Reproducibility of cerebral blood flow, oxygen metabolism, and lactate and N-acetyl-aspartate concentrations measured using magnetic resonance imaging and spectroscopy.

In humans, resting cerebral perfusion, oxygen consumption and energy metabolism demonstrate large intersubject variation regardless of methodology. Whether a similar large variation is also present longitudinally in individual subjects is much less studied, but knowing the time variance in reproducibility is important when designing and interpreting longitudinal follow-up studies examining brain physiology. Therefore, we examined the reproducibility of cerebral blood flow (CBF), global cerebral metabolic rate of oxygen (CMRO2), global arteriovenous oxygen saturation difference (A-V.O2), and cerebral lactate and N-acetyl-aspartate (NAA) concentrations measured using magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques through repeated measurements at 6 h, 24 h, 7 days and several weeks after initial baseline measurements in young healthy adults (N = 26, 13 females, age range 18-35 years). Using this setup, we calculated the correlation, limit of agreement (LoA) and within-subject coefficient of variation (CoVWS) between baseline values and the subsequent repeated measurements to examine the longitudinal variation in individual cerebral physiology. CBF and CMRO2 correlated significantly between baseline and all subsequent measurements. The strength of the correlations (R2) and reproducibility metrics (LoA and CoVWS) demonstrated the best reproducibility for the within-day measurements and generally declined with longer time between measurements. Cerebral lactate and NAA concentrations also correlated significantly for all measurements, except between baseline and the 7-day measurement for lactate. Similar to CBF and CMRO2, lactate and NAA demonstrated the best reproducibility for within-day repeated measurements. The gradual decline in reproducibility over time should be considered when designing and interpreting studies on brain physiology, for example, in the evaluation of treatment efficacy.

Effect of sevoflurane versus propofol on neutrophil-to-lymphocyte ratio in healthy individuals: a sub-study of a randomised crossover trial.

Background: Sevoflurane and propofol are commonly used drugs in general anaesthesia. However, their effects on perioperative immune function are incompletely understood. We hypothesised that sevoflurane and propofol differentially affect immune function in healthy individuals. Therefore, we investigated the effect of sevoflurane and propofol on neutrophil-to-lymphocyte ratio before, during, and after general anaesthesia. Methods: In this randomised crossover study, 19 healthy individuals underwent 2 h of general anaesthesia with either propofol or sevoflurane. After 4 weeks, anaesthesia was repeated using the other drug. Blood samples were obtained before, during, 1 h after, and 1 day after anaesthesia. The primary outcome was whole-blood neutrophil-to-lymphocyte ratio, and secondary outcomes were specific white blood cell differential counts. A linear mixed-effects model was used to estimate effect sizes. Results: The neutrophil-to-lymphocyte ratio was higher in the propofol compared with the sevoflurane group during anaesthesia, 2.8 (confidence interval [CI]: 2.3-3.3) vs 1.6 (CI: 1.1-2.1), and 1 day after anaesthesia, 2.6 (CI: 2.1-3.1) vs 1.9 (CI: 1.4-2.4). In all patients, we observed transient lymphopaenia during propofol anaesthesia, 1.1 × 109 cells × L-1 (CI: 0.9-1.4), compared with sevoflurane anaesthesia, 1.9 × 109 cells × L-1 (CI: 1.7-2.1). In addition, neutrophil counts were higher 1 day after propofol anaesthesia, 4.4 × 109 cells × L-1 (CI: 4.0-4.9), compared with sevoflurane anaesthesia, 3.5 × 109 cells × L-1 (CI: 3.1-4.0). We observed no differences in the remaining white blood cell subgroups. Conclusions: In healthy individuals undergoing general anaesthesia without surgery, the neutrophil-to-lymphocyte ratio was affected by the type of hypnotic used. Transient lymphopaenia was observed in all participants during propofol anaesthesia.

Neuroplasticity induced by general anaesthesia: study protocol for a randomised cross-over clinical trial exploring the effects of sevoflurane and propofol on the brain - A 3-T magnetic resonance imaging study of healthy volunteers.

