A novel speckle-tracking echocardiography parameter assessing left ventricular afterload.

BACKGROUND: Left ventricular stroke work index (LVSWI) and afterload-related cardiac performance (ACP) consider left ventricular (LV) afterload and could be better prognosticators in septic cardiomyopathy. However, their invasive nature prevents their routine clinical applications. This study aimed to investigate (1) whether a proposed speckle-tracking echocardiography parameter, Pressure-Strain Product (PSP), can non-invasively predict catheter-based LVSWI, ACP and serum lactate in an ovine model of septic cardiomyopathy; and (2) whether PSP can distinguish the sub-phenotypes of acute respiratory distress syndrome (ARDS) with or without sepsis-like conditions. METHODS: Sixteen sheep with ARDS were randomly assigned to either (1) sepsis-like (n = 8) or (2) non-sepsis-like (n = 8) group. Each ARDS and sepsis-like condition was induced by intravenous infusion of oleic acid and lipopolysaccharide, respectively. Pulmonary artery catheter-based LVSWI (the product of stroke work index, mean arterial pressure and .0136), ACP (the percentage of cardiac output measured to cardiac output predicted as normal) and serum lactate were measured simultaneously with transthoracic echocardiography. Two PSP indices were calculated by multiplying the mean arterial blood pressure and either global circumferential strain (PSPcirc) or radial strain (PSPrad). RESULTS: PSPcirc showed a significant correlation with LVSWI (r2 = .66, p < .001) and ACP (r2 = .82, p < .001) in the sepsis-like group. Although PSP could not distinguish subphenotypes, PSPcirc predicted LVSWI (AUC .86) and ACP (AUC .88), and PSPrad predicted serum lactate (AUC .75) better than LV ejection fraction, global circumferential and radial strain. CONCLUSIONS: A novel PSP has the potential to non-invasively predict catheter-based LVSWI and ACP, and was associated with serum lactate in septic cardiomyopathy.

A novel echocardiographic parameter considering left ventricular afterload during V-A ECMO support.

BACKGROUND: Left ventricular stroke work index (LVSWI) and cardiac power index (CPI) account for the haemodynamic load of the left ventricle and are promising prognostic values in cardiogenic shock. However, accurately and non-invasively measuring these parameters during veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is challenging and potentially biased by the extracorporeal circulation. This study aimed to investigate, in an ovine model of cardiogenic shock, whether Pressure-Strain Product (PSP), a novel speckle-tracking echocardiography parameter, (1) can correlate with pressure-volume catheter-based LVSWI and CPI, and (2) can be load-independent during the flow modification of V-A ECMO. METHODS: Nine Dorset-cross ewes (51 ± 4 kg) were included. After cardiogenic shock was induced, full support V-A ECMO (X L/min based on 60 mL/kg/min) commenced. At seven time points during 24-h observation, echocardiographic parameters as well as pressure-volume catheter-based LVSWI and CPI were simultaneously measured with X and following X-1 L/min of ECMO flow. PSP was calculated by multiplying global circumferential strain or global radial strain, and mean arterial pressure, for PSPcirc or PSPrad, respectively. RESULTS: PSPcirc showed a stronger correlation with LVSWI (correlation coefficient, CC = .360, p < .001) and CPI (CC = .283, p < .001) than other echocardiographic parameters. The predictability of PSPcirc for pressure-volume catheter-based LVSWI (AUC .82) and CPI (AUC .80) was also higher than other echocardiographic parameters. No statistically significant differences were identified between the two ECMO flow variations in PSPcirc (p = .558). CONCLUSIONS: A novel echocardiographic parameter, PSP, may non-invasively predict pressure-volume catheter-based LVSWI and CPI in a load-independent manner in a cardiogenic shock supported by V-A ECMO.

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.

The effects of nitric oxide on coagulation and inflammation in ex vivo models of extracorporeal membrane oxygenation and cardiopulmonary bypass.

