Cerebral autoregulation, brain injury, and the transitioning premature infant

Improvements in clinical management of the preterm infant have reduced the rates of the two most common forms of brain injury, such as severe intraventricular hemorrhage and white matter injury, both of which are contributory factors in the development of cerebral palsy. Nonetheless, they remain a persistent challenge and are associated with a significant increase in the risk of adverse neurodevelopment outcomes. Repeated episodes of ischemia–reperfusion represent a common pathway for both forms of injury, arising from discordance between systemic blood flow and the innate regulation of cerebral blood flow in the germinal matrix and periventricular white matter. Nevertheless, establishing firm hemodynamic boundaries, as a part of neuroprotective strategy, has challenged researchers. Existing measures either demonstrate inconsistent relationships with injury, as in the case of mean arterial blood pressure, or are not feasible for long-term monitoring, such as cardiac output estimated by echocardiography. These challenges have led some researchers to focus on the mechanisms that control blood flow to the brain, known as cerebrovascular autoregulation. Historically, the function of the cerebrovascular autoregulatory system has been difficult to quantify; however, the evolution of bedside monitoring devices, particularly near-infrared spectroscopy, has enabled new insights into these mechanisms and how impairment of blood flow regulation may contribute to catastrophic injury. In this review, we first seek to examine how technological advancement has changed the assessment of cerebrovascular autoregulation in premature infants. Next, we explore how clinical factors, including hypotension, vasoactive medications, acute and chronic hypoxia, and ventilation, alter the hemodynamic state of the preterm infant. Additionally, we examine how developmentally linked or acquired dysfunction in cerebral autoregulation contributes to preterm brain injury. In conclusion, we address exciting new approaches to the measurement of autoregulation and discuss the feasibility of translation to the bedside

Head position change is not associated with acute changes in bilateral cerebral oxygenation in stable preterm infants during the first 3 days of life

OBJECTIVE: Several recent intraventricular hemorrhage prevention bundles include midline head positioning to prevent potential disturbances in cerebral hemodynamics. We aimed to study the impact of head position change on regional cerebral saturations (SctO2) in preterm infants (< 30 weeks GA) during the first three days of life. STUDY DESIGN: Bilateral SctO2 was measured by near infrared spectroscopy. The infant's head was turned sequentially to each side from midline (baseline) in thirty-minute intervals while keeping the body supine. Bilateral SctO2 before and after each position change were compared using paired t-test. RESULTS: In relatively stable preterm infants (gestational age 26.5±1.7 weeks, birth weight 930±220g; n=20), bilateral SctO2 remained within normal range (71.1% - 75.3%) when the head was turned from midline position to either side. CONCLUSION: Stable preterm infants tolerated brief changes in head position from midline without significant alternation in bilateral SctO2; the impact on critically ill infants needs further evaluation

Wow, that portal vein is small: Preventing portal vein thrombosis in liver transplantation for small children

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107365/1/lt23865.pd

Response to Letter to the Editor

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/89557/1/j.1399-0012.2011.01437.x.pd

Gauge Symmetries of the N=2 String

We study the underlying gauge symmetry algebra of the $N=2$ string, which is broken down to a subalgebra in any spacetime background. For given toroidal backgrounds, the unbroken gauge symmetries (corresponding to holomorphic and antiholomorphic worldsheet currents) generate area-preserving diffeomorphism algebras of null 2-tori. A minimal Lie algebraic closure containing all the gauge symmetries that arise in this way, is the background--independent volume--preserving diffeomorphism algebra of the target Narain torus $T^{4,4}$. The underlying symmetries act on the ground ring of functions on $T^{4,4}$ as derivations, much as in the case of the $d=2$ string. A background--independent spacetime action valid for noncompact metrics is presented, whose symmetries are volume--preserving diffeomorphisms. Possible extensions to $N=2$ and $N=1$ heterotic strings are briefly discussed.Comment: 25 page

On String Field Theory and Effective Actions

A truncation of string field theory is compared with the duality invariant effective action of $D=4, N=4$ heterotic strings to cubic order. The three string vertex must satisfy a set of compatibility conditions. Any cyclic three string vertex is compatible with the $D=4, N=4$ effective field theory. The effective actions may be useful in understanding the non--polynomial structure and the underlying symmetry of covariant closed string field theory, and in addressing issues of background independence. We also discuss the effective action and string field theory of the $N=2$ string.Comment: 33 pages, IASSNS-HEP-92/3

An Experimental Approach for Detecting Brain Tumor from MRI Images using Digital Image Processing Techniques in MatLab

The Digital Image Process plays a very important role in Medical Research and processing the MRI images. Using image processing techniques the MRI images can be used to detect and analysis the tumor growing in brain. SAR images are the high resolution images which cannot be collected manually. In this work, we identified the SAR images randomly from web with different region inclusions. The comparative results are generated against the statistical observations obtained for existing and proposed approach. The parameters considered are the mean value, standard deviation, entropy etc. The comparative results show that the method has improved the accuracy of region classification

A RANDOMIZED CONTROLL TRIAL TO COMPARE THE EFFICACY OF SACCHAROMYCES BOULARDII, BACILLUS CLAUSII, AND LACTOBACILLUS RHAMNOSUS GG PREPARATION IN THE TREATMENT OF ACUTE DIARRHEA IN CHILDREN

Objective: Probiotics have been recommended as an adjunct to standard treatment of acute diarrhea but the choice of probiotics is unclear. The aim of study is to compare the efficacy of Saccharomyces boulardii, Bacillus clausii versus Lactobacillus rhamnosus in children with acute diarrhea and to expand the tolerability of S. boulardii, B. clausii versus L. rhamnosus GG in acute diarrhea. Methods: Hospital based Randomized Controlled Clinical trial (chit in box) carried out at the Department of Pediatrics, Mahatma Gandhi Hospital, Jaipur Rajasthan from January 2020 to June 2021. 120 Children were enrolled in the study and randomized to either Group A or Group B or Group C. Group A received S. boulardii, Group B received B. clausii and Group C received L. rhamnosus GG. Sample size was 40 samples for each group. Statistical analysis was done with the SPSS software. Results: There was statistically significant improvement in consistency observed in Group C as compared to Group A an Group B (p&lt;0.001). Significant higher cases (87.5%) were improved in Group C compare to Group B (67.5%), followed by Group A (65%). While all patients were observed well tolerated and accepted during the study. Conclusions: In our study, L. rhamnosus GG significantly reduce the frequency, improve the consistency of stools in diarrhea as compared to B. clausii and S. boulardii while tolerability of S. boulardii, B. clausii and L. rhamnosus GG was good with no adverse effect