Microcirculation-mediated preconditioning and intracellular hypothermia

Towards Non-Invasive Intravital Microscopy: Advantages of Using the Ear Lobe Instead of the Cremaster Muscle

Inflammation is essential in the protection of the organism and wound repair, but in cases of chronic inflammation can also cause microvasculature deterioration. Thus, inflammation monitorization studies are important to test potential therapeutics. The intravital microscopy (IVM) technique monitors leukocyte trafficking in vivo, being a commonly used procedure to report systemic conditions. Although the cremaster muscle, an established protocol for IVM, may affect the hemodynamics because of its surgical preparation, only male animals are used, and longitudinal studies over time are not feasible. Thinking how this impacts future studies, our aim is to understand if the IVM technique can be successfully performed using the ear lobe instead of the cremaster muscle. Elevated IL-1β plasmatic concentrations confirmed the systemic inflammation developed in a diabetic animal model, while the elevated number of adherent and rolling leukocytes in the ear lobe allowed for the same conclusion. Thus, this study demonstrates that albeit its thickness, the ear lobe protocol for IVM is efficient, non-invasive, more reliable, cost-effective and timesaving.

Asphyxia-Induced Bacterial Translocation in an Animal Experimental Model in Neonatal Piglets

BACKGROUND

The term "bacterial translocation" (BT) refers to the migration of bacteria or their products from the gastrointestinal tract to tissues located outside it, and may occur after intestinal ischemia-reperfusion injury. The term "endotoxin" is synonymous, and is used interchangeably with the term lipopolysaccharide (LPS). LPS, a component of Gram-negative gut bacteria, is a potent microbial virulence factor, that can trigger production of pro-inflammatory mediators, causing localized and systemic inflammation. The aim of this study is to investigate if neonatal asphyxia provokes BT and an increased concentration of LPS in an animal model of asphyxia in piglets.

METHODS

Twenty-one (21) newborn male Landrace/Large White piglets, 1-4 days old, were randomly allocated into three groups, Control (A), Asphyxia (B) and Asphyxia-Cardiopulmonary Resuscitation (CPR) (C). All animals were instrumented, anesthetized and underwent hemodynamic monitoring. In Group A, the animals were euthanized. In Group B, the endotracheal tube was occluded to cause asphyxia leading to cardiopulmonary arrest. In Group C, the animals were resuscitated after asphyxia and further monitored for 30'. Bacterial translocation was assessed by the measurement of endotoxin in blood from the portal vein and the aorta, and also by the measurement of endotoxin in mesenteric lymph nodes (MLNs) at euthanasia. The results are given as median (IQR) with LPS concentration in EU/mL.

RESULTS

BT was observed in all groups with minimum LPS concentration in the MLN and maximum concentration in the portal vein. LPS levels in the MLNs were higher in the Group B: 6.38 EU/mL (2.69-9.34) compared to the other groups (Group A: 2.1 EU/mL (1.08-2.52), Group C: 1.66 EU/mL (1.51-2.48), p = 0.012). The aorta to MLNs LPS difference (%) was lower in Group B: 0.13% (0.04-1.17), compared to Group A: 5.08% (2.2-10.7), and Group C: 3.42% (1.5-5.1)) (p = 0.042). The same was detected for portal to MLNs LPS difference (%) which was lower in Group B: 0.94% (0.5-3) compared to Group A: 4.9% (4-15), and Group C: 3.85% (1.5-5.1)) (p = 0.044).

CONCLUSIONS

Neonatal asphyxia can provoke ΒΤ and increased LPS concentration in blood and tissue located outside the gastrointestinal system.

Physiological features of cells and microvasculature under the local hypothermia influence

Hypothermia or cold therapy is the local or systemic application of cold for therapeutic purposes. Local application of cold is used to control inflammation: pain and swelling, hematoma and trismus reduction. Despite the frequent use of cooling in prosthodontic rehabilitation and in physical therapy, as evidenced by many reports in the literature, there is scientific documentation that suggests disadvantages of using this treatment in maxillofacial surgery and oral surgery. Also the clinical studies that have been carried out in maxillofacial surgery and oral surgery have been conducted in an empirical manner, which casts doubt on the results. In view of this, it is relevant to study the mechanisms of microcirculatory preconditioning and hypothermia. This physiological process is so interesting for the development of medical devices of controlled hardware hypothermia to prevent inflammatory symptoms at the stage of rehabilitation by targeting the vascular and cellular component of the inflammatory process in different areas of the human body. To date, the use of local hardware controlled hypothermia in various pathological conditions in humans is a topical trend in medicine. Microcirculatory bloodstream is directly related to temperature factors. Although there are concepts of vascular spasm or dilatation in the microcirculatory bloodstream during systemic hypothermia, there are no reliable data on the cellular and vascular reactions during local hypothermia. In this paper, a search for fundamental and current scientific work on the topic of cellular and vascular changes under the influence of hypothermia was conducted. The search for data revealed that the mechanisms of intracellular hypothermia are of particular interest for the development of therapeutic treatments after surgical interventions in areas with extensive blood supply. With this in mind, it is relevant to investigate several areas: the role of endothelium, glycocalyx and blood cells in microcirculatory-mediated preconditioning and intracellular hypothermia, and in the molecular mechanism that regulates these processes, whether they occur in the same way in all tissues.

