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.

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.

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.

Long-term pulmonary function and quality of life in adults after extracorporeal membrane oxygenation for respiratory failure.

BACKGROUND: There is a significant long-term burden on survivors after acute respiratory distress syndrome, even 5 years after discharge. This is not well investigated in patients treated with extracorporeal membrane oxygenation. The objective of this study was to describe very-long-term (⩾3 years) disability in lung function and morphology, quality of life, mood disorders, walking capacity, and return to work status in extracorporeal membrane oxygenation survivors. METHODS: Single-center retrospective cohort study on long-term survivors treated with extracorporeal membrane oxygenation for respiratory failure between 1995 and 2010 at a tertiary referral center in Sweden. Eligible patients were approached, and those who consented were interviewed and investigated during a day at the hospital. RESULTS: A total of 38 patients were investigated with a median follow-up time of 9.0 years. Quality of life was reduced in several Short form 36 (SF-36) subscales and all domains of the St George's Respiratory Questionnaire, similar to previous studies in conventionally managed acute respiratory distress syndrome survivors. A reduced diffusion capacity of carbon monoxide was seen in 47% of patients, and some degree of residual lung parenchymal pathology was seen in 82%. Parenchymal pathology correlated with reductions in quality of life and diffusion capacity. Symptoms of anxiety and depression were seen in 22% and 14%, respectively. CONCLUSION: A significant long-term burden remains even 3-17 years after extracorporeal membrane oxygenation treatment, similar to conventionally managed acute respiratory distress syndrome survivors. Future prospective studies are needed to elucidate risk factors for these sequelae.

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.

Extracorporeal membrane oxygenation (ECMO) and the acute respiratory distress syndrome (ARDS): a systematic review of pre-clinical models.

OBJECTIVES: Extracorporeal membrane oxygenation (ECMO) is an increasingly accepted means of supporting those with severe acute respiratory distress syndrome (ARDS). Given the high mortality associated with ARDS, numerous animal models have been developed to support translational research. Where ARDS is combined with ECMO, models are less well characterized. Therefore, we conducted a systematic literature review of animal models combining features of experimental ARDS with ECMO to better understand this situation. DATA SOURCES: MEDLINE and Embase were searched between January 1996 and December 2018. STUDY SELECTION: Inclusion criteria: animal models combining features of experimental ARDS with ECMO. EXCLUSION CRITERIA: clinical studies, abstracts, studies in which the model of ARDS and ECMO has been reported previously, and studies not employing veno-venous, veno-arterial, or central ECMO. DATA EXTRACTION: Data were extracted to fully characterize models. Variables related to four key features: (1) study design, (2) animals and their peri-experimental care, (3) models of ARDS and mechanical ventilation, and (4) ECMO and its intra-experimental management. DATA SYNTHESIS: Seventeen models of ARDS and ECMO were identified. Twelve were published after 2009. All were performed in large animals, the majority (n = 10) in pigs. The median number of animals included in each study was 17 (12-24), with a median study duration of 8 h (5-24). Oleic acid infusion was the commonest means of inducing ARDS. Most models employed peripheral veno-venous ECMO (n = 12). The reporting of supportive measures and the practice of mechanical ventilation were highly variable. Descriptions of ECMO equipment and its management were more complete. CONCLUSION: A limited number of models combine the features of experimental ARDS with ECMO. Among those that do, there is significant heterogeneity in both design and reporting. There is a need to standardize the reporting of pre-clinical studies in this area and to develop best practice in their design.

Administration of mesenchymal stem cells during ECMO results in a rapid decline in oxygenator performance.

Mesenchymal stem cells (MSCs) have attracted attention as a potential therapy for Acute Respiratory Distress Syndrome (ARDS). At the same time, the use of extracorporeal membrane oxygenation (ECMO) has increased among patients with severe ARDS. To date, early clinical trials of MSCs in ARDS have excluded patients supported by ECMO. Here we provide evidence from an ex-vivo model of ECMO to suggest that the intravascular administration of MSCs during ECMO may adversely impact the function of a membrane oxygenator. The addition of clinical grade MSCs resulted in a reduction of flow through the circuit in comparison to controls (0.6 ±0.35 L min-1vs 4.12 ± 0.03 L min-1, at 240 minutes) and an increase in the transoygenator pressure gradient (101±9 mmHg vs 21±4 mmHg, at 240 minutes). Subsequent immunohistochemistry analysis demonstrated quantities of MSCs highly adherent to membrane oxygenator fibres. This study highlights the potential harm associated with MSC therapy during ECMO and suggests further areas of research required to advance the translation of cell therapy in this population.