BACKGROUND: Extracorporeal life support (ECLS) has extensive applications in managing patients with acute cardiac and pulmonary failure. Two primary modalities of ECLS, cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO), include several similarities in their composition, complications, and patient outcomes. Both CPB and ECMO pose a high risk of thrombus formation and platelet activation due to the large surface area of the devices and bleeding due to system anticoagulation. Therefore, novel methods of anticoagulation are needed to reduce the morbidity and mortality associated with extracorporeal support. Nitric oxide (NO) has potent antiplatelet properties and presents a promising alternative or addition to anticoagulation with heparin during extracorporeal support. METHODS: We developed two ex vivo models of CPB and ECMO to investigate NO effects on anticoagulation and inflammation in these systems. RESULTS: Sole addition of NO as an anticoagulant was not successful in preventing thrombus formation in the ex vivo setups, therefore a combination of low-level heparin with NO was used. Antiplatelet effects were observed in the ex vivo ECMO model when NO was delivered at 80 ppm. Platelet count was preserved after 480 min when NO was delivered at 30 ppm. CONCLUSION: Combined delivery of NO and heparin did not improve haemocompatibility in either ex vivo model of CPB and ECMO. Anti-inflammatory effects of NO in ECMO systems have to be evaluated further.

Compromised right ventricular contractility in an ovine model of heart transplantation following 24 h donor brain stem death.

BACKGROUND: Heart failure is an inexorably progressive disease with a high mortality, for which heart transplantation (HTx) remains the gold standard treatment. Currently, donor hearts are primarily derived from patients following brain stem death (BSD). BSD causes activation of the sympathetic nervous system, increases endothelin levels, and triggers significant inflammation that together with potential myocardial injury associated with the transplant procedure, may affect contractility of the donor heart. We examined peri-transplant myocardial catecholamine sensitivity and cardiac contractility post-BSD and transplantation in a clinically relevant ovine model. METHODS: Donor sheep underwent BSD (BSD, n = 5) or sham (no BSD) procedures (SHAM, n = 4) and were monitored for 24h prior to heart procurement. Orthotopic HTx was performed on a separate group of donor animals following 24h of BSD (BSD-Tx, n = 6) or SHAM injury (SH-Tx, n = 5). The healthy recipient heart was used as a control (HC, n = 11). A cumulative concentration-effect curve to (-)-noradrenaline (NA) was established using left (LV) and right ventricular (RV) trabeculae to determine ß1-adrenoceptor mediated potency (-logEC50 [(-)-noradrenaline] M) and maximal contractility (Emax). RESULTS: Our data showed reduced basal and maximal (-)-noradrenaline induced contractility of the RV (but not LV) following BSD as well as HTx, regardless of whether the donor heart was exposed to BSD or SHAM. The potency of (-)-noradrenaline was lower in left and right ventricles for BSD-Tx and SH-Tx compared to HC. CONCLUSION: These studies show that the combination of BSD and transplantation are likely to impair contractility of the donor heart, particularly for the RV. For the donor heart, this contractile dysfunction appears to be independent of changes to ß1-adrenoceptor sensitivity. However, altered ß1-adrenoceptor signalling is likely to be involved in post-HTx contractile dysfunction.

Combined Mesenchymal Stromal Cell Therapy and Extracorporeal Membrane Oxygenation in Acute Respiratory Distress Syndrome. A Randomized Controlled Trial in Sheep.

Rationale: Mesenchymal stromal cell (MSC) therapy is a promising intervention for acute respiratory distress syndrome (ARDS), although trials to date have not investigated its use alongside extracorporeal membrane oxygenation (ECMO). Recent preclinical studies have suggested that combining these interventions may attenuate the efficacy of ECMO.Objectives: To determine the safety and efficacy of MSC therapy in a model of ARDS and ECMO.Methods: ARDS was induced in 14 sheep, after which they were established on venovenous ECMO. Subsequently, they received either endobronchial induced pluripotent stem cell-derived human MSCs (hMSCs) (n = 7) or cell-free carrier vehicle (vehicle control; n = 7). During ECMO, a low Vt ventilation strategy was employed in addition to protocolized hemodynamic support. Animals were monitored and supported for 24 hours. Lung tissue, bronchoalveolar fluid, and plasma were analyzed, in addition to continuous respiratory and hemodynamic monitoring.Measurements and Main Results: The administration of hMSCs did not improve oxygenation (PaO2/FiO2 mean difference = -146 mm Hg; P = 0.076) or pulmonary function. However, histological evidence of lung injury (lung injury score mean difference = -0.07; P = 0.04) and BAL IL-8 were reduced. In addition, hMSC-treated animals had a significantly lower cumulative requirement for vasopressor. Despite endobronchial administration, animals treated with hMSCs had a significant elevation in transmembrane oxygenator pressure gradients. This was accompanied by more pulmonary artery thromboses and adherent hMSCs found on explanted oxygenator fibers.Conclusions: Endobronchial hMSC therapy in an ovine model of ARDS and ECMO can impair membrane oxygenator function and does not improve oxygenation. These data do not recommend the safe use of hMSCs during venovenous ECMO.

