Oxygen Extraction Rate Research Articles

Effects of red blood cell transfusion on cerebral hemodynamics of preterm neonates.

Anemia is a common problem in preterm neonates, and red blood cell transfusion (RBCT) is used to improve oxygen delivery. However, RBCT is associated with complications, although an increase in cerebral oxygenation has been documented, and no universally accepted biomarker for the need for transfusion (i.e., the concentration of hemoglobin in the blood) has been defined. We used a hybrid optical device (BabyLux device) that merges time-domain near-infrared spectroscopy (TD-NIRS) and diffuse correlation spectroscopy (DCS) to potentially obtain a better assessment of the cerebral effects of RBCT compared with previous studies using continuous wave (CW) spatially resolved NIRS. Eighteen clinically stable preterm neonates were assessed before and after RBCT by the BabyLux device as five repetitions of 60s measurement (with 1s acquisition time), estimating the cerebral blood flow (CBF) as a blood flow index (BFI), the total hemoglobin concentration (tHb), and the cerebral tissue oxygen saturation ( ). was also continuously monitored by a commercial CW-NIRS device, as well as peripheral saturation, . Tissue oxygen extraction (TOE) and cerebral metabolic rate of oxygen consumption ( ) were computed, and the Wilcoxon signed-rank test for paired data was performed, comparing the data acquired before and after RBCT. The BabyLux data from four neonates did not meet quality criteria and were discarded. After the transfusion, tHb and (measured both with TD-NIRS and CW-NIRS devices) significantly increased, causing a significant decrease in TOE. CW-NIRS showed a wider dispersion of data compared with TD-NIRS. However, CBF did not decrease proportionally but the variation was high, as well as for . The results confirm previous CW-NIRS studies, but the wide variability of BFI makes the effects of RBCT on cerebral metabolism uncertain.

Effects of integrated blood purification on haemodynamics and oxygen metabolism in children with severe sepsis.

To investigate the effects of integrated blood purification on haemodynamics and oxygen metabolism in children with severe sepsis. Clinical data of 12 children with severe sepsis admitted to the pediatric intensive care unit of our hospital between October 2021 and June 2022 were retrospectively analyzed. All patients were treated with integrated blood purification, and changes in haemodynamic parameters, including heart rate, blood pressure, mean arterial pressure and cardiac output, and oxygen metabolism parameters (blood lactic acid, oxygen delivery, oxygen consumption and oxygen extraction rate) were observed before and after treatment. The heart rate (134[106,160] vs 111[101,128], p = 0.037), central venous pressure (9[7,10] vs 8[7,9], p = 0.04), stroke output (28[18,43] vs 21[15,31], p = 0.01), blood lactate (3.3[2,4] vs 2.5[1.3,3.6], p = 0.015), oxygen consumption (165.99[121.44,230.31] vs 124.18[82.51,162.86], p = 0.041) and oxygen extraction rate (38.83[31.87,44.62] vs 28.67[21.05,32.72], p = 0.019) were decreased, whereas systolic blood pressure (97[83,104] vs 107[94,116], p = 0.033) and central venous oxygen pressure (32[29, 37] vs 39[34,46], p = 0.005) were increased in the children after treatment compared with before treatment. There were no statistically significant differences in diastolic blood pressure, mean arterial pressure, cardiac output, arterial oxygen pressure and oxygen delivery before and after treatment (all p > 0.05). Integrated blood purification can improve haemodynamic and oxygen metabolism parameters in children with severe sepsis, with a high value in clinical application.

Aerobic capacity of healthy young men associated with muscle oxygen extraction rate of the vastus lateralis muscle.

The determinants of aerobic capacity are oxygen delivery by the cardiopulmonary system and oxygen extraction by the skeletal muscles. However, the impact of the oxygen extraction capacity of the skeletal muscle is unclear. This study aimed to examine the associations between aerobic capacity; muscle strength, endurance, mass, and quality; and oxygen extraction capacity. Twenty-seven healthy young men (mean age, 20.7 ± 0.8 years; body mass index, 21.6 ± 3.2 kg m-2) were recruited. The following parameters were determined: peak work rate (WR) and oxygen uptake (V˙O2) corrected for body mass using the cardiopulmonary exercise testing; muscle strength and endurance using isokinetic muscle testing; muscle mass using bioelectrical impedance; muscle quality (muscle echo intensity) using an ultrasound imaging device, and muscle oxygen extraction rate (MOER) using near-infrared spectroscopy. Multiple regression analysis was performed using WR/kg peak and V˙O2/kg peak as dependent variables and each assessment index as an independent variable. Multiple regression analysis with WR/kg peak as the dependent variable resulted in the adoption of SMI (β = -0.41, P = 0.036), muscle echo intensity (β=-0.45, P = 0.012) and ΔMOER (β = 0.73, P < 0.001) as significantly associated factors. Multiple regression analysis with V˙O2/kg peak as the dependent variable resulted in ΔMOER (β = 0.65, P = 0.001) being adopted as a significantly associated factor. These findings suggest that muscle oxygen extraction rate is associated with aerobic capacity. MOER is a useful indicator because it is not affected by body mass.

