In Vitro Model for Simulating Drug Delivery during Balloon-Occluded Transarterial Chemoembolization

Background: Balloon-occluded transarterial chemoembolization (B-TACE) has emerged as a safe and effective procedure for patients with liver cancer, which is one of the deadliest types of cancer worldwide. B-TACE consist of the transcatheter intraarterial infusion of chemotherapeutic agents, followed by embolizing particles, and it is performed with a microballoon catheter that temporarily occludes a hepatic artery. B-TACE relies on the blood flow redistribution promoted by the balloon-occlusion. However, flow redistribution phenomenon is not yet well understood. Methods: This study aims to present a simple in vitro model (IVM) where B-TACE can be simulated. Results: By visually analyzing the results of various clinically-realistic experiments, the IVM allows for the understanding of balloon-occlusion-related hemodynamic changes and the importance of the occlusion site. Conclusion: The IVM can be used as an educational tool to help clinicians better understand B-TACE treatments. This IVM could also serve as a base for a more sophisticated IVM to be used as a research tool.

Hierarchical Modeling of the Liver Vascular System

The liver plays a key role in the metabolic homeostasis of the whole organism. To carry out its functions, it is endowed with a peculiar circulatory system, made of three main dendritic flow structures and lobules. Understanding the vascular anatomy of the liver is clinically relevant since various liver pathologies are related to vascular disorders. Here, we develop a novel liver circulation model with a deterministic architecture based on the constructal law of design over the entire scale range (from macrocirculation to microcirculation). In this framework, the liver vascular structure is a combination of superimposed tree-shaped networks and porous system, where the main geometrical features of the dendritic fluid networks and the permeability of the porous medium, are defined from the constructal viewpoint. With this model, we are able to emulate physiological scenarios and to predict changes in blood pressure and flow rates throughout the hepatic vasculature due to resection or thrombosis in certain portions of the organ, simulated as deliberate blockages in the blood supply to these sections. This work sheds light on the critical impact of the vascular network on mechanics-related processes occurring in hepatic diseases, healing and regeneration that involve blood flow redistribution and are at the core of liver resilience.

Ultrasound Measurements of Intracranial Structures in Growth-Restricted Neonates with Fetal Blood Flow Redistribution: A Pilot Observational Study

<b><i>Background:</i></b> Fetal growth restriction (FGR) is associated with neonatal and long-term neuro-morbidity. Preferential redistribution of blood flow to the brain is a common antenatal adaptation in FGR. The impact of this “brain sparing,” which may signify severity of FGR, on the growth of brain structures has not been studied. <b><i>Aim:</i></b> To compare corpus callosum (CC), cerebellar, and ventricular measurements of FGR neonates with evidence of fetal blood flow redistribution with those of gestation-matched appropriately grown (AGA) neonates. <b><i>Methods:</i></b> This was a pilot, prospective observational study conducted at a tertiary level neonatal unit in Melbourne, Australia. Cranial ultrasound was done between days 1 and 3 of life in FGR and AGA neonates. <b><i>Results:</i></b> Cranial ultrasound on 20 FGR, gestation (mean ± SD) 31.4 ± 3.1 weeks, weight 1,205 ± 463 g, and 20 AGA neonates, 31.1 ± 3.0 weeks, 1,668 ± 490 g, was performed. CC length was significantly decreased in FGR neonates as compared to AGA neonates (35.28 ± 3.47 vs. 38.83 ± 4.05 mm, <i>p</i> = 0.0002). CC was significantly thinner at genu (3.36 ± 0.66 vs. 4.04 ± 0.83 mm, <i>p</i> = 0.007), body (1.97 ± 0.36 vs. 2.27 ± 0.39 mm, <i>p</i> = 0.02), and splenium (4.07 ± 0.76 vs. 4.72 ± 0.75 mm, <i>p</i> = 0.003) in FGR vs. AGA neonates. CC-fastigium length was also significantly decreased (39.65 ± 3.87 vs. 41.96 ± 4.50 mm, <i>p</i> = 0.04). Similarly, FGR neonates showed decreased transverse cerebellar diameter (36.15 ± 5.51 vs. 38.81 ± 7.21 mm, <i>p</i> = 0.02), but ventricular measurements were comparable. In multivariate analysis, these differences were evident independent of the birth weight. <b><i>Conclusions:</i></b>CC and cerebellar measurements are significantly smaller in FGR neonates with fetal blood flow redistribution, which warrants further study.