The effect of hyperoxia on inflammation and platelet responses in an ex vivo extracorporeal membrane oxygenation circuit.

Use of extracorporeal membrane oxygenation (ECMO) is expanding, however, it is still associated with significant morbidity and mortality. Activation of inflammatory and innate immune responses and hemostatic alterations contribute to complications. Hyperoxia may play a role in exacerbating these responses. Nine ex vivo ECMO circuits were tested using fresh healthy human whole blood, with two oxygen levels: 21% inspired fraction of oxygen (FiO2 ; mild hyperoxia; n = 5) and 100% FiO2 (severe hyperoxia; n = 4). Serial blood samples were taken for analysis of platelet aggregometry, leukocyte activation, inflammatory, and oxidative stress markers. ECMO resulted in reduced adenosine diphosphate- (P < .05) and thrombin receptor activating peptide-induced (P < .05) platelet aggregation, as well as increasing levels of the neutrophil activation marker, neutrophil elastase (P = .013). Additionally, levels of the inflammatory chemokine interleukin-8 were elevated (P < .05) and the activity of superoxide dismutase, a marker of oxidative stress, was increased (P = .002). Hyperoxia did not augment these responses, with no significant differences detected between mild and severe hyperoxia. Our ex vivo model of ECMO revealed that the circuit itself triggers a pro-inflammatory and oxidative stress response, however, exposure to supra-physiologic oxygen does not amplify that response. Extended-duration studies and inclusion of an endothelial component could be beneficial in characterizing longer term changes.

Unintended Consequences: Fluid Resuscitation Worsens Shock in an Ovine Model of Endotoxemia.

RATIONALE: Fluid resuscitation is widely considered a life-saving intervention in septic shock; however, recent evidence has brought both its safety and efficacy in sepsis into question. OBJECTIVES: In this study, we sought to compare fluid resuscitation with vasopressors with the use of vasopressors alone in a hyperdynamic model of ovine endotoxemia. METHODS: Endotoxemic shock was induced in 16 sheep, after which they received fluid resuscitation with 40 ml/kg of 0.9% saline or commenced hemodynamic support with protocolized noradrenaline and vasopressin. Microdialysis catheters were inserted into the arterial circulation, heart, brain, kidney, and liver to monitor local metabolism. Blood samples were recovered to measure serum inflammatory cytokines, creatinine, troponin, atrial natriuretic peptide, brain natriuretic peptide, and hyaluronan. All animals were monitored and supported for 12 hours after fluid resuscitation. MEASUREMENTS AND MAIN RESULTS: After resuscitation, animals that received fluid resuscitation required significantly more noradrenaline to maintain the same mean arterial pressure in the subsequent 12 hours (68.9 mg vs. 39.6 mg; P = 0.04). Serum cytokines were similar between groups. Atrial natriuretic peptide increased significantly after fluid resuscitation compared with that observed in animals managed without fluid resuscitation (335 ng/ml [256-382] vs. 233 ng/ml [144-292]; P = 0.04). Cross-sectional time-series analysis showed that the rate of increase of the glycocalyx glycosaminoglycan hyaluronan was greater in the fluid-resuscitated group over the course of the study (P = 0.02). CONCLUSIONS: Fluid resuscitation resulted in a paradoxical increase in vasopressor requirement. Additionally, it did not result in improvements in any of the measured microcirculatory- or organ-specific markers measured. The increase in vasopressor requirement may have been due to endothelial/glycocalyx damage secondary to atrial natriuretic peptide-mediated glycocalyx shedding.

Effect of ex vivo extracorporeal membrane oxygenation flow dynamics on immune response.