Using cerebral regional oxygen saturation and amplitude-integrated electroencephalography in neonates on extracorporeal membrane oxygenation: preliminary experience from a single center

ObjectiveThis study aims to evaluate the application value in neurological outcome of cerebral regional oxygen saturation (CrSO2) and amplitude-integrated electroencephalography (aEEG) monitoring during neonatal extracorporeal membrane oxygenation (ECMO) courses.Methods We retrospectively analyzed 18 neonates receiving veno-arterial ECMO (V-A ECMO) support at our hospital from July 2021 to December 2022. Continuous monitoring of CrSO2 and brain electrical activity was conducted using near-infrared spectroscopy (NIRS) and aEEG throughout the ECMO treatment. We collected and analyzed related clinical data.ResultsAmong the 11 survivors, 5 were categorized as the normal group (N group) and 6 as the abnormal group (AN group) based on post-ECMO brain MRI outcomes. The N group exhibited shorter time percentage of significant CrSO2 reduction (> 25% from baseline or absolute value < 40%), better fractional tissue oxygen extraction (FTOE) rates, and more stable mean percentage changes in CrSO2 compared to the AN group. Neonates in the N group predominantly showed mildly abnormal aEEG readings, with one patient displaying disrupted sleep-wake cycles. This particular patient also had more significant CrSO2 reduction and poorer FTOE compared to others in the N group. Additionally, the Test of Infant Motor Performance (TIMP) scores indicated hypoevolutism in this patient before discharge, while others in the N group had normal TIMP scores. In the AN group, 4 exhibited moderate and 2 severe aEEG abnormalities; 5 had hypoevolutism TIMP scores, and 1 with moderate aEEG abnormalities maintained a normal TIMP score, exhibiting lesser CrSO2 reduction and improved FTOE.ConclusionCrSO2 and aEEG monitoring show potential as routine assessments for neurological outcomes during neonatal ECMO. In our cohort, a tendency was observed where neonates with greater reductions in CrSO2 and more severe aEEG abnormalities experienced poorer neurological outcomes.

Hyperglycemia induces microglial pyroptosis by increasing oxygen extraction rate: Implication in neurological impairment during ischemic stroke.

Elevated levels of blood glucose in patients with ischemic stroke are associated with a worse prognosis. The present study aimed to explore whether hyperglycemia promotes microglial pyroptosis by increasing the oxygen extraction rate in an acute ischemic stroke model. C57BL/6 mice that underwent middle cerebral artery occlusion were used for assessment of blood glucose level and neurological function. The cerebral oxygen extraction ratio (CERO2), oxygen consumption rate (OCR) and partial pressure of brain tissue oxygen (PbtO2) were measured. To investigate the significance of the NOD‑like receptor protein 3 (NLRP3) inflammasome, NLRP3‑/‑ mice were used, and the expression levels of NLRP3, caspase‑1, full‑length gasdermin D (GSDMD‑FL), GSDMD‑N domain (GSDMD‑N), IL‑1β and IL‑18 were evaluated. In addition, Z‑YVAD‑FMK, a caspase‑1 inhibitor, was used to treat microglia to determine whether activation of the NLRP3 inflammasome was required for the enhancing effect of hyperglycemia on pyroptosis. It was revealed that hyperglycemia accelerated cerebral injury in the acute ischemic stroke model, as evidenced by decreased latency to fall and the percentage of foot fault. Hyperglycemia aggravated hypoxia by increasing the oxygen extraction rate, as evidenced by increased CERO2 and OCR, and decreased PbtO2 in response to high glucose treatment. Furthermore, hyperglycemia‑induced microglial pyroptosis was confirmed by detection of increased levels of caspase‑1, GSDMD‑N, IL‑1β and IL‑18 and a decreased level of GSDMD‑FL. However, the knockout of NLRP3 attenuated these effects. Pharmacological inhibition of caspase‑1 also reduced the expression levels of GSDMD‑N, IL‑1β and IL‑18 in microglial cells. These results suggested that hyperglycemia stimulated NLRP3 inflammasome activation by increasing the oxygen extraction rate, thus leading to the aggravation of pyroptosis following ischemic stroke.

Importance of Renal Graft Reperfusion Thermoregulation in Living Donor Kidney Transplant Patients: Gasometrical and Hemodynamical Study

