An eighth note.

Venous stenosis is the most common cause of arteriovenous fistula (AVF) failure in hemodialysis patients. For patients with AVF stenosis, the pressure over the antecedent part of the AVF stenotic lesion will increase if arterial inflow is sufficient. We report a chronic hemodialysis patient who received an angiographic examination for the juxta-anastomosis stenosis of his AVF. A unique feature of a collateral venous branch antecedent to the stenotic lesion was noted, resembling a musical sign as the "eighth note." After percutaneous transluminal angioplasty, the eighth note attenuated markedly at once. Of note, the eighth note sign is not seen frequently, and thus we postulate that the formation of an eighth note sign on the radiocephalic fistula should fulfill the following requirements, including a sufficient arterial inflow, an adjacent collateral branch close enough to the arteriovenous anastomosis, a severe juxta-anastomotic stenotic lesion, and an intact ulnar venous drainage system.

Motor asymmetry related cerebral perfusion patterns in Parkinson's disease: An arterial spin labeling study.

Persisting asymmetry of motor symptoms are characteristic of Parkinson's disease (PD). We investigated the possible lateralized effects on regional cerebral blood flow (CBF), CBF-connectivity, and laterality index (LI) among PD subtypes using arterial spin labeling (ASL). Forty-four left-sided symptom dominance patients (PDL), forty-eight right-sided symptom dominance patients (PDR), and forty-five matched HCs were included. Group comparisons were performed for the regional normalized CBF, CBF-connectivity and LI of basal ganglia (BA) subregions. The PDL patients had lower CBF in right calcarine sulcus and right supramarginal gyrus compared to the PDR and the HC subjects. Regional perfusion alterations seemed more extensive in the PDL than in the PDR group. In the PDL, correlations were identified between right thalamus and motor severity, between right fusiform gyrus and global cognitive performance. None of correlations survived after multiple comparisons correction. The significantly altered CBF-connectivity among the three groups included: unilateral putamen, unilateral globus pallidus, and right thalamus. LI score in the putamen was significantly different among groups. Motor-symptom laterality in PD may exhibit asymmetric regional and interregional abnormalities of CBF properties, particularly in PDL patients. This preliminary study underlines the necessity of classifying PD subgroups based on asymmetric motor symptoms and the potential application of CBF properties underlying neuropathology in PD.

Low and Oscillatory Wall Shear Stress Is Not Related to Aortic Dilation in Patients With Bicuspid Aortic Valve: A Time-Resolved 3-Dimensional Phase-Contrast Magnetic Resonance Imaging Study.

OBJECTIVE: To assess the relationship between regional wall shear stress (WSS) and oscillatory shear index (OSI) and aortic dilation in patients with bicuspid aortic valve (BAV). Approach and Results: Forty-six consecutive patients with BAV (63% with right-left-coronary-cusp fusion, aortic diameter ≤ 45 mm and no severe valvular disease) and 44 healthy volunteers were studied by time-resolved 3-dimensional phase-contrast magnetic resonance imaging. WSS and OSI were quantified at different levels of the ascending aorta and the aortic arch, and regional WSS and OSI maps were obtained. Seventy percent of BAV had ascending aorta dilation. Compared with healthy volunteers, patients with BAV had increased WSS and decreased OSI in most of the ascending aorta and the aortic arch. In both BAV and healthy volunteers, regions of high WSS matched regions of low OSI and vice versa. No regions of both low WSS and high OSI were identified in BAV compared with healthy volunteers. Patients with BAV with dilated compared with nondilated aorta presented low and oscillatory WSS in the aortic arch, but not in the ascending aorta where dilation is more prevalent. Furthermore, no regions of concomitant low WSS and high OSI were identified when BAV were compared according to leaflet fusion pattern, despite the well-known differences in regional dilation prevalence. CONCLUSIONS: Regions with low WSS and high OSI do not match those with the highest prevalence of dilation in patients with BAV, thus providing no evidence to support the low and oscillatory shear stress theory in the pathogenesis of proximal aorta dilation in the presence of BAV.

Evaluation of radial and ulnar artery blood flow after radial artery decannulation using colour Doppler ultrasound.

