Development of a Model of Pediatric Lung Failure Pathophysiology

A pediatric artificial lung (PAL) is under development as a bridge to transplantation or lung remodeling for children with end-stage lung failure (ESLF). To evaluate the efficiency of a PAL, a disease model mimicking the physiologic derangements of pediatric ESLF is needed. Our previous right pulmonary artery (rPA) ligation model (rPA-LM) achieved that goal, but caused immediate mortality in nearly half of the animals. In this study, we evaluated a new technique of gradual postoperative right pulmonary artery occlusion using a Rummel tourniquet (rPA-RT) in seven (25–40 kg) sheep. This technique created a stable model of ESLF pathophysiology, characterized by high alveolar dead space (58.0% ± 3.8%), pulmonary hypertension (38.4 ± 2.2 mm Hg), tachypnea (79 ± 20 breaths per minute), and intermittent supplemental oxygen requirement. This improvement to our technique provides the necessary physiologic derangements for testing a PAL, whereas avoiding the problem of high immediate perioperative mortality

The effect of matrix metalloproteinase 2 and matrix metalloproteinase 2/9 deletion in experimental post-thrombotic vein wall remodeling

BackgroundVein wall fibrotic injury following deep venous thrombosis (VT) is associated with elevated matrix metalloproteinases (MMPs). Whether and by what mechanism MMP2 contributes to vein wall remodeling after VT is unknown.MethodsStasis VT was produced by ligation of the inferior vena cava and tissue was harvested at 2, 8, and 21 days in MMP2 -/- and genetic wild type (WT) mice. Tissue analysis by immunohistochemistry, enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and zymography was performed.ResultsThrombus resolution was less at 8 days in MMP2 -/- compared with WT, evidenced by a 51% increase in VT size (P < .01), and threefold fewer von Willebrand's factor positive channels (P < .05). In MMP2 -/- mice, the main phenotypic fibrotic differences occurred at 8 days post-VT, with significantly less vein wall collagen content (P = .013), fourfold lower procollagen III gene expression (P < .01), but no difference in procollagen I compared with WT. Decreased inflammation in MMP2 -/- vein walls was suggested by ∼ threefold reduced TNFα and IL-1β at 2 days and 8 days post-VT (P < .05). A fourfold increase in vein wall monocytes (P = .03) with threefold decreased apoptosis (P < .05), but no difference in cellular proliferation at 8 days was found in MMP2 -/- compared with WT. As increased compensatory MMP9 activity was observed in the MMP2 -/-mice, MMP2/9 double null mice had thrombus induced with VT harvest at 8 days. Consistently, twofold larger VT, a threefold decrease in vein wall collagen, and a threefold increase in monocytes were found (all P < .05). Similar findings were observed in MMP9 -/- mice administered an exogenous MMP2 inhibitor.ConclusionsIn stasis VT, deletion of MMP2 was associated with less midterm vein wall fibrosis and inflammation, despite an increase in monocytes. Consideration that VT resolution was impaired with MMP2 (and MMP2/9) deletion suggests direct inhibition will likely also require anticoagulant therapy.Clinical RelevancePost-thrombotic syndrome has no direct therapies and causes significant morbidity. Anticoagulation limits thrombosis but does not clinically impact directly the vein wall response to injury as well as has bleeding risks. In this experimental study, we show that matrix metalloproteinase 2 genetic deletion lessens fibrotic injury and inflammation at the midterm timepoint, yet is also important for thrombus resolution. Future therapies that positively impact vein wall remodeling will need to account for how the thrombus responds as well

29 Cardio-Omentopexy to Reduce Myocardial Scarring and Promote Regeneration

OBJECTIVES/GOALS: While the current management of single ventricle repairs has drastically prolonged life expectancy, the repair fails over time primarily through pathologic inflammation and fibrosis. Our goal is to demonstrate that cardio-omentopexy can decrease inflammation and fibrosis in swine after cryoinjury. METHODS/STUDY POPULATION: A cryoinjury is created using a liquid nitrogen cooled probe to the right ventricle of 15-20kg swine for three minutes. In half the groups the omentum is attached to the heart over the area of the injury. The swine are recovered and monitored for 4 or 8 weeks at which time they are euthanized. The injured area is evaluated via histological and immunohistochemical testing for markers of inflammation and scarring including collagen type, scar area, macrophage activity. RESULTS/ANTICIPATED RESULTS: Currently, we have successfully validated the animal model to create myocardial scar validated by histological testing. We anticipate that the addition of omentopexy to cryoinjury will decrease scar area, fibrosis and markers of chronic inflammation. Additionally, we expect an increase in myocytes in the area of injury. We expect that this will occur through the anti-inflammatory and protective mechanism of the omentum. DISCUSSION/SIGNIFICANCE: Cardio-omentopexy, if able to decrease fibrosis and preserve myocytes, may provide a useful adjunct to the treatment of single ventricle repair by prolonging the longevity of the repair. Additionally, as these repairs often require a ventriculotomy, decreasing the operative scar may preserve myocardial function

Normoxic re-oxygenation ameliorates end-organ injury after cardiopulmonary bypass

