The intricate physiology of veno-venous extracorporeal membrane oxygenation: an overview for clinicians

During veno-venous extracorporeal membrane oxygenation (V-V ECMO), blood is drained from the central venous circulation to be oxygenated and decarbonated by an artificial lung. It is then reinfused into the right heart and pulmonary circulation where further gas-exchange occurs. Each of these steps is characterized by a peculiar physiology that this manuscript analyses, with the aim of providing bedside tools for clinical care: we begin by describing the factors that affect the efficiency of blood drainage, such as patient and cannulae position, fluid status, cardiac output and ventilatory strategies. We then dig into the complexity of extracorporeal gas-exchange, with particular reference to the effects of extracorporeal blood-flow (ECBF), fraction of delivered oxygen (FdO2) and sweep gas-flow (SGF) on oxygenation and decarbonation. Subsequently, we focus on the reinfusion of arterialized blood into the right heart, highlighting the effects on recirculation and, more importantly, on right ventricular function. The importance and challenges of haemodynamic monitoring during V-V ECMO are also analysed. Finally, we detail the interdependence between extracorporeal circulation, native lung function and mechanical ventilation in providing adequate arterial blood gases while allowing lung rest. In the absence of evidence-based strategies to care for this particular group of patients, clinical practice is underpinned by a sound knowledge of the intricate physiology of V-V ECMO.

Extracorporeal Carbon Dioxide Removal to Avoid Invasive Ventilation During Exacerbations of Chronic Obstructive Pulmonary Disease: VENT-AVOID Trial - A Randomized Clinical Trial

Rationale: It is unclear whether extracorporeal CO2 removal (ECCO2R) can reduce the rate of intubation or the total time on invasive mechanical ventilation (IMV) in adults experiencing an exacerbation of chronic obstructive pulmonary disease (COPD). Objectives: To determine whether ECCO2R increases the number of ventilator-free days within the first 5 days postrandomization (VFD-5) in exacerbation of COPD in patients who are either failing noninvasive ventilation (NIV) or who are failing to wean from IMV. Methods: This randomized clinical trial was conducted in 41 U.S. institutions (2018-2022) (ClinicalTrials.gov ID: NCT03255057). Subjects were randomized to receive either standard care with venovenous ECCO2R (NIV stratum: n = 26; IMV stratum: n = 32) or standard care alone (NIV stratum: n = 22; IMV stratum: n = 33). Measurements and Main Results: The trial was stopped early because of slow enrollment and enrolled 113 subjects of the planned sample size of 180. There was no significant difference in the median VFD-5 between the arms controlled by strata (P = 0.36). In the NIV stratum, the median VFD-5 for both arms was 5 days (median shift = 0.0; 95% confidence interval [CI]: 0.0-0.0). In the IMV stratum, the median VFD-5 in the standard care and ECCO2R arms were 0.25 and 2 days, respectively; median shift = 0.00 (95% confidence interval: 0.00-1.25). In the NIV stratum, all-cause in-hospital mortality was significantly higher in the ECCO2R arm (22% vs. 0%, P = 0.02) with no difference in the IMV stratum (17% vs. 15%, P = 0.73). Conclusions: In subjects with exacerbation of COPD, the use of ECCO2R compared with standard care did not improve VFD-5. Clinical trial registered with www.clinicaltrials.gov (NCT03255057).

Extracorporeal Life Support Organization Registry International Report 2022: 100,000 Survivors

The Extracorporeal Life Support Organization (ELSO) maintains the world's largest extracorporeal membrane oxygenation (ECMO) registry by volume, center participation, and international scope. This 2022 ELSO Registry Report describes the program characteristics of ECMO centers, processes of ECMO care, and reported outcomes. Neonates (0-28 days), children (29 days-17 years), and adults (≥18 years) supported with ECMO from 2009 through 2022 and reported to the ELSO Registry were included. This report describes adjunctive therapies, support modes, treatments, complications, and survival outcomes. Data are presented descriptively as counts and percent or median and interquartile range (IQR) by year, group, or level. Missing values were excluded before calculating descriptive statistics. Complications are reported per 1,000 ECMO hours. From 2009 to 2022, 154,568 ECMO runs were entered into the ELSO Registry. Seven hundred and eighty centers submitted data during this time (557 in 2022). Since 2009, the median annual number of adult ECMO runs per center per year increased from 4 to 15, whereas for pediatric and neonatal runs, the rate decreased from 12 to 7. Over 50% of patients were transferred to the reporting ECMO center; 20% of these patients were transported with ECMO. The use of prone positioning before respiratory ECMO increased from 15% (2019) to 44% (2021) for adults during the coronavirus disease-2019 (COVID-19) pandemic. Survival to hospital discharge was greatest at 68.5% for neonatal respiratory support and lowest at 29.5% for ECPR delivered to adults. By 2022, the Registry had enrolled its 200,000th ECMO patient and 100,000th patient discharged alive. Since its inception, the ELSO Registry has helped centers measure and compare outcomes across its member centers and strategies of care. Continued growth and development of the Registry will aim to bolster its utility to patients and centers.

Routine Metagenomics Service for ICU Patients with Respiratory Infection

Rationale: Respiratory metagenomics (RMg) needs evaluation in a pilot service setting to determine utility and inform implementation into routine clinical practice. Objectives: Feasibility, performance, and clinical impacts on antimicrobial prescribing and infection control were recorded during a pilot RMg service. Methods: RMg was performed on 128 samples from 87 patients with suspected lower respiratory tract infection (LRTI) on two general and one specialist respiratory ICUs at Guy's and St Thomas' NHS Foundation Trust, London. Measurements and Main Results: During the first 15 weeks, RMg provided same-day results for 110 samples (86%), with a median turnaround time of 6.7 hours (interquartile range = 6.1-7.5 h). RMg was 93% sensitive and 81% specific for clinically relevant pathogens compared with routine testing. Forty-eight percent of RMg results informed antimicrobial prescribing changes (22% escalation; 26% deescalation) with escalation based on speciation in 20 out of 24 cases and detection of acquired-resistance genes in 4 out of 24 cases. Fastidious or unexpected organisms were reported in 21 samples, including anaerobes (n = 12), Mycobacterium tuberculosis, Tropheryma whipplei, cytomegalovirus, and Legionella pneumophila ST1326, which was subsequently isolated from the bedside water outlet. Application to consecutive severe community-acquired LRTI cases identified Staphylococcus aureus (two with SCCmec and three with luk F/S virulence determinants), Streptococcus pyogenes (emm1-M1uk clone), S. dysgalactiae subspecies equisimilis (STG62647A), and Aspergillus fumigatus with multiple treatments and public health impacts. Conclusions: This pilot study illustrates the potential of RMg testing to provide benefits for antimicrobial treatment, infection control, and public health when provided in a real-world critical care setting. Multicenter studies are now required to inform future translation into routine service.

Physiotherapy for patients on extracorporeal membrane oxygenation support: How, When, and Who. An international EuroELSO survey

BACKGROUND AND PURPOSE

Extracorporeal membrane oxygenation (ECMO) continues to play an essential role in organ support in cardiogenic shock or acute respiratory distress syndrome and bridging to transplantation. The main purpose of the present survey was to define which clinical and organizational practices are adopted for the administration of physiotherapy in adult patients undergoing ECMO support worldwide.

METHODS

This international survey was conceived in November 2021. The survey launch was announced at the 10th EuroELSO (European ELSO chapter) Congress, London, May 2022.

RESULTS

The survey returned 32 questionnaires from 29 centers across 14 countries. 17 centers (53.1%) had more than 30 intensive care unit beds available and most (46.8%) were able to care for five to 10 patients on extracorporeal life support simultaneously. The predominant physiotherapist-to-patient ratio was 1:>5 (37.5%); physiotherapy was available 5/7 days and 7/7 days by 31.2% and 25% respectively. Respiratory physiotherapy was not defined by a specific protocol in most centers (46.8%) while 31.2% declared that the treatment commences less than 12 h after sedation is stopped/reduced. Mostly, early physiotherapy in non-cooperative ventilated patients was provided within the first 48 h (68.6%) and consisted of as passive range of motion, in-bed positioning, and splinting. Postural passages and sitting were provided to patients and walking was included in those advanced motor activities which are part of the treatment.

CONCLUSION

Physiotherapy in patients on ECLS is feasible, however substantial variability exists between centers with a trend of delivering not protocolized and understaffed rehabilitation practices.

State of the art: Monitoring of the respiratory system during veno-venous extracorporeal membrane oxygenation

Monitoring the patient receiving veno-venous extracorporeal membrane oxygenation (VV ECMO) is challenging due to the complex physiological interplay between native and membrane lung. Understanding these interactions is essential to understand the utility and limitations of different approaches to respiratory monitoring during ECMO. We present a summary of the underlying physiology of native and membrane lung gas exchange and describe different tools for titrating and monitoring gas exchange during ECMO. However, the most important role of VV ECMO in severe respiratory failure is as a means of avoiding further ergotrauma. Although optimal respiratory management during ECMO has not been defined, over the last decade there have been advances in multimodal respiratory assessment which have the potential to guide care. We describe a combination of imaging, ventilator-derived or invasive lung mechanic assessments as a means to individualise management during ECMO.