BACKGROUND: Extracorporeal membrane oxygenation is a life-saving support for heart and/or lung failure patients. Despite technological advancement, abnormal physiology persists and has been associated with subsequent adverse events. These include thrombosis, bleeding, systemic inflammatory response syndrome and infection. However, the underlying mechanisms are yet to be elucidated. We aimed to investigate whether the different flow dynamics of extracorporeal membrane oxygenation would alter immune responses, specifically the overall inflammatory response, leukocyte numbers and activation/adhesion surface antigen expression. METHODS: An ex vivo model was used with human whole blood circulating at 37°C for 6 hours at high (4 L/minute) or low (1.5 L/minute) flow dynamics, with serial blood samples taken for analysis. RESULTS: During high flow, production of interleukin-1ß (p < 0.0001), interleukin-6 (p = 0.0075), tumour necrosis factor-α (p = 0.0013), myeloperoxidase (p < 0.0001) and neutrophil elastase (p < 0.0001) were significantly elevated over time compared to low flow, in particular at 6 hours. While the remaining assessments exhibited minute changes between flow dynamics, a consistent trend of modulation in leukocyte subset numbers and phenotype was observed at 6 hours. CONCLUSION: We conclude that prolonged circulation at high flow triggers a prominent pro-inflammatory cytokine response and activates neutrophil granule release, but further research is needed to better characterize the effect of flow during extracorporeal membrane oxygenation.

Mesenchymal stem cells may ameliorate inflammation in an ex vivo model of extracorporeal membrane oxygenation.

INTRODUCTION: Mesenchymal stem cells exhibit immunomodulatory properties which are currently being investigated as a novel treatment option for Acute Respiratory Distress Syndrome. However, the feasibility and efficacy of mesenchymal stem cell therapy in the setting of extracorporeal membrane oxygenation is poorly understood. This study aimed to characterise markers of innate immune activation in response to mesenchymal stem cells during an ex vivo simulation of extracorporeal membrane oxygenation. METHODS: Ex vivo extracorporeal membrane oxygenation simulations (n = 10) were conducted using a commercial extracorporeal circuit with a CO2-enhanced fresh gas supply and donor human whole blood. Heparinised circuits (n = 4) were injected with 40 × 106-induced pluripotent stem cell-derived human mesenchymal stem cells, while the remainder (n = 6) acted as controls. Simulations were maintained, under physiological conditions, for 240 minutes. Circuits were sampled at 15, 30, 60, 120 and 240 minutes and assessed for levels of interleukin-1ß, interleukin-6, interleukin-8, interleukin-10, tumour necrosis factor-α, transforming growth factor-ß1, myeloperoxidase and α-Defensin-1. In addition, haemoglobin, platelet and leukocyte counts were performed. RESULTS: There was a trend towards reduced levels of pro-inflammatory cytokines in mesenchymal stem cell-treated circuits and a significant increase in transforming growth factor-ß1. Blood cells and markers of neutrophil activation were reduced in mesenchymal stem cell circuits during the length of the simulation. As previously reported, the addition of mesenchymal stem cells resulted in a reduction of flow and increased trans-oxygenator pressures in comparison to controls. CONCLUSIONS: The addition of mesenchymal stem cells during extracorporeal membrane oxygenation may cause an increase in transforming growth factor-ß1. This is despite their ability to adhere to the membrane oxygenator. Further studies are required to confirm these findings.

Inflammation and lung injury in an ovine model of fluid resuscitated endotoxemic shock.

BACKGROUND: Sepsis is a multi-system syndrome that remains the leading cause of mortality and critical illness worldwide, with hemodynamic support being one of the cornerstones of the acute management of sepsis. We used an ovine model of endotoxemic shock to determine if 0.9% saline resuscitation contributes to lung inflammation and injury in acute respiratory distress syndrome, which is a common complication of sepsis, and investigated the potential role of matrix metalloproteinases in this process. METHODS: Endotoxemic shock was induced in sheep by administration of an escalating dose of lipopolysaccharide, after which they subsequently received either no fluid bolus resuscitation or a 0.9% saline bolus. Lung tissue, bronchoalveolar fluid (BAL) and plasma were analysed by real-time PCR, ELISA, flow cytometry and immunohistochemical staining to assess inflammatory cells, cytokines, hyaluronan and matrix metalloproteinases. RESULTS: Endotoxemia was associated with decreased serum albumin and total protein levels, with activated neutrophils, while the glycocalyx glycosaminoglycan hyaluronan was significantly increased in BAL. Quantitative real-time PCR studies showed higher expression of IL-6 and IL-8 with saline resuscitation but no difference in matrix metalloproteinase expression. BAL and tissue homogenate levels of IL-6, IL-8 and IL-1ß were elevated. CONCLUSIONS: This data shows that the inflammatory response is enhanced when a host with endotoxemia is resuscitated with saline, with a comparatively higher release of inflammatory cytokines and endothelial/glycocalyx damage, but no change in matrix metalloproteinase levels.