Abstract Background In a rabbit model of cardiopulmonary bypass (CPB) and cardioplegic arrest, we previously showed that hyperoxic myocardial reperfusion was associated with increased left ventricular (LV) systolic dysfunction and myocardial injury compared with normoxic reperfusion. The aim of this study was to evaluate in our experimental model the impact of post-CPB reperfusion conditions on other organs potentially vulnerable to ischemic injury such as the brain and kidney. Methods After 60 min of CPB, aortic cross-clamp, and cold cardioplegic arrest, rabbits were reperfused under hyperoxic or normoxic conditions for 120 min. Left ventricular systolic contractility (LV + dP/dt) and diastolic relaxation (LV –dP/dt) were continuously recorded, and end-organ injury was assessed by measuring circulating biomarkers specific for kidney (cystatin C and creatinine) and brain injury [S100B and neuron specific enolase (NSE)]. At completion of the protocol, kidney and brain tissues were harvested for measuring oxidant stress (OS), inflammation and apoptosis. Results Following aortic cross-clamp removal, rabbits exposed to normoxic reperfusion demonstrated preserved LV systolic and diastolic function compared with hyperoxic reperfusion (LV + dP/dt: 70 ± 14% of pre-CPB vs. 36 ± 21%, p = 0.018; LV -dP/dt: 72 ± 36% of pre-CPB vs. 33 ± 20%, p = 0.023). Similarly, CPB increased plasma creatinine, S100B and NSE that were significantly attenuated by normoxic reperfusion compared with hyperoxic reperfusion (creatinine: 4.0 ± 0.5 vs. 7.1 ± 0.8 mg/dL, p = 0.004; S100B: 4.0 ± 0.8 vs. 6.7 ± 1.0 ng/mL, p = 0.047; NSE: 57.7 ± 6.8 vs. 101.3 ± 16.1 pg/mL, p = 0.040). Furthermore, both kidney and brain tissues showed increased mRNA expression and activation of pathways for OS, inflammation, and apoptosis, that were reduced under normoxic compared with hyperoxic conditions. Conclusions Normoxic reperfusion ameliorates cardiac, renal and neural injury compared with hyperoxic reperfusion in an in vivo animal model of CPB and cardioplegic arrest. This protective effect of normoxic reperfusion may be due to a reduction in signaling pathways for OS, inflammation, and apoptosis.http://deepblue.lib.umich.edu/bitstream/2027.42/173806/1/13019_2020_Article_1173.pd

Long term veno-venous extracorporeal life support without intravenous anticoagulation for diffuse alveolar hemorrhage

Introduction: Diffuse alveolar damage is the histologic hallmark for the acute phase of acute respiratory distress syndrome and can occasionally present as diffuse alveolar hemorrhage. Case report: We report a patient with diffuse alveolar hemorrhage and acute respiratory distress syndrome requiring veno-venous extracorporeal life support for 210 days, who was successfully treated for a period of 130 consecutive days without intravenous anticoagulation. Discussion: Although there are a few brief reports detailing long extracorporeal life support runs, the literature is largely devoid of data regarding long-term extracorporeal life support without full systemic anticoagulation. Regular inspection of the extracorporeal membrane oxygenation circuit is critical because externally visible thrombi may predict internal thrombus generation with the potential for systemic embolization or abrupt oxygenator failure. In our case, multiple circuit and oxygenators changes were required. Conclusion: We have demonstrated that a patient with a contraindication for systemic anticoagulation can safely have veno-venous extracorporeal life support for prolonged periods without catastrophic thrombotic complications

Von Willebrand Factor-GP1bα Interactions in Venoarterial Extracorporeal Membrane Oxygenation Patients

Objective: Evaluate extracorporeal membrane oxygenation (ECMO) patients’ platelet adhesion and aggregation under shear stress and determine whether addition of von Willebrand factor (VWF) concentrate improves platelet function. Also, explore whether reduced platelet adhesion and aggregation is associated with clinical bleeding during ECMO. Design: Prospective observational cohort study with translational component. Setting: Academic medical center. Participants: Consecutive venoarterial (VA) ECMO patients were screened and 20 patients enrolled. Interventions: VWF multimers, VWF antigen, ristocetin cofactor activity, and plasma glycocalicin levels were measured and values were compared at study points: ECMO day 1 or 2, day 3, and day 5. Platelet adhesion and aggregation were measured in vitro using the total thrombus analysis system. Platelet function was expressed as area under the flow-pressure curve (AUC). VWF concentrate was added in vitro and the AUC after VWF supplementation (VWF AUC) was compared with baseline AUC. Further, baseline AUCs and VWF AUCs were compared between patients who experienced bleeding during ECMO and those who did not. Measurements and Main Results: ECMO patients had high VWF antigen levels, high ristocetin cofactor activity, and large VWF multimer loss. Platelet counts fell over the first 5 days on ECMO, and plasma glycocalicin levels were elevated mildly. ECMO patients had severely low platelet adhesion and aggregation in vitro: median AUC = 5.8 (3.5-9.7) ECMO day 1 or 2, median AUC = 6.3 (5.3-11.1) day 3, and median AUC = 5.5 (4.1-8.1) day 5. There was no significant change in AUC over time (p = 0.47). Addition of VWF concentrate increased the AUC compared to baseline at each point (all p \u3c 0.05), but VWF AUC values remained low. Patients with bleeding during ECMO had a low VWF AUC at all points, whereas those without bleeding had a higher VWF AUC on ECMO day 3. Conclusions: VA ECMO patients have severely impaired platelet function, which improved but did not normalize with VWF concentrate. The data suggest that GP1bα receptor loss of dysfunction also contributes to impaired platelet adhesion and aggregation during ECMO. Based on these findings, clinical bleeding in ECMO patients is unlikely to be correctable with VWF supplementation alone