Bilateral Femoral Cannulation Is Associated With Reduced Severe Limb Ischemia-Related Complications Compared With Unilateral Femoral Cannulation in Adult Peripheral Venoarterial Extracorporeal Membrane Oxygenation: Results From the Extracorporeal Life Support Registry

OBJECTIVES

Peripheral venoarterial extracorporeal membrane oxygenation (ECMO) with femoral access is obtained through unilateral or bilateral groin cannulation. Whether one cannulation strategy is associated with a lower risk for limb ischemia remains unknown. We aim to assess if one strategy is preferable.

DESIGN

A retrospective cohort study based on the Extracorporeal Life Support Organization registry.

SETTING

ECMO centers worldwide included in the Extracorporeal Life Support Organization registry.

PATIENTS

All adult patients (≥ 18 yr) who received peripheral venoarterial ECMO with femoral access and were included from 2014 to 2020.

INTERVENTIONS

Unilateral or bilateral femoral cannulation.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the occurrence of limb ischemia defined as a composite endpoint including the need for a distal perfusion cannula (DPC) after 6 hours from implantation, compartment syndrome/fasciotomy, amputation, revascularization, and thrombectomy. Secondary endpoints included bleeding at the peripheral cannulation site, need for vessel repair, vessel repair after decannulation, and in-hospital death. Propensity score matching was performed to account for confounders. Overall, 19,093 patients underwent peripheral venoarterial ECMO through unilateral ( n = 11,965) or bilateral ( n = 7,128) femoral cannulation. Limb ischemia requiring any intervention was not different between both groups (bilateral vs unilateral: odds ratio [OR], 0.92; 95% CI, 0.82-1.02). However, there was a lower rate of compartment syndrome/fasciotomy in the bilateral group (bilateral vs unilateral: OR, 0.80; 95% CI, 0.66-0.97). Bilateral cannulation was also associated with lower odds of cannulation site bleeding (bilateral vs unilateral: OR, 0.87; 95% CI, 0.76-0.99), vessel repair (bilateral vs unilateral: OR, 0.55; 95% CI, 0.38-0.79), and in-hospital mortality (bilateral vs unilateral: OR, 0.85; 95% CI, 0.81-0.91) compared with unilateral cannulation. These findings were unchanged after propensity matching.

CONCLUSIONS

This study showed no risk reduction for overall limb ischemia-related events requiring DPC after 6 hours when comparing bilateral to unilateral femoral cannulation in peripheral venoarterial ECMO. However, bilateral cannulation was associated with a reduced risk for compartment syndrome/fasciotomy, lower rates of bleeding and vessel repair during ECMO, and lower in-hospital mortality.

The Effect of Lower Tidal Volume Ventilation Facilitated by Extracorporeal Carbon Dioxide Removal Compared With Conventional Lung Protective Ventilation on Cardiac Function

OBJECTIVES

Lower tidal volume ventilation (targeting 3 mL/kg predicted body weight, PBW) facilitated by extracorporeal carbon dioxide removal (ECCO2R) has been investigated as a potential therapy for acute hypoxemic respiratory failure (AHRF) in the pRotective vEntilation with veno-venouS lung assisT in respiratory failure (REST) trial. We investigated the effect of this strategy on cardiac function, and in particular the right ventricle.

DESIGN

Substudy of the REST trial.

SETTING

Nine U.K. ICUs.

PATIENTS

Patients with AHRF (Pao2/Fio2 < 150 mm Hg [20 kPa]).

INTERVENTION

Transthoracic echocardiography and N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurements were collected at baseline and postrandomization in patients randomized to ECCO2R or usual care.

MEASUREMENTS

The primary outcome measures were a difference in tricuspid annular plane systolic excursion (TAPSE) on postrandomization echocardiogram and difference in NT-proBNP postrandomization.

RESULTS

There were 21 patients included in the echocardiography cohort (ECCO2R, n = 13; usual care, n = 8). Patient characteristics were similar in both groups at baseline. Median (interquartile range) tidal volumes were lower in the ECCO2R group compared with the usual care group postrandomization; 3.6 (3.1-4.2) mL/kg PBW versus 5.2 (4.9-5.7) mL/kg PBW, respectively (p = 0.01). There was no difference in the primary outcome measure of mean (sd) TAPSE in the ECCO2R and usual care groups postrandomization; 21.3 (5.4) mm versus 20.1 (3.2) mm, respectively (p = 0.60). There were 75 patients included in the NT-proBNP cohort (ECCO2R, n = 36; usual care, n = 39). Patient characteristics were similar in both groups at baseline. Median (interquartile range [IQR]) tidal volumes were lower in the ECCO2R group than the usual care group postrandomization; 3.8 (3.3-4.2) mL/kg PBW versus 6.7 (5.8-8.1) mL/kg PBW, respectively (p < 0.0001). There was no difference in median (IQR) NT-proBNP postrandomization; 1121 (241-5370) pg/mL versus 1393 (723-4332) pg/mL in the ECCO2R and usual care groups, respectively (p = 0.30).

CONCLUSIONS

In patients with AHRF, a reduction in tidal volume facilitated by ECCO2R, did not modify cardiac function.

Clinical impact of screening computed tomography in extracorporeal membrane oxygenation: a retrospective cohort study

BACKGROUND

Data on the prevalence and clinical impact of extrapulmonary findings at screening computed tomography (CT) on initiation of veno-venous extracorporeal membrane oxygenation (V-V ECMO) are limited. We aimed to identify the prevalence of extrapulmonary findings on screening CT following V-V ECMO initiation. We hypothesized that extrapulmonary findings would influence clinical management and outcome.

METHODS

Retrospective analysis (2011-2021) of admission screening CT including head, abdomen and pelvis with contrast of consecutive patients on initiation of V-V ECMO. CT findings identified by the attending consultant radiologist were extracted. Demographics, admission physiological and laboratory data, clinical decision-making following CT and ECMO ICU mortality were recorded from the electronic medical record. We used multivariable logistic regression and Kaplan-Meier curves to evaluate associations between extrapulmonary findings and ECMO ICU mortality.

RESULTS

Of the 833 patients receiving V-V ECMO, 761 underwent routine admission CT (91.4%). ECMO ICU length of stay was 19 days (IQR 12-23); ICU mortality at the ECMO centre was 18.9%. An incidental extrapulmonary finding was reported in 227 patients (29.8%), leading to an invasive procedure in 12/227 cases (5.3%) and a change in medical management (mainly in anticoagulation strategy) in 119/227 (52.4%). Extrapulmonary findings associated with mortality were intracranial haemorrhage (OR 2.34 (95% CI 1.31-4.12), cerebral infarction (OR 3.59 (95% CI 1.26-9.86) and colitis (OR 2.80 (95% CI 1.35-5.67).

CONCLUSIONS

Screening CT frequently identifies extrapulmonary findings of clinical significance. Newly detected intracranial haemorrhage, cerebral infarction and colitis were associated with increased ICU mortality.

Prevalence and Indications for Oxygenator Circuit Replacement in Patients Receiving Venovenous Extracorporeal Membrane Oxygenation

In this retrospective observational cohort study, we aimed to describe the rate of extracorporeal membrane oxygenation (ECMO) circuit change, the associated risk factors and its relationship with patient characteristics and outcome in patients receiving venovenous (VV) ECMO at our center between January 2015 and November 2017. Twenty-seven percent of the patients receiving VV ECMO (n = 224) had at least one circuit change, which was associated with lower ICU survival (68% vs 82% p=0.032) and longer ICU stay (30 vs . 17 days p < 0.001). Circuit duration was similar when stratified by gender, clinical severity, or prior circuit change. Hematological abnormalities and increased transmembrane lung pressure (TMLP) were the most frequent indication for circuit change. The change in transmembrane lung resistance (Δ TMLR) gave better prediction of circuit change than TMLP, TMLR, or ΔTMLP. Low postoxygenator PO 2 was indicated as a reason for one-third of the circuit changes. However, the ECMO oxygen transfer was significantly higher in cases of circuit change with documented "low postoxygenator PO 2 " than those without (244 ± 62 vs. 200 ± 57 ml/min; p = 0.009). The results suggest that circuit change in VV ECMO is associated with worse outcomes, that the Δ TMLR is a better predictor of circuit change than TMLP, and that the postoxygenator PO 2 is an unreliable proxy for the oxygenator function.

Relationship between D-dimers and dead-space on disease severity and mortality in COVID-19 acute respiratory distress syndrome: A retrospective observational cohort study

BACKGROUND

Despite its diagnostic and prognostic importance, physiologic dead space fraction is not included in the current ARDS definition or severity classification. ARDS caused by COVID-19 (C-ARDS) is characterized by increased physiologic dead space fraction and hypoxemia. Our aim was to investigate the relationship between dead space indices, markers of inflammation, immunothrombosis, severity and intensive care unit (ICU) mortality.

RESULTS

Retrospective data including demographics, gas exchange, ventilatory parameters, and respiratory mechanics in the first 24 h of invasive ventilation. Plasma concentrations of D-dimers and ferritin were not significantly different across C-ARDS severity categories. Weak relationships were found between D-dimers and VR (r = 0.07, p = 0.13), P_ETCO₂/PaCO₂ (r = -0.1, p = 0.02), or estimated dead space fraction (r = 0.019, p = 0.68). Age, PaO₂/FiO₂, pH, P_ETCO₂/PaCO₂ and ferritin, were independently associated with ICU mortality. We found no association between D-dimers or ferritin and any dead-space indices adjusting for PaO₂/FiO₂, days of ventilation, tidal volume, and respiratory system compliance.

