Disparities in access to and timing of interventional therapies for pulmonary embolism across the United States.

BACKGROUND: Interventional therapies (ITs) are an emerging treatment modality for pulmonary embolism (PE); however, the degree of racial, sex-based, and sociodemographic disparities in access and timing is unknown. OBJECTIVES: To investigate barriers to access and timing of ITs for PE across the United States. METHODS: A retrospective cohort study utilizing the Nationwide Inpatient Sample from 2016-2020 included adult patients with PE. The use of ITs (mechanical thrombectomy and catheter-directed thrombolysis) was identified via International Classification of Diseases 10th revision codes. Early IT was defined as procedure performed within the first 2 days after admission. RESULTS: A total of 27 805 273 records from the 2016-2020 Nationwide Inpatient Sample database were examined. There were 387 514 (1.4%) patients with PE, with 14 249 (3.6%) of them having undergone IT procedures (11 115 catheter-directed thrombolysis, 2314 thrombectomy, and 780 both procedures). After multivariate adjustment, factors associated with less use of IT included Black race (odds ratio [OR], 0.90; 95% CI, 0.86-0.94; P < .01), Hispanic race (OR, 0.73; 95% CI, 0.68-0.79; P < .01), female sex (OR, 0.88; 95% CI, 0.85-0.91; P < .01), treatment in a rural hospital (OR, 0.49; 95% CI, 0.44-0.54; P < .01), and lack of private insurance (Medicare OR, 0.77; 95% CI, 0.73-0.80; P < .01; Medicaid OR, 0.65; 95% CI, 0.61-0.69; P < .01; no coverage OR, 0.87; 95% CI, 0.82-0.93; P < .01). Among the patients who received IT, 11 315 (79%) procedures were conducted within 2 days of admission and 2934 (21%) were delayed. Factors associated with delayed procedures included Black race (OR, 1.12; 95% CI, 1.01-1.26; P = .04), Hispanic race (OR, 1.52; 95% CI, 1.28-1.80; P < .01), weekend admission (OR, 1.37; 95% CI, 1.25-1.51; P < .01), Medicare coverage (OR, 1.24; 95% CI, 1.10-1.40; P < .01), and Medicaid coverage (OR, 1.29; 95% CI, 1.12-1.49; P < .01). CONCLUSION: Significant racial, sex-based, and geographic barriers exist in overall access to IT for PE in the United States.

Impact of age on the host response to sepsis in a murine model of fecal-induced peritonitis.

INTRODUCTION: Despite older adults being more vulnerable to sepsis, most preclinical research on sepsis has been conducted using young animals. This results in decreased scientific validity since age is an independent predictor of poor outcome. In this study, we explored the impact of aging on the host response to sepsis using the fecal-induced peritonitis (FIP) model developed by the National Preclinical Sepsis Platform (NPSP). METHODS: C57BL/6 mice (3 or 12 months old) were injected intraperitoneally with rat fecal slurry (0.75 mg/g) or a control vehicle. To investigate the early stage of sepsis, mice were culled at 4 h, 8 h, or 12 h to investigate disease severity, immunothrombosis biomarkers, and organ injury. Mice received buprenorphine at 4 h post-FIP. A separate cohort of FIP mice were studied for 72 h (with buprenorphine given at 4 h, 12 h, and then every 12 h post-FIP and antibiotics/fluids starting at 12 h post-FIP). Organs were harvested, plasma levels of Interleukin (IL)-6, IL-10, monocyte chemoattract protein (MCP-1)/CCL2, thrombin-antithrombin (TAT) complexes, cell-free DNA (CFDNA), and ADAMTS13 activity were quantified, and bacterial loads were measured. RESULTS: In the 12 h time course study, aged FIP mice demonstrated increased inflammation and injury to the lungs compared to young FIP mice. In the 72 h study, aged FIP mice exhibited a higher mortality rate (89%) compared to young FIP mice (42%) (p < 0.001). Aged FIP non-survivors also exhibited a trend towards elevated IL-6, TAT, CFDNA, CCL2, and decreased IL-10, and impaired bacterial clearance compared to young FIP non-survivors. CONCLUSION: To our knowledge, this is the first study to investigate the impact of age on survival using the FIP model of sepsis. Our model includes clinically-relevant supportive therapies and inclusion of both sexes. The higher mortality rate in aged mice may reflect increased inflammation and worsened organ injury in the early stage of sepsis. We also observed trends in impaired bacterial clearance, increase in IL-6, TAT, CFDNA, CCL2, and decreased IL-10 and ADAMTS13 activity in aged septic non-survivors compared to young septic non-survivors. Our aging model may help to increase the scientific validity of preclinical research and may be useful for identifying mechanisms of age-related susceptibility to sepsis as well as age-specific treatment strategies.

