Electrical Impedance Tomography to Monitor Hypoxemic Respiratory Failure.

Hypoxemic respiratory failure is one of the leading causes of mortality in intensive care. Frequent assessment of individual physiological characteristics and delivery of personalized mechanical ventilation (MV) settings is a constant challenge for clinicians caring for these patients. Electrical impedance tomography (EIT) is a radiation-free bedside monitoring device that is able to assess regional lung ventilation and changes in aeration. With real-time tomographic functional images of the lungs obtained through a thoracic belt, clinicians can visualize and estimate the distribution of ventilation at different ventilation settings or following procedures such as prone positioning. Several studies have evaluated the performance of EIT to monitor the effects of different MV settings in patients with acute respiratory distress syndrome, allowing more personalized MV. For instance, EIT could help clinicians find the positive end-expiratory pressure that represents a compromise between recruitment and overdistension and assess the effect of prone positioning on ventilation distribution. The clinical impact of the personalization of MV remains to be explored. Despite inherent limitations such as limited spatial resolution, EIT also offers a unique noninvasive bedside assessment of regional ventilation changes in the ICU. This technology offers the possibility of a continuous, operator-free diagnosis and real-time detection of common problems during MV. This review provides an overview of the functioning of EIT, its main indices, and its performance in monitoring patients with acute respiratory failure. Future perspectives for use in intensive care are also addressed.

Prone Positioning During Extracorporeal Membrane Oxygenation in Patients With Severe ARDS: The PRONECMO Randomized Clinical Trial.

Importance: Prone positioning may improve outcomes in patients with severe acute respiratory distress syndrome (ARDS), but it is unknown whether prone positioning improves clinical outcomes among patients with ARDS who are undergoing venovenous extracorporeal membrane oxygenation (VV-ECMO) compared with supine positioning. Objective: To test whether prone positioning vs supine positioning decreases the time to successful ECMO weaning in patients with severe ARDS supported by VV-ECMO. Design, Setting, and Participants: Randomized clinical trial of patients with severe ARDS undergoing VV-ECMO for less than 48 hours at 14 intensive care units (ICUs) in France between March 3, 2021, and December 7, 2021. Interventions: Patients were randomized 1:1 to prone positioning (at least 4 sessions of 16 hours) (n = 86) or to supine positioning (n = 84). Main Outcomes and Measures: The primary outcome was time to successful ECMO weaning within 60 days following randomization. Secondary outcomes included ECMO and mechanical ventilation-free days, ICU and hospital length of stay, skin pressure injury, serious adverse events, and all-cause mortality at 90-day follow-up. Results: Among 170 randomized patients (median age, 51 [IQR, 43-59] years; n = 60 women [35%]), median respiratory system compliance was 15.0 (IQR, 10.7-20.6) mL/cm H2O; 159 patients (94%) had COVID-19-related ARDS; and 164 (96%) were in prone position before ECMO initiation. Within 60 days of enrollment, 38 of 86 patients (44%) had successful ECMO weaning in the prone ECMO group compared with 37 of 84 (44%) in the supine ECMO group (risk difference, 0.1% [95% CI, -14.9% to 15.2%]; subdistribution hazard ratio, 1.11 [95% CI, 0.71-1.75]; P = .64). Within 90 days, no significant difference was observed in ECMO duration (28 vs 32 days; difference, -4.9 [95% CI, -11.2 to 1.5] days; P = .13), ICU length of stay, or 90-day mortality (51% vs 48%; risk difference, 2.4% [95% CI, -13.9% to 18.6%]; P = .62). No serious adverse events were reported during the prone position procedure. Conclusions and Relevance: Among patients with severe ARDS supported by VV-ECMO, prone positioning compared with supine positioning did not significantly reduce time to successful weaning of ECMO. Trial Registration: ClinicalTrials.gov Identifier: NCT04607551.

Asymmetrical Lung Injury: Management and Outcome.

