associated with FO [slope estimate 0.92 (95% confidence interval 0.83 to 1.02) ml/kg/hr per 1 l of FO, P value &amp;lt; 0.0001] (Figure 1). This was also the case in subgroup analyses of fluid depleted (r = 0.94, P&amp;lt;0.001), normohydrated (r = 1.03, P&amp;lt;0.0001), and fluid overloaded subjects (r = 0.83, P&amp;lt;0.0001). Conclusion Across the entire fluid status spectrum, from fluid depletion to fluid overload, higher FO was associated with higher PRR on average (overall, an increase of 0.92 ml/kg/hr in PRR for each additional liter of FO). While patients with greater FO would be expected to better tolerate higher ultrafiltration rates, there is large inter-individual variability in PRR. Further investigation of the utility of PRR throughout HD may offer novel insights into fluid management and intradialytic symptom mitigation.

Interactions between intradialytic central venous oxygen saturation, relative blood volume, and all-cause mortality in maintenance hemodialysis patients.

In maintenance hemodialysis (HD) patients, low central venous oxygen saturation (ScvO2 ) and small decline in relative blood volume (RBV) have been associated with adverse outcomes. Here we explore the joint association between ScvO2 and RBV change in relation to all-cause mortality. We conducted a retrospective study in maintenance HD patients with central venous catheters as vascular access. During a 6-month baseline period, Crit-Line (Fresenius Medical Care, Waltham, MA) was used to measure continuously intradialytic ScvO2 and hematocrit-based RBV. We defined four groups per median change of RBV and median ScvO2 . Patients with ScvO2 above median and RBV change below median were defined as reference. Follow-up period was 3 years. We constructed Cox proportional hazards model with adjustment for age, diabetes, and dialysis vintage to assess the association between ScvO2 and RBV and all-cause mortality during follow-up. Baseline comprised 5231 dialysis sessions in 216 patients. The median RBV change was -5.5% and median ScvO2 was 58.8%. During follow-up, 44 patients (20.4%) died. In the adjusted model, all-cause mortality was highest in patients with ScvO2 below median and RBV change above median (HR 6.32; 95% confidence interval [CI] 1.37-29.06), followed by patients with ScvO2 below median and RBV change below median (HR 5.04; 95% CI 1.14-22.35), and ScvO2 above median and RBV change above median (HR 4.52; 95% CI 0.95-21.36). Concurrent combined monitoring of intradialytic ScvO2 and RBV change may provide additional insights into a patient's circulatory status. Patients with low ScvO2 and small changes in RBV may represent a specifically vulnerable group of patients at particularly high risk for adverse outcomes, possibly related to poor cardiac reserve and fluid overload.

Relative Blood Volume Profiles Hours After Loop Diuretic Administration: A Systematic Review and Meta-analysis

BackgroundPlasma refill rates can be estimated by combining measurements of urine output with relative blood volume profiles. Change in plasma refill rates could guide decongestive loop diuretic therapy in acute heart failure. The objective of the study was to assess average relative blood volume profiles generated from 2 or 3 follow-up measurements obtained hours after loop diuretic administration in subjects with vs without baseline congestion. MethodsA systematic review was conducted of articles written in English, French, Spanish, and German, using MEDLINE (1964 to 2019), Cochrane Reviews (1996 to 2019), and Embase (1974 to 2019). Search terms included the following: diuretics, hemoconcentration, plasma volume, and blood volume. We included studies of adults given a loop diuretic with at least one baseline and one follow-up measurement. A single author extracted subject- or group-level blood volume measurements, aggregated them when needed, and converted them to relative changes. ResultsAcross all 16 studies that met the prespecified inclusion criteria, relative blood volume maximally decreased 9.2% (6.6% to 12.0%) and returned to baseline after 3 or more hours. Compared to subjects without congestion, those with congestion experienced smaller decreases in relative blood volume across all follow-up periods (P = 0.001) and returned to baseline within the final follow-up period. ConclusionsSingle doses of loop diuretics produce measurable changes in relative blood volume that follow distinct profiles for subjects with vs without congestion. Measured alongside urine output, these profiles may be used to estimate plasma refill rates—potential patient-specific targets for decongestive therapy across serial diuretic doses.

Molecular Ultrasound Imaging Depicts the Modulation of Tumor Angiogenesis by Acetylsalicylic Acid.

Acetylsalicylic acid (ASA) is a well-established drug for heart attack and stroke prophylaxis. Furthermore, numerous studies have reported an anti-carcinogenic effect, but its exact mechanism is still unknown. Here, we applied VEGFR-2-targeted molecular ultrasound to explore a potential inhibitory effect of ASA on tumor angiogenesis in vivo. Daily ASA or placebo therapy was performed in a 4T1 tumor mouse model. During therapy, ultrasound scans were performed using nonspecific microbubbles (CEUS) to determine the relative intratumoral blood volume (rBV) and VEGFR-2-targeted microbubbles to assess angiogenesis. Finally, vessel density and VEGFR-2 expression were assessed histologically. CEUS indicated a decreasing rBV in both groups over time. VEGFR-2 expression increased in both groups up to Day 7. Towards Day 11, the binding of VEGFR-2-specific microbubbles further increased in controls, but significantly (p = 0.0015) decreased under ASA therapy (2.24 ± 0.46 au vs. 0.54 ± 0.55 au). Immunofluorescence showed a tendency towards lower vessel density under ASA and confirmed the result of molecular ultrasound. Molecular US demonstrated an inhibitory effect of ASA on VEGFR-2 expression accompanied by a tendency towards lower vessel density. Thus, this study suggests the inhibition of angiogenesis via VEGFR-2 downregulation as one of the anti-tumor effects of ASA.