Association Between The Posterior Part Of The Circle Of Willis And Vertebral Artery Hypoplasia

BackgroundIt is not clear whether the configuration of the posterior part of the circle of Willis (CW) depends on the proximal part of the vertebrobasilar system. Our aim is to evaluate the posterior part of CW in association with different size of vertebral arteries (VA) in subjects free from stroke and TIA.Materials and methodsThe present study was based on a sample of 923 subjects free from stroke and TIA who were examined from 2013 through 2018. All the participants underwent MRA examination. The duplex ultrasonographic examination of the extracranial arteries (vertebral and carotid) was performed. VA was defined as hypoplastic (VAH) when VA diameter in the entire course was less than 2.5 mm. We classified the posterior communicating arteries (PCoA) as presence PCoA, absence/hypoplastic PCoA and fetal CW (FCW). The comparison of the posterior part of CW was made in subjects with normal VA and VAH of a different degree (communicating with basilar artery (VAH-BA) and not communicating with the basilar artery and terminating in PICA, neck or aplasia (VAH-PICA)).ResultsFCW was found in 15.9% of subjects, bilaterally – in 2.3 %. The coexisting VAH was more common in subjects with FCW rather than in those with adult CW (respectively, 28.6% and 13.4%, p<0.001). Aplasia of A1 of the anterior cerebral artery, i.e. blood flow redistribution in the anterior part of anterior circulation in the majority of cases (in 6 of 7 cases) was found ipsilaterally to FCW. FCW was recorded in 50% of the subjects with VA - PICA in comparison with 13.5% of those with normal VA and 22.8% with VAH - BA, p<0.005. On the contrary, absence/hypoplasia of both PCoA was mostly found in the group with normal VA in comparison with VAH-BA and VAH-PICA (accordingly, 50.7%, 38.6% and 12.5%, p<0.01).ConclusionIndividuals with VAH have a different pattern of the posterior part of CW in comparison with those with normal VA. With the increasing degree of VAH, the proportion of FCW increases, while the proportion of absence/hypoplastic of both PCoA decreases.

Regional Tissue Oxygen Extraction and Severity of Anemia in Very Low Birth Weight Neonates: A Pilot NIRS Analysis

Objective Anemia causes blood flow redistribution and altered tissue metabolic behavior to sustain homeostatic oxygen consumption. We hypothesized that anemia severity would correlate with increased regional fractional tissue oxygen extraction among premature neonates. Study Design Regional oxygen extraction was calculated using pulse oximetry and near-infrared spectroscopy data among neonates <1,250 g during their first 10 postnatal days. Oxygen extraction was assessed for correlations with raw hematocrit levels and following grouping into hematocrit quartiles. Results Twenty-seven neonates with gestational age 27 ± 2 weeks and birth weight 966 ± 181 g underwent 116 hematocrit determinations. Cerebral and flank oxygen extraction inversely correlated with hematocrit (cerebral r = −0.527, p = 0.005; flank r = −0.485, p = 0.01). Increased cerebral oxygen extraction was observed for the lowest three hematocrit quartiles (Q1 0.26 ± 0.08, p = 0.004; Q2 0.24 ± 0.09, p = 0.01; Q3 0.25 ± 0.09, p = 0.03; all compared with Q4 0.18 ± 0.10). Increased flank oxygen extraction occurred for the lowest two quartiles (Q1 0.36 ± 0.12, p < 0.001; Q2 0.35 ± 0.11, p < 0.001; compared with Q4 0.22 ± 0.13). Splanchnic oxygen extraction demonstrated no similar correlations. Conclusion Increases in tissue oxygen extraction may indicate early pathophysiologic responses to nascent anemia in premature neonates.