Among mechanically ventilated patients, asymmetrical lung injury is probably extremely frequent in the intensive care unit but the lack of standardized measurements does not allow to describe any prevalence among mechanically ventilated patients. Many past studies have focused only on unilateral injury and have mostly described the effect of lateral positioning. The good lung put downward might receive more perfusion while the sick lung placed upward receive more ventilation than supine. This usually results in better oxygenation but can also promote atelectasis in the healthy lung and no consensus has emerged on the clinical indication of this posture. Recently, electrical impedance tomography (EIT) has allowed for the first time to precisely describe the distribution of ventilation in each lung and to better study asymmetrical lung injury. At low positive-end-expiratory pressure (PEEP), a very heterogeneous ventilation exists between the two lungs and the initial increase in PEEP first helps to recruit the sick lung and protect the healthier lung. However, further increasing PEEP distends the less injured lung and must be avoided. The right level can be found using EIT and transpulmonary pressure. In addition, EIT can show that in the two lungs, airway closure is present but with very different airway opening pressures (AOPs) which cannot be identified on a global assessment. This may suggest a very different PEEP level than on a global assessment. Lastly, epidemiological studies suggest that in hypoxemic patients, the number of quadrants involved has a strong prognostic value. The number of quadrants is more important than the location of the unilateral or bilateral nature of the involvement for the prognosis, and hypoxemic patients with unilateral lung injury should probably be considered as requiring lung protective ventilation as classical acute respiratory distress syndrome.

Mechanical Ventilation Management during Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome. An International Multicenter Prospective Cohort.

Rationale: Current practices regarding mechanical ventilation in patients treated with extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome are unknown.Objectives: To report current practices regarding mechanical ventilation in patients treated with ECMO for severe acute respiratory distress syndrome (ARDS) and their association with 6-month outcomes.Methods: This was an international, multicenter, prospective cohort study of patients undergoing ECMO for ARDS during a 1-year period in 23 international ICUs.Measurements and Main Results: We collected demographics, daily pre- and per-ECMO mechanical ventilation settings and use of adjunctive therapies, ICU, and 6-month outcome data for 350 patients (mean ± SD pre-ECMO PaO2/FiO2 71 ± 34 mm Hg). Pre-ECMO use of prone positioning and neuromuscular blockers were 26% and 62%, respectively. Vt (6.4 ± 2.0 vs. 3.7 ± 2.0 ml/kg), plateau pressure (32 ± 7 vs. 24 ± 7 cm H2O), driving pressure (20 ± 7 vs. 14 ± 4 cm H2O), respiratory rate (26 ± 8 vs. 14 ± 6 breaths/min), and mechanical power (26.1 ± 12.7 vs. 6.6 ± 4.8 J/min) were markedly reduced after ECMO initiation. Six-month survival was 61%. No association was found between ventilator settings during the first 2 days of ECMO and survival in multivariable analysis. A time-varying Cox model retained older age, higher fluid balance, higher lactate, and more need for renal-replacement therapy along the ECMO course as being independently associated with 6-month mortality. A higher Vt and lower driving pressure (likely markers of static compliance improvement) across the ECMO course were also associated with better outcomes.Conclusions: Ultraprotective lung ventilation on ECMO was largely adopted across medium- to high-case volume ECMO centers. In contrast with previous observations, mechanical ventilation settings during ECMO did not impact patients' prognosis in this context.

A diaphragmatic electrical activity-based optimization strategy during pressure support ventilation improves synchronization but does not impact work of breathing.

BACKGROUND: Poor patient-ventilator synchronization is often observed during pressure support ventilation (PSV) and has been associated with prolonged duration of mechanical ventilation and poor outcome. Diaphragmatic electrical activity (Eadi) recorded using specialized nasogastric tubes is a surrogate of respiratory brain stem output. This study aimed at testing whether adapting ventilator settings during PSV using a protocolized Eadi-based optimization strategy, or Eadi-triggered and -cycled assisted pressure ventilation (or PSVN) could (1) improve patient-ventilator interaction and (2) reduce or normalize patient respiratory effort as estimated by the work of breathing (WOB) and the pressure time product (PTP). METHODS: This was a prospective cross-over study. Patients with a known chronic pulmonary obstructive or restrictive disease, asynchronies or suspected intrinsic positive end-expiratory pressure (PEEP) who were ventilated using PSV were enrolled in the study. Four different ventilator settings were sequentially applied for 15 minutes (step 1: baseline PSV as set by the clinician, step 2: Eadi-optimized PSV to adjust PS level, inspiratory trigger, and cycling settings, step 3: step 2 + PEEP adjustment, step 4: PSVN). The same settings as step 3 were applied again after step 4 to rule out a potential effect of time. Breathing pattern, trigger delay (Td), inspiratory time in excess (Tiex), pressure-time product (PTP), and work of breathing (WOB) were measured at the end of each step. RESULTS: Eleven patients were enrolled in the study. Eadi-optimized PSV reduced Td without altering Tiex in comparison with baseline PSV. PSVN reduced Td and Tiex in comparison with baseline and Eadi-optimized PSV. Respiratory pattern did not change during the four steps. The improvement in patient-ventilator interaction did not lead to changes in WOB or PTP. CONCLUSIONS: Eadi-optimized PSV allows improving patient ventilator interaction but does not alter patient effort in patients with mild asynchrony. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT 02067403 . Registered 7 February 2014.