BACKGROUND: Although used extensively worldwide, the effects of general anaesthesia on the human brain remain largely elusive. Moreover, general anaesthesia may contribute to serious conditions or adverse events such as postoperative cognitive dysfunction and delirium. To understand the basic mechanisms of general anaesthesia, this project aims to study and compare possible de novo neuroplastic changes induced by two commonly used types of general anaesthesia, i.e. inhalation anaesthesia by sevoflurane and intravenously administered anaesthesia by propofol. In addition, we wish to to explore possible associations between neuroplastic changes, neuropsychological adverse effects and subjective changes in fatigue and well-being. METHODS: This is a randomised, participant- and assessor-blinded, cross-over clinical trial. Thirty healthy volunteers (male:female ratio 1:1) will be randomised to general anaesthesia by either sevoflurane or propofol. Multimodal magnetic resonance imaging (MRI) of the brain will be performed before and after general anaesthesia and repeated after 1 and 8 days. Each magnetic resonance imaging session will be accompanied by cognitive testing and questionnaires on fatigue and well-being. After a wash-out period of 4 weeks, the volunteers will receive the other type of anaesthetic (sevoflurane or propofol), followed by the same series of tests. Primary outcomes: changes in T1-weighted 3D anatomy and diffusion tensor imaging. SECONDARY OUTCOMES: changes in resting-state functional magnetic resonance imaging, fatigue, well-being, cognitive function, correlations between magnetic resonance imaging findings and the clinical outcomes (questionnaires and cognitive function). Exploratory outcomes: changes in cerebral perfusion and oxygen metabolism, lactate, and response to visual stimuli. DISCUSSION: To the best of our knowledge, this is the most extensive and advanced series of studies with head-to-head comparison of two widely used methods for general anaesthesia. Recruitment was initiated in September 2019. TRIAL REGISTRATION: Approved by the Research Ethics Committee in the Capital Region of Denmark, ref. H-18028925 (6 September 2018). EudraCT and Danish Medicines Agency: 2018-001252-35 (23 March 2018). www.clinicaltrials.gov , ID: NCT04125121 . Retrospectively registered on 10 October 2019.

Dental caries and weight among children in Nuuk, Greenland, at school entry.

OBJECTIVE: To explore the possible association between weight class and prevalence of caries among children born 2005-2007, living in Nuuk, Greenland, at time of school entry. DESIGN: A cross-sectional register study based on data from electronic medical records(EMR) and oral health data from public health and dental care facilities. METHODS: Data from routine examinations of children at time of primary school entry, including height and weight, were obtained from the EMRs. Dental charts recording oral health and caries were collected from public dental healthcare service. The prevalence of caries was calculated as the proportion of included children with dft score (decayed and/or filled non-permanent teeth) ≥1. RESULTS: 55%(373/681) had relevant data recorded in EMRs and dental charts, and could be included in the study. The prevalence of dental caries was 57.1%(213/373). The prevalence of caries increased with higher weight class,but no statistically significant trend was observed(p=0.063). CONCLUSIONS: Increasing prevalence of caries with increasing weight class was observed in this study. A linear trend could not be confirmed statistically. The high prevalence of caries and overweight indicate the need for continued focus on preventative initiatives and monitoring. A combined strategy targeting both caries and overweight may be considered.

Clinical evaluation of synthetic aperture harmonic imaging for scanning focal malignant liver lesions.

The purpose of the study was to perform a clinical comparison of synthetic aperture sequential beamforming tissue harmonic imaging (SASB-THI) sequences with a conventional imaging technique, dynamic receive focusing with THI (DRF-THI). Both techniques used pulse inversion and were recorded interleaved using a commercial ultrasound system (UltraView 800, BK Medical, Herlev, Denmark). Thirty-one patients with malignant focal liver lesions (confirmed by biopsy or computed tomography/magnetic resonance) were scanned. Detection of malignant focal liver lesions and preference of image quality were evaluated blinded off-line by eight radiologists. In total, 2,032 evaluations of 127 image sequences were completed. The sensitivity (77% SASB-THI, 76% DRF-THI, p = 0.54) and specificity (71% SASB-THI, 72% DRF-THI, p = 0.67) of detection of liver lesions and the evaluation of image quality (p = 0.63) did not differ between SASB-THI and DRF-THI. This study indicates the ability of SASB-THI in a true clinical setting.