Efficacy and Safety of Umbilical Cord-Derived Mesenchymal Stromal Cell Therapy in Preclinical Models of Sepsis: A Systematic Review and Meta-analysis.

BACKGROUND: In preclinical studies, mesenchymal stromal cells (MSCs), including umbilical cord-derived MSCs (UC-MSCs), demonstrate the ability to modulate numerous pathophysiological processes related to sepsis; however, a systematic synthesis of the literature is needed to assess the efficacy of UC-MSCs for treating sepsis. OBJECTIVE: To examine the effects of UC-MSCs on overall mortality (primary outcome) as well as on organ dysfunction, coagulopathy, endothelial permeability, pathogen clearance, and systemic inflammation (secondary outcomes) at prespecified time intervals in preclinical models of sepsis. METHODS: A systematic search was conducted on Embase, Ovid MEDLINE, and Web of Science up to June 20, 2023. Preclinical controlled studies using in vivo sepsis models with systemic UC-MSC administration were included. Meta-analyses were conducted and expressed as odds ratios (OR) and ratios of the weighted means with 95% CI for categorical and continuous data, respectively. Risk of bias was assessed with the SYRCLE tool. RESULTS: Twenty-six studies (34 experiments, n = 1258 animals) were included in this review. Overall mortality was significantly reduced with UC-MSC treatment as compared to controls (OR: 0.26, 95% CI: 0.18-0.36). At various prespecified time intervals, UC-MSCs reduced surrogate measures of organ dysfunction related to the kidney, liver, and lung; reduced coagulopathy and endothelial permeability; and enhanced pathogen clearance from multiple sites. UC-MSCs also modulated systemic inflammatory mediators. No studies were rated as low risk across all SYCLE domains. CONCLUSIONS: These results demonstrate the efficacy of UC-MSC treatment in preclinical sepsis models and highlight their potential as a therapeutic intervention for septic shock.

Protocol for co-producing a framework and integrated resource platform for engaging patients in laboratory-based research.

BACKGROUND: Patient engagement in research is the meaningful and collaborative interaction between patients and researchers throughout the research process. Patient engagement can help to ensure patient-oriented values and perspectives are incorporated into the development, conduct, and dissemination of research. While patient engagement is increasingly prevalent in clinical research, it remains relatively unrealized in preclinical laboratory research. This may reflect the nature of preclinical research, in which routine interactions or engagement with patients may be less common. Our team of patient partners and researchers has previously identified few published examples of patient engagement in preclinical laboratory research, as well as a paucity of guidance on this topic. Here we propose the development of a process framework to facilitate patient engagement in preclinical laboratory research. METHODS: Our team, inclusive of researchers and patient partners, will develop a comprehensive, empirically-derived, and stakeholder-informed process framework for 'patient engagement in preclinical laboratory research.' First, our team will create a 'deliberative knowledge space' to conduct semi-structured discussions that will inform a draft framework for preclinical patient engagement. Over the course of several sessions, we will identify actions, activities, barriers, and enablers (e.g. considerations and motivations for patient engagement in preclinical laboratory research, define roles of key players). The resulting draft process framework will be further populated with examples and refined through an international consensus-building Delphi survey with patients, researchers, and other collaborator organizations. We will then conduct pilot field tests to evaluate the framework with preclinical laboratory research groups paired with patient partners. These results will be used to create a refined framework enriched with real-world examples and considerations. All resources developed will be made available through an online repository. DISCUSSION: Our proposed process framework will provide guidance, best practices, and standardized procedures to promote patient engagement in preclinical laboratory research. Supporting and facilitating patient engagement in this setting presents an exciting new opportunity to help realize the important impact that patients can make.

