Echocardiographic surrogate of left ventricular stroke work in a model of brain stem death donors.

BACKGROUND: The commonest echocardiographic measurement, left ventricular ejection fraction, can not necessarily predict mortality of recipients following heart transplantation potentially due to afterload dependency. Afterload-independent left ventricular stroke work index (LVSWI) is alternatively recommended by the current guideline; however, pulmonary artery catheters are rarely inserted in organ donors in most jurisdictions. We propose a novel non-invasive echocardiographic parameter, Pressure-Strain Product (PSP), as a potential surrogate of catheter-based LVSWI. This study aimed to investigate if PSP could correlate with catheter-based LVSWI in an ovine model of brain stem death (BSD) donors. The association between PSP and myocardial mitochondrial function in the post-transplant hearts was also evaluated. METHODS: Thirty-one female sheep (weight 47 ± 5 kg) were divided into two groups; BSD (n = 15), and sham neurologic injury (n = 16). Echocardiographic parameters including global circumferential strain (GCS) and global radial strain (GRS) and pulmonary artery catheter-based LVSWI were simultaneously measured at 8-timepoints during 24-h observation. PSP was calculated as a product of GCS or GRS, and mean arterial pressure for PSPcirc or PSPrad, respectively. Myocardial mitochondrial function was evaluated following 6-h observation after heart transplantation. RESULTS: In BSD donor hearts, PSPcirc (n = 96, rho = .547, p < .001) showed the best correlation with LVSWI among other echocardiographic parameters. PSPcirc returned AUC of .825 to distinguish higher values of cardiomyocyte mitochondrial function (cut-off point; mean value of complex 1,2 O2 Flux) in post-transplant hearts, which was greater than other echocardiographic parameters. CONCLUSIONS: PSPcirc could be used as a surrogate of catheter-based LVSWI reflecting mitochondrial function.

Impact of Positive End-Expiratory Pressure and FiO2 on Lung Mechanics and Intrapulmonary Shunt in Mechanically Ventilated Patients with ARDS Due to COVID-19 Pneumonia.

Purpose: This study aimed to investigate the effects of inspired oxygen fraction (FiO2) and positive end-expiratory pressure (PEEP) on gas exchange in mechanically ventilated patients with COVID-19. Methods: Two FiO2 (100%, 40%) were tested at 3 decreasing levels of PEEP (15, 10, and 5 cmH2O). At each FiO2 and PEEP, gas exchange, respiratory mechanics, hemodynamics, and the distribution of ventilation and perfusion were assessed with electrical impedance tomography. The impact of FiO2 on the intrapulmonary shunt (delta shunt) was analyzed as the difference between the calculated shunt at FiO2 100% (shunt) and venous admixture at FiO2 40% (venous admixture). Results: Fourteen patients were studied. Decreasing PEEP from 15 to 10 cmH2O did not change shunt (24 [21-28] vs 27 [24-29]%) or venous admixture (18 [15-26] vs 23 [18-34]%) while partial pressure of arterial oxygen (FiO2 100%) was higher at PEEP 15 (262 [198-338] vs 256 [147-315] mmHg; P < .05). Instead when PEEP was decreased from 10 to 5 cmH2O, shunt increased to 36 [30-39]% (P < .05) and venous admixture increased to 33 [30-43]% (P < .05) and partial pressure of arterial oxygen (100%) decreased to 109 [76-177] mmHg (P < .05). At PEEP 15, administration of 100% FiO2 resulted in a shunt greater than venous admixture at 40% FiO2, ((24 [21-28] vs 18 [15-26]%, P = .005), delta shunt 5.5% (2.3-8.8)). Compared to PEEP 10, PEEP of 5 and 15 cmH2O resulted in decreased global and pixel-level compliance. Cardiac output at FiO2 100% resulted higher at PEEP 5 (5.4 [4.4-6.5]) compared to PEEP 10 (4.8 [4.1-5.5], P < .05) and PEEP 15 cmH2O (4.7 [4.5-5.4], P < .05). Conclusion: In this study, PEEP of 15 cmH2O, despite resulting in the highest oxygenation, was associated with overdistension. PEEP of 5 cmH2O was associated with increased shunt and alveolar collapse. Administration of 100% FiO2 was associated with an increase in intrapulmonary shunt in the setting of high PEEP. Trial registration: NCT05132933.