INTRODUCTION: Hypothermia, defined as a decrease in core body temperature below 36°C, has a notable influence on hemodynamic variables during anesthesia, which is of great interest in perioperative medicine. Temperature regulation is crucial in anesthetic management because hypothermia can significantly impact the patient's cardiovascular functioning. Accidental (uncontrolled) hypothermia during anesthetic and surgical procedures carries considerable risks such as: Increases the incidence of surgical site infections, prolongs the effects of drugs administered during anesthesia, and disrupts normal coagulation, potentially increasing the risk of bleeding. For these reasons, body temperature regulation is a critical aspect to monitor and control during anesthesia. MATERIAL AND METHODS: A descriptive, observational, single-center, and retrospective study was carried out in patients undergoing a related living donor kidney transplant between June 2022-2023 at the Juarez Hospital in Mexico. All data were collected from the demographic sheets, laboratories and trans anesthetic sheets of the patient's file. The data was integrated into an Excel database and statistical processing was performed in SPSS or STATSm software. The statistical analysis was tested for normality according to Kolmogorov-Smirnov with Lilliefors correction, where it was found that the population has a normal or non-normal distribution. The Mann-Whitney U test was performed to compare the difference of the means between the two groups. A correlation was made with Kendall´s Tau coefficient; All statistical analyzes were performed with a value of p&lt;0.05, considering these significantly. RESULTS: Of the 65 transplanted patients between Jun 2023 and June 2024 only 28 have appropriate inclusion criteria. Of the remaining 28, 16 were female (57.14%) and 12 were male (42.8%) with an average age of recipients of 30.2430.46 ±11.45 years with a weight of 58.23 ±10.47 kg, height 154.20 ±15.32 cm. Gasometrical and Hemodynamic Values upon Reperfusion with a Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.41±0.05 (p=0.046); Arterial pH 7.40±0.04 (p=0.015); Venous Oxygen Saturation 68.2±9.74% (p = 0.039). Hemodynamic variables before reperfusion were: IC 3.67±1.77 lt/min/m2 (p=0.001); Stroke Volume 79.5±39.6 ml/beat (p=0.022), Oxygen Extraction 25.1±9.95% (p=0.001) and Myocardial Efficiency 0.28±0.06 (p=0.024); The gasometrical variables after reperfusion were: Venous pH 7.40±0.03; Arterial pH 7.380±0.04; Venous Oxygen Saturation 60.03±4.37%; The hemodynamic variables after reperfusion were: IC 2.88±0.48 liter/min/m2; Stroke Volume 65.4±16.01 ml/beat; Oxygen Extraction Rate 36.9±4.31% (p = 0.039) and Myocardial Efficiency 0.32±0.06 Gasometrical and Hemodynamic Values upon Reperfusion without Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.32±0.04 (p=0.012); Arterial pH 7.30±0.04 (p=0.019); Venous Oxygen Saturation 64.7±8.27% (p = 0.026). Hemodynamic variables before reperfusion were Cardiac Index 3.28±1.66 lt/min/m2 (p=0.006); Stroke Volume 72.39±45.44 ml/beat (p=0.029); Oxygen Extraction 29.11±9.65% (p=0.001) and Myocardial Efficiency 0.268±0.08 (p=0.022). The gasometrical variables after reperfusion were: Venous pH 7.33±0.04; Arterial pH 7.320±0.05; Venous Oxygen Saturation 58.593±5.41%. The hemodynamic variables after reperfusion were: Cardiac Index 2.75±0.69 liter/min/m2, Stroke Volume 59.05±18.81 ml/beat, Oxygen Extraction Rate 38.47±6.17% and Myocardial Efficiency 0.31±0.05. CONCLUSIONS: Understanding the behavior of blood gas and hemodynamic variables upon reperfusion in transplant patients is essential for adequate kidney graft survival. In these patients, the use of a hot forced air turbine improves the conditions under which said reperfusion is performed, impacting not only at the blood gas level (venous pH, arterial pH and venous oxygen saturation) but also at the hemodynamic level (cardiac index, stroke volume, myocardial efficiency The limitations of the study are heterogeneity of the etiologies of CKD, sample size, and volume status prior to the procedure. To date the published works are consistent with the literature.

Research progress of diagnostic and therapeutic value of carbon dioxide-derived indicators in patients with sepsis

Effectively assessing oxygen delivery and demand is one of the key targets for fluid resuscitation in sepsis. Clinical signs and symptoms, blood lactic acid levels, and mixed venous oxygen saturation (SvO2) or central venous oxygen saturation (ScvO2) all have their limitations. In recent years, these limitations have been overcome through the use of derived indicators from carbon dioxide (CO2) such as mixed veno-arterial carbon dioxide partial pressure difference (Pv-aCO2, PCO2 gap, or ΔPCO2), the ratio of mixed veno-arterial carbon dioxide partial pressure difference to arterial-mixed venous oxygen content difference (Pv-aCO2/Ca-vO2). Pv-aCO2, PCO2 gap or ΔPCO2 is not a purely anaerobic metabolism indicator as it is influenced by oxygen consumption. However, it reliably indicates whether blood flow is sufficient to carry CO2 from peripheral tissues to the lungs for clearance, thus reflecting the adequacy of cardiac output and metabolism. The Pv-aCO2/Ca-vO2 may serve as a marker of hypoxia. SvO2 and ScvO2 represent venous oxygen saturation, reflecting tissue oxygen utilization. When oxygen delivery decreases but tissues still require more oxygen, oxygen extraction rate usually increases to meet tissue demands, resulting in decreased SvO2 and ScvO2. But in some cases, even if the oxygen delivery rate and tissue utilization rate of oxygen are reduced, it may still lead to a decrease in SvO2 and ScvO2. Sepsis is a classic example where tissue oxygen utilization decreases due to factors such as microcirculatory dysfunction, even when oxygen delivery is sufficient, leading to decrease in SvO2 and ScvO2. Additionally, the solubility of CO2 in plasma is approximately 20 times that of oxygen. Therefore, during sepsis or septic shock, derived variables of CO2 may serve as sensitive markers for monitoring tissue perfusion and microcirculatory hemodynamics. Its main advantage over blood lactic acid is its ability to rapidly change and provide real-time monitoring of tissue hypoxia. This review aims to demonstrate the principles of CO2-derived variables in sepsis, assess the available techniques for evaluating CO2-derived variables during the sepsis process, and discuss their clinical relevance.