Engaging patients as partners or collaborators in clinical research is becoming more common, but it is still new in preclinical research. Preclinical researchers work in laboratories on cell and animal experiments. They traditionally don't have frequent interactions with patients compared to their clinical research colleagues. Integrating patient engagement in preclinical laboratory research may help ensure that patient perspectives and values are considered. To help preclinical laboratory research align with patient-centred priorities we propose the development of a practical framework. This framework will facilitate patient engagement in preclinical laboratory research. To achieve this, we will first hold in-depth discussions with patient partners, researchers, and other collaborators to understand views on patient engagement in preclinical laboratory research. Together, we will identify key considerations to draft a framework, including motivations for patient engagement in preclinical laboratory research, and defining the roles of those who need to be involved. We will refine the framework through an international survey where we will collect feedback from researchers, patient partners, and other collaborators to make further improvements. The framework will then be tested and refined by preclinical laboratory teams inclusive of patient partners. The finalized framework and other resources to facilitate patient engagement in preclinical laboratory research will be hosted in a 'one-stop-shop' of online resources. Ultimately, this framework will enable partnerships between patients and researchers and provide a roadmap for patient engagement in preclinical laboratory research. This presents an exciting new opportunity for patients and researchers to collaborate and potentially improve translation of laboratory-based research.

Development and characterization of a fecal-induced peritonitis model of murine sepsis: results from a multi-laboratory study and iterative modification of experimental conditions.

BACKGROUND: Preclinical sepsis models have been criticized for their inability to recapitulate human sepsis and suffer from methodological shortcomings that limit external validity and reproducibility. The National Preclinical Sepsis Platform (NPSP) is a consortium of basic science researchers, veterinarians, and stakeholders in Canada undertaking standardized multi-laboratory sepsis research to increase the efficacy and efficiency of bench-to-bedside translation. In this study, we aimed to develop and characterize a 72-h fecal-induced peritonitis (FIP) model of murine sepsis conducted in two independent laboratories. The experimental protocol was optimized by sequentially modifying dose of fecal slurry and timing of antibiotics in an iterative fashion, and then repeating the experimental series at site 1 and site 2. RESULTS: Escalating doses of fecal slurry (0.5-2.5 mg/g) resulted in increased disease severity, as assessed by the modified Murine Sepsis Score (MSS). However, the MSS was poorly associated with progression to death during the experiments, and mice were found dead without elevated MSS scores. Administration of early antibiotics within 4 h of inoculation rescued the animals from sepsis compared with late administration of antibiotics after 12 h, as evidenced by 100% survival and reduced bacterial load in peritoneum and blood in the early antibiotic group. Site 1 and site 2 had statistically significant differences in mortality (60% vs 88%; p < 0.05) for the same dose of fecal slurry (0.75 mg/g) and marked differences in body temperature between groups. CONCLUSIONS: We demonstrate a systematic approach to optimizing a 72-h FIP model of murine sepsis for use in multi-laboratory studies. Alterations to experimental conditions, such as dose of fecal slurry and timing of antibiotics, have clear impact on outcomes. Differences in mortality between sites despite rigorous standardization warrants further investigations to better understand inter-laboratory variation and methodological design in preclinical studies.

The role of the microcirculation and integrative cardiovascular physiology in the pathogenesis of ICU-acquired weakness.

Skeletal muscle dysfunction after critical illness, defined as ICU-acquired weakness (ICU-AW), is a complex and multifactorial syndrome that contributes significantly to long-term morbidity and reduced quality of life for ICU survivors and caregivers. Historically, research in this field has focused on pathological changes within the muscle itself, without much consideration for their in vivo physiological environment. Skeletal muscle has the widest range of oxygen metabolism of any organ, and regulation of oxygen supply with tissue demand is a fundamental requirement for locomotion and muscle function. During exercise, this process is exquisitely controlled and coordinated by the cardiovascular, respiratory, and autonomic systems, and also within the skeletal muscle microcirculation and mitochondria as the terminal site of oxygen exchange and utilization. This review highlights the potential contribution of the microcirculation and integrative cardiovascular physiology to the pathogenesis of ICU-AW. An overview of skeletal muscle microvascular structure and function is provided, as well as our understanding of microvascular dysfunction during the acute phase of critical illness; whether microvascular dysfunction persists after ICU discharge is currently not known. Molecular mechanisms that regulate crosstalk between endothelial cells and myocytes are discussed, including the role of the microcirculation in skeletal muscle atrophy, oxidative stress, and satellite cell biology. The concept of integrated control of oxygen delivery and utilization during exercise is introduced, with evidence of physiological dysfunction throughout the oxygen delivery pathway - from mouth to mitochondria - causing reduced exercise capacity in patients with chronic disease (e.g., heart failure, COPD). We suggest that objective and perceived weakness after critical illness represents a physiological failure of oxygen supply-demand matching - both globally throughout the body and locally within skeletal muscle. Lastly, we highlight the value of standardized cardiopulmonary exercise testing protocols for evaluating fitness in ICU survivors, and the application of near-infrared spectroscopy for directly measuring skeletal muscle oxygenation, representing potential advancements in ICU-AW research and rehabilitation.