BACKGROUND: There is a lack of reports in the literature regarding changes in radial artery blood flow after decannulation. The objective of this study was to investigate changes in radial and ulnar artery blood flow after radial artery decannulation using Doppler ultrasound and to explore the factors that influence radial artery blood flow recovery. METHODS: In current observational study, we used colour Doppler ultrasound to measure the cross-sectional area of the radial (SR) and ulnar artery (SU) and peak systolic velocity of the radial (PSVR) and ulnar artery (PSVU) for both hands at four time points in patients with radial artery cannulation: pre-cannulation (T0), 30 min after decannulation (T1), 24 h after decannulation (T2), and 7 days after decannulation (T3). Repeated measures analysis of variance and logistic regression analysis were performed to analyse the data. RESULTS: Overall, 120 patients were included in the present study. We obtained the following results on the side ipsilateral to the cannulation: compared with T0, the ratio of PSVU/PSVR increased significantly at T1 and T2 (p < 0.01); compared with T1, the ratio of PSVU/PSVR decreased significantly at T2 and T3 (p < 0.01); compared with T2, the ratio of PSVU/PSVR decreased significantly at T3 (p < 0.01). Female sex (OR, 2.76; 95% CI, 1.01-7.57; p = 0.048) and local hematoma (OR 3.04 [1.12-8.25]; p = 0.029) were factors that were significantly associated with the recovery of radial artery blood flow 7 days after decannulation. CONCLUSIONS: There was a compensatory increase in blood flow in the ulnar artery after ipsilateral radial artery decannulation. Female sex and local hematoma formation are factors that may affect the recovery of radial artery blood flow 7 days after catheter removal.

Migraine Genetic Variants Influence Cerebral Blood Flow.

OBJECTIVE: To investigate the association of migraine genetic variants with cerebral blood flow (CBF). BACKGROUND: Migraine is a common disorder with many genetic and non-genetic factors affecting its occurrence. The exact pathophysiological mechanisms underlying the disease remain unclear, but are known to involve hemodynamic and vascular disruptions. Recent genome-wide association studies have identified 44 genetic variants in 38 genetic loci that affect the risk of migraine, which provide the opportunity to further disentangle these mechanisms. METHODS: We included 4665 participants of the population-based Rotterdam Study (mean age 65.0 ± 10.9 years, 55.6% women). Cross-sectional area (mm2 ), flow velocity (mm/s), and blood flow (mL/min) were measured in both carotids and the basilar artery using 2-dimensional phase-contrast magnetic resonance imaging. We analyzed 43 previously identified migraine variants separately and calculated a genetic risk score (GRS). To assess the association with CBF, we used linear regression models adjusted for age, sex, and total brain volume. Hierarchical clustering was performed based on the associations with CBF measures and tissue enrichment. RESULTS: The rs67338227 risk allele was associated with higher flow velocity and smaller cross-sectional area in the carotids (Pminimum  = 3.7 × 10-8 ). Other variants were related to CBF with opposite directions of effect, but not significantly after multiple testing adjustments (P < 1.4 × 10-4 ). The migraine GRS was not associated with CBF after multiple testing corrections. Migraine risk variants were found to be enriched for flow in the basilar artery (λ = 2.39). CONCLUSIONS: These findings show that genetic migraine risk is complexly associated with alterations in cerebral hemodynamics.

Impact of stressors in the aviation environment on xenobiotic dosimetry in humans: physiologically based prediction of the effect of barometric pressure or altitude.

Standard health risks from volatile organic compounds (VOCs) are generally interpreted at ambient environmental conditions. The aim of this study was to develop a strategy for using physiologically based pharmacokinetic (PBPK) modeling to compare known risks in the general population to calculated risks in pilots experiencing pressure-based stressors. PBPK models facilitate these comparisons by prediction of how target-tissue specific doses are altered when a stressor, such as high altitude, produces changes in physiological parameters. Cardiac output, regional blood flow, and alveolar ventilation rate following acute exposure to altitude ranging from moderate to extremely high were estimated from published data from 52 groups of human subjects. Scenarios where pilots might inhale toluene, 1,2,4-trimethylbenzene (1,2,4-TMB), or cyclohexane during routine military flight training were simulated. At the recommended Threshold Limit Values (TLV), arterial blood concentrations were predicted to be higher for exposure at 15000 ft (4572 m) than at sea level. The differences were greater for toluene and TMB, which have higher blood: air and fat: blood partition coefficients than less lipophilic cyclohexane. In summary, quantitative approaches to internal dosimetry prediction that take advantage of existing knowledge of physiological changes induced by occupational stressors possess potential as tools in performing a human health risk assessment.