Long-Term Cognitive Outcome and Brain Imaging in Adults After Extracorporeal Membrane Oxygenation.

OBJECTIVES: To investigate the presence of cognitive dysfunction and brain lesions in long-term survivors after treatment with extracorporeal membrane oxygenation for severe respiratory failure, and to see whether patients with prolonged hypoxemia were at increased risk. DESIGN: A single-center retrospective cohort study. SETTING: Tertiary referral center for extracorporeal membrane oxygenation in Sweden. PATIENTS: Long-term survivors treated between 1995 and July 2009. Seven patients from a previously published study investigated with a similar protocol were included. INTERVENTIONS: Brain imaging, neurocognitive testing, interview. MEASUREMENTS AND MAIN RESULTS: Thirty-eight patients (i.e., n = 31 + 7) were enrolled and investigated in median 9.0 years after discharge. Only memory tests were performed in 10 patients, mainly due to a lack of formal education necessary for the test results to be reliable. Median full-scale intelligence quotient, memory index, and executive index were 97, 101, and 104, respectively (normal, 100 ± 15). Cognitive function was not reduced in the group with prolonged hypoxemia. Brain imaging showed cerebrovascular lesions in 14 of 38 patients (37%), most commonly in the group treated with venoarterial extracorporeal membrane oxygenation (7/11, 64%). In this group, memory function and executive function were significantly reduced. CONCLUSIONS: Patients treated with extracorporeal membrane oxygenation for respiratory failure may have normal cognitive function years after treatment, if not affected by cerebrovascular lesions. Permissive hypoxemia was not correlated with long-term cognitive dysfunction in the present study. Further prospective studies with minimal loss to follow-up are direly needed to confirm our findings.

Long-Term Survival in Adults Treated With Extracorporeal Membrane Oxygenation for Respiratory Failure and Sepsis.

OBJECTIVE: The use of extracorporeal membrane oxygenation in adults with respiratory failure and sepsis is steadily increasing, but the knowledge on long-term survival in this group is scarce. The aim of the present study was to investigate the 5-year survival rates and causes of late death in this group of patients. DESIGN: Single-center retrospective cohort study. SETTING: Karolinska University Hospital, Stockholm, Sweden. PATIENTS: Adult patients treated with extracorporeal membrane oxygenation for respiratory failure and sepsis between the service being established for adults in 1995 and December 2013. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Survival status was attained from a national Causes of Death registry. Minimal patient background data, along with data on survival and causes of death were collected. Survival rates were calculated using the Kaplan-Meier method. Of 255 subjects, 64% survived to discharge. The median follow-up time in survivors was 4.4 years. There was a high mortality rate within the first months after discharge. In the group of patients who survived the first 90 days after treatment, the 5-year survival rate was 87% and was particularly beneficial in patients treated for infectious diseases (88-100%). Late deaths were seen in most diagnostic groups, but the Kaplan-Meier curves flattened out over time. CONCLUSIONS: Extracorporeal membrane oxygenation treatment in adult patients with respiratory failure and sepsis can be lifesaving in appropriately selected patients. For patients who survive the first months after extracorporeal membrane oxygenation treatment, long-term survival seems good, especially in patients treated for infections.

Long-Term Survival and Causes of Late Death in Children Treated With Extracorporeal Membrane Oxygenation.