Sepsis: network pathophysiology and implications for early diagnosis.

Sepsis, a medical emergency, is the overwhelming host response to infection leading to organ failure. The pathophysiology of this heterogeneous disease includes an inflammatory response that stimulates a complex interaction between endothelial and complements with associated coagulation abnormalities. Despite a more comprehensive understanding of sepsis pathophysiology, there exists a translational gap to improve sepsis diagnosis clinically. Many of the proposed biomarkers to diagnose sepsis lack sufficient specificity and sensitivity to be used in routine clinical practice. There has also been a lack of progress in diagnostic tools due to the focus on the inflammatory pathway. Inflammation and coagulation are known to be linked to the innate immune response. Early immunothrombotic changes could result in the early switch from infection to sepsis and aid in sepsis diagnosis. This review integrates both preclinical and clinical studies that highlight sepsis pathophysiology providing a framework for how the development of immunothrombosis could be used as a starting point to investigate biomarkers for early sepsis diagnosis.

Sex-based analysis of treatment responses in animal models of sepsis: a preclinical systematic review protocol.

BACKGROUND: The importance of investigating sex- and gender-dependent differences has been recently emphasized by major funding agencies. Notably, the influence of biological sex on clinical outcomes in sepsis is unclear, and observational studies suffer from the effect of confounding factors. The controlled experimental environment afforded by preclinical studies allows for clarification and mechanistic evaluation of sex-dependent differences. We propose a systematic review to assess the impact of biological sex on baseline responses to disease induction as well as treatment responses in animal models of sepsis. Given the lack of guidance surrounding sex-based analyses in preclinical systematic reviews, careful consideration of various factors is needed to understand how best to conduct analyses and communicate findings. METHODS: MEDLINE and Embase will be searched (2011-present) to identify preclinical studies of sepsis in which any intervention was administered and sex-stratified data reported. The primary outcome will be mortality. Secondary outcomes will include organ dysfunction, bacterial load, and IL-6 levels. Study selection will be conducted independently and in duplicate by two reviewers. Data extraction will be conducted by one reviewer and audited by a second independent reviewer. Data extracted from included studies will be pooled, and meta-analysis will be conducted using random effects modeling. Primary analyses will be stratified by animal age and will assess the impact of sex at the following time points: pre-intervention, in response to treatment, and post-intervention. Risk of bias will be assessed using the SYRCLE's risk-of-bias tool. Illustrative examples of potential methods to analyze sex-based differences are provided in this protocol. DISCUSSION: Our systematic review will summarize the current state of knowledge on sex-dependent differences in sepsis. This will identify current knowledge gaps that future studies can address. Finally, this review will provide a framework for sex-based analysis in future preclinical systematic reviews. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42022367726.

Pharmacokinetics of small hyperbranched polyglycerols as an osmotic agent for peritoneal dialysis: Plasma exposure, organ distribution and excretion in rats.

BACKGROUND: Small hyperbranched polyglycerol (HPG) has been recently of interest for peritoneal dialysis, but its pharmacokinetics is barely understood. This study investigated the absorption, distribution and excretion of 1 and 3 kDa HPG. METHODS: Rats (naive, 5/6 nephrectomy (5/6 Nx) or bilateral nephrectomy (BNx)) received a single dose of 3H-labelled HPG-containing solutions intraperitoneally (IP) or intravenously (IV). Radioactivity in tissues, urine and faeces was counted using a scintillation counter. Pharmacokinetic parameters were calculated using WinNonlin software. RESULTS: During 8-h dwell with IP injected therapeutic dose of HPG-based hypertonic solutions, the plasma levels of 1 kDa HPG reached the peak at 2 h, followed by a decrease to the end, whereas 3 kDa HPG increased for the duration of the 8 h. At the experimental endpoint, the distribution of both sizes of HPG in major organs was minimal, whereas most of 1 kDa HPG was excreted via urine, and of 3 kDa remained in peritoneal cavity. The elimination of both 1 and 3 kDa HPG after either IP or IV administration was significantly delayed by 5/6 Nx or BNx as compared to naive controls. Further, 24-h faecal excretion of HPG (3 kDa) was <5% of injected dose that was not different between healthy and BNx rats. CONCLUSION: Data suggest size-dependent peritoneal absorption of osmotic HPG that are not specifically absorbed by any of the organs tested. The clearance of small HPG mainly depends on kidney excretion, implying the risk of HPG accumulation in patients with end-stage kidney disease who receive maintenance dialysis with HPG.