Physiological features of cells and microvasculature under the local hypothermia influence

Hypothermia or cold therapy is the local or systemic application of cold for therapeutic purposes. Local application of cold is used to control inflammation: pain and swelling, hematoma and trismus reduction. Despite the frequent use of cooling in prosthodontic rehabilitation and in physical therapy, as evidenced by many reports in the literature, there is scientific documentation that suggests disadvantages of using this treatment in maxillofacial surgery and oral surgery. Also the clinical studies that have been carried out in maxillofacial surgery and oral surgery have been conducted in an empirical manner, which casts doubt on the results. In view of this, it is relevant to study the mechanisms of microcirculatory preconditioning and hypothermia. This physiological process is so interesting for the development of medical devices of controlled hardware hypothermia to prevent inflammatory symptoms at the stage of rehabilitation by targeting the vascular and cellular component of the inflammatory process in different areas of the human body. To date, the use of local hardware controlled hypothermia in various pathological conditions in humans is a topical trend in medicine. Microcirculatory bloodstream is directly related to temperature factors. Although there are concepts of vascular spasm or dilatation in the microcirculatory bloodstream during systemic hypothermia, there are no reliable data on the cellular and vascular reactions during local hypothermia. In this paper, a search for fundamental and current scientific work on the topic of cellular and vascular changes under the influence of hypothermia was conducted. The search for data revealed that the mechanisms of intracellular hypothermia are of particular interest for the development of therapeutic treatments after surgical interventions in areas with extensive blood supply. With this in mind, it is relevant to investigate several areas: the role of endothelium, glycocalyx and blood cells in microcirculatory-mediated preconditioning and intracellular hypothermia, and in the molecular mechanism that regulates these processes, whether they occur in the same way in all tissues.

Sinus bradycardia is associated with poor outcome in critically ill patients with COVID-19 due to the B.1.1.7 Lineage

The progress of COVID-19 from moderate to severe may be precipitous, while the characteristics of the disease are heterogenous. The aim of this study was to describe the development of sinus bradycardia in critically ill patients with COVID-19 and its association with outcome in outbreak due to the SARS-CoV-2 B.1.1.7 Lineage. We leveraged the multi-center SuPAR in Adult Patients With COVID-19 (SPARCOL) study and identified patients who required admission to intensive care unit (ICU). Inclusion criteria were: (a) adult (≥18 years old) patients hospitalized primarily for COVID-19; (b) a confirmed SARS-CoV-2 infection diagnosed through reverse transcriptase polymerase chain reaction test of nasopharyngeal or oropharyngeal samples; and (c) at least one blood sample collected at admission and stored for suPAR, hs-CRP, and ferritin testing. All patients had continuous heart rate monitoring during hospitalization. In total, 81 patients were included. Of them, 17 (21 %) and 64 (79 %) were intubated and admitted to the ICU during the first and second wave, respectively. Two (12 %) and 62 (97 %) developed bradycardia before ICU admission, respectively (p < 0.001). Patients with bradycardia had increased suPAR (p < 0.001) and hs-CRP level (p < 0.001). Infusion of isoprenaline and/or noradrenaline was necessary to maintain an adequate rate and peripheral perfusion in all patients. Mortality was significantly higher in patients with bradycardia (p < 0.001). In conclusion, bradycardia was associated with poor outcome. As B.1.1.7 variant strain is spreading more rapidly in many countries, our findings help in the identification of patients who may require early admission to ICU.

