Evaluation of microvascular endothelial function in patients with infective endocarditis using laser speckle contrast imaging and skin video-capillaroscopy: research proposal of a case control prospective study

Laser speckle contrast imaging to monitor microcirculation: An effective method to predict outcome in patients with sepsis and septic shock

Background: This study examines the microcirculation of patients with sepsis and septic shock using Laser Speckle Contrast Imaging (LSCI) technology, to enhance monitoring and predict outcomes of sepsis and septic shock. Methods: From 01 July 2021, to 31 January 2022, 44 patients diagnosed with septic shock and sepsis were included in the study, their clinical data were collected, and LSCI was used to monitor the mean peripheral blood flow perfusion index (PI). Results: The average peripheral blood flow PI of septic shock patients was significantly lower than that of septic patients, with a cutoff value of 26.25. The average peripheral blood flow PI negatively correlated with acute physiology and chronic health evaluation (APACHE) Ⅱ score (p = .01 < .05), sequential organ failure assessment (SOFA) score (p < .01), and lactic acid levels (p = .01 < .05). We report average peripheral blood flow no correlation with age, mean arterial pressure, body temperature, oxygen saturation, heart rate, and body mass index. There was no correlation with procalcitonin, C-reactive protein (CRP), red blood cell distribution width, or platelet distribution width (p > .05). PI significantly correlated with the group sepsis and septic shock (p < .001, r = -.865). And PI significantly correlated with the outcome or mortality (p = .007 < .05, r = -.398). The ROC curve was calculated for PI and the sensitivity was 81.3%, and the specificity was 75% when PI cutoff value chooses 20.88. Conclusion: LSCI technology successfully detected the fingertip microcirculation of patients with septic shock. LSCI can reliably differentiate patients with sepsis vs patients with septic shock. Additionally, the average peripheral blood PI negatively correlated with APACHE Ⅱ, SOFA score, and lactate acid levels, providing useful and supplementary information for the diagnosis and monitoring of septic shock. Trial registration: Chictr2100046761. Registered on May 28, 2021. Clinical Trial Registration: clinicaltrials.gov, identifier Chictr2100046761.

Blind spot in sepsis management - Tissue level changes in microcirculation

In sepsis cytokine-mediated inflammation, clotting cascade activation and glycocalyx shedding impair both function and structure of the microcirculation, compromising adequate tissue oxygenation/perfusion. Such mismatch results in "dysoxia", an imbalance in mitochondrial respiration.Microvessel injuries can be grouped into four types: cytotoxic oedema, micro-vessel heterogeneity, sluggish/absent flow, and focal anaemia. Recognition of such diversity in microcirculatory pathology, alongside with the implementation of novel biomarkers might reveal previously unobserved heterogeneity in adults diagnosed with sepsis. Early identification of distinct subtypes may help not only to better stratify disease severity but may also provide explanation to the often seen insufficient/absent response to resuscitative treatment. Experimental evidence suggests that impaired microcirculatory flow may correlate with organ dysfunction and mortality. Therefore, reliable/reproducible diagnostic tools, that provide real-time information about the dynamic state of the microcirculation, might be practice changers in managing the critically ill.The sublingual mucosa and the nailfolds provide easy access to microcirculation via hand-held, point-of-care devices. Accessing these windows, clinicians may recognise, understand and potentially correct the underlying tissue oxygenation/perfusion mismatch. This new clinical information might facilitate an individualised approach vs protocolised care aiming to administer the right balance of intravenous fluids/vasopressors, time/dose auxiliary treatment modalities and, most importantly, might also guide determining the optimal duration of resuscitation to avoid/minimise harm and maximise benefits in sepsis management. However, before every-day clinical use of such point-of-care microcameras, validation studies are needed to establish not only feasibility but reliability and reproducibility as well.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Age-related decline in peripheral vascular health predicts cognitive impairment

Preclinical studies demonstrate that generalized endothelial cell dysfunction and microvascular impairment are potentially reversible causes of age-related vascular cognitive impairment and dementia (VCID). The present study was designed to test the hypothesis that severity of age-related macro- and microvascular dysfunction measured in the peripheral circulation is an independent predictor of cognitive performance in older adults. In this study, we enrolled 63 healthy individuals into young (< 45 years old) and aged (> 65 years old) groups. We used principal component analysis (PCA) to construct a comprehensive peripheral vascular health index (VHI) encompassing peripheral microvascular reactivity, arterial endothelial function, and vascular stiffness, as a marker of aging-induced generalized vascular dysfunction. Peripheral macrovascular and microvascular endothelial function were assessed using flow-mediated dilation (FMD) and laser speckle contrast imaging tests. Pulse waveform analysis was used to evaluate the augmentation index (AIx), a measure of arterial stiffness. Cognitive function was measured using a panel of CANTAB cognitive tests, and PCA was then applied to generate a cognitive impairment index (CII) for each participant. Aged subjects exhibited significantly impaired macrovascular endothelial function (FMD, 5.6 ± 0.7% vs. 8.3 ± 0.6% in young, p = 0.0061), increased arterial stiffness (AIx 29.3 ± 1.8% vs 4.5 ± 2.6% in young, p < 0.0001), and microvascular dysfunction (2.8 ± 0.2 vs 3.4 ± 0.1-fold change of perfusion in young, p = 0.032). VHI showed a significant negative correlation with age (r = - 0.54, p < 0.0001) and CII significantly correlated with age (r = 0.79, p < 0.0001). VHI significantly correlated with the CII (r = - 0.46, p = 0.0003). A decline in peripheral vascular health may reflect generalized vascular dysfunction and predict cognitive impairment in older adults.

Short-term weight loss reverses obesity-induced microvascular endothelial dysfunction

Obesity is one of the major risk factors for cardiovascular diseases and its prevalence is increasing in all age groups, with the biggest impact observed in middle-aged and older adults. A critical mechanism by which obesity promotes vascular pathologies in these patients involves impairment of endothelial function. While endothelial dysfunction in large vessels promotes atherogenesis, obesity-induced microvascular endothelial dysfunction impairs organ perfusion and thereby is causally related to the pathogenesis of ischemic heart disease, chronic kidney disease, intermittent claudication, exercise intolerance, and exacerbates cognitive decline in aging. Reduction of weight via calorie-based diet and exercise in animal models of obesity results in significant improvement of endothelial function both in large vessels and in the microcirculation, primarily due to attenuation of oxidative stress and inflammation. Clinical data on the protective effects of weight loss on endothelial function is limited to studies of flow-mediated dilation assessed in brachial arteries. Currently, there is no guideline on testing the effects of different weight management strategies on microvascular endothelial function in obese patients. Here, we provide proof-of-concept that weight loss-induced improvement of microvascular endothelial function can be reliably assessed in the setting of a geriatric outpatient clinic using a fast, reproducible, non-invasive method: laser speckle contrast imaging-based measurement of endothelium-dependent microvascular responses during post-occlusive reactive hyperemia tests. Our study also provides initial evidence that short-term weight loss induced by consumption of a low-carbohydrate low-calorie diet can reverse microvascular endothelial dysfunction associated with obesity.