CONCLUSIONS

We report no association between dead space and inflammatory markers in mechanically ventilated patients with C-ARDS. Our results support theories suggesting that multiple mechanisms, in addition to immunothrombosis, play a role in the pathophysiology of respiratory failure and degree of dead space in C-ARDS.

"Bridging the Gap" international ECLS training and simulation - evaluation of the 10th educational corner on EuroELSO congress 2022 in London, United Kingdom

Introduction: Simulation training offers an authentic team-based learning opportunity without risk to real patients. The Educational Corner at the annual congress of the European Branch of Extracorporeal Life Support Organisation (EuroELSO) provided an opportunity for multiple simulation training sessions facilitated by experts from all over the world.Aim: We aimed to review the educational impact of EuroELSO Educational Corner and whether it provides a quality ECLS training to a wide spectrum of multidisciplinary international attendees utilising high and low fidelity simulation, workshops and hands on sessions.Methods: During the congress, 43 sessions were conducted dedicated to ECLS education with identified educational objectives. The sessions focused on management of adults and children on V-V or V-A ECMO. Adult sessions covered emergencies on mechanical circulatory support with management of LVAD and Impella, managing refractory hypoxemia on V-V ECMO, emergencies on ECMO, renal replacement therapy on ECMO, V-V ECMO, ECPR cannulation and performing perfect simulation. Paediatric sessions covered ECPR neck and central cannulation, renal replacement on ECMO, troubleshooting, cannulation workshop, V-V recirculation, ECMO for single ventricle, PIMS-TS and CDH, ECMO transport and neurological injury.Results: The Educational Corner was attended by more than 400 participants over the two congress days. Majority of responders (88%) reported that training sessions met the set educational goals and objectives and that this would change their current practice. Almost all (94%) reported that they received useful information and 95% would recommend the session to their colleagues.Conclusion: The Educational Corner, as an integral component of the annual EuroELSO congress, achieved the set educational goals and provided quality education based on the recipient survey. Structured multidisciplinary ECLS education with standardised curriculum and feedback is an important key step in delivering quality training to an international audience. Standardisation of European ECLS education remains an important focus of the EuroELSO.

International survey of neuromonitoring and neurodevelopmental outcome in children and adults supported on extracorporeal membrane oxygenation in Europe

BACKGROUND

Adverse neurological events during extracorporeal membrane oxygenation (ECMO) are common and may be associated with devastating consequences. Close monitoring, early identification and prompt intervention can mitigate early and late neurological morbidity. Neuromonitoring and neurocognitive/neurodevelopmental follow-up are critically important to optimize outcomes in both adults and children.

OBJECTIVE

To assess current practice of neuromonitoring during ECMO and neurocognitive/neurodevelopmental follow-up after ECMO across Europe and to inform the development of neuromonitoring and follow-up guidelines.

METHODS

The EuroELSO Neurological Monitoring and Outcome Working Group conducted an electronic, web-based, multi-institutional, multinational survey in Europe.

RESULTS

Of the 211 European ECMO centres (including non-ELSO centres) identified and approached in 23 countries, 133 (63%) responded. Of these, 43% reported routine neuromonitoring during ECMO for all patients, 35% indicated selective use, and 22% practiced bedside clinical examination alone. The reported neuromonitoring modalities were NIRS (n = 88, 66.2%), electroencephalography (n = 52, 39.1%), transcranial Doppler (n = 38, 28.5%) and brain injury biomarkers (n = 33, 24.8%). Paediatric centres (67%) reported using cranial ultrasound, though the frequency of monitoring varied widely. Before hospital discharge following ECMO, 50 (37.6%) reported routine neurological assessment and 22 (16.5%) routinely performed neuroimaging with more paediatric centres offering neurological assessment (65%) as compared to adult centres (20%). Only 15 (11.2%) had a structured longitudinal follow-up pathway (defined followup at regular intervals), while 99 (74.4%) had no follow-up programme. The majority (n = 96, 72.2%) agreed that there should be a longitudinal structured follow-up for ECMO survivors.

CONCLUSIONS

This survey demonstrated significant variability in the use of different neuromonitoring modalities during and after ECMO. The perceived importance of neuromonitoring and follow-up was noted to be very high with agreement for a longitudinal structured follow-up programme, particularly in paediatric patients. Scientific society endorsed guidelines and minimum standards should be developed to inform local protocols.

Steroid exposure and outcome in COVID-19 pneumonia

Background

Corticosteroids are used to treat COVID-19 pneumonia. However, the optimal dose is unclear. This study describes the association between corticosteroid exposure with disease severity and outcome in COVID-19 pneumonia.

Methods

This is a single-centre retrospective, observational study including adult ICU patients who received systemic corticosteroids for COVID-19 pneumonia between March 2020 and March 2021. We recorded patient characteristics, disease severity, total steroid exposure, respiratory support and gas exchange data, and 90-day mortality.

Results

We included 362 patients. We allocated patients to groups with increasing disease severity according to the highest level of respiratory support that they received: high-flow nasal oxygen or continuous positive airway pressure (HFNO/CPAP) in 12.7%, invasive mechanical ventilation (IMV) in 61.6%, and extracorporeal membrane oxygenation (ECMO) in 25.7%. For these three groups, the median (inter-quartile range [IQR]) age was 61 (54-71) vs 58 (50-66) vs 46 (38-53) yr, respectively (P<0.001); median (IQR) APACHE (Acute Physiology and Chronic Health Evaluation) II scores were 12 (9-15) vs 14 (12-18) vs 15 (12-17), respectively (P=0.006); the median (IQR) lowest P a O 2 /FiO₂ ratio was 15.1 (11.8-21.7) vs 15.1 (10.7-22.2) vs 9.5 (7.9-10.9) kPa, respectively (P<0.001). Ninety-day mortality was 9% vs 27% vs 37% (P=0.002). Median (IQR) dexamethasone-equivalent exposure was 37 (24-62) vs 174 (86-504) vs 535 (257-1213) mg (P<0.001). 'Pulsed' steroids were administered to 26% of the IMV group and 48% of the ECMO group. Patients with higher disease severity who received pulse steroids had a higher 90-day mortality.

Conclusions

Corticosteroid exposure increased with the severity of COVID-19 pneumonia. Pulsed dose steroids were used more frequently in patients receiving greater respiratory support. Future studies should address patient selection and outcomes associated with pulsed dose steroids in patients with severe and deteriorating COVID-19 pneumonia.

Changing epidemiology of acute kidney injury in critically ill patients with COVID-19: a prospective cohort

BACKGROUND

Acute kidney injury (AKI) is common in critically ill patients with coronavirus disease-19 (COVID-19). We aimed to explore the changes in AKI epidemiology between the first and the second COVID wave in the United Kingdom (UK).

METHODS

This was an observational study of critically ill adult patients with COVID-19 in an expanded tertiary care intensive care unit (ICU) in London, UK. Baseline characteristics, organ support, COVID-19 treatments, and patient and kidney outcomes up to 90 days after discharge from hospital were compared.

RESULTS

A total of 772 patients were included in the final analysis (68% male, mean age 56 ± 13.6). Compared with wave 1, patients in wave 2 were older, had higher body mass index and clinical frailty score, but lower baseline serum creatinine and C-reactive protein (CRP). The proportion of patients receiving invasive mechanical ventilation (MV) on ICU admission was lower in wave 2 (61% vs 80%; p < 0.001). AKI incidence within 14 days of ICU admission was 76% in wave 1 and 51% in wave 2 (p < 0.001); in wave 1, 32% received KRT compared with 13% in wave 2 (p < 0.001). Patients in wave 2 had significantly lower daily cumulative fluid balance (FB) than in wave 1. Fewer patients were dialysis dependent at 90 days in wave 2 (1% vs. 4%; p < 0.001).

CONCLUSIONS

In critically ill adult patients admitted to ICU with COVID-19, the risk of AKI and receipt of KRT significantly declined in the second wave. The trend was associated with less MV, lower PEEP and lower cumulative FB.

TRIAL REGISTRATION

NCT04445259.

Long-term outcomes in patients who received veno-venous extracorporeal membrane oxygenation and renal replacement therapy: a retrospective cohort study

Background

Acute kidney injury (AKI) is a frequent complication in patients with severe respiratory failure receiving extracorporeal membrane oxygenation (ECMO). However, little is known of long-term kidney function in ECMO survivors. We aimed to assess the long-term mortality and kidney outcomes in adult patients treated with veno-venous ECMO (VV-ECMO).

Methods

This was a single-centre retrospective study of adult patients (≥ 18 years old) who were treated with VV-ECMO at a commissioned ECMO centre in the UK between 1st September 2010, and 30th November 2016. AKI was defined and staged using the serum creatinine and urine output criteria of the Kidney Diseases: Improving Global Outcomes (KDIGO) classification. The primary outcome was 1-year mortality. Secondary outcomes were long-term mortality (up to March 2020), 1-year incidence of end-stage kidney disease (ESKD) or chronic kidney disease (CKD) among AKI patients who received renal replacement therapy (AKI-RRT), AKI patients who did not receive RRT (AKI-no RRT) and patients without AKI (non-AKI).