Novel In Vivo Micro-Computed Tomography Imaging Techniques for Assessing the Progression of Non-Alcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is a growing global health issue, and the impact of NAFLD is compounded by the current lack of effective treatments. Considerable limiting factors hindering the timely and accurate diagnosis (including grading) and monitoring of NAFLD, as well as the development of potential therapies, are the current inadequacies in the characterization of the hepatic microenvironment structure and the scoring of the disease stage in a spatiotemporal and non-invasive manner. Using a diet-induced NAFLD mouse model, we investigated the use of in vivo micro-computed tomography (CT) imaging techniques as a non-invasive method to assess the progression stages of NAFLD, focusing predominantly on the hepatic vascular network due to its significant involvement in NAFLD-related hepatic dysregulation. This imaging methodology allows for longitudinal analysis of liver steatosis and functional tissue uptake, as well as the evaluation of the relative blood volume, portal vein diameter, and density of the vascular network. Understanding the adaptations of the hepatic vascular network during NAFLD progression and correlating this with other ways of characterizing the disease progression (steatosis, inflammation, fibrosis) using the proposed method can pave the way toward the establishment of new, more efficient, and reproducible approaches for NAFLD research in mice. This protocol is also expected to upgrade the value of preclinical animal models for investigatingthe development of novel therapies against disease progression.

Ultrafiltration-induced decrease in relative blood volume is larger in hemodialysis patients with low specific blood volume: Results from a dialysate bolus administration study.

Prescribing the ultrafiltration in hemodialysis patients remains challenging and might benefit from the information on absolute blood volume, estimated by intradialytic dialysate bolus administration. Here, we aimed at determining the relationship between absolute blood volume, normalized for body mass (specific blood volume, Vs), and ultrafiltration-induced decrease in relative blood volume (∆RBV) as well as clinical parameters including body mass index (BMI). This retrospective analysis comprised 77 patients who had their dialysate bolus-based absolute blood volume extracted routinely with an automated method. Patient-specific characteristics and ∆RBV were analyzed as a function of Vs, dichotomizing the data above or below a previously proposed threshold of 65 ml/kg for Vs. Statistical methodology comprised descriptive analyses, two-group comparisons, and correlation analyses. Median Vs was 68.6 ml/kg (54.9ml/kg [Quartile 1], 83.4ml/kg [Quartile 3]). Relative blood volume decreased by 6.3% (2.6%, 12.2%) over the entire hemodialysis session. Vs correlated inversely with BMI (rs =-0.688, p < 0.001). ∆RBV was 9.8% in the group of patients with Vs <65 ml/kg versus 6.0% in the group of patients with Vs ≥65 ml/kg (p=0.024). The two groups did not differ significantly regarding their specific ultrafiltration volume, normalized for body mass, which amounted to 34.1ml/kg and 36.0ml/kg in both groups, respectively (p=0.630). ∆RBV correlated inversely with Vs (rs =-0.299, p=0.008). The present study suggests that patients with higher BMI and lower Vs experience larger blood volume changes, despite similar ultrafiltration requirements. These results underline the clinical plausibility and importance of dialysate bolus-based absolute blood volume determination in the assessment of target weight, especially in view of a previous study where intradialytic morbid events could be decreased when the target weight was adjusted, based on Vs.

Comparable Hemodilution with Hypertonic Glucose in Patients with and without Type-2 Diabetes Mellitus during Hemodialysis.

(1) Background: It was examined whether glucose-induced changes in the relative blood volume are suitable to identify subjects with and without type-2 diabetes mellitus (T2D) during hemodialysis. (2) Methods: The relative blood volume was continuously recorded during hemodialysis and perturbed by the infusion of glucose comparable to the dose used for intravenous glucose tolerance tests. Indices of glucose metabolism were determined by the homeostatic model assessment (HOMA). Body composition was measured by a bioimpedance analysis. The magnitude and the time course of hemodilution were described by a modified gamma variate model and five model parameters. (3) Results: A total of 34 subjects were studied, 14 with and 20 without T2D. The magnitude of the hemodilution and the selected model parameters correlated with measures of anthropometry, body mass index, absolute and relative fat mass, volume excess, baseline insulin concentration, and HOMA indices such as insulin resistance and glucose disposition in a continuous analysis, but were not different in a dichotomous analysis of patients with and without T2D. (4) Conclusions: Even though the parameters of the hemodilution curve were correlated with measures of impaired glucose metabolism and body composition, the distinction between subjects with and without T2D was not possible using glucose-induced changes in the relative blood volume during hemodialysis.