Physiological effects of PFAS exposure in seabird chicks: A multi-species study of thyroid hormone triiodothyronine, body condition and telomere length in South Western France.

There is growing evidence that poly and perfluoroalkyl substances (PFAS) exposure leads to the disruption of thyroid hormones including thyroxine (T4) and triiodothyronine (T3), and may affect telomeres, repetitive nucleotide sequences which protect chromosome ends. Many seabird species are long-lived top predators thus exhibit high contaminant levels, and PFAS-disrupting effects on their physiology have been documented especially in relation to the endocrine system in adults. On the contrary, studies on the developmental period (i.e., chicks), during which exposure to environmental contaminants may have a greater impact on physiological traits, remain scarce to this date. We carried out a multi-species study with the aim to assess whether and to which extent chicks of four gull species (herring gull, great and lesser black-backed gull, yellow-legged gull) in South Western France are contaminated by PFAS, and to bring further evidence about their potential physiological consequences. Linear PFOS showed concentrations of concern as it was generally >10 times higher than the other PFAS, and exceeded a threshold toxicity level (calculated from previous studies in birds) in almost all sampled chicks. Nonetheless, in herring gull male chicks, total T3 levels were significantly and negatively associated with perfluorodecanoate (PFDA) and perfluorododecanoate (PFDoDA) and positively associated with perfluorotetradecanoate (PFTeDA) in female chicks. Total T3 levels were also positively associated with PFDoDA in great black backed gull male chicks and with perfluorotridecanoate (PFTrDA) in lesser black backed gull chicks. In lesser and great black-backed gulls, both females and males showed significant negative associations between several PFAS and their body condition, and a positive association between telomere length and L-PFOS in the yellow-legged gull was also found. These results corroborate previous findings and need to be further explored as they suggest that PFAS may interfere with the physiological status of chicks during the developmental period, potentially inducing long-lasting consequences.

Donor heart ischemic time can be extended beyond 9 hours using hypothermic machine perfusion in sheep.

BACKGROUND: The global shortage of donor hearts available for transplantation is a major problem for the treatment of end-stage heart failure. The ischemic time for donor hearts using traditional preservation by standard static cold storage (SCS) is limited to approximately 4 hours, beyond which the risk for primary graft dysfunction (PGD) significantly increases. Hypothermic machine perfusion (HMP) of donor hearts has been proposed to safely extend ischemic time without increasing the risk of PGD. METHODS: Using our sheep model of 24 hours brain death (BD) followed by orthotopic heart transplantation (HTx), we examined post-transplant outcomes in recipients following donor heart preservation by HMP for 8 hours, compared to donor heart preservation for 2 hours by either SCS or HMP. RESULTS: Following HTx, all HMP recipients (both 2 hours and 8 hours groups) survived to the end of the study (6 hours after transplantation and successful weaning from cardiopulmonary bypass), required less vasoactive support for hemodynamic stability, and exhibited superior metabolic, fluid status and inflammatory profiles compared to SCS recipients. Contractile function and cardiac damage (troponin I release and histological assessment) was comparable between groups. CONCLUSIONS: Overall, compared to current clinical SCS, recipient outcomes following transplantation are not adversely impacted by extending HMP to 8 hours. These results have important implications for clinical transplantation where longer ischemic times may be required (e.g., complex surgical cases, transport across long distances). Additionally, HMP may allow safe preservation of "marginal" donor hearts that are more susceptible to myocardial injury and facilitate increased utilization of these hearts for transplantation.

Enhanced extracorporeal carbon dioxide removal by acidification and metabolic control.

