Traditional Cardiopulmonary Resuscitation In Cardiac Arrest For Patients On Venovenous Extracorporeal Membrane Oxygenation

Introduction: Mortality for patients on VV-ECMO remains high despite increased use during the COVID-19 pandemic. Unlike VA-ECMO which provides life support for cardiac failure and can be used as a bridge to definitive therapy during cardiac arrest (e-CPR), patients who arrest while on VV-ECMO currently may undergo traditional cardiopulmonary resuscitation (CPR). This poses many challenges such as potential cannula position disruption of the VV-ECMO system during compressions and it is unclear if patients on VV-ECMO will benefit from being offered traditional CPR. Hypothesis: Traditional CPR is effective in patients who arrest while on VV-ECMO. Method(s): A retrospective chart review of inpatient cardiac arrest data from a high-volume ECMO center was performed. Patients who arrested while on VV-ECMO were included. Data including demographics, etiology of arrest, return of spontaneous circulation (ROSC) and survival to discharge were reviewed. Survival data was compared with the ECLS International Summary of Statistics. Result(s): We identified 19 patients on VV-ECMO who underwent CPR for cardiac arrest between September 2012 and November 2021. The average age of the patients was 42.7 years and 89.5% (n=17) were men. Seven of the nineteen total patients (36.8%) were being treated for ARDS from COVID-19 pneumonia. The arrest occurred on average 35.6 days into hospitalization (range: 1-132 days). The initial rhythm was pulseless electrical activity in 13 patients (68.4%), and the etiologies of arrest included hypoxemia (n=10, 52.6%), ECMO machine failure or during oxygenator exchange (n=3, 15.8%), pneumothorax (n=2, 10.5%), and cardiac tamponade (n=1, 5.3%). ROSC occurred in all 19 patients (100%), however only 4 patients (21.1%) survived to discharge with good neurologic recovery. Survival to discharge for all-comers on VV-ECMO is 66%. Conclusion(s): While there is limited evidence for the effectiveness of traditional CPR for patients on VV-ECMO, in this sample, ROSC was universal and one-fifth of patients survived to discharge. Future studies should continue to study the utility of CPR on VV-ECMO and how to optimize technique to improve outcomes for these critically-ill patients.

Neutrophil extracellular trap formation (NETOSIS) increases with severity of disease in COVID-19 patients

Background: Neutrophils are key players in the immune and aid in the defense against microorganisms. Neutrophil extracellular traps (NETs) are extracellular DNA complexes, which are released during NETosis, a programmed form of cell death. Although NETs are crucial in the fight against infectious agents, an overabundance of neutrophils has been implicated in many inflammatory lung conditions. Our aim is to determine whether an overabundance of NETosis is associated with clinical deterioration of patients with COVID-19. Methods: Circulating polymorphonuclear cells (neutrophils) were isolated from human peripheral blood of 20 human subjects with COVID-19. Neutrophils were seeded in 96-well plates and treated with 0, 2.5 nM, 25 nM, and 250 nM of phorbol 12-myrisate 13-acetate (PMA) or 12 uM nigericin for 2 hours to stimulate NET production via canonical and noncanonical pathways, respectively. Following incubation, wells were treated with micrococcal nuclease, supernatants were collected from each well, and extracellular DNA content to quantify NETosis was detected by fluorescent plate reader. We calculated acute physiology and chronic health evaluation (APACHE-II) scores for every human subject. These were calculated at the same time point at which the neutrophils were collected. They were then compared to the degree of NETosis and absolute neutrophil count (ANC). These were analyzed using a simple linear regression model. We also categorized participants based on APACHE-II scores (APACHE-II <15, APACHE-II>15) and compared them to rates of NETosis using a bar graph. Results: APACHE II is a widely used ICU mortality prediction score that is used to risk-stratify patients. We found that participants with higher APACHE-II scores had higher rates of NETosis, both at 0 nM PMA and when stimulated with nigericin (figure 1a-b). This suggests that higher rates of NETosis correlate with increased disease severity. Additionally, we found a positive correlation between ANC and NETosis (Figure 1c-1d), suggesting that ANC itself is a reliable marker of NETosis and disease severity. Conclusion: NETosis is an important player in immune system defense but has also been implicated in various inflammatory lung conditions. We found that in patients with COVID-19, there was a positive correlation between worsening disease state, measure by APACHE II scores, and increased NETosis. This suggests that over-activation of neutrophils may play a role in disease progression. We also found a positive correlation between NETosis and ANC, indicating that the degree of circulating neutrophils is a reliable marker of the functional state of neutrophils, as well as disease severity.

