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Precise fluid therapy is extremely important during surgeries, as enough circulating blood volume ensures tissue perfusion and cell oxygenation. Yet, extra fluid volume could cause other adverse events, such as heart failure, intestinal swelling, etc. Thus, precise evaluation of the circulating blood volume is essential for maintaining sufficient circulating blood volume and avoiding excessive fluid infusion. This study aimed to evaluate the relationship between SVV and circulating blood volume during intraoperative fluid therapy. SVV was measured by FloTrac/Vigileo in the study. A prospective cohort study was conducted. 103 patients aged from 20 to 60 years old with an ASA Grade I-II and a diagnosis of meningioma less than 3 centimeters planning for selective neurosurgery were randomly divided into the Crystalloid Group and the Colloid Group. After induction, each Patient received 15 ml/kg of Plasma-Lyte-A or 6% hydroxyethyl starch in 30 min followed by continuous infusion at the speed of 0.1 ml/kg during the next 60 min. Hb concentration, Hct, Delta-BV/kg, and Delta-SVV were recorded every 5 minutes. The delta-SVV and Delta-bv/kg were significantly higher in the Crystalloid Group than that of the Colloid Group. There was a strong linear correlation between Delta-SVV and Delta-bv/kg in both Crystalloid Group (Delta-bv / kg = 1.108 Delta-SVV + 0.0712, P < .001) and Colloid Group (Delta-bv / kg = 1.047 Delta-SVV + 0.4153, P < .001). An equation between Delta-bv/kg and Delta-SVV was established (Delta-bv / kg = 1.099 Delta-SVV + 0.1139, P < .001). In conclusion, SVV measured by FloTrac / Vigileo could guile fluid therapy precisely by predicting the blood volume of patients during the intraoperative period, as it has a strong linear correlation with the blood volume of patients who underwent general anesthesia, meaning anesthesiologist could calculate the exact fluid volume for patients' infusion. Further studies with large cohorts and centers would be needed to validate its efficiency.

Magnetic Particle Imaging (MPI) is a rapidly developing imaging modality that directly measures and maps the concentration of injected superparamagnetic iron oxide nanoparticles (SPIOs). Since the agent does not cross the blood-brain barrier, cerebral SPIO concentration provides a direct probe of Cerebral Blood Volume (CBV). Here we provide an initial demonstration of the ability of MPI to detect functional CBV changes (fCBV) by monitoring SPIO concentration during hypercapnic manipulation in a rat model. As a tracer detection method, MPI offers a more direct probe of agent concentration and therefore fCBV than MRI measurements in which the agent is indirectly detected through perturbation of water relaxation time constants such as T2∗. We found that MPI detection could measure CBV changes during hypercapnia with high CNR (CNR = 50) and potentially with high temporal resolution. Although the detection process more closely resembles a tracer method, we also identify evidence of physiological noise in the MPI time-series, with higher time-series variance at higher concentration levels. Our findings suggest that CBV-based MPI can provide a detection modality for hemodynamic changes. Further investigation with tomographic imaging is needed to assess tomographic ability of the method and further study the presence of time-series fluctuations which scale with signal level similar to physiological noise in resting fMRI time-courses. •A single-sided Magnetic Particle (MP) detector was developed for rodent CBV measurements.•Phantom experiments validated sensitivity to physiologically relevant SPIO concentrations.•fCBV measurements during hyper/hypocapnia detected CBV modulations with CNR = 50.•Observed physiological noise in the resting-state merits further study.