Results

A total of 300 patients [57% male; median age 44.5; interquartile range (IQR) 34–54] were included in the final analysis. Past medical histories included diabetes (12%), hypertension (17%), and CKD (2.3%). The main cause of severe respiratory failure was pulmonary infection (72%). AKI occurred in 230 patients (76.7%) and 59.3% received renal replacement therapy (RRT). One-year mortality was 32% in AKI-RRT patients vs. 21.4% in non-AKI patients (p = 0.014). The median follow-up time was 4.35 years. Patients who received RRT had a higher risk of 1-year mortality than those who did not receive RRT (adjusted HR 1.80, 95% CI 1.06, 3.06; p = 0.029). ESKD occurred in 3 patients, all of whom were in the AKI-RRT group. At 1-year, 41.2% of survivors had serum creatinine results available. Among these, CKD was prevalent in 33.3% of AKI-RRT patients vs. 4.3% in non-AKI patients (p = 0.004).

Conclusions

VV-EMCO patients with AKI-RRT had high long-term mortality. Monitoring of kidney function after hospital discharge was poor. In patients with follow-up creatinine results available, the CKD prevalence was high at 1 year, especially in AKI-RRT patients. More awareness about this serious long-term complication and appropriate follow-up interventions are required.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01046-0.

A randomised controlled trial of non-invasive ventilation compared with extracorporeal carbon dioxide removal for acute hypercapnic exacerbations of chronic obstructive pulmonary disease

Background

Patients presenting with acute hypercapnic respiratory failure due to exacerbations of chronic obstructive pulmonary disease (AECOPD) are typically managed with non-invasive ventilation (NIV). The impact of low-flow extracorporeal carbon dioxide removal (ECCO₂R) on outcome in these patients has not been explored in randomised trials.

Methods

Open-label randomised trial comparing NIV (NIV arm) with ECCO₂R (ECCO₂R arm) in patients with AECOPD at high risk of NIV failure (pH < 7.30 after ≥ 1 h of NIV). The primary endpoint was time to cessation of NIV. Secondary outcomes included device tolerance and complications, changes in arterial blood gases, hospital survival.

Results

Eighteen patients (median age 67.5, IQR (61.5–71) years; median GOLD stage 3 were enrolled (nine in each arm). Time to NIV discontinuation was shorter with ECCO₂R (7:00 (6:18–8:30) vs 24:30 (18:15–49:45) h, p = 0.004). Arterial pH was higher with ECCO₂R at 4 h post-randomisation (7.35 (7.31–7.37) vs 7.25 (7.21–7.26), p < 0.001). Partial pressure of arterial CO₂ (PaCO₂) was significantly lower with ECCO₂R at 4 h (6.8 (6.2–7.15) vs 8.3 (7.74–9.3) kPa; p = 0.024). Dyspnoea and comfort both rapidly improved with commencement of ECCO₂R. There were no severe or life-threatening complications in the study population. There were no episodes of major bleeding or red blood cell transfusion in either group. ICU and hospital length of stay were longer with ECCO₂R, and there was no difference in 90-day mortality or functional outcomes at follow-up.

Interpretation

There is evidence of benefit associated with ECCO₂R with time to improvement in respiratory acidosis, in respiratory physiology and an immediate improvement in patient comfort and dyspnoea with commencement of ECCO₂R. In addition, there was minimal clinically significant adverse events associated with ECCO₂R use in patients with AECOPD at risk of failing or not tolerating NIV. However, the ICU and hospital lengths of stay were longer in the ECCO₂R for similar outcomes.

Trial registration The trial is prospectively registered on ClinicalTrials.gov: NCT02086084. Registered on 13th March 2014, https://clinicaltrials.gov/ct2/show/NCT02086084?cond=ecco2r&draw=2&rank=8

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01006-8.

Evaluating the potential for respiratory metagenomics to improve treatment of secondary infection and detection of nosocomial transmission on expanded COVID-19 intensive care units

BACKGROUND

Clinical metagenomics (CMg) has the potential to be translated from a research tool into routine service to improve antimicrobial treatment and infection control decisions. The SARS-CoV-2 pandemic provides added impetus to realise these benefits, given the increased risk of secondary infection and nosocomial transmission of multi-drug-resistant (MDR) pathogens linked with the expansion of critical care capacity.

METHODS

CMg using nanopore sequencing was evaluated in a proof-of-concept study on 43 respiratory samples from 34 intubated patients across seven intensive care units (ICUs) over a 9-week period during the first COVID-19 pandemic wave.

RESULTS

An 8-h CMg workflow was 92% sensitive (95% CI, 75-99%) and 82% specific (95% CI, 57-96%) for bacterial identification based on culture-positive and culture-negative samples, respectively. CMg sequencing reported the presence or absence of β-lactam-resistant genes carried by Enterobacterales that would modify the initial guideline-recommended antibiotics in every case. CMg was also 100% concordant with quantitative PCR for detecting Aspergillus fumigatus from 4 positive and 39 negative samples. Molecular typing using 24-h sequencing data identified an MDR-K. pneumoniae ST307 outbreak involving 4 patients and an MDR-C. striatum outbreak involving 14 patients across three ICUs.

CONCLUSION

CMg testing provides accurate pathogen detection and antibiotic resistance prediction in a same-day laboratory workflow, with assembled genomes available the next day for genomic surveillance. The provision of this technology in a service setting could fundamentally change the multi-disciplinary team approach to managing ICU infections. The potential to improve the initial targeted treatment and rapidly detect unsuspected outbreaks of MDR-pathogens justifies further expedited clinical assessment of CMg.

Discharge Documentation and Follow-Up of Critically Ill Patients With Acute Kidney Injury Treated With Kidney Replacement Therapy: A Retrospective Cohort Study

Leading organisations recommend follow-up of acute kidney injury (AKI) survivors, as these patients are at risk of long-term complications and increased mortality. Information transfer between specialties and from tertiary to primary care is essential to ensure timely and appropriate follow-up. Our aim was to examine the association between completeness of discharge documentation and subsequent follow-up of AKI survivors who received kidney replacement therapy (KRT) in the Intensive Care Unit (ICU). We retrospectively analysed the data of 433 patients who had KRT for AKI during ICU admission in a tertiary care centre in the UK between June 2017 and May 2018 and identified patients who were discharged from hospital alive. Patients with pre-existing end-stage kidney disease and patients who were transferred from hospitals outside the catchment area were excluded. The primary objective was to assess the completeness of discharge documentation from critical care and hospital; secondary objectives were to determine cardiovascular medications reconciliation after AKI, and to investigate kidney care and outcomes at 1 year. The development of AKI and the need for KRT were mentioned in 85 and 82% of critical care discharge letters, respectively. Monitoring of kidney function post-discharge was recommended in 51.6% of critical care and 36.3% of hospital discharge summaries. Among 35 patients who were prescribed renin-angiotensin-aldosterone system inhibitors before hospitalisation, 15 (42.9%) were not re-started before discharge from hospital. At 3 months, creatinine and urine protein were measured in 88.2 and 11.8% of survivors, respectively. The prevalence of chronic kidney disease stage III or worse increased from 27.2% pre-hospitalisation to 54.9% at 1 year (p < 0.001). Our data demonstrate that discharge summaries of patients with AKI who received KRT lacked essential information. Furthermore, even in patients with appropriate documentation, renal follow-up was poor suggesting the need for more education and streamlined care pathways.

Effect of Lower Tidal Volume Ventilation Facilitated by Extracorporeal Carbon Dioxide Removal vs Standard Care Ventilation on 90-Day Mortality in Patients With Acute Hypoxemic Respiratory Failure: The REST Randomized Clinical Trial

IMPORTANCE

In patients who require mechanical ventilation for acute hypoxemic respiratory failure, further reduction in tidal volumes, compared with conventional low tidal volume ventilation, may improve outcomes.

OBJECTIVE

To determine whether lower tidal volume mechanical ventilation using extracorporeal carbon dioxide removal improves outcomes in patients with acute hypoxemic respiratory failure.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, randomized, allocation-concealed, open-label, pragmatic clinical trial enrolled 412 adult patients receiving mechanical ventilation for acute hypoxemic respiratory failure, of a planned sample size of 1120, between May 2016 and December 2019 from 51 intensive care units in the UK. Follow-up ended on March 11, 2020.

INTERVENTIONS

Participants were randomized to receive lower tidal volume ventilation facilitated by extracorporeal carbon dioxide removal for at least 48 hours (n = 202) or standard care with conventional low tidal volume ventilation (n = 210).

MAIN OUTCOMES AND MEASURES

The primary outcome was all-cause mortality 90 days after randomization. Prespecified secondary outcomes included ventilator-free days at day 28 and adverse event rates.

RESULTS

Among 412 patients who were randomized (mean age, 59 years; 143 [35%] women), 405 (98%) completed the trial. The trial was stopped early because of futility and feasibility following recommendations from the data monitoring and ethics committee. The 90-day mortality rate was 41.5% in the lower tidal volume ventilation with extracorporeal carbon dioxide removal group vs 39.5% in the standard care group (risk ratio, 1.05 [95% CI, 0.83-1.33]; difference, 2.0% [95% CI, -7.6% to 11.5%]; P = .68). There were significantly fewer mean ventilator-free days in the extracorporeal carbon dioxide removal group compared with the standard care group (7.1 [95% CI, 5.9-8.3] vs 9.2 [95% CI, 7.9-10.4] days; mean difference, -2.1 [95% CI, -3.8 to -0.3]; P = .02). Serious adverse events were reported for 62 patients (31%) in the extracorporeal carbon dioxide removal group and 18 (9%) in the standard care group, including intracranial hemorrhage in 9 patients (4.5%) vs 0 (0%) and bleeding at other sites in 6 (3.0%) vs 1 (0.5%) in the extracorporeal carbon dioxide removal group vs the control group. Overall, 21 patients experienced 22 serious adverse events related to the study device.