Changes in the Gasometric and Hemodynamic Profile upon Graft Reperfusion in Living Donor Kidney Transplant Patients

Introduction: In the field of medicine, the study of hemodynamics is fundamental to understanding the functioning of the cardiovascular system and its impact on tissue oxygenation. Within this context, crucial parameters such as mean systemic filling pressure (MSFP), cardiac output (CO) and oxygen extraction rate (EO2) play essential roles in regulating tissue perfusion and oxygen delivery to the lungs the vital organs. In the case of kidney transplant recipient patients, the interaction between these parameters acquires unique relevance, given the intimate relationship between cardiovascular function and the new implanted kidney. Material And Methods: Material And Methods: A descriptive, observational, single-center, and retrospective study was carried out undergoing living donor kidney transplant patients between June 2022-2023 at the Hospital Juarez de Mexico. Results: 54 patient records were examined, 24 with exclusion criteria. Remaining 30, 18 were female (60%) and 12 were male (40%); Receiver: Age 30.46±11.68 years; Weight: 59.93±11.87kg; Size: 156.20±18.74cm; Hemoglobin: 9.87±1.62g/dl. Prior hemodynamic values to reperfusion: CaO2 (arterial content) 13.44 ± 2.22, CvO2 (venous content) 9.07 ± 2.20, Da-vO2 (arterio-venous difference) 3.67 ± 1.48, CO (cardiac output) 5.65 ± 3.13, VS ( stroke volume) 76.05±41.73, SVR(systemic vascular resistance) 852.61±396.72, DO2(oxygen delivery) 770.89±444.07, VO2(oxygen consumption) 239.33±29.38, EO2(oxygen extraction) 26.83±9.82, PMSF (mean systemic filling pressure) 17.47±3.09 mm Hg with Student's T con values of p&lt;0.05 statistically significant; Hemodynamic values after reperfusion: CaO2 13.3±2.18, CvO2 8.11±1.61, Da-vO2 5.03±1.04, CO 4.57±1.26, VS 62.32±17.41, SVR 1265.97±419.41, DO2 621.66±150.83, VO2 239.33±29.38, EO2 37.62 ±5.28, PMSF 14.27±2.44 mm Hg with Student's T statistically significant values of p&lt;0.05. Conclusions: Undergoing kidney transplantation patients strategies that include the optimization of PMSF, CO and EO2 based on their determinants can be implemented to improve perfusion and oxygenation of kidney transplanted prior kidney graft reperfusion, which in turn contributes to longterm viability and improved quality of life for the transplant recipient.

In vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle through ultrasound-guided hybrid near-infrared spectroscopies

Objective. In this paper, we present a detailed in vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle (SCM), obtained through ultrasound-guided near-infrared time-domain and diffuse correlation spectroscopies. Approach. A total of sixty-five subjects (forty-nine females, sixteen males) among healthy volunteers and thyroid nodule patients have been recruited for the study. Their SCM hemodynamic (oxy-, deoxy- and total hemoglobin concentrations, blood flow, blood oxygen saturation and metabolic rate of oxygen extraction) and optical properties (wavelength dependent absorption and reduced scattering coefficients) have been measured by the use of a novel hybrid device combining in a single unit time-domain near-infrared spectroscopy, diffuse correlation spectroscopy and simultaneous ultrasound imaging. Main results. We provide detailed tables of the results related to SCM baseline (i.e. muscle at rest) properties, and reveal significant differences on the measured parameters due to variables such as side of the neck, sex, age, body mass index, depth and thickness of the muscle, allowing future clinical studies to take into account such dependencies. Significance. The non-invasive monitoring of the hemodynamics and metabolism of the sternocleidomastoid muscle during respiration became a topic of increased interest partially due to the increased use of mechanical ventilation during the COVID-19 pandemic. Near-infrared diffuse optical spectroscopies were proposed as potential practical monitors of increased recruitment of SCM during respiratory distress. They can provide clinically relevant information on the degree of the patient's respiratory effort that is needed to maintain an optimal minute ventilation, with potential clinical application ranging from evaluating chronic pulmonary diseases to more acute settings, such as acute respiratory failure, or to determine the readiness to wean from invasive mechanical ventilation.

In-situ oxygen extraction from TiO2 using laser thermal vacuum metallurgy

One of the greatest challenges for long-term human activities on the Moon is the development of in-situ resource utilization (ISRU) technologies, including in-situ oxygen extraction. In this study, a novel method called laser thermal vacuum metallurgy (LTVM) was proposed for oxygen extraction from lunar regolith, specifically using TiO2 as raw material. Firstly, the theoretical feasibility of oxygen production from TiO2 was elucidated through thermodynamic calculations. Subsequently, the impact of laser power density on the decomposition behavior of TiO2 was investigated. The results demonstrate that through the augmentation of laser power density to elevate temperatures, there is a substantial enhancement observed in both the pyrolysis and vaporization processes of TiO2. Under the conditions of a laser power density of 2.48 kW/cm2, the surface temperature of TiO2 can be maintained at approximately 2175 °C. The resulting pyrolysis products consist of Ti6O11 (8.2 ± 0.5 wt %), Ti5O9 (23.7 ± 0.6 wt %), Ti4O7 (10.9 ± 0.4 wt %), and Ti3O5 (57.2 ± 0.8 wt %). Further combining with the result of gas collection, the estimated oxygen extraction rate is approximately 43.3 L per kilogram of TiO2. Therefore, LTVM holds the potential to provide a new approach for in-situ oxygen extraction from titanium-containing lunar regolith on the Moon.