Mitochondrial Damage and Necroptosis in Aging Cochlea.

Age-related hearing loss (ARHL) is an irreversible, progressive neurodegenerative disorder and is presently untreatable. Previous studies using animal models have suggested mitochondrial damage and programmed cell death to be involved with ARHL. Thus, we further investigated the pathophysiologic role of mitochondria and necroptosis in aged C57BL/6J male mice. Aged mice (20 months old) exhibited a significant loss of hearing, number of hair cells, neuronal fibers, and synaptic ribbons compared to young mice. Ultrastructural analysis of aged cochleae revealed damaged mitochondria with absent or disorganized cristae. Aged mice also showed significant decrease in cochlear blood flow, and exhibited increase in gene expression of proinflammatory cytokines (IL-1ß, IL-6, and TNF-α), receptor-interacting serine/threonine-protein kinase 1 and 3 (RIPK1 and RIPK3) and the pseudokinase mixed-lineage kinase domain-like (MLKL). Immunofluorescence (IF) assays of cytochrome C oxidase I (COX1) confirmed mitochondrial dysfunction in aged cochleae, which correlated with the degree of mitochondrial morphological damage. IF assays also revealed localization and increased expression of RIPK3 in sensorineural tissues that underwent significant necroptosis (inner and outer hair cells and stria vascularis). Together, our data shows that the aging cochlea exhibits damaged mitochondria, enhanced synthesis of proinflammatory cytokines, and provides new evidence of necroptosis in the aging cochlea in in vivo.

[Peripapillary and macular vessel density in eyes with different phases of thyroid-associated ophthalmopathy].

Objective: To analyze the characteristics of vessel density in the optic disc and macular area of patients with different phases of thyroid-associated ophthalmopathy (TAO) and their correlation with visual function. Methods: This case-control study was conducted at the Department of Ophthalmology of Peking Union Medical College Hospital between June 2019 and September 2019. TAO patients and healthy volunteers were included in the study. Patients with a clinical activity score greater than or equal to 3 points were categorized as active TAO. Dysthyroid optic neuropathy (DON) patients with a course less than 6 months were categorized as acute phase of DON, and those more than 6 months were in the chronic group. Healthy volunteers were in the control group. Each group included 12 subjects, with right eyes for analysis. There were 6 males and 6 females in each group. All participants underwent comprehensive ophthalmic examination including best corrected visual acuity and visual field examination for the mean defect (MD). Best corrected visual acuity was subsequently converted to logarithm of minimum angle of resolution (logMAR). Optical coherence tomography was used to measure the thickness of the retinal nerve fiber layer (RNFL) and retinal ganglion cell complex (GCC). Optical coherence tomography angiography was used to the peripapillary and macular vessel density. The differences in the vessel densities in the optic disc and macular area between groups and their correlation with different factors were analyzed. Analysis of variance, non-parametric Mann-Whitney U test and Spearman coefficient were conducted for statistical analysis. Results: There was no significant difference in age among the four groups (P>0.05). The logMAR of the acute DON group was 0.1 (0.0, 0.2), worse than the control group, which was 0.0 (0.0, 0.0) (U=114.000, P<0.05). The overall vessel densities of the optic disc in acute DON and chronic DON were significantly lower than the control group (54.70%±2.31% and 54.31%±3.65% vs. 57.54%±2.17%; t=3.104, 2.636; both P<0.05). The overall superficial vessel densities of the macular area in active TAO, acute DON and chronic DON were significantly lower than the control group (46.07%±3.06% and 42.26%±5.05% and 45.63%±3.87% vs. 49.34%±3.08%), and the differences were statistically significant (t=2.614, 4.147, 2.603; all P<0.05). There was no statistically significant difference in the size of the foveal avascular zone or the density of deep blood vessels in the macular area among the four groups (all P>0.05). In the active TAO period, there was no correlation between the MD value, RNFL thickness, GCC thickness and the vessel densities of the optic disc and macular area (all P>0.05). The vascular density of the whole layer of the optic disc in acute DON was negatively correlated with the MD value (r=-0.591, P<0.05) and positively correlated with the RNFL thickness and GCC thickness (r=0.595, 0.693; both P<0.05). In chronic DON, the overall capillary density of the optic disc was negatively correlated with the MD value (r=-0.673, P<0.05); the superficial overall blood vessel density of the macular area was positively correlated with the thickness of RNFL and GCC (r=0.732, 0.712;both P<0.01). Conclusions: In active TAO, only the blood supply to the superficial layer of the macular area is decreased. In the acute and chronic phases of DON, the blood supply to the superficial layer of the macular area and the optic disc is both reduced; the smaller the blood vessel density, the more severe the visual field defect, and the thinner the RNFL and GCC. (Chin J Ophthalmol, 2020, 56:824-831).