Abstract Context Controversy exists regarding if and how body mass index (BMI) impacts antimüllerian hormone (AMH) in women with and without polycystic ovary syndrome (PCOS). Understanding the BMI-AMH relationship has critical implications for clinical interpretation of laboratory values and could illuminate underlying ovarian physiology. Objective To test the hypotheses that (1) BMI is associated with reduced AMH in PCOS and ovulatory controls (OVAs) and (2) the reduction in AMH is not accounted for by dilutional effects. Design/Setting Multicenter cohort. Participants Women aged 25 to 40 years from 2 clinical populations: 640 with PCOS, 921 women as OVAs. Main Outcome Measures Ovarian reserve indices: AMH, antral follicle count (AFC), and AMH to AFC ratio (AMH/AFC) as a marker of per-follicle AMH production. Results In both cohorts, increasing BMI and waist circumference were associated with reductions in AMH and AMH/AFC, after adjusting for age, race, smoking, and site in multivariate regression models. Increasing BMI was associated with reduced AFC in PCOS but not OVAs. Body surface area (BSA), which unlike BMI is strongly proportional to plasma volume, was added to investigate a potential dilutive effect of body size on AMH concentrations. After controlling for BSA, BMI retained independent associations with AMH in both cohorts; BSA no longer associated with AMH. Conclusions In an adjusted analysis, BMI, but not BSA, was associated with reduced AMH; these data do not support a role for hemodilution in mediating the relationship between increased body size and reduced AMH. Decreased AMH production by the follicle unit may be responsible for reduced AMH with increasing BMI.

The prognostic implications of intravascular volume status assessed by blood volume analysis (BVA) in ambulatory heart failure (HF) remain uncertain. The incremental benefits of assessing volume status, beyond the well-established filling pressures, in predicting HF outcomes are unknown.

In contrast to Andean natives, high-altitude Tibetans present with a lower hemoglobin concentration that correlates with reproductive success and exercise capacity. Decades of physiological and genomic research have assumed that the lower hemoglobin concentration in Himalayan natives results from a blunted erythropoietic response to hypoxia (i.e., no increase in total hemoglobin mass). In contrast, herein we test the hypothesis that the lower hemoglobin concentration is the result of greater plasma volume, rather than an absence of increased hemoglobin production. We assessed hemoglobin mass, plasma volume and blood volume in lowlanders at sea level, lowlanders acclimatized to high altitude, Himalayan Sherpa, and Andean Quechua, and explored the functional relevance of volumetric hematological measures to exercise capacity. Hemoglobin mass was highest in Andeans, but also was elevated in Sherpa compared with lowlanders. Sherpa demonstrated a larger plasma volume than Andeans, resulting in a comparable total blood volume at a lower hemoglobin concentration. Hemoglobin mass was positively related to exercise capacity in lowlanders at sea level and in Sherpa at high altitude, but not in Andean natives. Collectively, our findings demonstrate a unique adaptation in Sherpa that reorientates attention away from hemoglobin concentration and toward a paradigm where hemoglobin mass and plasma volume may represent phenotypes with adaptive significance at high altitude.

Functional MRI using blood oxygenation level-dependent (BOLD) contrast indirectly probes neuronal activity via evoked cerebral blood volume (CBV) and oxygenation changes. Thus, its spatio-temporal characteristics are determined by vascular physiology and MRI parameters. In this paper, we focus on the spatial distribution and time course of the fMRI signal and their magnetic field strength dependence. Even though much is still unknown, the following consistent picture is emerging: a) For high spatial resolution imaging, fMRI contrast-to-noise increases supra-linearly with field strength. b) The location and spacing of penetrating arteries and ascending veins in the cortical tissue are not correlated to cortical columns, imposing limitations on achievable point-spread function (PSF) in fMRI. c) Baseline CBV distribution may vary over cortical layers biasing fMRI signal to layers with high CBV values. d) The largest CBV change is in the tissue microvasculature, less in surface arteries and even less in pial veins. e) Venous CBV changes are only relevant for longer stimuli, and oxygenation changes are largest in post-capillary blood vessels. f) The balloon effect (i.e. slow recovery of CBV to baseline) is located in the tissue, consistent with the fact that the post-stimulus undershoot has narrower spatial PSF than the positive BOLD response. g) The onset time following stimulation has been found to be shortest in middle/lower layers, both in optical imaging and high-resolution fMRI, but we argue and demonstrate with simulations that varying signal latencies can also be caused by vascular properties and, therefore, may potentially not be interpreted as neural latencies. With simulations, we illustrate the field strength dependency of fMRI signal transients, such as the adaptation during stimulation, initial dip and the post-stimulus undershoot. In sum, vascular structure and function impose limitations on the achievable PSF of fMRI and give rise to complex fMRI transients, which contain time-varying amount of excitatory and inhibitory neuronal information. Nevertheless, non-invasive fMRI at ultra-high magnetic fields not only provides high contrast-to-noise but also an unprecedented detailed view on cognitive processes in the human brain. •FMRI signal dynamics contain rich information on excitatory and inhibitory neuronal processes.•However, vascular anatomy and physiology and MRI parameters impose limitations on achievable point-spread function using the fMRI signal.•Spatial and temporal specificity of the fMRI signal change with magnetic field strength.•Laminar and columnar imaging with fMRI has great potential after taking vascular and MRI confounding factors into account.