Assessment of oxygen extraction rate changes following red blood cell transfusion in the intensive care unit: a protocol for a prospective observational non-interventional study

IntroductionHaemoglobin transfusion thresholds have been used in the intensive care unit (ICU) to guide red blood cell transfusion (RBCT) decisions. Recent research has also focused on physiological indicators of tissue...

Lower baseline cerebral oxygen extraction and metabolic rate are associated with faster cognitive decline and brain atrophy over a longitudinal follow‐up period

AbstractBackgroundOxygen extraction fraction (OEF), cerebral blood flow (CBF), and cerebral metabolic rate of oxygen (CMRO2) are complexly interrelated. Low OEF and CMRO2 are promising early indicators of Alzheimer’s disease (AD) pathophysiology. To better understand how alterations in cerebral oxygen utilization relate to abnormal brain aging, we investigated baseline oxygen metabolism variables (OEF, CBF, CMRO2) in relation to longitudinal cognition and brain structure, and if these associations were different among individuals at genetic risk for sporadic AD (i.e., apolipoprotein E (APOE)‐ε4 carriers).MethodsVanderbilt Memory and Aging Project participants (n=244, 74±7 years, mean follow‐up=3.7 years) underwent serial neuropsychological testing and multimodal 3T brain MRI. We used T2‐relaxation‐under‐spin‐tagging to calculate OEF and pseudo‐continuous arterial spin‐labeling to assess grey matter CBF. CMRO2 was calculated as: CMRO2=OEF*CBF*arterial oxygen content. Linear mixed‐effects regression models related time x oxygen metabolism variable (one predictor per model) to longitudinal cognitive and brain MRI outcomes. Models were adjusted for baseline age, sex, race/ethnicity, education, Framingham Stroke Risk Profile, cognitive status, intracranial volume (for MRI outcomes), APOE‐ε4 status, and time. Models were repeated testing anAPOE‐ε4 status x oxygen metabolism variable x time interaction term.ResultsLower baseline OEF was associated with faster hippocampal atrophy (p=0.02). Lower baseline CBF was associated with faster cortical thinning in regions susceptible to AD‐related neurodegeneration (p=0.008). Lower baseline CMRO2 was associated with faster language decline (p=0.01) and hippocampal atrophy (p=0.01) and inferior lateral ventricle volume increase (reflecting faster atrophy of adjacent tissue; p=0.02). OEF interacted with APOE‐ε4 status on executive function (p=0.002), language (p=0.006), and visuospatial performances (p=0.02), and inferior lateral ventricle volume (p=0.007). CBF interacted with APOE‐ε4 status on executive function performance (p=0.0003). CMRO2 interacted with APOE‐ε4 status on temporal lobe volume (p=0.03). In stratified models, lower baseline OEF and CMRO2 tended to relate to faster brain health decline among APOE‐ε4 carriers.ConclusionsLower OEF, CBF, and CMRO2 are associated with worse brain health trajectories over a 4‐year follow‐up. Assessing oxygen metabolism variables in combination may provide more comprehensive insight into longitudinal brain aging and serve as an early biomarker of disease, particularly among older adults at genetic risk for AD.FundingT32‐AG058524, IIRG‐08‐88733, R01‐AG034962, R01‐NS100980

Kinetics of oxygen sorption-desorption processes in manganites of La0.7Sr0.3Mn0.9Fe0.1O3-δ composition

Based on the data of thermogravimetric analysis the values of the oxygen index (3-δ) in the manganite of the La0.7Sr0.3Mn0.9Fe0.1O3-δ composition, obtained by solid-phase reaction technique, have been calculated. The analysis of oxygen sorption-desorption curves showed that the processes of oxygen release and absorption at pO2 = 10 Pa and pO2 = 400 Pa are not reversible. The minima of the derivative dδ/dt = f (T) corresponding to the maxima of the oxygen extraction rate indicate the complex character of changes in the oxygen desorption rate from manganite. The decrease in the heating and cooling rate from 6.6 K/min to 2.6 K/min resulted in a significant change in the value ∆δ, indicating the dependence of anion mobility on the oxygen concentration in the magnet structure. It has been revealed that in the La0.7Sr0.3Mn0.9Fe0.1O3-δ manganite the oxygen desorption kinetics is well described by the exponential dependence on the Kramers model, which implies no return of desorbed oxygen to the sample. This model indicates the non-stationarity of the diffusion flux through the barrier during desorption of oxygen from samples. The calculation of the activation energy of oxygen desorption by the Merzhanov method at various partial pressures of oxygen has shown that at the initial stage of oxygen extraction from La0.7Sr0.3Mn0.9Fe0.1O3-δ, the activation energy of oxygen desorption has a minimum value (Еа = 103.7 kJ/mol at δ = 0.005) and as the concentration of oxygen vacancies increases, it rises reaching saturation (Еа = 134.3 kJ/mol at δ = 0.06). It is assumed that with an increase in the concentration of oxygen vacancies, an interaction occurs between them, followed by the processes of their ordering with the formation of associates.