Does weight matter? Outcomes in adult patients on venovenous extracorporeal membrane oxygenation when stratified by obesity class

BACKGROUND: Many believe obesity is associated with higher rates of mortality in the critically ill. The purpose of this retrospective observational study is to evaluate the association between body mass index (BMI) and survival in patients receiving venovenous (VV) extracorporeal membrane oxygenation (ECMO) for acute hypoxic or hypercarbic respiratory failure. METHODS: All of the patients admitted to a dedicated VV ECMO unit were included. Patients \u3c18 years of age, listed for lung transplant, or underweight were excluded. ECMO outcomes, including hospital length of stay and survival to discharge, were analyzed after stratification according to BMI. Multivariate logistic and linear regression techniques were used to assess variables associated with the outcomes of death and length of stay, respectively. RESULTS: One hundred ninety-four patients with a median BMI of 35.7 kg/m2(33-42 kg/m2) were included. Obese patients were older, had higher creatinine levels, and required higher levels of positive end-expiratory pressure and mean airway pressure at time of cannulation. Survival to discharge in any group did not differ when stratified by BMI classification (P =.36). Multivariable regression did not reveal any association with greater odds of death or longer length of stay when controlling for BMI and other variables. CONCLUSIONS: We did not detect an association between obesity and increased mortality in patients requiring VV ECMO for acute hypoxic or hypercarbic respiratory failure. These data suggest that obesity alone should not exclude candidacy for VV ECMO. Evidence for the obesity paradox in this population of VV ECMO patients may be supported by these data

Epidemiology of blood stream infection in adult extracorporeal membrane oxygenation patients: A cohort study

Purpose: The purpose of our study was to characterize the epidemiology of blood stream infection (BSI) in adult extracorporeal membrane oxygenation (ECMO) patients at a single tertiary care academic medical center with standardized post-cannulation antibiotic prophylaxis practices. Methods: A single-center retrospective cohort study was performed over a five-year period. BSI incidence was characterized and patients who developed BSI during ECMO were compared with those who did not. Results: Nineteen of 145 VV ECMO patients (13.1%) developed BSI while 7 of 123 VA ECMO patients (5.7%) developed BSI. When accounting for total ECMO days, the incidence rate was 8 BSIs per 1,000 ECMO days for both VV and VA ECMO patients. VV ECMO patients with BSI had longer ECMO runs and more red blood cell transfusion (both p\u3c0.05). VA ECMO patients who developed BSI had longer ECMO runs and more platelet transfusion (both p\u3c0.05). In VV ECMO patients there was an association between renal failure and BSI and in VA ECMO patients there was an association between hepatic failure and BSI. Conclusions: BSIs are common in ECMO patients even with post-cannulation antimicrobial prophylaxis and are associated with ECMO duration, blood transfusion, and organ failure. Further work is needed to clarify the optimal duration and type of antimicrobial prophylaxis, as well as surveillance strategies for BSIs during adult ECMO

Platelet Transfusion and In-Hospital Mortality in Veno-Arterial Extracorporeal Membrane Oxygenation Patients

Thrombocytopenia is common during extracorporeal membrane oxygenation (ECMO), and platelets are sometimes transfused to meet arbitrary goals. We performed a retrospective cohort study of veno-arterial (VA) ECMO patients from a single academic medical center and explored the relationship between platelet transfusion and in-hospital mortality using multivariable logistic regression. One hundred eighty-eight VA ECMO patients were included in the study. Ninety-one patients (48.4%) were transfused platelets during ECMO. Patients who received platelet transfusion had more coronary artery disease, lower platelet counts at cannulation, higher predicted mortality, lower nadir platelet counts, more ECMO days, and more red blood cell (RBC) and plasma transfusion. Mortality was 19.6% for patients who received no platelets, 40.8% for patients who received 1-3 platelets, and 78.6% for patients who received 4 or more platelets ( P \u3c 0.001). After controlling for confounding variables including baseline severity of illness, central cannulation, postcardiotomy status, RBC and plasma transfusion, major bleeding, and total ECMO days, transfusion of 4 or more platelets remained associated with in-hospital mortality; OR = 4.68 (95% CI = 1.18-27.28), P = 0.03. Our findings highlight the need for randomized controlled trials that compare different platelet transfusion triggers, so that providers can better understand when platelet transfusion is indicated in VA ECMO patients