CONCLUSIONS AND RELEVANCE

Among patients with acute hypoxemic respiratory failure, the use of extracorporeal carbon dioxide removal to facilitate lower tidal volume mechanical ventilation, compared with conventional low tidal volume mechanical ventilation, did not significantly reduce 90-day mortality. However, due to early termination, the study may have been underpowered to detect a clinically important difference.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02654327.

Implementation of new ECMO centers during the COVID-19 pandemic: experience and results from the Middle East and India

Purpose

Extracorporeal membrane oxygenation (ECMO) use for severe coronavirus disease 2019 (COVID-19) patients has increased during the course of the pandemic. As uncertainty existed regarding patient’s outcomes, early guidelines recommended against establishing new ECMO centers. We aimed to explore the epidemiology and outcomes of ECMO for COVID-19 related cardiopulmonary failure in five countries in the Middle East and India and to evaluate the results of ECMO in 5 new centers.

Methods

This is a retrospective, multicenter international, observational study conducted in 19 ECMO centers in five countries in the Middle East and India from March 1, 2020, to September 30, 2020. We included patients with COVID-19 who received ECMO for refractory hypoxemia and severe respiratory acidosis with or without circulatory failure. Data collection included demographic data, ECMO-related specific data, pre-ECMO patient condition, 24 h post-ECMO initiation data, and outcome. The primary outcome was survival to home discharge. Secondary outcomes included mortality during ECMO, survival to decannulation, and outcomes stratified by center type.

Results

Three hundred and seven COVID-19 patients received ECMO support during the study period, of whom 78 (25%) were treated in the new ECMO centers. The median age was 45 years (interquartile range IQR 37–52), and 81% were men. New center patients were younger, were less frequently male, had received higher PEEP, more frequently inotropes and prone positioning before ECMO and were less frequently retrieved from a peripheral center on ECMO. Survival to home discharge was 45%. In patients treated in new and established centers, survival was 55 and 41% (p = 0.03), respectively. Multivariable analysis retained only a SOFA score < 12 at ECMO initiation as associated with survival (odds ratio, OR 1.93 (95% CI 1.05–3.58), p = 0.034), but not treatment in a new center (OR 1.65 (95% CI 0.75–3.67)).

Conclusions

During pandemics, ECMO may provide favorable outcomes in highly selected patients as resources allow. Newly formed ECMO centers with appropriate supervision of regional experts may have satisfactory results.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00134-021-06451-w.

ECLS Training and Simulation - Evaluation of the 8th Educational Corner of the EuroELSO Congress 2019 Held in Barcelona

Introduction: Simulation-based learning and hands-on learning are popular in medicine, particularly in areas where life-saving manoeuvres and team skills are required. Simulations can be provided in different environments: directly in hospitals (in situ), in dedicated facilities (simulation rooms) or, on occasion, at scientific meetings, thus taking advantage of the delegates' motivation. Simulation-based learning in extracorporeal life support is also increasingly relevant due to the inherent features of the often difficult and emergent decision-making, approaches and management involved, as well as to the challenging multidisciplinary teamwork. Aim: Based on these premises and on the constant rise in interest in starting new extracorporeal life support programmes, the EuroELSO organization has, since the beginning of its scientific activities, established an 'ad hoc' space (Educational Corner) for training and hands-on sessions with a limited number of attendees per session during its annual congress. Methods: Experienced trainers deliver repeated dedicated sessions on fundamental aspects of extracorporeal life support management. After several years of sessions, a questionnaire was prepared and delivered to the attendees at the 8th annual congress in Barcelona. Results: More than 90% of the responders indicated that they would recommend the workshop to their colleagues and that they received useful information during the workshops. Over 85% of the responders (85-97%) indicated that the workshops met the set educational goals and objectives and indicated that the simulation sessions would have a positive impact on their daily practice. Conclusion: The Educational Corner during the EuroELSO Congress has achieved great popularity, as shown by the number of attendees participating each year, and presumably improves many technical and behavioural skills among the attendees.

Perception of prolonged extracorporeal membrane oxygenation in Europe: an EuroELSO survey

The substantial increase in the number of patients receiving extracorporeal membrane oxygenation over the last decade has led to an evolution of indications and an expansion into wider patient groups. One of the unanticipated benefits of the increase in extracorporeal membrane oxygenation has been a change in the understanding of the natural history of many respiratory diseases. Development in technology and materials, reduced extracorporeal membrane oxygenation-specific complications, and improvement of critical care, in general, have facilitated longer extracorporeal membrane oxygenation runs, and the definition of prolonged extracorporeal membrane oxygenation was recently expanded to continuous support for more than 28 days. This survey aimed to describe European ECMO centers' perception and arbitrary definition of prolonged extracorporeal membrane oxygenation, patient management, and futility. Of 94 center responses, 37% regarded 14-21 days, 30% 21-28 days, and 28% >28 days as prolonged treatment. Bridge to recovery (64%) or to transplantation (20%) was the most common causes. Awake, and ambulation while on extracorporeal membrane oxygenation was reported from 34% of the centers. In case of perceived futility, decision to withdraw was taken in 65% of the centers in agreement between profession and family and in 30% by profession only. One-fourth of the centers did not discontinue support. Large differences prevail among European ECMO centers concerning local perception and patient management in prolonged extracorporeal membrane oxygenation.

Prediction of readiness to decannulation from venovenous extracorporeal membrane oxygenation

OBJECTIVE

The criteria and process for liberation from extracorporeal membrane oxygenation in patients with severe acute respiratory distress syndrome are not standardized. The predictive accuracy of the oxygen challenge test as a diagnostic test in determining weaning and decannulation from venovenous extracorporeal membrane oxygenation was tested.

DESIGN

A single-centre, retrospective, observational cohort study.

SETTING

Tertiary referral severe respiratory failure centre in a university hospital in the United Kingdom.

PATIENTS

253 adults with severe acute respiratory distress syndrome requiring extracorporeal membrane oxygenation.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Patients had median age: 43 years (interquartile range: 32-52) years, extracorporeal membrane oxygenation days: 9 (interquartile range: 6-14) and acute physiology and chronic health evaluation II score 17.5 (interquartile range: 15-20). Oxygen challenge test value (PaO_2-OCT) with best prediction was 31 kPa (232 mmHg; sensitivity 0.74; specificity 0.70; area under curve 0.77 (confidence interval: 0.73-0.81)). PaO_2-OCT did not perform well as a prospective test to identify readiness to decannulation. Only 24 patients (10%) were decannulated 48 hours after their first positive oxygen challenge test (true positive) and 73.4% patients were false positives (positive oxygen challenge test but not decannulated). True positives had higher tidal volume (541 ± 218 vs 368 mL ± 210; p < 0.05) and minute ventilation (9.34 ± 5.36 vs 6.33 L/min ± 4.43; p < 0.05). Blood flow (3.17 ± 0.23 vs 3.53 L/min ± 0.56; p < 0.05), sweep gas flow (1.42 ±1.83 vs 3.74 L/min ± 2.43; p < 0.05) and extracorporeal membrane oxygenation minute volume at time of first positive oxygen challenge test was lower in true positives (1.66 ± 2.26 vs 4.82 ± 3.43 L/min). This was a strong predictor for decannulation within 48 hours (area under curve: 0.88, confidence interval: 0.88-0.89).

CONCLUSIONS

In severe acute respiratory distress syndrome requiring venovenous extracorporeal membrane oxygenation, the PaO_2-OCT is a poor predictor of readiness to decannulate from extracorporeal membrane oxygenation. Additional factors involved in the control of respiratory drive and carbon dioxide clearance, particularly native lung dead space and total minute ventilation, should be assessed.

A survey on the practices and capabilities in the management of respiratory failure in South East England

Introduction

The variability of acute respiratory distress syndrome management may affect the referral practice to severe respiratory failure centres. We described the management of acute respiratory distress syndrome in our catchment area.

Methods

An electronic survey was administered to 42 intensive care units in South-East England.

Results

Response rate was 71.4%. High-flow nasal oxygen and non-invasive ventilation were used 'often' in moderate-acute respiratory distress syndrome by 46.7% and 60%. During invasive ventilation, 90% preferred pressure control, targeting tidal volumes of 6-8 ml/kg (53.3%) or 4-6 ml/kg (46.7%). Positive end-expiratory pressure was selected by positive end-expiratory pressure/inspiratory fraction of oxygen tables (50%) or decremental positive end-expiratory pressure trials (20%). Neuro-muscular blockers were widely used, although routinely by only 3.3%. High-frequency oscillatory ventilation (10%) and inhaled nitric oxide (13.3%) were rarely used. None used oesophageal manometry. Recruitment manoeuvres were used 'often' by 26.7%. Equipment (90%) and protocols (80%) for prone position were common, with sessions mostly lasting 12-18 h.

Conclusions

Although variable, practice well reflected the available evidence. Proning was widely practiced with good availability of educational resources and protocolised care.