Cardiovascular effects of intravenous morphine in anesthetized horse.

ObjectivesTo investigate whether morphine causes a change in mean arterial blood pressure (MAP) heart rate (HR) and oxygen extraction (OE) rate in healthy horses anesthetized with isoflurane and a dexmedetomidine infusion.Material and methodsThe study design was prospective clinical, randomized, blinded two groups including 33 horses. All horses were sedated with romifidine IV, and anesthesia was induced with midazolam IV and ketamine IV and maintained with isoflurane in oxygen and medical air and a dexmedetomidine infusion. As a baseline venous and arterial blood, HR and MAP were sampled. Thereafter either morphine 0.1 mg kg−1 IV or an equivalent volume of NaCl 0.9% IV was administered. HR and MAP were then further sampled for 5 min before venous and arterial blood was again sampled. OE was calculated based upon arterial and venous blood gas analysis. To evaluate the change in minimum MAP, mean HR, and OE, the differences between baseline and observation period values were further termed delta MAP, delta HR, and delta OE. Individual delta MAPs were normalized to the minimum baseline value and are reported as a percentage. Alpha was set to 0.05. Confidence intervals 95% (CI) were calculated for delta MAP, delta HR, and delta OE within groups, and for the difference between groups.ResultsThe 95% CIs for delta MAP (%), delta HR (min−1), and delta OE (mL/dL) in the morphine group were −20.5 to −9.0, 0.6 to 3.1, and −0.1 to 0.6 and in the placebo group were −17.4 to −10.1, 0.2 to 2.0, and −0.2 to 0.3, respectively. The 95% CI for the differences in delta MAP (%), delta HR (min−1), and delta OE (mL/dL) were −5.5 to 7.6, −2.3 to 0.7, and −0.7 to 0.2, respectively. The minimum MAP of one horse in the morphine group decreased around 50% between baseline and observation period with almost unchanged OE and HR.Conclusion and clinical relevanceThe effects of morphine 0.1 mg kg−1 IV on HR, MAP, and OE in healthy horses anesthetized with isoflurane and a CRI of dexmedetomidine are minimal.

The Clinical Efficacy and Possible Mechanism of Combination Treatment of Cerebral Ischemic Stroke with Ginkgo Biloba Extract and Low-Frequency Repetitive Transcranial Magnetic Stimulation

To study the effect of the combination treatment of ginkgo biloba extract and low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) on the oxidative stress and brain neurotransmitters of patients who had cerebral ischemic stroke (CIS). A retrospective analysis was conducted, and 93 CIS patients admitted to the Sichuan Academy of Medical Sciences/Sichuan Provincial People's Hospital from January 2018 to January 2020 were included in the study. They were divided into three groups, the regular treatment group (31 cases), the LF-rTMS group (31 cases), and the combination treatment group (31 cases). Patients in the regular treatment group were given the conventional drug therapy and exercise regimen. The LF-rTMS group received LF-rTMS therapy (for 20-30 min each time, 1 time/d and 5 times/week) in addition to the treatment given to the regular treatment group. The combination treatment group was given ginkgo biloba extract (intravenous drips, once per day) in addition to the treatment given to the LF-rTMS group. The treatment was given continuously for 4 weeks and comparison was made at the end of the 4-week treatment regarding the clinical efficacy, oxidative stress response, cerebral oxygen metabolism, and brain neurotransmitter as shown by the three groups. The treatment efficacy in the combination treatment group (96.77%) was higher than those of the LF-rTMS group (80.65%) and the regular treatment group (54.84%). The LF-rTMS group showed higher treatment efficacy than that of the regular group. The serum superoxide dismutase (SOD) of the combination treatment group was higher than that of the LF-rTMS group and that of the routine group, while the malondialdehyde (MDA) and endothelin-1 (ET-1) of the combination treatment group were lower than those of the LF-rTMS group and the regular treatment group ( P<0.05). The serum SOD of the LF-rTMS group was higher than that of the regular treatment group, while the MDA and ET-1 of the group was lower than those of the regular treatment group ( P<0.05). The arterial oxygen content (CaO 2), arterio-venous oxygen content difference (Ca-vO 2) and cerebral extraction rate of oxygen (CERO 2) in the combination treatment group were lower than those of the LF-rTMS group and the regular treatment group ( P<0.05). The levels of these three indicators of the LF-rTMS group were lower than those of the regular treatment group ( P<0.05). EEG frequencies of gamma-aminobutyric acid (GABA), 5-hydroxytryptamine (5-HT) and dopamine (DA) of the combination treatment group were higher than those of the LF-rTMS group and the regular treatment group, while the acetylcholine (Ach) EEG frequency of the combination treatment group was lower than that of the LF-rTMS group and regular treatment group ( P<0.05). The LF-rTMS group showed higher GABA, 5-HT and DA EEG frequencies than those of the regular treatment group, while the Ach EEG frequency of the group was lower than that of the regular treatment group ( P<0.05). All the patients were followed up for 6 months, and recurrence rate was lower in the combination treatment group (3.23%) than that of the LF-rTMS group (19.35%) and the regular treatment group (25.81%) ( P<0.05). The combination treatment of ginkgo biloba extract and LF-rTMS helped to improve the clinical outcome of CIS patients, which may be related to the inhibition of oxidative stress, improvement in cerebral oxygen metabolism, and regulation of brain neurotransmitter.