Circulating neutrophils from critically ill covid-19 patients have increased netosis via canonical and non-canonical pathways

Introduction. The pathophysiology of infection with SARS-CoV-2 involves the lower airways and host-launched aggressive inflammatory responses leading to exacerbated lung damage in these vital tissues. Early clinical studies found that COVID-19 patients have higher levels of neutrophils in the circulation. Neutrophils are the most abundant leukocyte in circulation and are known to be highly proinflammatory due to production of neutrophil extracellular traps (NETosis). NETs are web-like chromatin structures coated with histones and proteases that both capture and kill invading pathogens. However, while being an effective countermeasure towards foreign microbes, this process also causes undesirable damage in host tissues. Therefore, we sought to characterize NETosis in circulating neutrophils from COVID-19 patients to determine whether this immunological response might be exacerbating or driving the disease state in COVID-19, rather than mitigating the virus. Methods.Blood was drawn daily from critically ill COVID-19 patients (n=16) after consent was obtained. Healthy controls (n=13) were screened for COVID-19 and gave blood once a week. Blood was drawn into lithium heparin tubes (BD Vacutainer). Neutrophils were isolated using PolymorphprepTM(PROGEN) per manufacturer's instructions. Cells were resuspended at 2x106 cells/ml for functional assays. Neutrophils were stimulated with increasing concentrations of PMA (Phorbol 12-myristate 13-acetate) of 2.5nM, 25nM and 250nM to stimulate NETosis via the canonical pathway, and nigericin at 15uM for the non-canonical pathway. NETosis was quantified using the Quant-iT™ PicoGreen™ dsDNA Assay Kit (Invitrogen) and by NET visualization via myeloperoxidase and nuclear staining (using Polyclonal Rabbit Anti-Human Myeloperoxidase by Dako and Hoescht stain by Invitrogen). Results.Functional NETosis assays of circulating neutrophils from COVID-19 patients demonstrate overall increased NETosis determined by increased release of dsDNA. This enhanced NETosis occurred at baseline and after stimulation with PMA when compared to healthy controls (Figure 1A, p <0.0001). Fluorescent microscopy also demonstrated increased NETosis in neutrophils from COVID-19 patients (Figure 1B;MPO-green and nucleus-blue). NETosis via the non-canonical pathway (induction with nigericin) was also increased in COVID-19 patients versus controls (p=0.02). Conclusions.Circulating neutrophils from critically ill COVID-19 patients are more prone to produce NETs than circulating neutrophils from healthy individuals. This is likely to lead to NETmediated tissue injury once neutrophils enter inflamed tissue, where they can potentially drive acute lung injury and acute respiratory distress syndrome, common causes of mortality in COVID-19. The finding of increased production of NETs by both canonical and non-canonical pathways is consistent with an overall hyper-activated state in COVID-19.

Very-low driving pressure ventilation in patients with acute respiratory distress syndrome on extracorporeal membrane oxygenation

Rationale: The ideal ventilator settings in patients with severe acute respiratory distress syndrome (ARDS) while on Extracorporeal Membrane Oxygenation (ECMO) are unknown. ELSO recommends modest driving pressures and PEEP (i.e., “lung rest”) during ECMO to minimize ventilator induced lung injury (VILI) and improve mortality. However, even lower driving pressures (DP) may improve inflammatory and lung injury biomarker profiles, and possibly improve mortality. The focus of this study was to evaluate the feasibility and impact of very-low DP in patients with ARDS on ECMO. Methods: Patients on ECMO due to ARDS from coronavirus disease 2019 had their DP decreased from 10 to 1-5 cmH2O for two hours, as tolerated. The other ventilator settings were unchanged and were consistent with ELSO guidelines;positive end-expiratory pressure (10-15 cmH2O) and a respiratory rate 10 breaths per minute. During the low DP protocol, the transpulmonary pressure was monitored with esophageal manometry. Plasma (for IL6 and sRAGE) and urine were collected before and after the protocol. Results: Thirty patients were enrolled and ultimately 21 patients underwent the low DP protocol. Seventeen were male, aged 51 ± 9 years, median BMI of 31.7 kg/m2 (IQR 27.4-35.2), with a median SOFA score of 10 (IQR 8-12) at ICU admission. There were no complications during the low DP protocol (1-5 cm H2O). The protocol was performed a median of 16 (IQR 13.5-20) hours after ECMO initiation. Average ECMO days were 21 (IQR 12.5-41) with a survival to hospital discharge of 43% (9/21). Baseline average tidal volume (TV) was 3.4±2.6 ml/kg of predicted body weight (PBW), during the low DP protocol the TV decreased to 2.7±3.2 ml/kg of PDW. Two groups were noted-those who had spontaneous breaths vs. those who did not (see Figure 1). Ten patients during the low DP protocol continued to have unchanged TV, 5.2±2.8 to 5.4±2.7 ml/kg of PBW due to spontaneous breathing found on esophageal manometry. Eleven patients had no spontaneous breaths and TV decreased from 1.76±0.57 to 0.2±0.38 ml/kg of PBW during the low DP protocol. The spontaneous vs. nonspontaneous breathing groups has a statistically different TV before, during, and after the low DP protocol (p<0.001). Conclusions: Very-low DP is feasible in patients on ECMO support which may decrease VILI. However, in the absence of neuromuscular blockade patients might spontaneously breathe with the same transpulmonary pressure. Thus, whether low DP offers any advantage in spontaneous breathing vs. non-spontaneous breathing requires further study. (Table Presented).