On the same page? A qualitative study protocol on collaboration in a multi-laboratory preclinical study.

INTRODUCTION: Medical advancements are slow to reach the patient bedside due to issues with knowledge translation from preclinical studies. Multi-laboratory preclinical studies are a promising strategy for addressing the methodological deficiencies that weaken the translational impact of single laboratory findings. However, multi-laboratory preclinical studies are rare and difficult, requiring strong collaboration to plan and execute a shared protocol. In multiteam systems such as these, collaboration is enhanced when members have cohesive ways of thinking about their goals and how to achieve them-that is, when they have "shared mental models". In this research project, we will examine how members of Canada's first multi-laboratory preclinical study build shared mental models and collaborate in the execution of their study. METHODS: Six independent labs in Canada will conduct a preclinical study using a common protocol. To investigate mental models and collaboration in this multiteam system we will conduct a longitudinal qualitative study involving interviews at four time points, team observation, and document analysis. We will analyze interview transcripts using deductive coding to produce a matrix analysis of mental model content over time and inductive coding to produce a thematic analysis of members' experiences of collaboration over time. We will also triangulate data sources to "tell the story" of teamwork, capturing events and contextual information that explain changes in mental models and collaboration over time. DISCUSSION: This study will be one of the most comprehensive longitudinal analyses of a real-world multiteam system, and the first within a preclinical laboratory setting. The results will contribute to our understanding of collaboration in multiteam systems, an organizational form increasingly used to tackle complex scientific and social problems. The results will also inform the implementation of future multi-laboratory preclinical studies, enhancing the likelihood of effective collaboration and improved 'bench to bedside' translation.

Continuous Determination of the Optimal Bispectral Index Value Based on Cerebrovascular Reactivity in Moderate/Severe Traumatic Brain Injury: A Retrospective Observational Cohort Study of a Novel Individualized Sedation Target.

BACKGROUND: We have sought to develop methodology for deriving optimal bispectral index (BIS) values (BISopt) for patients with moderate/severe traumatic brain injury, using continuous monitoring of cerebrovascular reactivity and bispectral electroencephalography. METHODS: Arterial blood pressure, intracranial pressure, and BIS (a bilateral measure that is associated with sedation state) were continuously recorded. The pressure reactivity index, optimal cerebral perfusion pressure (CPPopt), and BISopt were calculated. Using BIS values and the pressure reactivity index, a curve fitting method was applied to determine the minimum value for the pressure reactivity index thus giving the BISopt. RESULTS AND CONCLUSIONS: Identification of BISopt was possible in all of the patients, with both visual inspection of data and using our method of BISopt determination, demonstrating a similarity of median values of 44.62 (35.03-59.98) versus 48 (39.75-57.50) (p = 0.1949). Furthermore, our method outperformed common CPPopt curve fitting methods applied to BISopt with improved percent (%) yields on both the left side 52.1% (36.3-72.4%) versus 31.2% (23.0-48.9%) (p < 0.0001) and the right side 54.1% (35.95-75.9%) versus 33.5% (12.5-47.9%) (p < 0.0001). The BIS values and BISopt were compared with cerebral perfusion pressure, mean arterial pressure, and CPPopt. The results indicated that BISopt's impact on pressure reactivity was distinct from CPPopt, cerebral perfusion pressure, or mean arterial pressure. Real-time BISopt can be derived from continuous physiologic monitoring of patients with moderate/severe traumatic brain injury. This BISopt value appears to be unassociated with arterial blood pressure or CPPopt, supporting its role as a novel physiologic metric for evaluating cerebral autoregulation. BISopt management to optimize cerebrovascular pressure reactivity should be the subject of future studies in moderate/severe traumatic brain injury.

Capillary module haemodynamics and mechanisms of blood flow regulation in skeletal muscle capillary networks: Experimental and computational analysis.