Sildenafil in endotoxin-induced pulmonary hypertension: an experimental study

BackgroundSepsis and septic shock still represent great challenges in critical care medicine. Sildenafil has been largely used in the treatment of pulmonary arterial hypertension, but its effects in sepsis are unknown. The aim of this study was to investigate the hypothesis that sildenafil can attenuate endotoxin-induced pulmonary hypertension in a porcine model of endotoxemia. MethodsTwenty pigs were randomly assigned to Control group (n.ß=.ß10), which received saline solution; or to Sildenafil group (n.ß=.ß10), which received sildenafil orally (100.ßmg). After 30.ßminutes, both groups were submitted to endotoxemia with intravenous bacterial lipopolysaccharide endotoxin (LPS) infusion (4.ß..g.kg-1.h-1) for 180.ßminutes. We evaluated hemodynamic and oxygenation functions, and also lung histology and plasma cytokine (TNF.., IL-1.., IL6, and IL10) and troponin I response. ResultsSignificant hemodynamic alterations were observed after 30.ßminutes of LPS continuous infusion, mainly in pulmonary arterial pressure (from Baseline 19.ß...ß2.ßmmHg to LPS30 52.ß...ß4.ßmmHg, p.ß<.ß0.05). There was also a significant decrease in PaO2/FiO2 (from Baseline 411.ß...ß29 to LPS180 334.ß...ß49, p.ß<.ß0.05). Pulmonary arterial pressure was significantly lower in the Sildenafil group (35.ß...ß4.ßmmHg at LPS30, p.ß<.ß0.05). The Sildenafil group also presented lower values of systemic arterial pressure. Sildenafil maintained oxygenation with higher PaO2/FiO2 and lower oxygen extraction rate than Control group but had no effect on intrapulmonary shunt. All cytokines and troponin increased after LPS infusion in both groups similarly. ConclusionSildenafil attenuated endotoxin-induced pulmonary hypertension preserving the correct heart function without improving lung lesions or inflammation.

Prevention of hemorrhage-induced renal vasoconstriction and hypoxia by angiotensin II type 1 receptor antagonism in pigs.

Angiotensin II (ANG II) is a potent vasoconstrictor and may reduce renal blood flow (RBF), causing renal hypoxia. Hypotensive hemorrhage elevates plasma ANG II levels and is associated with increased risk of acute kidney injury. We hypothesized that ANG II antagonism prevents renal vasoconstriction and hypoxia caused by hemorrhage. Pigs were anaesthetized, surgically prepared, and randomized to intravenous losartan (1.5 mg·kg-1·h-1, n = 8) or an equal volume of intravenous Ringer acetate (vehicle-treated, n = 8). Hemorrhage was induced by continuous aspiration of blood to reach and sustain mean arterial pressure of <50 mmHg for 30 min. Plasma ANG II levels, hemodynamics and oxygenation were assessed 60 min prehemorrhage, 30-min after the start of hemorrhage, and 60 min posthemorrhage. Erythropoietin mRNA was analyzed in cortical and medullary tissue sampled at the end of the experiment. Hypotensive hemorrhage increased plasma ANG II levels and decreased RBF and oxygen delivery in both groups. Losartan-treated animals recovered in RBF and oxygen delivery, whereas vehicle-treated animals had persistently reduced RBF and oxygen delivery. In accordance, renal vascular resistance increased over time post hemorrhage in vehicle-treated animals but was unchanged in losartan-treated animals. Renal oxygen extraction rate and cortical erythropoietin mRNA levels increased in the vehicle group but not in the losartan group. In conclusion, ANG II antagonism alleviates prolonged renal vasoconstriction and renal hypoxia in a large animal model of hypotensive hemorrhage.

Assessment of inner retinal oxygen metrics and thickness in a mouse model of inherited retinal degeneration