Long-term cognitive and psychiatric outcomes of acute respiratory distress syndrome managed with Extracorporeal Membrane Oxygenation

BACKGROUND

Cognitive dysfunction is often reported in patients who have experienced acute respiratory distress syndrome (ARDS). Extra Corporeal Membrane Oxygenation (ECMO) therapy is increasingly used to manage ARDS patients in ICU, transforming survival rates. However, few studies have examined cognitive outcomes.

METHODS

We examined self-reported cognitive complaints, psychiatric outcomes and neuropsychological test performance in survivors of severe hypoxaemia managed with VV-ECMO, at 18-24 month follow-up, compared with a group of healthy controls.

RESULTS

Over 70% of ECMO-treated patients (N = 46) complained of difficulty in at least one aspect of cognition on self-report measures (study 1). However, a much lower frequency of cognitive impairment was found on formal neuropsychological testing (study 2). Mean neuropsychological test scores of the ECMO group (N = 24) did not significantly differ from healthy controls (N = 23) after controlling for depression. Less than 30% of ECMO-treated patients showed impairments in anterograde memory, and deficits on general IQ or executive function were seen in <17% of patients. However, we observed high levels of self-reported anxiety and depression in the ECMO-treated patients.

CONCLUSIONS

Cognitive outcomes in ECMO-treated patients were generally good, with preserved neuropsychological function in the majority of patients, despite severe hypoxaemia and high rates of self-reported difficulties. However, we saw high levels of mental health symptoms in these patients, highlighting a need for psychological support.

Initial setting of high-flow nasal oxygen post extubation based on mean inspiratory flow during a spontaneous breathing trial

PURPOSE

High flow nasal cannula (HFNC) is commonly used post-extubation in intensive care (ICU). Patients' comfort during HFNC is affected by flow rate. The study aims to describe the relationship between pre-extubation inspiratory flow requirements and the post-extubation flow rates on HFNC that maximises patient's comfort.

METHODS

This was an observational, retrospective study conducted in a university-affiliated ICU. We included patients extubated following successful spontaneous breathing trial (SBT). During the SBT we recorded variables including inspiratory flow. Patients who passed the SBT were extubated onto HFNC. HFNC was titrated from 20 L/min and increased in steps of 10 L/min, up to 60 L/min. At each step, patient's level of comfort was assessed. Fraction of inspired oxygen was titrated to maintain oxygen saturation 92-97%.

RESULTS

Nineteen participants were enrolled in the study. There was a significant positive correlation between mean inspiratory flow pre-extubation and the flow setting on HFNC which achieved the best comfort post-extubation (r² 0.88; p < 0.001). Overall, greatest comfort was observed for HFNC flows between 30 and 40 L/min but with individual variability.

CONCLUSION

Measuring mean inspiratory flow during an SBT allows for individualised setting of HFNC flow rate immediately post-extubation and achieves the greatest comfort and interface tolerance.

Veno-venous extracorporeal membrane oxygenation in coronavirus disease 2019: a case series

Background

The use of veno-venous extracorporeal membrane oxygenation (VV-ECMO) in severe hypoxaemic respiratory failure from coronavirus disease 2019 (COVID-19) has been described, but reported utilisation and outcomes are variable, and detailed information on patient characteristics is lacking. We aim to report clinical characteristics, management and outcomes of COVID-19 patients requiring VV-ECMO, admitted over 2 months to a high-volume centre in the UK.

Methods

Patient information, including baseline characteristics and clinical parameters, was collected retrospectively from electronic health records for COVID-19 VV-ECMO admissions between 3 March and 2 May 2020. Clinical management is described. Data are reported for survivors and nonsurvivors.

Results

We describe 43 consecutive patients with COVID-19 who received VV-ECMO. Median age was 46 years (interquartile range 35.5–52.5) and 76.7% were male. Median time from symptom onset to VV-ECMO was 14 days (interquartile range 11–17.5). All patients underwent computed tomography imaging, revealing extensive pulmonary consolidation in 95.3%, and pulmonary embolus in 27.9%. Overall, 79.1% received immunomodulation with methylprednisolone for persistent maladaptive hyperinflammatory state. Vasopressors were used in 86%, and 44.2% received renal replacement therapy. Median duration on VV-ECMO was 13 days (interquartile range 8–20). 14 patients died (32.6%) and 29 survived (67.4%) to hospital discharge. Nonsurvivors had significantly higher d-dimer (38.2 versus 9.5 mg·L⁻¹, fibrinogen equivalent units; p=0.035) and creatinine (169 versus 73 μmol·L⁻¹; p=0.022) at commencement of VV-ECMO.

Conclusions

Our data support the use of VV-ECMO in selected COVID-19 patients. The cohort was characterised by high degree of alveolar consolidation, systemic inflammation and intravascular thrombosis.

VV-ECMO, when offered to #COVID19 patients in refractory respiratory failure, can be associated with favourable outcomes. This is a detailed case series of 43 COVID-19 patients requiring VV-ECMO from a UK centre. 67.4% survived to hospital discharge.https://bit.ly/3ko9Ucu

Extra-corporeal membrane oxygenation for severe respiratory failure in the UK

An overview of the current system for referrals and management of severe respiratory failure in the United Kingdom. We outline the history of severe respiratory failure centres, the process of retrieving a patient for veno-venous extra corporeal membrane oxygenation and highlight some common difficulties and pitfalls when referring these critically unwell patients.

Use of Intravenous Immunoglobulins in Patients with Suspected Toxin-Mediated Shock Requiring Extracorporeal Membrane Oxygenation

BACKGROUND

Toxin-producing, gram-positive bacteria can lead to severe and refractory septic shock with high attributable mortality. Adjunctive therapies such as intravenous immunoglobulins (IVIG) have been proposed for these patients. However, at presentation the presence of a toxin-producing organism is most often unknown. As IVIG is a potentially valuable but also limited resource, we investigated the use of IVIG in our critically ill patients requiring extracorporeal membrane oxygenation (ECMO).

MATERIALS AND METHODS

Retrospective cohort study (April 2016 to March 2018) of adult patients with clinically suspected toxin-mediated shock requiring ECMO and who received IVIG in our regional severe respiratory failure (SRF)/ECMO center.

RESULTS

In 44% (15/34) of the patients, group A Streptococcus or Panton-Valentine Leukocidin producing S aureus was isolated. IVIG use in these patients was safe. The mortality was 30%, lower than the predicted mortality of >90% based on the SOFA scores.

CONCLUSION

IVIG administration can be considered in a selected group of patients presenting with acute and very severe septic shock.

Nonantibiotic Pharmacological Treatment of Severe Chronic Obstructive Pulmonary Disease Exacerbations

Severe, acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a rapid deterioration of the respiratory symptoms of patients with COPD, requiring hospital admission and escalation of pharmacological and nonpharmacological care including the more severe cases of respiratory failure and admission to an intensive care unit (ICU). These events severely impact patients' quality of life and prognosis. This review will describe the nonantibiotic, pharmacological treatment options available for critically ill patients with AECOPD. The aim of treatment is to alleviate symptoms, improve patient's functional and respiratory status, reduce mortality, reduce the risk or the duration of invasive mechanical ventilation, and prevent reexacerbations. Inhaled bronchodilators (i.e., short-acting β2-agonists and anticholinergics) and systemic corticosteroids are the main drugs used in the treatment of AECOPD. These drugs are also used in the treatment of stable COPD and in the treatment of AECOPD patients in the non-ICU or community setting. Other drugs are essentially only used in the ICU setting such as inhaled anesthetic agents, ketamine, intravenous methylxanthines, and magnesium. Finally, recently developed drugs, such as the specific phosphodiesterase-4 inhibitors, may play a role in the prevention of relapsing AECOPD following a critical event than the treatment of the exacerbation itself. Although they significantly improve the survival of critically ill patients with AECOPD, none of available drugs, alone or combined, is able to significantly modify the prognosis of patients with COPD. This remains an open challenge for the current and future generations of researchers and clinicians.

Pressure and flow properties of dual-lumen cannulae for extracorporeal membrane oxygenation

INTRODUCTION

In the last decade, dual-lumen cannulae have been increasingly applied in patients undergoing extracorporeal life support. Well-performing vascular access is crucial for efficient extracorporeal membrane oxygenation support; thus, guidance for proper cannulae size is required. Pressure-flow charts provided by manufacturers are often based on tests performed using water, rarely blood. However, blood is a shear-thinning and viscoelastic fluid characterized by different flow properties than water.

METHODS

We performed a study evaluating pressure-flow curves during standardized conditions using human whole blood in two commonly available dual-lumen cannulae used in neonates, pediatric, and adult patients. Results were merged and compared with the manufacturer's corresponding curves obtained from the public domain.

RESULTS

The results showed that using blood as compared with water predominantly influenced drainage flow. A 10-80% higher pressure-drop was needed to obtain same drainage flow (hematocrit of 26%) compared with manufacturer's water charts in 13-31 Fr bi-caval dual-lumen cannulae. The same net difference was found in cavo-atrial cannulae (16-32 Fr), where a lower drainage pressure was required (Hct of 26%) compared with the manufacturer's test using blood with an Hct of 33%. Return pressure-flow data were similar, independent whether pumping blood or water, to the data reported by manufacturers.

CONCLUSION

Non-standardized testing of pressure-flow properties of extracorporeal membrane oxygenation dual-lumen cannulae prevents an adequate prediction of pressure-flow results when these cannulae are used in patients. Properties of dual-lumen cannulae may vary between sizes within same cannula family, in particular concerning the drainage flow.