BACKGROUND: Extracorporeal carbon dioxide removal (ECCO2R) promotes protective ventilation in patients with acute respiratory failure, but devices with high CO2 extraction capacity are required for clinically relevant impact. This study evaluates three novel low-flow techniques based on dialysate acidification, also combined with renal replacement therapy, and metabolic control. METHODS: Eight swine were connected to a low-flow (350 mL/min) extracorporeal circuit including a dialyzer with a closed-loop dialysate circuit, and two membrane lungs on blood (MLb) and dialysate (MLd), respectively. The following 2-hour steps were performed: 1) MLb-start (MLb ventilated); 2) MLbd-start (MLb and MLd ventilated); 3) HLac (lactic acid infusion before MLd); 4) HCl-NaLac (hydrochloric acid infusion before MLd combined with renal replacement therapy and reinfusion of sodium lactate); 5) HCl-ßHB-NaLac (hydrochloric acid infusion before MLd combined with renal replacement therapy and reinfusion of sodium lactate and sodium 3-hydroxybutyrate). Caloric and fluid inputs, temperature, blood glucose and arterial carbon dioxide pressure were kept constant. RESULTS: The total MLs CO2 removal in HLac (130±25 mL/min), HCl-NaLac (130±21 mL/min) and HCl-ßHB-NaLac (124±18 mL/min) were higher compared with MLbd-start (81±15 mL/min, P<0.05) and MLb-start (55±7 mL/min, P<0.05). Minute ventilation in HLac (4.3±0.9 L/min), HCl-NaLac (3.6±0.8 L/min) and HCl-ßHB-NaLac (3.6±0.8 L/min) were lower compared to MLb-start (6.2±1.1 L/min, P<0.05) and MLbd-start (5.8±2.1 L/min, P<0.05). Arterial pH was 7.40±0.03 at MLb-start and decreased only during HCl-ßHB-NaLac (7.35±0.03, P<0.05). No relevant changes in electrolyte concentrations, hemodynamics and significant adverse events were detected. CONCLUSIONS: The three techniques achieved a significant extracorporeal CO2 removal allowing a relevant reduction in minute ventilation with a sufficient safety profile.

A clinically relevant sheep model of orthotopic heart transplantation 24 h after donor brainstem death.

BACKGROUND: Heart transplantation (HTx) from brainstem dead (BSD) donors is the gold-standard therapy for severe/end-stage cardiac disease, but is limited by a global donor heart shortage. Consequently, innovative solutions to increase donor heart availability and utilisation are rapidly expanding. Clinically relevant preclinical models are essential for evaluating interventions for human translation, yet few exist that accurately mimic all key HTx components, incorporating injuries beginning in the donor, through to the recipient. To enable future assessment of novel perfusion technologies in our research program, we thus aimed to develop a clinically relevant sheep model of HTx following 24 h of donor BSD. METHODS: BSD donors (vs. sham neurological injury, 4/group) were hemodynamically supported and monitored for 24 h, followed by heart preservation with cold static storage. Bicaval orthotopic HTx was performed in matched recipients, who were weaned from cardiopulmonary bypass (CPB), and monitored for 6 h. Donor and recipient blood were assayed for inflammatory and cardiac injury markers, and cardiac function was assessed using echocardiography. Repeated measurements between the two different groups during the study observation period were assessed by mixed ANOVA for repeated measures. RESULTS: Brainstem death caused an immediate catecholaminergic hemodynamic response (mean arterial pressure, p = 0.09), systemic inflammation (IL-6 - p = 0.025, IL-8 - p = 0.002) and cardiac injury (cardiac troponin I, p = 0.048), requiring vasopressor support (vasopressor dependency index, VDI, p = 0.023), with normalisation of biomarkers and physiology over 24 h. All hearts were weaned from CPB and monitored for 6 h post-HTx, except one (sham) recipient that died 2 h post-HTx. Hemodynamic (VDI - p = 0.592, heart rate - p = 0.747) and metabolic (blood lactate, p = 0.546) parameters post-HTx were comparable between groups, despite the observed physiological perturbations that occurred during donor BSD. All p values denote interaction among groups and time in the ANOVA for repeated measures. CONCLUSIONS: We have successfully developed an ovine HTx model following 24 h of donor BSD. After 6 h of critical care management post-HTx, there were no differences between groups, despite evident hemodynamic perturbations, systemic inflammation, and cardiac injury observed during donor BSD. This preclinical model provides a platform for critical assessment of injury development pre- and post-HTx, and novel therapeutic evaluation.

Design and Rationale of a Prospective International Follow-Up Study on Intensive Care Survivors of COVID-19: The Long-Term Impact in Intensive Care Survivors of Coronavirus Disease-19-AFTERCOR.

