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Background Severe COVID-19 induced acute respiratory distress syndrome (ARDS) often requires extracorporeal membrane oxygenation (ECMO). Recent German health insurance data revealed low ICU survival rates. Patient characteristics and experience of the ECMO center may determine intensive care unit (ICU) survival. The current study aimed to identify factors affecting ICU survival of COVID-19 ECMO patients. Methods 673 COVID-19 ARDS ECMO patients treated in 26 centers between January 1st 2020 and March 22nd 2021 were included. Data on clinical characteristics, adjunct therapies, complications, and outcome were documented. Block wise logistic regression analysis was applied to identify variables associated with ICU-survival. Results Most patients were between 50 and 70 years of age. PaO 2 /FiO 2 ratio prior to ECMO was 72 mmHg (IQR: 58–99). ICU survival was 31.4%. Survival was significantly lower during the 2nd wave of the COVID-19 pandemic. A subgroup of 284 (42%) patients fulfilling modified EOLIA criteria had a higher survival (38%) ( p  = 0.0014, OR 0.64 (CI 0.41–0.99)). Survival differed between low, intermediate, and high-volume centers with 20%, 30%, and 38%, respectively ( p  = 0.0024). Treatment in high volume centers resulted in an odds ratio of 0.55 (CI 0.28–1.02) compared to low volume centers. Additional factors associated with survival were younger age, shorter time between intubation and ECMO initiation, BMI > 35 (compared to < 25), absence of renal replacement therapy or major bleeding/thromboembolic events. Conclusions Structural and patient-related factors, including age, comorbidities and ECMO case volume, determined the survival of COVID-19 ECMO. These factors combined with a more liberal ECMO indication during the 2nd wave may explain the reasonably overall low survival rate. Careful selection of patients and treatment in high volume ECMO centers was associated with higher odds of ICU survival. Trial registration Registered in the German Clinical Trials Register (study ID: DRKS00022964, retrospectively registered, September 7th 2020, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00022964 . Graphical abstract

PurposeThe question of whether cancer patients with severe respiratory failure benefit from veno-venous extracorporeal membrane oxygenation (vv-ECMO) remains unanswered. We, therefore, analyzed clinical characteristics and outcomes of a large cohort of cancer patients treated with vv-ECMO with the aim to identify prognostic factors.Methods297 cancer patients from 19 German and Austrian hospitals who underwent vv-ECMO between 2009 and 2019 were retrospectively analyzed. A multivariable cox proportional hazards analysis for overall survival was performed. In addition, a propensity score-matched analysis and a latent class analysis were conducted.ResultsPatients had a median age of 56 (IQR 44–65) years and 214 (72%) were males. 159 (54%) had a solid tumor and 138 (47%) a hematologic malignancy. The 60-day overall survival rate was 26.8% (95% CI 22.1–32.4%). Low platelet count (HR 0.997, 95% CI 0.996–0.999; p = 0.0001 per 1000 platelets/µl), elevated lactate levels (HR 1.048, 95% CI 1.012–1.084; p = 0.0077), and disease status (progressive disease [HR 1.871, 95% CI 1.081–3.238; p = 0.0253], newly diagnosed [HR 1.571, 95% CI 1.044–2.364; p = 0.0304]) were independent adverse prognostic factors for overall survival. A propensity score-matched analysis with patients who did not receive ECMO treatment showed no significant survival advantage for treatment with ECMO.ConclusionThe overall survival of cancer patients who require vv-ECMO is poor. This study shows that the value of vv-ECMO in cancer patients with respiratory failure is still unclear and further research is needed. The risk factors identified in the present analysis may help to better select patients who may benefit from vv-ECMO.