OBJECTIVE: Extracorporeal membrane oxygenation has been used in patients with severe circulatory or respiratory failure since the 1970s, but the knowledge on long-term survival in this group is scarce. The aim of the present study was to investigate the 10-year survival rates and causes of late death in children treated with extracorporeal membrane oxygenation. DESIGN: Single-center, retrospective cohort study. SETTING: Tertiary referral center for extracorporeal life support. PATIENTS: Neonatal and pediatric patients treated with extracorporeal membrane oxygenation from 1987 to December 2013. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Survival status was obtained from the national Causes of Death registry. Patient background data along with data on survival and causes of death were collected. Survival rates were calculated using the Kaplan-Meier method. Of 400 subjects, 76% survived to discharge. The median follow-up time in survivors was 7.2 years. There was a high mortality rate within the first months after discharge. In the group of patients who survived the first 90 days after treatment, the 10-year survival rates were 93% in neonates and 89% in pediatric patients and were particularly beneficial in patients whose indication for extracorporeal membrane oxygenation was meconium aspiration syndrome, trauma, or infectious diseases. Late deaths were seen in some diagnostic groups, but the Kaplan-Meier curves plateaued over time. CONCLUSIONS: Children who survive the first months after treatment with extracorporeal membrane oxygenation have a high long-term survival rate. The prognosis is especially favorable in patients with reversible conditions.

Does permissive hypoxaemia during extracorporeal membrane oxygenation cause long-term neurological impairment?: A study in patients with H1N1-induced severe respiratory failure.

BACKGROUND: The Extracorporeal Life Support Organisation accepts permissive hypoxaemia in adult patients during extracorporeal membrane oxygenation (ECMO). The neurological long-term outcome of this approach has not yet been studied. OBJECTIVES: We investigated the prevalence of brain lesions and cognitive dysfunction in survivors from the Influenza A/H1N1 2009 pandemic treated with permissive hypoxaemia during ECMO for severe acute respiratory distress syndrome (ARDS). Our hypothesis was that this method is reasonable if tissue hypoxia is avoided. DESIGN: Long-term follow-up study after ECMO. SETTING: Karolinska University Hospital, Sweden, from October 2012 to July 2013. PATIENTS: Seven patients treated with ECMO for severe influenza A/H1N1-induced ARDS were studied 3.2 years after treatment. Blood lactate concentrations were used as a surrogate for tissue oxygenation. INTERVENTIONS: Neurocognitive outcome was studied with standardised cognitive tests and MRI of the brain. MAIN OUTCOME MEASURES: Cognitive functioning and hypoxic brain lesions after permissive hypoxaemia during ECMO. The observation period was the first 10 days of ECMO or the entire treatment period if shorter than 10 days. RESULTS: Eleven of 13 patients were still alive 3 years after ECMO. We were able to contact seven of these patients (mean age 31 years), who all agreed to participate in this study. Mean ±â€ŠSD peripherally measured arterial saturation during the observation period was 79 ±â€Š10%. Full-scale Intelligence Quotient was within one standard deviation or above from the mean of a healthy population in five patients, and was 1.5 SD below the mean in one patient. In one other patient, it could not be determined because of a lack of formal education. Memory functioning was normal in all patients. MRI showed no changes related to cerebral hypoxia. CONCLUSIONS: Permissive hypoxaemia during ECMO might not negatively affect long-term cognitive outcome if adequate organ perfusion is maintained. TRIAL REGISTRATION: at Clinicaltrials.gov NCT01763060.

[Good long-term survival after ECMO treatment]. / God långtidsöverlevnad efter ECMO-behandling.

ECMO is used more and more globally, and to date more than 60,000 patients have undergone ECMO treatment. At the ECMO Center Karolinska in Stockholm, Sweden, more than 900 neonatal, pediatric and adult patients with primarily respiratory failure have been treated since 1987. This study investigated 217 consecutive patients of all ages who were treated 1995-2005 at our center, of which 76 % survived treatment. The mean follow-up time was 7.9 years. Of the patients who survived more than 90 days after treatment, 91 % were alive at follow-up 5 years later, similar in all age categories (89-93 %). The highest mortality risk was observed within the first months after ECMO. We conclude that both short and long-term survival is high in all age categories, especially considering the high mortality risk of the patients eligible for ECMO treatment. More studies are needed to evaluate long term prognostic markers, cognitive functions and quality of life, especially in the adult.