We report a study on twenty-two healthy human subjects of the dynamic relationship between cerebral hemoglobin concentration ([HbT]), measured with near-infrared spectroscopy (NIRS) in the prefrontal cortex, and systemic arterial blood pressure (ABP), measured with finger plethysmography. [HbT] is a measure of local cerebral blood volume (CBV). We induced hemodynamic oscillations at discrete frequencies in the range 0.04-0.20 Hz with cyclic inflation and deflation of pneumatic cuffs wrapped around the subject's thighs. We modeled the transfer function of ABP and [HbT] in terms of effective arterial (K(a)) and venous (K(v)) compliances, and a cerebral autoregulation time constant (τ(AR)). The mean values (± standard errors) of these parameters across the twenty-two subjects were K(a) = 0.01 ± 0.01 μM/mmHg, K(v) = 0.09 ± 0.05 μM/mmHg, and τ(AR) = 2.2 ± 1.3 s. Spatially resolved measurements in a subset of eight subjects reveal a spatial variability of these parameters that may exceed the inter-subject variability at a set location. This study sheds some light onto the role that ABP and cerebral blood flow (CBF) play in the dynamics of [HbT] measured with NIRS, and paves the way for new non-invasive optical studies of cerebral blood flow and cerebral autoregulation.

Heart failure (HF) is among the most prevalent health issues worldwide and is associated with high mortality. Adequate decongestion remain the main clinical challenge in HF management. Sodium glucose cotransporter-2 inhibitors (SGLT-2i) have been recently introduced as a new treatment option in patients with HF irrespective of left ventricular ejection fraction. Although the favorable effects of SGLT-2i are profoundly evident, the underlying mechanisms are not yet well understood. The aim of this study is to provide novel insights into the effects of dapagliflozin, a SGLT-2i with proven cardiovascular benefit, on blood volume profile and vascular function in HF patients who had a recent event of acute decompensated heart failure (ADHF). Eighty adult patients with diagnosis of de novo or chronic HF (NYHA class II-IV), clinically stabilized after an ADHF event and with preserved renal function, who were not on treatment with SGLT-2i, are aimed to be included. The patients are randomized with 1:1 allocation to either dapagliflozin 10 mg p.o. once daily or placebo in addition to guideline-directed medical therapy. The primary outcome is the mean change in plasma volume status (PVS) in the dapagliflozin group compared to placebo. PVS is assessed via optimized carbon monoxide rebreathing technique, a reliable and safe method to measure total hemoglobin mass and to estimate blood volume profile, i.e., blood volume, plasma volume and red blood cell volume. Secondary outcomes include differences between the two study groups regarding blood volume profile, micro- and macro-vascular function assessed by retinal vessel analysis and flow-mediated vasodilation, respectively, changes in body water distribution, quality of life, exercise capacity, echocardiographic and laboratory parameters. The study has been approved by the Cantonal Ethics Committee Zurich (BASEC-Nr.:2020-01920, Swissmedic-Nr.:2020DR4175) and has been registered at www.ClinicalTrials.gov‌ (NCT04869124). The results will be published in a peer-reviewed medical journal.