Background: There is ongoing debate whether lung physiology of COVID-19-associated acute respiratory distress syndrome (ARDS) differs from ARDS of other origin. Objective: The aim of this study was to analyze and compare how critically ill patients with COVID-19 and Influenza A or B were ventilated in our tertiary care center with or without extracorporeal membrane oxygenation (ECMO). We ask if acute lung failure due to COVID-19 requires different intensive care management compared to conventional ARDS. Methods: 25 patients with COVID-19-associated ARDS were matched to a cohort of 25 Influenza patients treated in our center from 2011 to 2021. Subgroup analysis addressed whether patients on ECMO received different mechanical ventilation than patients without extracorporeal support. Results: Compared to Influenza-associated ARDS, COVID-19 patients had higher ventilatory system compliance (40.7 mL/mbar [31.8–46.7 mL/mbar] vs. 31.4 mL/mbar [13.7–42.8 mL/mbar], p = 0.198), higher ventilatory ratio (1.57 [1.31–1.84] vs. 0.91 [0.44–1.38], p = 0.006) and higher minute ventilation at the time of intubation (mean minute ventilation 10.7 L/min [7.2–12.2 L/min] for COVID-19 vs. 6.0 L/min [2.5–10.1 L/min] for Influenza, p = 0.013). There were no measurable differences in P/F ratio, positive end-expiratory pressure (PEEP) and driving pressures (ΔP). Respiratory system compliance deteriorated considerably in COVID-19 patients on ECMO during 2 weeks of mechanical ventilation (Crs, mean decrease over 2 weeks −23.87 mL/mbar ± 32.94 mL/mbar, p = 0.037) but not in ventilated Influenza patients on ECMO and less so in ventilated COVID-19 patients without ECMO. For COVID-19 patients, low driving pressures on ECMO were strongly correlated to a decline in compliance after 2 weeks (Pearson’s R 0.80, p = 0.058). Overall mortality was insignificantly lower for COVID-19 patients compared to Influenza patients (40% vs. 48%, p = 0.31). Outcome was insignificantly worse for patients requiring veno-venous ECMO in both groups (50% mortality for COVID-19 on ECMO vs. 27% without ECMO, p = 0.30/56% vs. 34% mortality for Influenza A/B with and without ECMO, p = 0.31). Conclusion: The pathophysiology of early COVID-19-associated ARDS differs from Influenza-associated acute lung failure by sustained respiratory mechanics during the early phase of ventilation. We question whether intubated COVID-19 patients on ECMO benefit from extremely low driving pressures, as this appears to accelerate derecruitment and consecutive loss of ventilatory system compliance.

Extracorporeal membrane oxygenation (ECMO) is an important rescue therapy method for the treatment of severe hypoxic lung injury. In some cases, oxygen saturation and oxygen partial pressure in the arterial blood are low despite ECMO therapy. There are case reports in which patients with such instances of refractory hypoxemia received a second membrane lung, either in series or in parallel, to overcome the hypoxemia. It remains unclear whether the parallel or serial connection is more effective. Therefore, we used an improved version of our full-flow ECMO mock circuit to test this. The measurements were performed under conditions in which the membrane lungs were unable to completely oxygenate the blood. As a result, only the photometric pre- and post-oxygenator saturations, blood flow and hemoglobin concentration were required for the calculation of oxygen transfer rates. The results showed that for a pre-oxygenator saturation of 45% and a total blood flow of 10 L/min, the serial connection of two identical 5 L rated oxygenators is 17% more effective in terms of oxygen transfer than the parallel connection. Although the idea of using a second membrane lung if refractory hypoxia occurs is intriguing from a physiological point of view, due to the invasiveness of the solution, further investigations are needed before this should be used in a wider clinical setting.

Background Even though bleeding and thromboembolic events are major complications of extracorporeal membrane oxygenation (ECMO), data on the incidence of venous thrombosis (VT) and thromboembolism (VTE) under ECMO are scarce. This study analyzes the incidence and predictors of VTE in patients treated with ECMO due to respiratory failure. Methods Retrospective analysis of patients treated on ECMO in our center from 04/2010 to 11/2015. Patients with thromboembolic events prior to admission were excluded. Diagnosis was made by imaging in survivors and postmortem examination in deceased patients. Results Out of 102 screened cases, 42 survivors and 21 autopsy cases [mean age 46.0 ± 14.4 years; 37 (58.7 %) males] fulfilling the above-mentioned criteria were included. Thirty-four patients (54.0 %) underwent ECMO therapy due to ARDS, and 29 patients (46.0 %) with chronic organ failure were bridged to lung transplantation. Despite systemic anticoagulation at a mean PTT of 50.6 ± 12.8 s, [VT/VTE 47.0 ± 12.3 s and no VT/VTE 53.63 ± 12.51 s ( p  = 0.037)], VT and/or VTE was observed in 29 cases (46.1 %). The rate of V. cava thrombosis was 15/29 (51.7 %). Diagnosis of pulmonary embolism prevailed in deceased patients [5/21 (23.8 %) vs. 2/42 (4.8 %) ( p  = 0.036)]. In a multivariable analysis, only aPTT and time on ECMO predicted VT/VTE. There was no difference in the incidence of clinically diagnosed VT in ECMO survivors and autopsy findings. Conclusions Venous thrombosis and thromboembolism following ECMO therapy are frequent. Quality of anticoagulation and ECMO runtime predicted thromboembolic events.