Background: In a disease that has only existed for 18 months, it is difficult to be fully informed of the long-term sequelae of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Evidence is growing that most organ systems can be affected by the virus, causing severe disabilities in survivors. The extent of the aftermath will declare itself over the next 5-10 years, but it is likely to be substantial with profound socio-economic impact on society. Methods: This is an international multi-center, prospective long-term follow-up study of patients who developed severe coronavirus disease-2019 (COVID-19) and were admitted to Intensive Care Units (ICUs). The study will be conducted at international tertiary hospitals. Patients will be monitored from time of ICU discharge up to 24 months. Information will be collected on demographics, co-existing illnesses before ICU admission, severity of illness during ICU admission and post-ICU quality of life as well as organ dysfunction and recovery. Statistical analysis will consist of patient trajectories over time for the key variables of quality of life and organ function. Using latent class analysis, we will determine if there are distinct patterns of patients in terms of recovery. Multivariable regression analyses will be used to examine associations between baseline characteristics and severity variables upon admission and discharge in the ICU, and how these impact outcomes at all follow-up time points up to 2 years. Ethics and Dissemination: The core study team and local principal investigators will ensure that the study adheres to all relevant national and local regulations, and that the necessary approvals are in place before a site may enroll patients. Clinical Trial Registration:anzctr.org.au: ACTRN12620000799954.

Platelets and Matrix Metalloproteinases: A Bidirectional Interaction with Multiple Pathophysiologic Implications.

Platelets contain and release several matrix metalloproteinases (MMPs), a highly conserved protein family with multiple functions in organism defense and repair. Platelet-released MMPs as well as MMPs generated by other cells within the cardiovascular system modulate platelet function in health and disease. In particular, a normal hemostatic platelet response to vessel wall injury may be transformed into pathological thrombus formation by platelet-released and/or by locally generated MMPs. However, it is becoming increasingly clear that platelets play a role not only in hemostasis but also in immune response, inflammation and allergy, atherosclerosis, and cancer development, and MMPs seem to contribute importantly to this role. A deeper understanding of these mechanisms may open the way to novel therapeutic approaches to the inhibition of their pathogenic effects and lead to significant advances in the treatment of cardiovascular, inflammatory, and neoplastic disorders.

High levels of fluoroalkyl substances and potential disruption of thyroid hormones in three gull species from South Western France.

Per- and poly-fluoroalkyl substances (PFAS) raised increasing concerns over the past years due to their persistence and global distribution. Understanding their occurrence in the environment and their disruptive effect on the physiology of humans and wildlife remains a major challenge in ecotoxicological studies. Here, we investigate the occurrence of several carboxylic and sulfonic PFAS in 105 individuals of three seabird species (27 great black-backed gull Larus marinus; 44 lesser black-backed gull Larus fuscus graellsii; and 34 European herring gull Larus argentatus) from South western France. We further estimated the relationship between plasma concentrations of PFAS and i) the body condition of the birds and ii) plasma concentrations of thyroid hormone triiodothyronine (TT3). We found that great and lesser black-backed gulls from South Western France are exposed to PFAS levels comparable to highly contaminated species from other geographical areas, although major emission sources (i.e. related to industrial activities) are absent in the region. We additionally found that PFAS are negatively associated with the body condition of the birds in two of the studied species, and that these results are sex-dependent. Finally, we found positive associations between exposure to PFAS and TT3 in the great black-backed gull, suggesting a potential disrupting mechanism of PFAS exposure. Although only three years of data have been collected, we investigated PFAS trend over the study period, and found that great black-backed gulls document an increasing trend of plasma PFAS concentration from 2016 to 2018. Because PFAS might have detrimental effects on birds, French seabird populations should be monitored since an increase of PFAS exposure may impact on population viability both in the short- and long-term.

Noninvasive mechanical ventilation in the COVID-19 era: Proposal for a continuous positive airway pressure closed-loop circuit minimizing air contamination, oxygen consumption, and noise.