The capillary module (CM), consisting of parallel capillaries from terminal arteriole to post-capillary venule, is classically considered to be the building block of complex capillary networks. In skeletal muscle, CMs form interconnected columns spanning thousands of microns, which we recently described as the capillary fascicle. However, detailed evaluation of CM haemodynamics has not been described, and may provide insight into mechanisms of blood flow regulation in the microcirculation. We used intravital videomicroscopy from resting extensor digitorum longus muscle in rats (n = 9 networks, 112 capillary modules), as well as dual-phase computational modelling of blood flow in simulated CM geometries. We found that the mean driving pressure across CMs was 3.236 ± 1.833 mmHg. Red blood cell (RBC) flow was independent of CM resistance, and the ratio of blood flow in adjacent modules was not correlated with their ratio of resistances. In simulated CM geometries, increases to driving pressure produced a direct linear increase to RBC and plasma flow, with no changes to RBC distribution; increases to arteriolar inflow haematocrit resulted in increased RBC flow, but with viscosity-dependent increases to CM resistance. CM RBC flow heterogeneity was higher than plasma flow heterogeneity in experimental data, in contrast to simulated geometries, suggesting that time-dependent flow variability may have important consequences for RBC distribution. In summary, these findings suggest that CMs are active participants in microvascular flow regulation, likely achieved through adjustments to CM driving pressure using pre- and post-capillary loci of flow control. Increases to CM viscosity may be important during the regulation of functional hyperaemia. KEY POINTS: The capillary module (CM), consisting of parallel capillaries from the arteriole to venule, is classically considered to be the building block of capillary networks in skeletal muscle. A detailed evaluation of module haemodynamics may provide insight into mechanisms of blood flow regulation in the microcirculation. Using experimental data from resting skeletal muscle in rats, as well as dual-phase computational models of blood flow, we analysed haemodynamic relationships and the impact of variations to boundary conditions on red blood cell and plasma distribution. We showed that driving pressure across CMs is low, and that simulated increases to inflow haematocrit have important viscosity-dependent effects on module resistance. We found that red blood cell flow was independent from module resistance, which strongly suggests the regulation of driving pressure at the level of the capillary module using pre- and post-capillary loci of flow control. These findings place CMs as central participants in microvascular flow regulation, with important consequences for disease and functional hyperaemia.

Integrated Dynamic Autonomic and Cardiovascular Regulation during Postural Transitions in Older Adults Living with Frailty: A Systematic Review Protocol.

Older adults often experience episodes of a sudden drop in blood pressure when standing, known as orthostatic hypotension (OH). OH is associated with an increased risk of life-threatening health problems, falls, and death. Although OH has been studied in older adults, the integrated dynamic autonomic and cardiovascular regulation during postural transitions in older adults with frailty remains scarce and poorly understood. The primary aim of this systematic review is to determine the association between how active (e.g., lie-to-stand) and passive (head-up tilt) postural transitions affect the dynamic integrated autonomic and cardiovascular regulatory responses, comparing older adults with different levels of frailty (non-frail, pre-frail, or frail). A second aim is to perform a meta-analysis to compare autonomic and cardiovascular responses during active postural transitions in non-frail, pre-frail, and frail older adults. The systematic review will be outlined according to the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols. The meta-analysis will generate estimates of the comparative autonomic and cardiovascular responses after active postural transitions in adults who are non-frail, pre-frail, and frail. This systematic review will provide critical information on how integrated dynamic autonomic and cardiovascular regulation occurs during postural transitions in older adults with different frailty statuses.

Near Infrared Spectroscopy for High-Temporal Resolution Cerebral Physiome Characterization in TBI: A Narrative Review of Techniques, Applications, and Future Directions.

Multimodal monitoring has been gaining traction in the critical care of patients following traumatic brain injury (TBI). Through providing a deeper understanding of the individual patient's comprehensive physiologic state, or "physiome," following injury, these methods hold the promise of improving personalized care and advancing precision medicine. One of the modalities being explored in TBI care is near-infrared spectroscopy (NIRS), given it's non-invasive nature and ability to interrogate microvascular and tissue oxygen metabolism. In this narrative review, we begin by discussing the principles of NIRS technology, including spatially, frequency, and time-resolved variants. Subsequently, the applications of NIRS in various phases of clinical care following TBI are explored. These applications include the pre-hospital, intraoperative, neurocritical care, and outpatient/rehabilitation setting. The utility of NIRS to predict functional outcomes and evaluate dysfunctional cerebrovascular reactivity is also discussed. Finally, future applications and potential advancements in NIRS-based physiologic monitoring of TBI patients are presented, with a description of the potential integration with other omics biomarkers.