Evidence of altered haemostasis in an ovine model of venovenous extracorporeal membrane oxygenation support.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) is a life-saving modality used in the management of cardiopulmonary failure that is refractory to conventional medical and surgical therapies. The major problems clinicians face are bleeding and clotting, which can occur simultaneously. To discern the impact of pulmonary injury and ECMO on the host's haemostatic response, we developed an ovine model of smoke-induced acute lung injury (S-ALI) and ECMO. The aims of this study were to determine if the ECMO circuit itself altered haemostasis and if this was augmented in a host with pulmonary injury. METHODS: Twenty-seven South African meat merino/Border Leicester Cross ewes underwent instrumentation. Animals received either sham injury (n = 12) or S-ALI (n = 15). Control animal groups consisted of healthy controls (ventilation only for 24 h) (n = 4), ECMO controls (ECMO only for 24 h) (n = 8) and S-ALI controls (S-ALI but no ECMO for 24 h) (n = 7). The test group comprised S-ALI sheep placed on ECMO (S-ALI + ECMO for 24 h) (n = 8). Serial blood samples were taken for rotational thromboelastometry, platelet aggregometry and routine coagulation laboratory tests. Animals were continuously monitored for haemodynamic, fluid and electrolyte balances and temperature. Pressure-controlled intermittent mandatory ventilation was used, and mean arterial pressure was augmented by protocolised use of pressors, inotropes and balanced fluid resuscitation to maintain mean arterial pressure >65 mmHg. RESULTS: Rotational thromboelastometry, platelet aggregometry and routine coagulation laboratory tests demonstrated that S-ALI and ECMO independently induced changes to platelet function, delayed clot formation and reduced clot firmness. This effect was augmented with the combination of S-ALI and ECMO, with evidence of increased collagen-induced platelet aggregation as well as changes in factor VIII (FVIII), factor XII and fibrinogen levels. CONCLUSIONS: The introduction of an ECMO circuit itself increases collagen-induced platelet aggregation, decreases FVIII and von Willebrand factor, and induces a transient decrease in fibrinogen levels and function in the first 24 h. These changes to haemostasis are amplified when a host with a pre-existing pulmonary injury is placed on ECMO. Because patients are often on ECMO for extended periods, longer-duration studies are required to characterise ECMO-induced haemostatic changes over the long term. The utility of point-of-care tests for guiding haemostatic management during ECMO also warrants further exploration.

Inflammation and lung injury in an ovine model of extracorporeal membrane oxygenation support.

Extracorporeal membrane oxygenation (ECMO) is a life-saving treatment for patients with severe refractory cardiorespiratory failure. Exposure to the ECMO circuit is thought to trigger/exacerbate inflammation. Determining whether inflammation is the result of the patients' underlying pathologies or the ECMO circuit is difficult. To discern how different insults contribute to the inflammatory response, we developed an ovine model of lung injury and ECMO to investigate the impact of smoke-induced lung injury and ECMO in isolation and cumulatively on pulmonary and circulating inflammatory cells, cytokines, and tissue remodeling. Sheep receiving either smoke-induced acute lung injury (S-ALI) or sham injury were placed on veno-venous (VV) ECMO lasting either 2 or 24 h, with controls receiving conventional ventilation only. Lung tissue, bronchoalveolar fluid, and plasma were analyzed by RT-PCR, immunohistochemical staining, and zymography to assess inflammatory cells, cytokines, and matrix metalloproteinases. Pulmonary compliance decreased in sheep with S-ALI placed on ECMO with increased numbers of infiltrating neutrophils, monocytes, and alveolar macrophages compared with controls. Infiltration of neutrophils was also observed with S-ALI alone. RT-PCR studies showed higher expression of matrix metalloproteinases 2 and 9 in S-ALI plus ECMO, whereas IL-6 was elevated at 2 h. Zymography revealed higher levels of matrix metalloproteinase 2. Circulating plasma levels of IL-6 were elevated 1-2 h after commencement of ECMO alone. These data show that the inflammatory response is enhanced when a host with preexisting pulmonary injury is placed on ECMO, with increased infiltration of neutrophils and macrophages, the release of inflammatory cytokines, and upregulation of matrix metalloproteinases.

Angiotensin receptors as sensitive markers of acute bronchiole injury after lung transplantation.