Pressure and flow properties of cannulae for extracorporeal membrane oxygenation II: drainage (venous) cannulae

The use of extracorporeal life support devices such as extracorporeal membrane oxygenation in adults requires cannulation of the patient's vessels with comparatively large diameter cannulae to allow circulation of large volumes of blood (>5 L/min). The cannula diameter and length are the major determinants for extracorporeal membrane oxygenation flow. Manufacturing companies present pressure-flow charts for the cannulae; however, these tests are performed with water. Aims of this study were 1. to investigate the specified pressure-flow charts obtained when using human blood as the circulating medium and 2. to support extracorporeal membrane oxygenation providers with pressure-flow data for correct choice of the cannula to reach an optimal flow with optimal hydrodynamic performance. Eighteen extracorporeal membrane oxygenation drainage cannulae, donated by the manufacturers (n = 6), were studied in a centrifugal pump driven mock loop. Pressure-flow properties and cannula features were described. The results showed that when blood with a hematocrit of 27% was used, the drainage pressure was consistently higher for a given flow (range 10%-350%) than when water was used (data from each respective manufacturer's product information). It is concluded that the information provided by manufacturers in line with regulatory guidelines does not correspond to clinical performance and therefore may not provide the best guidance for clinicians.

Pressure and flow properties of cannulae for extracorporeal membrane oxygenation I: return (arterial) cannulae

Adequate extracorporeal membrane oxygenation support in the adult requires cannulae permitting blood flows up to 6-8 L/minute. In accordance with Poiseuille's law, flow is proportional to the fourth power of cannula inner diameter and inversely proportional to its length. Poiseuille's law can be applied to obtain the pressure drop of an incompressible, Newtonian fluid (such as water) flowing in a cylindrical tube. However, as blood is a pseudoplastic non-Newtonian fluid, the validity of Poiseuille's law is questionable for prediction of cannula properties in clinical practice. Pressure-flow charts with non-Newtonian fluids, such as blood, are typically not provided by the manufacturers. A standardized laboratory test of return (arterial) cannulae for extracorporeal membrane oxygenation was performed. The aim was to determine pressure-flow data with human whole blood in addition to manufacturers' water tests to facilitate an appropriate choice of cannula for the desired flow range. In total, 14 cannulae from three manufacturers were tested. Data concerning design, characteristics, and performance were graphically presented for each tested cannula. Measured blood flows were in most cases 3-21% lower than those provided by manufacturers. This was most pronounced in the narrow cannulae (15-17 Fr) where the reduction ranged from 27% to 40% at low flows and 5-15% in the upper flow range. These differences were less apparent with increasing cannula diameter. There was a marked disparity between manufacturers. Based on the measured results, testing of cannulae including whole blood flows in a standardized bench test would be recommended.

Performing cardiac investigations after VA ECMO implementation in adults

Veno-arterial extracorporeal membrane oxygenation (VA ECMO) is commenced for adult patients with severe acute cardiac failure refractory to conventional therapy or following protracted cardiac arrest refractory to cardiopulmonary resuscitation.¹ Following the commencement of ECMO there are several key questions which need to be addressed.

Initial investigations are those which are designed to understand the cause of the cardiac event, gain an understanding of the consequences of the event, particularly on other organ functions and also to direct initial treatment. At this stage, consideration should be given to basic biochemistry, electrocardiography, echocardiography, coronary angiography and computed tomography.² These investigations can explain the origin of the cardiogenic shock and direct therapy, for example stenting of culprit lesions or management of an autoimmune cardiomyopathy.

Additionally, clinical monitoring tools should be implemented to allow understanding of the consequences of the cardiac insult and the impact of ECMO. One of the key problems of peripheral VA ECMO is the increase in afterload for the native heart which prevents appropriate left ventricular emptying.³ An early understanding of left ventricular end diastolic pressure as well as left ventricular emptying can assist in planning the need for left ventricular unloading devices. Investigations including direct measurements of left ventricular pressure at the time of the coronary angiogram can give a static measure of the impact of afterload. Continuous monitoring using pulmonary artery catheterisation with measurement of pulmonary capillary wedge pressure as well as intermittent echocardiography can help identify rises in left ventricular end diastolic pressure which may result in serious complications including pulmonary oedema, pulmonary haemorrhage, left ventricular distension and left ventricular thrombosis.

Investigations or clinical monitoring is also essential to facilitate optimal patient management. Early in the course of VA ECMO, there are naturally concerns about the ability of the ventricle to empty, however during cardiac recovery there is also the potential for the heart to eject deoxygenated blood, particularly if the lungs are yet to recover. Monitoring including continuous peripheral saturation monitors, arterial blood gases and cerebral near-infrared spectroscopy can all assist in understanding the relative provision of blood to the brain from ECMO or the native circulations.⁴ Similarly, continuous investigations of the blood supply distal to the cannulated peripheral artery are essential. There is a substantial risk of femoral arterial thrombosis and this can be managed through the use of intermittent doppler signals for the distal vessels or through the use of near-infrared spectroscopy for the legs.⁴

Finally, there is a requirement for monitoring and investigation of the pump and its function/impact on the patient. This includes identification of complications such as haemolysis, microthrombosis, air embolism and disseminated intravascular coagulopathy.⁵ Circuit gases can also be used to demonstrate functioning of the circuit and to prevent exposure of organs to profound hyperoxia or non-physiological pH.

In conclusion, there are a number of key investigations and clinical monitoring devices which should be undertaken following the commencement of VA ECMO to both understand the cause and to predict/prevent complications.

In vivo carbon dioxide clearance of a low-flow extracorporeal carbon dioxide removal circuit in patients with acute exacerbations of chronic obstructive pulmonary disease

BACKGROUND

Veno-venous extracorporeal carbon dioxide removal allows clearance of CO₂ from the blood and is becoming popular to enhance protective mechanical ventilation and assist in the management of acute exacerbations of chronic obstructive pulmonary disease, including the prevention of intubation. The main factor determining CO₂ transfer across a membrane lung for any given blood flow rate and venous CO₂ content is the sweep gas flow rate. The in vivo characteristics of CO₂ clearance using ultra-low blood flow devices in patients with acute exacerbations of chronic obstructive pulmonary disease has not been previously described.

METHODS

Patients commenced on extracorporeal carbon dioxide removal for acute exacerbations of chronic obstructive pulmonary disease recruited to a randomized controlled trial of non-invasive ventilation versus extracorporeal carbon dioxide removal had pre- and post-membrane circuit gases measured after each increment of sweep gas flow to allow calculation of the transmembrane CO₂ clearance. This was compared with the clearance reported by the device and also corrected to inlet PCO₂ to allow characterization of the CO₂ clearance of the device at different sweep gas flow rates.

RESULTS

CO₂ clearance was calculated using both the transmembrane CO₂ whole-blood content difference and CO₂ clearance reported by the device. The two methods demonstrated a linear relationship and agreement with a bias of 14 mL/minute (SD = ±10) and an R² of 0.92. The membrane CO₂ clearance was non-linear with nearly two thirds of total clearance achieved with sweep gas flow below 2 L/minute (VCO₂ of 40 ± 16.7 mL/minute) and a plateau above 5 L/minute sweep gas flow (VCO₂ 64 ± 1 2.4 mL/minute).

CONCLUSION

The extracorporeal carbon dioxide removal device used in the study provides efficient clearance of CO₂ at low sweep flow rates which then plateaus. This has implications for how the device may be used in clinical practice, particularly during the weaning phase where the final discontinuation of the device may take longer than anticipated. (ClinicalTrials.gov: NCT02086084, registered 13 March 2014, https://clinicaltrials.gov/ct2/show/NCT02086084 ).

Assessment of Work of Breathing in Patients with Acute Exacerbations of Chronic Obstructive Pulmonary Disease

The assessment of the work of breathing (WOB) of patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) is difficult, particularly when the patient first presents with acute hypercapnia and respiratory acidosis. Acute exacerbations of COPD patients are in significant respiratory distress and noninvasive measurements of WOB are easier for the patient to tolerate. Given the interest in using alternative therapies to noninvasive ventilation, such as high flow nasal oxygen therapy or extracorporeal carbon dioxide removal, understanding the physiological changes are key and this includes assessment of WOB. This narrative review considers the role of three different methods of assessing WOB in patients with acute exacerbations of COPD. Esophageal pressure is a very well validated measure of WOB, however the ability of patients with acute exacerbations of COPD to tolerate esophageal tubes is poor. Noninvasive alternative measurements include parasternal electromyography (EMG) and electrical impedance tomography (EIT). EMG is easily applied and is a well validated measure of neural drive but is more likely to be degraded by the electrical environment in intensive care or high dependency. EIT is less well validated as a tool for WOB in COPD but extremely well tolerated by patients. Each of the different methods assess WOB in a different way and have different advantages and disadvantages. For research into therapies treating acute exacerbations of COPD, combinations of EIT, EMG and esophageal pressure are likely to be better than only one of these.

In-vitro performance of a low flow extracorporeal carbon dioxide removal circuit

INTRODUCTION

Extracorporeal gas exchange requires the passage of oxygen and carbon dioxide (CO₂) across an artificial membrane. Current European Union regulations do not require the transfer to be assessed in models using clinically relevant haemoglobin, making it difficult for clinicians to understand the CO₂ clearance of a membrane, and how it changes in relation to sweep gas flow through the membrane. The characteristics of membrane CO₂ clearance are described using a single membrane at different sweep gas flows in an in vitro model with clinically relevant haemoglobin concentrations using three separate methods of calculating CO₂ clearance.