Patient engagement in preclinical laboratory research: A scoping review.

BACKGROUND: 'Patient engagement' involves meaningful collaboration between researchers and 'patient partners' to co-create research. It helps ensure that research being conducted is relevant to its ultimate end-users. Although patient engagement within clinical research has been well documented, the prevalence and effects of patient engagement in translational preclinical laboratory research remain unclear. The aim of this scoping review is to present current patient engagement activities reported in preclinical laboratory research. METHODS: MEDLINE, Embase, and grey literature were systematically searched from inception to April 2021. Studies that described or investigated patient engagement in preclinical laboratory research were included. Patient engagement activities where patients (i.e. patients, family members, caregivers or community members) provided input, or consultation on at least one element of the research process were eligible for inclusion. Study characteristics and outcomes were extracted and organized thematically. FINDINGS: 32 reports were included (30 primary studies, 1 narrative review, and 1 researcher guide). Most studies engaged patients at the education or priority setting stages (n=26). The most frequently reported benefit of patient engagement was 'providing a mutual learning opportunity'. Reported barriers to patient engagement reflected concerns around 'differences in knowledge and research experience' and how this may challenge communication and limit meaningful collaboration. INTERPRETATION: Patient engagement is feasible and beneficial for preclinical laboratory research. Future work should focus on assessing the impacts of patient engagement in this area of research. FUNDING: None.

The Effects of Biological Sex on Sepsis Treatments in Animal Models: A Systematic Review and a Narrative Elaboration on Sex- and Gender-Dependent Differences in Sepsis.

Preclinical studies provide an opportunity to evaluate the relationship between sex and sepsis, and investigate underlying mechanisms in a controlled experimental environment. The objective of our systematic review was to assess the impact of biological sex on treatment response to fluid and antibiotic therapy in animal models of sepsis. Furthermore, we provide a narrative elaboration of sex-dependent differences in preclinical models of sepsis. DATA SOURCES: MEDLINE and Embase were searched from inception to March 16, 2020. STUDY SELECTION: All studies reporting sex-stratified data comparing antibiotics and/or fluid resuscitation with a placebo or no treatment arm in an in vivo model of sepsis were included. DATA EXTRACTION: Outcomes of interest were mortality (primary) and organ dysfunction (secondary). Risk of bias was assessed. Study selection and data extraction were conducted independently and in duplicate. DATA SYNTHESIS: The systematic search returned 2,649 unique studies, and two met inclusion criteria. Both studies used cecal ligation and puncture models with imipenem/cilastatin antibiotics. No eligible studies investigated fluids. In one study, antibiotic therapy significantly reduced mortality in male, but not female, animals. The other study reported no sex differences in organ dysfunction. Both studies were deemed to be at a high overall risk of bias. CONCLUSIONS: There is a remarkable and concerning paucity of data investigating sex-dependent differences in fluid and antibiotic therapy for the treatment of sepsis in animal models. This may reflect poor awareness of the importance of investigating sex-dependent differences. Our discussion therefore expands on general concepts of sex and gender in biomedical research and sex-dependent differences in key areas of sepsis research such as the cardiovascular system, immunometabolism, the microbiome, and epigenetics. Finally, we discuss current clinical knowledge, the potential for reverse translation, and directions for future studies. REGISTRATION: PROSPERO CRD42020192738.

National Preclinical Sepsis Platform: developing a framework for accelerating innovation in Canadian sepsis research.

Despite decades of preclinical research, no experimentally derived therapies for sepsis have been successfully adopted into routine clinical practice. Factors that contribute to this crisis of translation include poor representation by preclinical models of the complex human condition of sepsis, bias in preclinical studies, as well as limitations of single-laboratory methodology. To overcome some of these shortcomings, multicentre preclinical studies-defined as a research experiment conducted in two or more research laboratories with a common protocol and analysis-are expected to maximize transparency, improve reproducibility, and enhance generalizability. The ultimate objective is to increase the efficiency and efficacy of bench-to-bedside translation for preclinical sepsis research and improve outcomes for patients with life-threatening infection. To this end, we organized the first meeting of the National Preclinical Sepsis Platform (NPSP). This multicentre preclinical  research collaboration of Canadian sepsis researchers and stakeholders was established to study the pathophysiology of sepsis and accelerate movement of promising therapeutics into early phase clinical trials. Integrated knowledge translation and shared decision-making were emphasized to ensure the goals of the platform align with clinical researchers and patient partners. 29 participants from 10 independent labs attended and discussed four main topics: (1) objectives of the platform; (2) animal models of sepsis; (3) multicentre methodology and (4) outcomes for evaluation. A PIRO model (predisposition, insult, response, organ dysfunction) for experimental design was proposed to strengthen linkages with interdisciplinary researchers and key stakeholders. This platform represents an important resource for maximizing translational impact of preclinical sepsis research.