[Related risk factors of PET/CT detected coronary microvascular disease in patients with chest pain and no obstructive coronary artery disease].

Objective: To explore the related factors of the coronary microvascular disease (CMD) diagnosed with positron emission tomography(PET)/CT in patients with chest pain and without obstructive coronary artery disease (NOCA). Methods: This study was a single-center retrospective cross-sectional study. Consecutive patients with chest pain and NOCA on coronary angiography, who underwent PET/CT quantitative myocardial blood flow measurements at TEDA International Cardiovascular Hospital from August 2018 to January 2019, were enrolled for this study. The diagnostic criteria for NOCA was the absence of coronary artery diameter stenosis ≥50% on coronary angiography. Clinical data, global left ventricular myocardial blood flow on stress and rest, and the coronary flow reserve (CFR) were analyzed. Patients were divided into two groups according to CFR. Patients with CFR<2 were defined as CMD group, and the rest were classified as control group. Pearson correlation analysis and Logistics regression analysis were used for exploring the risk factors of the CMD. Results: A total of 66 patients, with an mean age of (56.7±9.6) years, were included in the study, including 41 females (62%). There were 20 patients with CMD (30%). Body mass index (BMI) was significantly higher in CND group than in control group ((28.1±3.6) kg/m2 vs. (25.6±3.5) kg/m2, P=0.01). Total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) were also significantly higher in CMD group than in control group ((4.89±1.03) mmol/L vs. (4.30±1.02) mmol/L and (3.23±0.81) mmol/L vs. (2.71±0.95) mmol/L respectively, P=0.038). Pearson correlation analysis showed that CFR was moderately correlated with BMI (r=-0.45, P<0.001), and was weakly correlated with TC and LDL-C (r=-0.271 and r=-0.280, respectively, P<0.05). Multivariate logistic regression analysis showed that BMI (the risk of CMD increased by 1.528 times for every 5 kg/m2 increase in BMI, 95%CI 1.083-5.897, P<0.05) was an independent risk factor of CMD after adjusted by gender, hypertension, diabetic mellites and LDL-C. Conclusion: For patients with NOCA and chest pain, high BMI is independent risk factor of CMD diagnosed by PET/CT.

Acoustic Trauma Modulates Cochlear Blood Flow and Vasoactive Factors in a Rodent Model of Noise-Induced Hearing Loss.

Noise exposure affects the organ of Corti and the lateral wall of the cochlea, including the stria vascularis and spiral ligament. Although the inner ear vasculature and spiral ligament fibrocytes in the lateral wall consist of a significant proportion of cells in the cochlea, relatively little is known regarding their functional significance. In this study, 6-week-old male C57BL/6 mice were exposed to noise trauma to induce transient hearing threshold shift (TTS) or permanent hearing threshold shift (PTS). Compared to mice with TTS, mice with PTS exhibited lower cochlear blood flow and lower vessel diameter in the stria vascularis, accompanied by reduced expression levels of genes involved in vasodilation and increased expression levels of genes related to vasoconstriction. Ultrastructural analyses by transmission electron microscopy revealed that the stria vascularis and spiral ligament fibrocytes were more damaged by PTS than by TTS. Moreover, mice with PTS expressed significantly higher levels of proinflammatory cytokines in the cochlea (e.g., IL-1ß, IL-6, and TNF-α). Overall, our findings suggest that cochlear microcirculation and lateral wall pathologies are differentially modulated by the severity of acoustic trauma and are associated with changes in vasoactive factors and inflammatory responses in the cochlea.