Quantifying cerebral blood arrival times using hypoxia-mediated arterial BOLD contrast

Cerebral blood arrival and tissue transit times are sensitive measures of the efficiency of tissue perfusion and can provide clinically meaningful information on collateral blood flow status. We exploit the arterial blood oxygen level dependent (BOLD) signal contrast established by precisely decreasing, and then increasing, arterial hemoglobin saturation using respiratory re-oxygenation challenges to quantify arterial blood arrival times throughout the brain. We term this approach the Step Hemoglobin re-Oxygenation Contrast Stimulus (SHOCS). Carpet plot analysis yielded measures of signal onset (blood arrival), global transit time (gTT) and calculations of relative total blood volume. Onset times averaged across 12 healthy subjects were 1.1 ± 0.4 and 1.9 ± 0.6 for cortical gray and deep white matter, respectively. The average whole brain gTT was 4.5 ± 0.9 s. The SHOCS response was 1.7 fold higher in grey versus white matter; in line with known differences in tissue-specific blood volume fraction. SHOCS was also applied in a patient with unilateral carotid artery occlusion revealing ipsilateral prolonged signal onset with normal perfusion in the unaffected hemisphere. We anticipate that SHOCS will further inform on the extent of collateral blood flow in patients with upstream steno-occlusive vascular disease, including those already known to manifest reductions in vasodilatory reserve capacity or vascular steal.

Use of Relative Blood Volume Monitoring to Reduce Intradialytic Hypotension in Hospitalized Patients Receiving Dialysis

Use of Relative Blood Volume Monitoring to Reduce Intradialytic Hypotension in Hospitalized Patients Receiving Dialysis

Dynamics of vascular refilling in extended nocturnal hemodialysis.

Long dialysis treatments are generally assumed to mitigate the ultrafiltration (UF) induced volume perturbation and to improve vascular refilling because of reduced UF rates and sufficient time for volume re-equilibration. The time course of vascular refilling was therefore examined during extended nocturnal dialysis. For each hour of dialysis, vascular refilling volume was calculated from the absolute blood volume changes and UF volume removed. Absolute blood volume was estimated by indicator dilution at the beginning of dialysis and then tracked with a relative blood volume monitor. The refilling fraction was defined as the ratio of refilling volume to UF volume. Ten stable chronic hemodialysis (HD) patients were studied during extended (7h) nocturnal treatment sessions. Specific UF rate was 4.8 ± 1.8ml/kg/h. In the 1 h, refilling volume amounted to only 23% of UF volume. Thereafter, refilling fraction steeply increased and reached maximum values in the 2, 3 and 4 h at about mean 90% (91.5%, 88.7%, and 91.1% respectively). From the 5 h on, refilling volume decreased (5 h 81.3%, 6 h 72.5%, 7 h 70.0% of UF volume). Cumulative refilling reached 73.6% of UF volume after 4h of treatment time. This did not change during the further course of HD. Cumulative refilling volume showed a strong correlation (r=0.94; p < 0.001) with UF volume. The ratio of blood volume to extracellular volume (Rbex ) was 0.306 ± 0.029 before and slightly but significantly increased to 0.326 ± 0.030 after UF. In spite of low-UF rates and extended treatment times, overall refilling fraction reached only 74% and was not different from the refilling fraction observed in regular HD. This value seems to represent a point where UF-induced volume perturbation is adequately compensated by physiologic control mechanisms.

Prediction of response to radiotherapy in locally advanced carcinoma cervix using multiparametric MRI: A prospective, single-center, longitudinal study.

To evaluate the possible role of a multiparametric magnetic resonance imaging (MRI) and semiquantitative fusion map for the prediction of response to radiotherapy in carcinoma cervix. This was a prospective, single-center, longitudinal observational study performed on patients with locally advanced carcinoma cervix. Relative blood flow (rBF), relative blood volume (rBV), and apparent diffusion coefficient (ADC) values were obtained before and after the onset of radiotherapy. rBV, rBF, and ADC values were used to generate a semiquantitative pharmacokinetic model map to identify any hypoxic component of the tumor. The subjects were retrospectively classified as responders and nonresponders based on response to treatment. Prospective prediction of response status was done using pretreatment multiparametric MRI parameters (rBF, rBV, and ADC) and semiquantitative parametric map. In 32 patients (29 with parametrial involvement and 15 with lymphadenopathy), pretreatment ADC of the primary tumor was the most accurate measure for predicting response to treatment as well as for treatment-induced fractional volume reduction. Although rBV and rBF were insignificant metrics in isolation for predicting response status, a combination with ADC in the form of parametric map had a sensitivity of 86.4% and 77.2%, specificity of 70% and 70%, positive predictive value of 86.4% and 85%, and negative predictive value 70% and 59% respectively by two independent observers. ADC is the most accurate measure for predicting the response to treatment. A manual parametric map generated by an off-line fusion of the above map with those generated by pharmacokinetic modeling of perfusion-weighted MRI may be a useful tool for the prediction of response to radiotherapy.