Noninvasive continuous positive airway pressure (NIV-CPAP) is effective in patients with hypoxemic respiratory failure. Building evidence during the COVID-19 emergency reported that around 50% of patients in Italy treated with NIV-CPAP avoided the need for invasive mechanical ventilation. Standard NIV-CPAP systems operate at high gas flow rates responsible for noise generation and inadequate humidification. Furthermore, open-configuration systems require a high concentration of oxygen to deliver the desired FiO2 . Concerns outlined the risk for aerosolization in the ambient air and the possible pressure drop in hospital supply pipes. A new NIV-CPAP system is proposed that includes automatic control of patient respiratory parameters. The system operates as a closed-loop breathing circuit that can be assembled, combining a sleep apnea machine with existing commercially available components. Analytical simulation of a breathing patient and simulation with a healthy volunteer at different FiO2 were performed. Inspired and expired oxygen fraction and inspired and expired carbon dioxide pressure were recorded at different CPAP levels with different oxygen delivery. Among the main findings, we report (a) a significant (up to 30-fold) reduction in oxygen feeding compared to standard open high flow NIV-CPAP systems, to assure the same FiO2 levels, and (b) a negligible production of the noise generated in ventilatory systems, and consequent minimization of patients' discomfort. The proposed NIV-CPAP circuit, reshaped in closed-loop configuration with the blower outside of the circuit, has the advantages of minimizing aerosol generation, environmental contamination, oxygen consumption, and noise to the patient. The system is easily adaptable and can be implemented using standard CPAP components.

Heart Transplantation From Brain Dead Donors: A Systematic Review of Animal Models.

Despite advances in mechanical circulatory devices and pharmacologic therapies, heart transplantation (HTx) is the definitive and most effective therapy for an important proportion of qualifying patients with end-stage heart failure. However, the demand for donor hearts significantly outweighs the supply. Hearts are sourced from donors following brain death, which exposes donor hearts to substantial pathophysiological perturbations that can influence heart transplant success and recipient survival. Although significant advances in recipient selection, donor and HTx recipient management, immunosuppression, and pretransplant mechanical circulatory support have been achieved, primary graft dysfunction after cardiac transplantation continues to be an important cause of morbidity and mortality. Animal models, when appropriate, can guide/inform medical practice, and fill gaps in knowledge that are unattainable in clinical settings. Consequently, we performed a systematic review of existing animal models that incorporate donor brain death and subsequent HTx and assessed studies for scientific rigor and clinical relevance. Following literature screening via the U.S National Library of Medicine bibliographic database (MEDLINE) and Embase, 29 studies were assessed. Analysis of included studies identified marked heterogeneity in animal models of donor brain death coupled to HTx, with few research groups worldwide identified as utilizing these models. General reporting of important determinants of heart transplant success was mixed, and assessment of posttransplant cardiac function was limited to an invasive technique (pressure-volume analysis), which is limitedly applied in clinical settings. This review highlights translational challenges between available animal models and clinical heart transplant settings that are potentially hindering advancement of this field of investigation.

Platelet-targeted pharmacologic treatments as anti-cancer therapy.

Platelets act as multifunctional cells participating in immune response, inflammation, allergy, tissue regeneration, and lymphoangiogenesis. Among the best-established aspects of a role of platelets in non-hemostatic or thrombotic disorders, there is their participation in cancer invasion and metastasis. The interaction of many different cancer cells with platelets leads to platelet activation, and on the other hand platelet activation is strongly instrumental to the pro-carcinogenic and pro-metastatic activities of platelets. It is thus obvious that over the last years a lot of interest has focused on the possible chemopreventive effect of platelet-targeted pharmacologic treatments. This article gives an overview of the platelet-targeted pharmacologic approaches that have been attempted in the prevention of cancer development, progression, and metastasis, including the application of anti-platelet drugs currently used for cardiovascular disease and of new and novel pharmacologic strategies. Despite the fact that very promising results have been obtained with some of these approaches in pre-clinical models, with the exclusion of aspirin, clinical evidence of a beneficial effect of anti-platelet agents in cancer is however still largely missing. Future studies with platelet-targeted drugs in cancer must carefully deal with design issues, and in particular with the careful selection of patients, and/or explore novel platelet targets in order to provide a solution to the critical issue of the risk/benefit profile of long-term anti-platelet therapy in the prevention of cancer progression and dissemination.

Endothelial and platelet function alterations in HIV-infected patients.