BACKGROUND: Although lung transplantation is the only means of survival for patients with end-stage pulmonary disease, outcomes from this intervention are inferior to other solid organ transplants. The reason for the poor outcomes may be linked to an early reaction, such as primary graft dysfunction, and associated with marked inflammatory response, bronchiole injury, and later fibrotic responses. Mediators regulating these effects include angiotensin II and matrix metalloproteinases (MMPs). METHODS: We investigated changes to these mediators over the course of cardiopulmonary bypass (CPB) and up to 72 h after lung transplantation, using immunohistochemistry, Western blot, and ELISA techniques. RESULTS: We found 4- and 16-fold increases in plasma angiotensin II and MMP-9, respectively, from pre-CPB to post-CPB. MMP-9 levels remained elevated 1 h after transplantation. MMP-2 levels were elevated 6-24 h after lung transplantation. Type 2 angiotensin II receptor (ATR2) expression was 3.5-fold higher in bronchoalveolar cells 1-6 h after transplantation than in controls. CONCLUSIONS: The study suggests that the combination of cardiopulmonary bypass and lung transplantation is associated with early changes in the angiotensin II receptor system and in MMPs, and that altered expression of these mediators may be a useful marker to examine pathological changes that occur in lungs during transplant surgery.

Long-term impacts on macroinvertebrates downstream of reclaimed mountaintop mining valley fills in Central Appalachia.

Recent studies have documented adverse effects to biological communities downstream of mountaintop coal mining and valley fills (VF), but few data exist on the longevity of these impacts. We sampled 15 headwater streams with VFs reclaimed 11-33 years prior to 2011 and sampled seven local reference sites that had no VFs. We collected chemical, habitat, and benthic macroinvertebrate data in April 2011; additional chemical samples were collected in September 2011. To assess ecological condition, we compared VF and reference abiotic and biotic data using: (1) ordination to detect multivariate differences, (2) benthic indices (a multimetric index and an observed/expected predictive model) calibrated to state reference conditions to detect impairment, and (3) correlation and regression analysis to detect relationships between biotic and abiotic data. Although VF sites had good instream habitat, nearly 90 % of these streams exhibited biological impairment. VF sites with higher index scores were co-located near unaffected tributaries; we suggest that these tributaries were sources of sensitive taxa as drifting colonists. There were clear losses of expected taxa across most VF sites and two functional feeding groups (% scrapers and %shredders) were significantly altered. Percent VF and forested area were related to biological quality but varied more than individual ions and specific conductance. Within the subset of VF sites, other descriptors (e.g., VF age, site distance from VF, the presence of impoundments, % forest) had no detectable relationships with biological condition. Although these VFs were constructed pursuant to permits and regulatory programs that have as their stated goals that (1) mined land be reclaimed and restored to its original use or a use of higher value, and (2) mining does not cause or contribute to violations of water quality standards, we found sustained ecological damage in headwaters streams draining VFs long after reclamation was completed.

An appraisal of lung computer tomography in very early anti-inflammatory treatment of two different ovine ARDS phenotypes.

Mortality and morbidity of Acute Respiratory Distress Syndrome (ARDS) are largely unaltered. A possible new approach to treatment of ARDS is offered by the discovery of inflammatory subphenotypes. In an ovine model of ARDS phenotypes, matching key features of the human subphenotypes, we provide an imaging characterization using computer tomography (CT). Nine animals were randomized into (a) OA (oleic acid, hypoinflammatory; n = 5) and (b) OA-LPS (oleic acid and lipopolysaccharides, hyperinflammatory; n = 4). 48 h after ARDS induction and anti-inflammatory treatment, CT scans were performed at high (H) and then low (L) airway pressure. After CT, the animals were euthanized and lung tissue was collected. OA-LPS showed a higher air fraction and OA a higher tissue fraction, resulting in more normally aerated lungs in OA-LPS in contrast to more non-aerated lung in OA. The change in lung and air volume between H and L was more accentuated in OA-LPS, indicating a higher recruitment potential. Strain was higher in OA, indicating a higher level of lung damage, while the amount of lung edema and histological lung injury were largely comparable. Anti-inflammatory treatment might be beneficial in terms of overall ventilated lung portion and recruitment potential, especially in the OA-LPS group.

The Impact of Acute Exercise on Hemostasis and Angiogenesis Mediators in Patients With Continuous-Flow Left Ventricular Assist Devices: A Prospective Observational Pilot Study.