Risk of Burns During Active External Rewarming for Accidental Hypothermia.

This article describes 3 incidents in which therapeutic or experimental warming of cold individuals caused first- to third-degree burns to the skin. Mechanisms for these injuries are considered. We conclude that active external rewarming of the trunk of a cold patient in the field can be administered safely and burn risk reduced if 1) manufacturer instructions are followed; 2) insulation is placed between the skin the and heat source; and 3) caregivers make regular efforts to observe heated skin for possible pending burn injury. Direct inspection is mandatory for the skin of areas that are on top of a heat source when the patient is lying on the heat source.

[Optic nerve morphology and vessel density in eyes with different phases of non-arteritic anterior ischemic optic neuropathy].

Objective: To compare the blood flow around the optic disc and related factors in patients with acute and chronic non-arteritic anterior ischemic optic neuropathy (NAION) and healthy volunteers with small disc cups under the same anatomical structure. Methods: This was a prospective case-control study. NAION patients with unilateral onset and healthy volunteers of the same phase were included in the study conducted at the Department of Ophthalmology of Peking Union Medical College Hospital between February 2017 and September 2018. Patients with a course of ≤ 3 months were categorized in the acute phase of NAION, and those with a course of >3 months were in the chronic phase of NAION. Healthy volunteers were in the control group. All subjects underwent the examination of best corrected visual acuity converted to logarithm of the minimum angle of resolution (LogMAR), measurement of non-contact intraocular pressure, slit lamp examination, small pupil fundus examination, and axial measurement. Optical coherence tomography was used to measure the thickness of retinal nerve fiber layers (RNFL) and retinal ganglion cell complex (GCC). Optical coherence tomography angiography was used to measure the vessel density around the optic disc. NAION patients underwent the visual field examination. Analysis of variance, non-parametric Mann-Whitney U test and Spearman coefficient was used for statistical analysis. Results: This study included 16 patients with acute phase of NAION, aged (57±9) years, 6 males and 10 females. There were 17 patients with chronic disease, aged (56±10) years, 7 males and 10 females. There were 15 healthy controls, aged (57±10) years old, 6 males and 9 females. There were no significant differences in age and gender between the groups (both P>0.05). The RNFL and the GCC in the NAION chronic phase group were significantly thinner than those in the acute phase group [(78±38) µm vs. (191±99) µm, (75±19) µm vs. (98±28) µm; t=4.389, 2.758; both P<0.05]. The cup/disc area ratio, cup/disc vertical diameter ratio and cup/disc horizontal diameter ratio in the chronic phase group were larger than those in the acute phase group [0.18 (0.11, 0.31) vs. 0.05 (0.01, 0.18), 0.45 (0.39, 0.56) vs. 0.22 (0.11, 0.41), 0.39 (0.28, 0.54) vs. 0.20 (0.07, 0.42)], and the difference was statistically significant (U=212.000, 208.000, 205.000; all P<0.05). Compared with the optic disc vessel density in the control group (53%±6%), there was a significant decrease in the acute phase group and the chronic phase group (45%±7%, 41%±8%; t=3.705, 4.940; both P<0.01). The blood vessel density in the nasal inferior of the chronic phase group was significantly lower than that in the acute phase group (36%±8% vs. 42%±7%, P=0.039), other sections didn't have significant difference (all P>0.05). There were tortuous capillaries in 8/16 of the acute phase cases, with a low blood flow density and visual field defect in relative positions. Correlation analysis showed that the whole density and peripapillary density in the NAION patients were negatively correlated with LogMAR, mean visual field defect, cup/disc area ratio, focal loss of volume of GCC and general loss of volume of GCC (r=-0.510, -0.733, -0.372, -0.532, -0.648; all P<0.01), but positively correlated with GCC and RNFL thickness (r=0.604, 0.508; both P<0.01). Conclusions: The optic disc vessel density in the acute phase and chronic phase of NAION is significantly reduced. The vessel density in the nasal area of the chronic phase is significantly reduced compared with the acute phase. The vessel density is correlated with visual acuity, visual field defect, disc indexes, thickness of RNFL and GCC. (Chin J Ophthalmol, 2019, 55: 677-686).