The capillary fascicle in skeletal muscle: Structural and functional physiology of RBC distribution in capillary networks.

KEY POINTS: The capillary module, consisting of parallel capillaries from arteriole to venule, is classically considered as the building block of complex capillary networks. In skeletal muscle, this structure fails to address how blood flow is regulated along the entire length of the synchronously contracting muscle fibres. Using intravital video microscopy of resting extensor digitorum longus muscle in rats, we demonstrated the capillary fascicle as a series of interconnected modules forming continuous columns that align naturally with the dimensions of the muscle fascicle. We observed structural heterogeneity for module topology, and functional heterogeneity in space and time for capillary-red blood cell (RBC) haemodynamics within a module and between modules. We found that module RBC haemodynamics were independent of module resistance, providing direct evidence for microvascular flow regulation at the level of the capillary module. The capillary fascicle is an updated paradigm for characterizing blood flow and RBC distribution in skeletal muscle capillary networks. ABSTRACT: Capillary networks are the fundamental site of oxygen exchange in the microcirculation. The capillary module (CM), consisting of parallel capillaries from terminal arteriole (TA) to post-capillary venule (PCV), is classically considered as the building block of complex capillary networks. In skeletal muscle, this structure fails to address how blood flow is regulated along the entire length of the synchronously contracting muscle fibres, requiring co-ordination from numerous modules. It has previously been recognized that TAs and PCVs interact with multiple CMs, creating interconnected networks. Using label-free intravital video microscopy of resting extensor digitorum longus muscle in rats, we found that these networks form continuous columns of linked CMs spanning thousands of microns, herein denoted as the capillary fascicle (CF); this structure aligns naturally with the dimensions of the muscle fascicle. We measured capillary-red blood cell (RBC) haemodynamics and module topology (n = 9 networks, 327 modules, 1491 capillary segments). The average module had length 481 µm, width 157 µm and 9.51 parallel capillaries. We observed structural heterogeneity for CM topology, and functional heterogeneity in space and time for capillary-RBC haemodynamics within a module and between modules. There was no correlation between capillary RBC velocity and lineal density. A passive inverse relationship between module length and haemodynamics was remarkably absent, providing direct evidence for microvascular flow regulation at the level of the CM. In summary, the CF is an updated paradigm for characterizing RBC distribution in skeletal muscle, and strengthens the theory of capillary networks as major contributors to the signal that regulates capillary perfusion.

Advances in translational imaging of the microcirculation.

The past few decades have seen an explosion in the development and use of methods for imaging the human microcirculation during health and disease. The confluence of innovative imaging technologies, affordable computing power, and economies of scale have ushered in a new era of "translational" imaging that permit us to peer into blood vessels of various organs in the human body. These imaging techniques include near-infrared spectroscopy (NIRS), positron emission tomography (PET), and magnetic resonance imaging (MRI) that are sensitive to microvascular-derived signals, as well as computed tomography (CT), optical imaging, and ultrasound (US) imaging that are capable of directly acquiring images at, or close to microvascular spatial resolution. Collectively, these imaging modalities enable us to characterize the morphological and functional changes in a tissue's microcirculation that are known to accompany the initiation and progression of numerous pathologies. Although there have been significant advances for imaging the microcirculation in preclinical models, this review focuses on developments in the assessment of the microcirculation in patients with optical imaging, NIRS, PET, US, MRI, and CT, to name a few. The goal of this review is to serve as a springboard for exploring the burgeoning role of translational imaging technologies for interrogating the structural and functional status of the microcirculation in humans, and highlight the breadth of current clinical applications. Making the human microcirculation "visible" in vivo to clinicians and researchers alike will facilitate bench-to-bedside discoveries and enhance the diagnosis and management of disease.