Background Postoperative pulmonary complications (PPCs) increase morbidity and mortality of surgical patients, duration of hospital stay and costs. Postoperative atelectasis of dorsal lung regions as a common PPC has been described before, but its clinical relevance is insufficiently examined. Pulmonary electrical impedance tomography (EIT) enables the bedside visualization of regional ventilation in real-time within a transversal section of the lung. Dorsal atelectasis or effusions might cause a ventral redistribution of ventilation. We hypothesized the existence of ventral redistribution in spontaneously breathing patients during their recovery from abdominal and peripheral surgery and that vital capacity is reduced if regional ventilation shifts to ventral lung regions. Methods This prospective observational study included 69 adult patients undergoing elective surgery with an expected intermediate or high risk for PPCs. Patients undergoing abdominal and peripheral surgery were recruited to obtain groups of equal size. Patients received general anesthesia with and without additional regional anesthesia. On the preoperative, the first and the third postoperative day, EIT was performed at rest and during spirometry (forced breathing). The center of ventilation in dorso-ventral direction (COVy) was calculated. Results Both groups received intraoperative low tidal volume ventilation. Postoperative ventral redistribution of ventilation (forced breathing COVy; preoperative: 16.5 (16.0–17.3); first day: 17.8 (16.9–18.2), p  < 0.004; third day: 17.4 (16.2–18.2), p  = 0.020) and decreased forced vital capacity in percentage of predicted values (FVC%predicted) (median: 93, 58, 64%, respectively) persisted after abdominal surgery. In addition, dorsal to ventral shift was associated with a decrease of the FVC%predicted on the third postoperative day ( r  = − 0.66; p  < 0.001). A redistribution of pulmonary ventilation was not observed after peripheral surgery. FVC%predicted was only decreased on the first postoperative day (median FVC%predicted on the preoperative, first and third day: 85, 81 and 88%, respectively). In ten patients occurred pulmonary complications after abdominal surgery also in two patients after peripheral surgery. Conclusions After abdominal surgery ventral redistribution of ventilation persisted up to the third postoperative day and was associated with decreased vital capacity. The peripheral surgery group showed only minor changes in vital capacity, suggesting a role of the location of surgery for postoperative redistribution of pulmonary ventilation. Trial registration This prospective observational single centre study was submitted to registration prior to patient enrollment at ClinicalTrials.gov ( NCT02419196 , Date of registration: December 1, 2014). Registration was finalized at April 17, 2015.

Extracorporeal membrane oxygenation (ECMO) has become an important therapeutic approach in the COVID-19 pandemic. The development and research in this field strongly relies on animal models; however, efforts are being made to find alternatives. In this work, we present a new mock circuit for ECMO that allows measurements of the oxygen transfer rate of a membrane lung at full ECMO blood flow. The mock utilizes a large reservoir of heparinized porcine blood to measure the oxygen transfer rate of the membrane lung in a single passage. The oxygen transfer rate is calculated from blood flow, hemoglobin value, venous saturation, and post-membrane arterial oxygen pressure. Before the next measuring sequence, the blood is regenerated to a venous condition with a sweep gas of nitrogen and carbon dioxide. The presented mock was applied to investigate the effect of a recirculation loop on the oxygen transfer rate of an ECMO setup. The recirculation loop caused a significant increase in post-membrane arterial oxygen pressure (paO2). The effect was strongest for the highest recirculation flow. This was attributed to a smaller boundary layer on gas fibers due to the increased blood velocity. However, the increase in paO2 did not translate to significant increases in the oxygen transfer rate because of the minor significance of physically dissolved oxygen for gas transfer. In conclusion, our results regarding a new ECMO mock setup demonstrate that recirculation loops can improve ECMO performance, but not enough to be clinically relevant.