Blood flow index as an indicator of successful sciatic nerve block: a prospective observational study using laser speckle contrast imaging.

BACKGROUND: Laser speckle contrast imaging allows real-time, non-invasive, quantitative measurements of regional blood flow. The objectives of this prospective observational study were to use laser speckle contrast imaging to evaluate blood flow changes after sciatic nerve block, and to determine whether this novel optical technique can evaluate block success. METHODS: This observational study included 63 adult patients undergoing elective lower limb surgery with sciatic nerve block. Blood flow images and blood flow index (BFI) values of toes were recorded using laser speckle contrast imaging 5 min before nerve block and at 5 min intervals until 30 min after sciatic block. The sensitivity, specificity, and cut-off value of laser speckle contrast imaging for predicting successful sciatic block were determined by receiver operator characteristic (ROC) curve analysis. RESULTS: The BFI values of toes were significantly increased at each time point after successful sciatic block, compared with the baseline value obtained 5 min before nerve block; in failed sciatic block, there were no significant differences. For successful sciatic block, the highest increase of BFI value was at the big toe. BFI increase of the big toe at 10 min after sciatic block has great potential as an indicator of block success. The area under the ROC curve was 0.954 at a cut-off value of 8.48 perfusion units (PU) with a sensitivity of 89% and a specificity of 100%. CONCLUSIONS: Laser speckle contrast imaging might be an early, objective, quantitative, and reliable indicator of successful sciatic block. BFI increase of the big toe not reaching 8.48 PU within 10 min after sciatic block indicates block failure. CLINICAL TRIAL REGISTRATION: NCT03169517.

Body temperature, cutaneous heat loss and skin blood flow during epidural anaesthesia for emergency caesarean section.

It is not clear how converting epidural analgesia for labour to epidural anaesthesia for emergency caesarean section affects either cutaneous vasomotor tone or mean body temperature. We hypothesised that topping up a labour epidural blocks active cutaneous vasodilation (cutaneous heat loss and skin blood flow decrease), and that as a result mean body temperature increases. Twenty women in established labour had body temperature, cutaneous heat loss and skin blood flow recorded before and after epidural top-up for emergency caesarean section. Changes over time were analysed with repeated measures ANOVA. Mean (SD) mean body temperature was 36.8 (0.5)°C at epidural top-up and 36.9 (0.6)°C at delivery. Between epidural top-up and delivery, the mean (SD) rate of increase in mean body temperature was 0.5 (0.5) °C.h-1 . Following epidural top-up, chest (p < 0.001) and forearm (p = 0.004) heat loss decreased, but head (p = 0.05), thigh (p = 0.79) and calf (p = 1.00) heat loss did not change. The mean (SD) decrease in heat loss was 15 (19) % (p < 0.001). Neither arm (p = 0.06) nor thigh (p = 0.10) skin blood flow changed following epidural top-up. Despite the lack of change in skin blood flow, the most plausible explanation for the reduction in heat loss and the increase in mean body temperature is blockade of active cutaneous vasodilation. It is possible that a similar mechanism is responsible for the hyperthermia associated with labour epidural analgesia.

Integration of Quantitative Positron Emission Tomography Absolute Myocardial Blood Flow Measurements in the Clinical Management of Coronary Artery Disease.

In the >40 years since planar myocardial imaging with(43)K-potassium was introduced into clinical research and management of patients with coronary artery disease (CAD), diagnosis and treatment have undergone profound scientific and technological changes. One such innovation is the current state-of-the-art hardware and software for positron emission tomography myocardial perfusion imaging, which has advanced it from a strictly research-oriented modality to a clinically valuable tool. This review traces the evolving role of quantitative positron emission tomography measurements of myocardial blood flow in the evaluation and management of patients with CAD. It presents methodology, currently or soon to be available, that offers a paradigm shift in CAD management. Heretofore, radionuclide myocardial perfusion imaging has been primarily qualitative or at best semiquantitative in nature, assessing regional perfusion in relative terms. Thus, unlike so many facets of modern cardiovascular practice and CAD management, which depend, for example, on absolute values of key parameters such as arterial and left ventricular pressures, serum lipoprotein, and other biomarker levels, the absolute levels of rest and maximal myocardial blood flow have yet to be incorporated into routine clinical practice even in most positron emission tomography centers where the potential to do so exists. Accordingly, this review focuses on potential value added for improving clinical CAD practice by measuring the absolute level of rest and maximal myocardial blood flow. Physiological principles and imaging fundamentals necessary to understand how positron emission tomography makes robust, quantitative measurements of myocardial blood flow possible are highlighted.