Metabolomics improves the histopathological diagnosis of asphyxial deaths: an animal proof-of-concept model

The diagnosis of mechanical asphyxia remains one of the most difficult issues in forensic pathology. Asphyxia ultimately results in cardiac arrest (CA) and, as there are no specific markers, the differential diagnosis of primitive CA and CA secondary to asphyxiation relies on circumstantial details and on the pathologist experience, lacking objective evidence. Histological examination is currently considered the gold standard for CA post-mortem diagnosis. Here we present the comparative results of histopathology versus those previously obtained by ¹H nuclear magnetic resonance (NMR) metabolomics in a swine model, originally designed for clinical purposes, exposed to two different CA causes, namely ventricular fibrillation and asphyxia. While heart and brain microscopical analysis could identify the damage induced by CA without providing any additional information on the CA cause, metabolomics allowed the identification of clearly different profiles between the two groups and showed major differences between asphyxiated animals with good and poor outcomes. Minute-by-minute plasma sampling allowed to associate these modifications to the pre-arrest asphyxial phase showing a clear correlation to the cellular effect of mechanical asphyxia reproduced in the experiment. The results suggest that metabolomics provides additional evidence beyond that obtained by histology and immunohistochemistry in the differential diagnosis of CA.

Effects of Diabetes on Microcirculation and Leukostasis in Retinal and Non-Ocular Tissues: Implications for Diabetic Retinopathy

Changes in retinal microcirculation are associated with the development of diabetic retinopathy (DR). However, it is unclear whether such changes also develop in capillary beds of other non-retinal tissues. Here, we investigated microcirculatory changes involving velocity of rolling neutrophils, adherence of neutrophils, and leukostasis during development of retinal vascular lesions in diabetes in other non-retinal tissues. Intravital microscopy was performed on post-capillary venules of cremaster muscle and ear lobe of mice with severe or moderate diabetes and compared to those of non-diabetic mice. Additionally, number and velocity of rolling leukocytes, number of adherent leukocytes, and areas of leukostasis were quantified, and retinal capillary networks were examined for acellular capillaries (AC) and pericyte loss (PL), two prominent vascular lesions characteristic of DR. The number of adherent neutrophils and areas of leukostasis in the cremaster and ear lobe post-capillary venules of diabetic mice was increased compared to those of non-diabetic mice. Similarly, a significant increase in the number of rolling neutrophils and decrease in their rolling velocities compared to those of non-diabetic control mice were observed and severity of diabetes exacerbated these changes. Understanding diabetes-induced microcirculatory changes in cremaster and ear lobe may provide insight into retinal vascular lesion development in DR.

Assessment of Post-Resuscitation Intestinal Injury and Timing of Bacterial Translocation in Swine Anaesthetized With Propofol-Based Total Intravenous Anaesthesia

Introduction and objectives Bacterial translocation (BT) is the passage of viable bacteria or endotoxins from the gastrointestinal lumen to extra-luminal tissues and is usually observed after intestinal ischaemia-reperfusion injury. The aim of this study was to investigate post-resuscitation BT after cardiac arrest and resuscitation in a swine anaesthetized with propofol-based total intravenous anaesthesia. Materials and methods Eighteen female Landrace/Large White piglets were randomly divided into control (CON), cardiac arrest (CA) and cardiac arrest-cardiopulmonary resuscitation (CA-CPR) groups. In the CON group, the animals were only monitored for two hours. In the CA group, the animals were not resuscitated and underwent necropsy immediately after cardiac arrest. In the CA-CPR group, the animals were resuscitated until the return of spontaneous circulation (ROSC) and were monitored for two hours. The animals of the CON and CA-CPR groups underwent necropsy 24 hours later. Bacterial translocation was assessed by blood and tissue cultures and endotoxin measurement in the portal and systemic circulation. Malondialdehyde content calculation and histological analysis of the intestine were performed in order to estimate ischemia and reperfusion (I/R) tissue damage. Results  Malondialdehyde content, an indicator of oxidative stress, was significantly higher in the CA-CPR group compared to the CA in homogenized ileum (p=0.016). Malondialdehyde content in homogenized colon revealed significantly higher levels in the CA-CPR group compared to the CON (p=0.004) and the CA group (p=0.016). We found significantly higher levels of portal endotoxin in the CA-CPR group compared to the CON (p=0.026) and the CA group (p=0.026). The number of positive mesenteric lymph nodes cultures for E. coli was greater in the CA-CPR group, followed by the CA and CON groups, although the difference was not significant (67%, 33%, and 33%, respectively; p=0.407). Conclusions Malondialdehyde content and portal endotoxin levels do not increase during the cardiac arrest interval, but only after CPR and ROSC. Although the number of positive MLNs cultures was greater in the CA-CPR animals, no statistically significant differences were observed between the three groups due to the short monitoring period.