The HIV epidemic has huge dimensions: in 2009, 33.3million people worldwide, including 2.5million children, were affected by human immunodeficiency virus (HIV) infection. The introduction of Highly Active Anti-Retroviral Therapy (HAART) has significantly modified the course of HIV disease, with longer survival and improved quality of life, but it has simultaneously lead to the appearance of previously unrecognized complications, such as ischemic cardiovascular events. Many studies have shown a higher rate of premature atherosclerosis in patients with HIV infection, leading to coronary, cerebrovascular, or peripheral arterial disease. However, it is still debated whether cardiovascular complications are a consequence of HIV infection itself or of the long-term use of HAART. In particular, myocardial infarction has been suggested to be associated with the use of abacavir. Endothelial dysfunction and platelet activation are markers of atherosclerosis and of increased cardiovascular risk. Here we review the evidence that endothelial dysfunction and platelet alterations are associated with chronic HIV infection, the possible role of different HAARTs, and the possible pathophysiologic mechanisms. Potential therapeutic implications are also discussed.

The role of dityrosine formation in the crosslinking of CUT-2, the product of a second cuticlin gene of Caenorhabditis elegans.

A second cuticlin gene, cut-2, of the nematode Caenorhabditis elegans, has been isolated and its genomic and cDNA sequences determined. The gene codes for a component of cuticlin, the insoluble residue of nematode cuticles. Conceptual translation of cut-2 reveals a 231-amino acid secreted protein which, like CUT-1, begins with a putative signal peptide of 16 residues. The central part of the protein consists of 13 repetitions of a short hydrophobic motif, which is often degenerated with substitutions and deletions. Parts of this motif are present also in CUT-1 (Caenorhabditis elegans) as well as in several protein components of the larval cuticle and of the eggshell layers of various insects (Locusta migratoria, Ceratitis capitata and Drosophila species). These sequence similarities are related to the similar functions of these proteins: they are all components of extracellular insoluble protective layers. Immunolocalisation and transcription analysis suggest that CUT-2 contributes to the cuticles of all larval stages and that it is not stage-specific. Analysis by reverse transcriptase-PCR suggests that it is not stage-specific. Analysis by reverse transcriptase-PCR suggests that transcription is not continuous throughout larval development but occurs in peaks which precede the moults. Dityrosine has been detected in the cuticle of nematodes and of insects; formation of dityrosine bridges may be one of the cross-linking mechanisms contributing to the insolubility of cuticlins. Recombinant, soluble CUT-2 is shown to be an excellent substrate for an in vitro cross-linking reaction, catalysed by horseradish peroxidase in the presence of H2O2, which results in the formation of insoluble, high-molecular weight CUT-2 and of dityrosine.

Amphid defective mutant of Caenorhabditis elegans.

Studies are reported on a chemoreception mutant which arose in a mutator strain. The mutant sensory neurons do not stain with fluoresceine isothiocyanate (Dyf phenotype), hence the name, dyf-1, given to the gene it identifies. The gene maps on LGI, 0.4 map units from dpy-5 on the unc-11 side. The response of mutant worms to various repellents has been studied and shown to be partially altered. Other chemoreception based behaviors are less affected. The cilia of the sensory neurons of the amphid are shorter than normal and the primary defect may be in the capacity of the sheath cells to secrete the matrix material that fills the space between cilia in the amphid channel. Progress toward the molecular cloning of the gene is also reported. Relevant results from other laboratories are briefly reviewed.

cut-1 a Caenorhabditis elegans gene coding for a dauer-specific noncollagenous component of the cuticle.

We have molecularly identified a new gene of Caenorhabditis elegans that codes for a component of the cuticle. The gene has been physically mapped on LGII near the locus sqt-1. The structure and the sequence of the gene have been determined and antisera have been raised against parts of the protein produced as fusions in Escherichia coli. By transcription analysis, and by the use of specific antisera, we have determined that this gene is expressed specifically during dauer larva formation. In extracts of worms completing the dauer transformation the product of this gene migrates in sodium dodecyl sulfate acrylamide gels with an apparent molecular mass of 40 kDa. By immunofluorescence we have determined that it is a component of the cuticles of dauer larvae. It forms a ribbon approximately 2 microns wide running along the lateral lines underneath the alae. Once it is assembled in the cuticle the protein becomes insoluble even in the presence of strong detergents and reducing agents in a manner that is similar to that described for the noncollagenous, insoluble residue of nematode cuticles called cuticlins; therefore, we have named the gene cut-1 for cuticlin 1. cut-1 represents the first gene for a noncollagenous component of C. elegans cuticle that has been characterized molecularly.