Cerebral blood flow laterality derived from arterial spin labeling as a biomarker for assessing the disease severity of parkinson's disease.

PURPOSE: To evaluate cerebral blood flow (CBF) laterality derived from arterial spin labeling (ASL) in early-stage Parkinson's disease (PD) patients compared with those with advanced stages. MATERIALS AND METHODS: Thirty-eight patients with PD (21 patients in early stages, 17 patients in advanced stages) were retrospectively studied. The CBF maps derived from 3T ASL data were co-registered to the corresponding 3DT1WI using SPM 12 software. Caudate nucleus (CN), putamen (PT), globus pallidus (GP), and thalamus (TH) were manually traced on the representative axial slices of 3DT1WI. CBF of the CN, PT, GP, and TH was measured using corresponding pixels on the co-registered CBF maps. A laterality index (LI) was calculated as the ratio of the contralateral CBF to primary affected side CBF. Each LI was compared between early and advanced stages of PD using the Mann-Whitney U-test. The LIs were also compared between each stage of PD. RESULTS: In the CN, the LIs were significantly higher in early stages (mean LI ± SD, 95% confidence interval = 1.06 ± 0.14, 1.00-1.13) than in advanced stages (0.94 ± 0.14, 0.87-1.01; P < 0.05). We also observed a tendency toward decreased LIs with disease severity (1.10 ± 0.14, 0.99-1.21 for Hoehn and Yahr stage I; 1.04 ± 0.14, 0.92-1.12 for stage II; 0.96 ± 0.11, 0.89-1.10 for stage III; 0.93 ± 0.17, 0.81-1.05 for stage IV). CONCLUSION: The evaluation of CBF laterality pattern in the CN using ASL may be useful for assessing the disease severity of PD patients. LEVEL OF EVIDENCE: 3 J. MAGN. RESON. IMAGING 2017;45:1821-1826.

Effects of lung protective mechanical ventilation associated with permissive respiratory acidosis on regional extra-pulmonary blood flow in experimental ARDS.

BACKGROUND: Lung protective mechanical ventilation with limited peak inspiratory pressure has been shown to affect cardiac output in patients with ARDS. However, little is known about the impact of lung protective mechanical ventilation on regional perfusion, especially when associated with moderate permissive respiratory acidosis. We hypothesized that lung protective mechanical ventilation with limited peak inspiratory pressure and moderate respiratory acidosis results in an increased cardiac output but unequal distribution of blood flow to the different organs of pigs with oleic-acid induced ARDS. METHODS: Twelve pigs were enrolled, 3 died during instrumentation and induction of lung injury. Thus, 9 animals received pressure controlled mechanical ventilation with a PEEP of 5 cmH2O and limited peak inspiratory pressure (17 ± 4 cmH2O) versus increased peak inspiratory pressure (23 ± 6 cmH2O) in a crossover-randomized design and were analyzed. The sequence of limited versus increased peak inspiratory pressure was randomized using sealed envelopes. Systemic and regional hemodynamics were determined by double indicator dilution technique and colored microspheres, respectively. The paired student t-test and the Wilcoxon test were used to compare normally and not normally distributed data, respectively. RESULTS: Mechanical ventilation with limited inspiratory pressure resulted in moderate hypercapnia and respiratory acidosis (PaCO2 71 ± 12 vs. 46 ± 9 mmHg, and pH 7.27 ± 0.05 vs. 7.38 ± 0.04, p < 0.001, respectively), increased cardiac output (140 ± 32 vs. 110 ± 22 ml/min/kg, p<0.05) and regional blood flow in the myocardium, brain and spinal cord, adrenal and thyroid glands, the mucosal layers of the esophagus and jejunum, the muscularis layers of the esophagus and duodenum, and the gall and urinary bladders. Perfusion of kidneys, pancreas, spleen, hepatic arterial bed, and the mucosal and muscularis blood flow to the other evaluated intestinal regions remained unchanged. CONCLUSIONS: In this porcine model of ARDS mechanical ventilation with limited peak inspiratory pressure resulting in moderate respiratory acidosis was associated with an increase in cardiac output. However, the better systemic blood flow was not uniformly directed to the different organs. This observation may be of clinical interest in patients, e.g. with cardiac, renal and cerebral pathologies.