METHODS

To define the CO₂ removal characteristics of the extra-corporeal CO₂ removal (ECCO₂R) device, we devised an in-vitro gas exchange circuit formed by a dedicated ECCO₂R circuit (ALung, Pittsburgh, USA) in series with two membrane oxygenators. The system was primed with donated expired human red cells provided by the local blood bank. The experimental set-up allowed constant CO₂ input (via one membrane oxygenator) with variable removal from a portion of the blood in a manner which was analogous to that seen in vivo. Blood gases were measured from different ports in the circuit in order to measure the experimental membrane CO₂ clearance (VCO₂).

RESULTS

Results demonstrate that the relationship between VCO₂ and gas flow at a constant blood flow of 0.4 L/minute with a haemoglobin of 7 g/dL increases sharply from a gas flow of 0 to 2 L/min but plateaus at gas flows >4 L/minute. VCO₂, calculated using three different methods, showed a strong linear correlation with minimal bias.

CONCLUSIONS

The CO₂ clearance of the membrane used in this bench test is non-linear. This has implications for clinical practice, especially during the weaning phase of the device.

Extracorporeal carbon dioxide removal for acute hypercapnic exacerbations of chronic obstructive pulmonary disease: study protocol for a randomised controlled trial

Background

Chronic obstructive pulmonary disease (COPD) is a common cause of chronic respiratory failure and its course is punctuated by a series of acute exacerbations which commonly lead to hospital admission. Exacerbations are managed through the application of non-invasive ventilation and, when this fails, tracheal intubation and mechanical ventilation. The need for mechanical ventilation significantly increases the risk of death. An alternative therapy, extracorporeal carbon dioxide removal (ECCO₂R), has been shown to be efficacious in removing carbon dioxide from the blood; however, its impact on respiratory physiology and patient outcomes has not been explored.

Methods/design

A randomised controlled open label trial of patients (12 in each arm) with acute exacerbations of COPD at risk of failing conventional therapy (NIV) randomised to either remaining on NIV or having ECCO₂R added to NIV with a primary endpoint of time to cessation of NIV. The change in respiratory physiology following the application of ECCO₂R and/or NIV will be measured using electrical impedance tomography, oesophageal pressure and parasternal electromyography. Additional outcomes, including patient tolerance, outcomes, need for readmission, changes in blood gases and biochemistry and procedural complications, will be measured. Physiological changes will be compared within one patient over time and between the two groups. Healthcare costs in the UK system will also be compared between the two groups.

Discussion

COPD is a common disease and exacerbations are a leading cause of hospital admission in the UK and worldwide, with a sizeable mortality. The management of patients with COPD consumes significant hospital and financial resources. This study seeks to understand the feasibility of a novel approach to the management of patients with acute exacerbations of COPD as well as to understand the underlying physiological changes to explain why the approach does or does not assist this patient cohort. Detailed respiratory physiology has not been previously undertaken using this technique and there are no other randomised controlled trials currently in the literature.

Trial registration

ClinicalTrials.gov, NCT02086084.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3548-4) contains supplementary material, which is available to authorized users.

Electromagnetically guided bedside placement of post-pyloric feeding tubes in critical care

Post-pyloric feeding is recommended in critically ill patients with gastro-intestinal intolerance. However, traditional placement methods are logistically difficult and carry potential risks. The authors retrospectively compared the position of post-pyloric feeding tubes (PPFTs) using an electromagnetic device that demonstrated by X-ray and analysed the complication rates, proportion of lung placements avoided and the time taken to establish enteral feeding. Forty placements in 37 mechanically ventilated patients were analysed; there was a success rate of 87.5%. Sensitivity and specificity were 77% (95% CI 59.9-89.6%) and 100% (95% CI 48.0-100%). Five lung placements were identified in real time and therefore avoided. The mean (SD) time from PPFT placement to X-ray was 134 minutes (± 139 minutes) and, to feeding, 276 minutes (± 213 minutes). In conclusion, placement of PPFT using an electromagnetic device carries a high success rate, is safe and feasible to undertake at the bedside in mechanically ventilated patients.

Outcomes of emergency laparotomy in patients on extracorporeal membrane oxygenation for severe respiratory failure: A retrospective, observational cohort study

PURPOSE

There is a paucity of literature to support undertaking emergency laparotomy when indicated in patients supported on ECMO. Our study aims to identify the prevalence, outcomes and complications of this high risk surgery at a large ECMO centre.

MATERIALS AND METHODS

A single centre, retrospective, observational cohort study of 355 patients admitted to a university teaching hospital Severe Respiratory Failure service between December 2011 and January 2017.

RESULTS

The prevalence of emergency laparotomy in patients on ECMO was 3.7%. These patients had significantly higher SOFA and APACHE II scores compared to similar patients not requiring laparotomy. There was no difference in the duration of ECMO or intensive care unit (ICU) stay post decannulation between the two groups. 31% of laparotomy patients survived to hospital discharge. Major haemorrhage was uncommon, however emergency change of ECMO oxygenator was commonly required.

CONCLUSION

Survival to hospital discharge is possible following emergency laparotomy on ECMO, however the mortality is higher than for those patients not requiring laparotomy, this likely reflects the severity of underlying organ failure rather than the surgery itself. Our service's collocation with a general surgical service has made this development in care possible. ECMO service planning should consider general surgical provision.

Monitoring of regional lung ventilation using electrical impedance tomography

Among recent lung imaging techniques and devices, electrical impedance tomography (EIT) can provide dynamic information on the distribution regional lung ventilation. EIT images possess a high temporal and functional resolution allowing the visualization of dynamic physiological and pathological changes on a breath-by-breath basis. EIT detects changes in electric impedance (i.e., changes in gas/fluid ratio) and describes them in real time, both visually through images and waveforms, and numerically, allowing the clinician to monitor disease evolution and response to treatment. The use of EIT in clinical practice is supported by several studies demonstrating a good correlation between impedance tomography data and other validated methods of measuring lung volume. In this review, we will provide an overview on the rationale, basic functioning and most common applications of EIT in the management of mechanically ventilated patients.

Diagnosis of death using neurological criteria in adult patients on extracorporeal membrane oxygenation: Development of UK guidance

The diagnosis of death using neurological criteria is an important legal method of establishing death in the UK. The safety of the diagnosis lies in the exclusion of conditions which may mask the diagnosis and the testing of the fundamental reflexes of the brainstem including the apnoea reflex. Extracorporeal membrane oxygenation for cardiac or respiratory support can impact upon these tests, both through drug sequestration in the circuit and also through the ability to undertake the apnoea test. Until recently, there has been no nationally accepted guidance regarding the conduct of the tests to undertake the diagnosis of death using neurological criteria for a patient on extracorporeal membrane oxygenation. This article considers both the background to and the process of guideline development.

Safety of Percutaneous Dilatational Tracheostomy During Veno-Venous Extracorporeal Membrane Oxygenation Support in Adults With Severe Respiratory Failure

OBJECTIVES

To investigate the safety of percutaneous dilatational tracheostomy in severe respiratory failure patients during veno-venous extracorporeal membrane oxygenation support.

DESIGN

A single-center, retrospective, observational cohort study.

SETTING

Tertiary referral severe respiratory failure center, university teaching hospital.

PATIENTS

Severe respiratory failure patients consecutively admitted and supported with veno-venous extracorporeal membrane oxygenation between January 2010 and December 2015.

INTERVENTION

A bronchoscopy-guided percutaneous dilatational tracheostomy was performed in all cases.

MEASUREMENTS AND MAIN RESULTS

Sixty-five veno-venous extracorporeal membrane oxygenation patients (median [interquartile range] age, 47 yr [interquartile range, 35-59 yr]; 39 males; Acute Physiology and Chronic Health Evaluation-II score, 18 [interquartile range, 17-22] Sequential Organ Failure Assessment score, 10 [interquartile range, 7-16]) underwent percutaneous dilatational tracheostomy. Ten patients (15%) developed one or more major complications. Of these, seven (11%) had major bleeding, and three of these also required circuit change due to extracorporeal membrane oxygenation circuit dysfunction. Two more patients (3.1%) presented with isolated extracorporeal membrane oxygenation circuit dysfunction requiring circuit change, and one developed bilateral pneumothoraces (1.5%) requiring intercostal drain insertion. Patients who developed complications had significantly lower extracorporeal membrane oxygenation postoxygenator PO2 prior to percutaneous dilatational tracheostomy (45.8 kPa [interquartile range, 36.9-56.5 kPa] vs 57.9 kPa [interquartile range, 45.1-64.2 kPa]; p = 0.019]. On multivariate analysis, including demographic, clinical, biochemical, hematologic variables, and extracorporeal membrane oxygenation circuit functional variables, extracorporeal membrane oxygenation postoxygenator PO2 was the only independent variable associated with major complications following percutaneous dilatational tracheostomy (beta = -0.09; odds ratio, 0.9; 95% CI, 0.84-0.99; p = 0.03).

CONCLUSIONS

Percutaneous dilatational tracheostomy is associated with a considerable complication rate in veno-venous extracorporeal membrane oxygenation patients. Preprocedure circuit performance as indicated by extracorporeal membrane oxygenation postoxygenator PO2 is an independent predictor of major complications following percutaneous dilatational tracheostomy.