Impaired primary hemostasis and dysregulated angiogenesis, known as a two-hit hypothesis, are associated with gastrointestinal (GI) bleeding in patients with continuous-flow left ventricular assist devices (CF-LVADs). Exercise is known to influence hemostasis and angiogenesis in healthy individuals; however, little is known about the effect in patients with CF-LVADs. The objective of this prospective observational study was to determine whether acute exercise modulates two-hit hypothesis mediators associated with GI bleeding in patients with a CF-LVAD. Twenty-two patients with CF-LVADs performed acute exercise either on a cycle ergometer for approximately 10 minutes or on a treadmill for 30 minutes. Blood samples were taken pre- and post-exercise to analyze hemostatic and angiogenic biomarkers. Acute exercise resulted in an increased platelet count (p < 0.00001) and platelet function (induced by adenosine diphosphate, p = 0.0087; TRAP-6, p = 0.0005; ristocetin, p = 0.0009). Additionally, high-molecular-weight vWF multimers (p < 0.00001), vWF collagen-binding activity (p = 0.0012), factor VIII (p = 0.034), angiopoietin-1 (p = 0.0026), and vascular endothelial growth factor (p = 0.0041) all increased after acute exercise. This pilot work demonstrates that acute exercise modulated two-hit hypothesis mediators associated with GI bleeding in patients with CF-LVADs.

Effect of flow change on brain injury during an experimental model of differential hypoxaemia in cardiogenic shock supported by extracorporeal membrane oxygenation.

Differential hypoxaemia (DH) is common in patients supported by femoral veno-arterial extracorporeal membrane oxygenation (V-A ECMO) and can cause cerebral hypoxaemia. To date, no models have studied the direct impact of flow on cerebral damage. We investigated the impact of V-A ECMO flow on brain injury in an ovine model of DH. After inducing severe cardiorespiratory failure and providing ECMO support, we randomised six sheep into two groups: low flow (LF) in which ECMO was set at 2.5 L min-1 ensuring that the brain was entirely perfused by the native heart and lungs, and high flow (HF) in which ECMO was set at 4.5 L min-1 ensuring that the brain was at least partially perfused by ECMO. We used invasive (oxygenation tension-PbTO2, and cerebral microdialysis) and non-invasive (near infrared spectroscopy-NIRS) neuromonitoring, and euthanised animals after five hours for histological analysis. Cerebral oxygenation was significantly improved in the HF group as shown by higher PbTO2 levels (+ 215% vs - 58%, p = 0.043) and NIRS (67 ± 5% vs 49 ± 4%, p = 0.003). The HF group showed significantly less severe brain injury than the LF group in terms of neuronal shrinkage, congestion and perivascular oedema (p < 0.0001). Cerebral microdialysis values in the LF group all reached the pathological thresholds, even though no statistical difference was found between the two groups. Differential hypoxaemia can lead to cerebral damage after only a few hours and mandates a thorough neuromonitoring of patients. An increase in ECMO flow was an effective strategy to reduce such damages.

Application of anti-inflammatory treatment in two different ovine Acute Respiratory Distress Syndrome injury models: a preclinical randomized intervention study.

Whilst the presence of 2 subphenotypes among the heterogenous Acute Respiratory Distress Syndrome (ARDS) population is becoming clinically accepted, subphenotype-specific treatment efficacy has yet to be prospectively tested. We investigated anti-inflammatory treatment in different ARDS models in sheep, previously shown similarities to human ARDS subphenotypes, in a preclinical, randomized, blinded study. Thirty anesthetized sheep were studied up to 48 h and randomized into: (a) OA: oleic acid (n = 15) and (b) OA-LPS: oleic acid and subsequent lipopolysaccharide (n = 15) to achieve a PaO2/FiO2 ratio of < 150 mmHg. Then, animals were randomly allocated to receive treatment with methylprednisolone or erythromycin or none. Assessed outcomes were oxygenation, pulmonary mechanics, hemodynamics and survival. All animals reached ARDS. Treatment with methylprednisolone, but not erythromycin, provided the highest therapeutic benefit in Ph2 animals, leading to a significant increase in PaO2/FiO2 ratio by reducing pulmonary edema, dead space ventilation and shunt fraction. Animals treated with methylprednisolone displayed a higher survival up to 48 h than all others. In animals treated with erythromycin, there was no treatment benefit regarding assessed physiological parameters and survival in both phenotypes. Treatment with methylprednisolone improves oxygenation and survival, more so in ovine phenotype 2 which resembles the human hyperinflammatory subphenotype.