The retinal degeneration 1 (rd1) mouse is a well-established model of inherited retinal degeneration, displaying photoreceptor degeneration and retinal vasculature damage. The purpose of the current study was to determine alterations in the rate of oxygen delivery from retinal circulation (DO2), the rate of oxygen extraction from the retinal circulation for metabolism (MO2), and oxygen extraction fraction (OEF) in rd1 mice. The study was performed in a total of 18 wild type (WT) and 10 rd1 mice at both 3-weeks and 12-weeks of age. Retinal arterial and venous oxygen contents (O2A and O2V) were measured using phosphorescence lifetime imaging. Total retinal blood flow (TRBF) was determined by fluorescence and red-free imaging. DO2 and MO2 were determined as TRBF × O2A and TRBF × (O2A-O2V), respectively. OEF was calculated as MO2/DO2. The thickness of individual retinal layers was measured from histology sections and inner retina (IR) and total retina (TR) thickness were calculated. TRBF, DO2 and MO2 were lower in rd1 mice compared to WT mice (P ≤ 0.001), whereas OEF was not significantly different between rd1 and WT mice (P = 0.4). TRBF and DO2 were lower at 3-weeks of age compared to 12-weeks of age (P ≤ 0.01), while MO2 was not significantly different between age groups (P = 0.4) and OEF was higher at 3-weeks of age compared to 12-weeks of age (P = 0.003). Additionally, the outer and inner retinal cell layer thicknesses were decreased in rd1 mice at 12-weeks of age compared to both age-matched WT mice and rd1 mice at 3-weeks of age (P ≤ 0.02). MO2 was directly correlated with both IR and TR thickness (R ≥ 0.50; P ≤ 0.03, N = 20). The findings indicate that the rate oxygen is supplied by the retinal circulation is decreased and the reduction in oxygen extracted for metabolism is related to retinal cell layer thinning in rd1 mice.

Compromised Resting Cerebral Metabolism After Sport-Related Concussion: A Calibrated MRI Study

Use calibrated MRI to model baseline cerebrovascular physiology parameters and investigate whether changes in resting cerebral blood flow (CBF0) following sport-related concussion (SRC) are concordant with changes in resting and dynamic cerebral physiologic markers, within two weeks of the injury. Altered CBF0 in the acute phase post-concussion may contribute to neurobehavioral deficiencies, often reported weeks after the injury. However, in addition to changes in CBF0, little is known about other physiologic mechanisms that may be disturbed within the cerebrovasculature. The aim of this study was to assess whether changes in baseline perfusion following SRC were co-localized with changes in cerebral metabolic demand. Forty-two subjects (15 SRC patients 8.0 ± 4.6 days post-injury and 27 age-matched healthy control athletes) were studied cross-sectionally. CBF0, cerebrovascular reactivity (CVR), resting oxygen extraction (OEF0) and cerebral metabolic rate of oxygen consumption (CMRO2|0) were measured using a combination of hypercapnic and hyperoxic breathing protocols, and the biophysical model developed in calibrated MRI. Blood Oxygenation Level Dependent and Arterial Spin Labelling data were acquired simultaneously using a dual-echo arterial spin labelling sequence. SRC patients showed significant decreases in CBF0 spread across the grey-matter (p < 0.05, corrected), and these differences were also confounded by the effects of baseline end-tidal CO2 (p < 0.0001). Lower perfusion was co-localized with reductions in regional CMRO2|0 (p = 0.006) post-SRC, despite finding no group-differences in OEF0 (p = 0.800). Higher CVR within voxels showing differences in CBF0 was also observed in the SRC group (p = 0.001), compared to controls. Reductions in metabolic demand despite no significant changes in OEF0 suggests that hypoperfusion post-SRC may reflect compromised metabolic function after the injury. These results provide novel insight about the possible pathophysiologic mechanisms underlying concussion that may affect the clinical recovery of athletes after sport-related head injuries.

Cerebral Oxygenation and Autoregulation in Very Preterm Infants Developing IVH During the Transitional Period: A Pilot Study.

Background: The transitional period, defined as the first 72 h after preterm birth, is often characterized by a significant hemodynamic instability, which represents an important risk factor for such neurological complications of prematurity as intraventricular hemorrhage (IVH). The impairment of cerebral autoregulation plays a key role in the pathogenesis of IVH, whose incidence is highest during the transitional period. This pilot study aimed to evaluate whether patterns of cerebral autoregulation and oxygenation differ in relation to IVH development in very preterm infants during the transitional period.Methods: Infants <32 weeks' gestation were enrolled within 12 h from birth. A simultaneous monitoring of cerebral oxygenation (CrSO2) by near-infrared spectroscopy and of heart rate and peripheral oxygen saturation by pulse oximetry was performed over the first 72 h. Cerebral fractional oxygen extraction (cFTOE) and tissue oxygenation-heart rate reactivity index (TOHRx), which represents a marker of cerebrovascular reactivity, were calculated. Daily cranial and cardiac ultrasound scans were performed, in order to assess the hemodynamic status and to detect a possible IVH onset. CrSO2 and cFTOE, clustered on 6-hour epochs, were compared between infants who developed IVH during the study period and those who did not. A between-group comparison of TOHRx before and after IVH detection was also performed.Results: Twenty preterm infants with a median gestational age of 27 weeks (interquartile range, IQR: 25-30 weeks) and median birth weight of 895 g (IQR: 822-1208 g) were enrolled. Of these, 8 developed IVH. The median age at IVH detection was 40 h (IQR: 30-48 h). Pre-IVH TOHRx was significantly higher compared to matched control periods (p <0.001). CrSO2 was significantly lower from 12 to 30 h and from 42 h onwards in cases compared to controls; however, a temporary CrSO2 rise preceded IVH detection. Similarly, cFTOE was significantly higher in IVH infants from 12 to 30 h and from 48 to 72 h, with a transient decrease between the two periods.Conclusions: In preterm infants during the transitional period, the development of IVH is preceded by transient changes in cerebral oxygenation and oxygen extraction which, in turn, may underlie an early impairment of cerebral autoregulation. Larger studies are needed to confirm these preliminary findings.