Muscle Tissue Saturation Compared With Muscle Tissue Perfusion During Low Blood Flows: An Experimental Study.

OBJECTIVE: To investigate whether changes in muscle tissue perfusion measured with positron emission tomography would be reflected by parallel changes in muscle tissue oxygen saturation (StO2) measured using near-infrared spectroscopy during high and low blood flow levels achieved using cardiopulmonary bypass (CPB) in an animal model. DESIGN: A prospective, randomized study. SETTING: Research laboratory, single institution. PARTICIPANTS: Eight pigs (69-71 kg). INTERVENTIONS: In anesthetized pigs, normothermic CPB was established with a blood flow of 60 mL/kg/min for 1 hour. Thereafter, a low blood flow of either 47.5 or 35 mL/kg/min was applied for 1 hour followed by a blood flow of 60 mL/kg/min for an additional hour. Regional StO2 was measured continuously by placing a near-infrared spectroscopy electrode on the skin above the gracilis muscle of the noncannulated back leg. Muscle tissue perfusion was measured using positron emission tomography with 15O-labeled water during spontaneous circulation and the different CPB blood flows. Systemic oxygen consumption was estimated by measurement of venous saturation and lactate levels. MEASUREMENTS AND MAIN RESULTS: The results showed profound systemic ischemia during low CPB blood flow. StO2 remained high until muscle tissue perfusion decreased to about 50%, after which StO2 paralleled the linear decrease in muscle tissue perfusion. CONCLUSION: In an experimental CPB animal model, StO2 was stable until muscle tissue perfusion was reduced by about 50%, and at lower blood flow levels, there was almost a linear relationship between StO2 and muscle tissue perfusion.

Perfusion monitoring and intraventricular hemorrhage in preterm infants.

Cardiovascular instability in preterm infants during the early postnatal period correlates with the development of intraventricular hemorrhage (IVH). Due to the correlation between hypotension and fluctuation of blood pressure, treatment was targeted specifically at hypotension to prevent IVH, but this was not successful. Recently, several novel perfusion markers have been found to be correlated with the development of IVH, and they are of current interest in cardiovascular management. In this review, the correlation between IVH and conventional, as well as novel, perfusion markers is examined.

[Dynamic detection of surface blood flow in rat heart and its application in real time identification of myocardial infarction model].

Objective: To establish a method for monitoring the surface blood flow in the heart of rats, and to clarify the relationship between the degree of myocardial infarction and the blood perfusion on the surface of the heart, so as to provide a new indicator for the identification of rat myocardial infarction model. Methods: The rats were divided into control group (n=23) and model group (n=107), the rat hearts were scanned by the laser doppler perfusion imager before and after operation respectively, and the data was analyzed to acquire the rate of surface blood flow change of the heart. Myocardial infarction size of model group was detected by NBT. Model group were divided into three subgroups of mild myocardial infarction, moderate myocardial infarction and severe myocardial infarction according to the myocardial infarction size, and an analysis was made on the correlativity between rate of surface blood flow change of the heart and myocardial infarction size. Results: Myocardial infarction size was highly correlated to the rate of surface blood flow change of the heart in model group (r=0.849 6, P<0.000 1). There was no significant correlation between infarction size and heart blood flow in the mild myocardial infarction subgroup (r=-0.133 6, P>0.05), while the correlation in moderate myocardial infarction was significant (r=0.721 7, P<0.000 1), and the highest correlation was shown in severe myocardial infarction subgroup (r=0.910 2, P<0.000 1). Conclusion: The heart surface blood flow has a close relationship with the myocardial infarction size in rat, so the change of heart blood perfusion can beused as an effective reference to establish and identify rat myocardial infarction model.