Background: Pulmonary embolism (PE) is a life-threatening condition with high mortality, particularly in high-risk cases where rapid clinical deterioration is common. The optimal management strategy for high-risk PE remains debated. Systemic thrombolysis (ST) is widely used but is associated with substantial bleeding risks. Surgical pulmonary embolectomy (SPE) has re-emerged as a viable alternative, particularly in patients with contraindications to thrombolysis or failed response. However, the evidence comparing SPE and ST in critically ill patients remains limited, and current guidelines provide only limited guidance. This study aims to evaluate the outcomes between SPE and ST in critically ill patients, focusing on mortality and complication rates. Methods: This retrospective study included 96 high risk patients with severe acute pulmonary embolism treated between 2015 and 2023, with 48 undergoing SPE and 48 receiving ST who were matched 1:1 based on baseline variables and hemodynamic presentation. Outcomes assessed included in-hospital mortality, PE-related death, neurological complications, bleeding events, hospitalization duration, as well as further postinterventional complications. Results: In-hospital mortality was 16.6% in the SPE group in contrast to 25.0% in the ST group (p = 0.765). Neurological complications were significantly lower in SPE (2.1%) compared to ST (12.5%) (p = 0.05). Life-threatening hemorrhage occurred at similar rates in both groups (SPE: 18.8%, ST: 14.6%); however, non-life-threatening bleeding was more common in ST (16.7% vs. 2.1%, p = 0.014). Hospitalization duration was significantly longer for SPE patients (mean 17.4 vs. 11.4 days, p < 0.001), who also presented with more severe disease, including higher ECMO utilization. Conclusions: SPE is a safe and effective alternative to ST in PE, offering comparable mortality, fewer neurologic complication and a reduced risk of bleeding. These findings highlight the importance of individualized, risk-adapted treatment pathways and support the inclusion of SPE as a frontline consideration in the management of PE in critically ill patients in experienced centers with multidisciplinary support.

Temporary hypercapnia has been shown to increase cerebral blood flow (CBF) and might be used as a therapeutical tool in patients with severe subarachnoid hemorrhage (SAH). It was the aim of this study was to investigate the optimum duration of hypercapnia. This point is assumed to be the time at which buffer systems become active, cause an adaptation to changes of the arterial partial pressure of carbon dioxide (PaCO 2 ) and annihilate a possible therapeutic effect. In this prospective interventional study in a neurosurgical ICU the arterial partial pressure of carbon dioxide (PaCO 2 ) was increased to a target range of 55 mmHg for 120 min by modification of the respiratory minute volume (RMV) one time a day between day 4 and 14 in 12 mechanically ventilated poor-grade SAH-patients. Arterial blood gases were measured every 15 min. CBF and brain tissue oxygen saturation (StiO 2 ) were the primary and secondary end points. Intracranial pressure (ICP) was controlled by an external ventricular drainage. Under continuous hypercapnia (PaCO 2 of 53.17 ± 5.07), CBF was significantly elevated between 15 and 120 min after the start of hypercapnia. During the course of the trial intervention, cardiac output also increased significantly. To assess the direct effect of hypercapnia on brain perfusion, the increase of CBF was corrected by the parallel increase of cardiac output. The maximum direct CBF enhancing effect of hypercapnia of 32% was noted at 45 min after the start of hypercapnia. Thereafter, the CBF enhancing slowly declined. No relevant adverse effects were observed. CBF and StiO 2 reproducibly increased by controlled hypercapnia in all patients. After 45 min, the curve of CBF enhancement showed an inflection point when corrected by cardiac output. It is concluded that 45 min might be the optimum duration for a therapeutic use and may provide an optimal balance between the benefits of hypercapnia and risks of a negative rebound effect after return to normal ventilation parameters. Trial registration: The study was approved by the institutional ethics committee (AZ 230/14) and registered at ClinicalTrials.gov (Trial-ID: NCT01799525). Registered 01/01/2015.