Background Distal medium vessel occlusions (DMVOs) contribute substantially to the incidence of acute ischemic strokes (AIS) and pose distinct challenges in clinical management and prognosis. Neuroimaging techniques, such as Fluid Attenuation Inversion Recovery (FLAIR) imaging and cerebral blood volume (CBV) index derived from perfusion imaging, have significantly improved our ability to assess the impact of strokes and predict their outcomes. The primary objective of this study was to investigate relationship between follow-up infarct volume (FIV) as assessed by FLAIR imaging in patients with DMVOs. Methods This prospectively collected, retrospective reviewed cohort study included patients from two comprehensive stroke centers within the Johns Hopkins Medical Enterprise, spanning August 2018–October 2022. The cohort consisted of adults with AIS attributable to DMVO. Detailed imaging analyses were conducted, encompassing non-contrast CT, CT angiography (CTA), CT perfusion (CTP), and FLAIR imaging. Univariable and multivariable linear regression models were employed to assess the association between different factors and FIV. Results The study included 79 patients with DMVO stroke with a median age of 69 years (IQR, 62–77 years), and 57% ( n  = 45) were female. There was a negative correlation between the CBV index and FIV in a univariable linear regression analysis (Beta =  – 16; 95% CI,  – 23 to  – 8.3; p  < 0.001) and a multivariable linear regression model (Beta =  – 9.1 per 0.1 change; 95% CI,  – 15 to  – 2.7; p  = 0.006). Diabetes was independently associated with larger FIV (Beta = 46; 95% CI, 16 to 75; p  = 0.003). Additionally, a higher baseline ASPECTS was associated with lower FIV (Beta =  – 30; 95% CI,  – 41 to  – 20; p  < 0.001). Conclusion Our findings underscore the CBV index as an independent association with FIV in DMVOs, which highlights the critical role of collateral circulation in determining stroke outcomes in this patient population. In addition, our study confirms a negative association of ASPECTS with FLAIR FIV and identifies diabetes as independent factor associated with larger FIV. These insights pave the way for further large-scale, prospective studies to corroborate these findings, thereby refining the strategies for stroke prognostication and management.

ObjectivesTo determine whether diffusion- and perfusion-weighted MRI–based radiomics features can improve prediction of isocitrate dehydrogenase (IDH) mutation and tumor aggressiveness in lower grade gliomas (LGGs)MethodsRadiomics features (n = 6472) were extracted from multiparametric MRI including conventional MRI, apparent diffusion coefficient (ADC), and normalized cerebral blood volume, acquired on 127 LGG patients with determined IDH mutation status and grade (WHO II or III). Radiomics models were constructed using machine learning–based feature selection and generalized linear model classifiers. Segmentation stability was calculated between two readers using concordance correlation coefficients (CCCs). Diagnostic performance to predict IDH mutation and tumor grade was compared between the multiparametric and conventional MRI radiomics models using the area under the receiver operating characteristics curve (AUC). The models were tested using a temporally independent validation set (n = 28).ResultsThe multiparametric MRI radiomics model was optimized with a random forest feature selector, with segmentation stability of a CCC threshold of 0.8. For IDH mutation, multiparametric MR radiomics showed similar performance (AUC 0.795) to the conventional radiomics model (AUC 0.729). In tumor grading, multiparametric model with ADC features showed higher performance (AUC 0.932) than the conventional model (AUC 0.555). The independent validation set showed the same trend with AUCs of 0.747 for IDH prediction and 0.819 for tumor grading with multiparametric MRI radiomics model.ConclusionMultiparametric MRI radiomics model showed improved diagnostic performance in tumor grading and comparable diagnostic performance in IDH mutation status, with ADC features playing a significant role.Key Points• The multiparametric MRI radiomics model was comparable with conventional MRI radiomics model in predicting IDH mutation.• The multiparametric MRI radiomics model outperformed conventional MRI in glioma grading.• Apparent diffusion coefficient played an important role in glioma grading and predicting IDH mutation status using radiomics.