Bioelectrical impedance spectroscopy to estimate fluid balance in critically ill patients.

Fluid management is a crucial issue in intensive-care medicine. This study evaluated the feasibility and reproducibility of bioimpedance spectroscopy to measure body-water composition in critically ill patients, and compared fluid balance and daily changes in total body water (TBW) measured by bioimpedance. This observational study included 25 patients under mechanical ventilation. Fluid balance and bioimpedance measurements were recorded on 3 consecutive days. Whole-body bioimpedance spectroscopy was performed with exact or ideal body weights entered into the device, and with or without ICU monitoring. Reproducibility of bioimpedance spectroscopy was very good in all conditions despite ICU monitoring and mechanical ventilation. Bioimpedance measurements using an ideal body weight varied significantly, making the weighing procedure necessary. Comparison of fluid balance and daily changes in body weight provided the best correlation (ρ = 0.74; P < 0.0001). Daily changes in TBW were correlated with fluid balance (Spearman coefficient ρ = 0.31; P = 0.003) and this correlation was improved after exclusion of patients with a SOFA score >10 (ρ = 0.36; P = 0.05) and with extracorporeal circulation (ρ = 0.50; P = 0.005). Regardless of the technique used to estimate volume status, important limits of agreement were observed. Non-invasive determination of body-water composition using bioimpedance spectroscopy is feasible in critically ill patients but requires knowledge of the patient's weight. The best method to assess volume status after fluid resuscitation and the value gained from information about body composition provided by bioimpedance techniques needs further evaluation.

Extracorporeal membrane oxygenation for pandemic influenza A(H1N1)-induced acute respiratory distress syndrome: a cohort study and propensity-matched analysis.

RATIONALE: Many patients with severe acute respiratory distress syndrome (ARDS) caused by influenza A(H1N1) infection receive extracorporeal membrane oxygenation (ECMO) as a rescue therapy. OBJECTIVES: To analyze factors associated with death in ECMO-treated patients and the influence of ECMO on intensive care unit (ICU) mortality. METHODS: Data from patients admitted for H1N1-associated ARDS to French ICUs were prospectively collected from 2009 to 2011 through the national REVA registry. We analyzed factors associated with in-ICU death in ECMO recipients, and the potential benefit of ECMO using a propensity score-matched (1:1) cohort analysis. MEASUREMENTS AND MAIN RESULTS: A total of 123 patients received ECMO. By multivariate analysis, increasing values of age, lactate, and plateau pressure under ECMO were associated with death. Of 103 patients receiving ECMO during the first week of mechanical ventilation, 52 could be matched to non-ECMO patients of comparable severity, using a one-to-one matching and using control subjects only once. Mortality did not differ between the two matched cohorts (odds ratio, 1.48; 95% confidence interval, 0.68-3.23; P = 0.32). Interestingly, the 51 ECMO patients who could not be matched were younger, had lower Pa(o(2))/Fi(o(2)) ratio, had higher plateau pressure, but also had a lower ICU mortality rate than the 52 matched ECMO patients (22% vs. 50%; P < 0.01). CONCLUSIONS: Under ECMO, an ultraprotective ventilation strategy minimizing plateau pressure may be required to improve outcome. When patients with severe influenza A(H1N1)-related ARDS treated with ECMO were compared with conventionally treated patients, no difference in mortality rates existed. The unmatched, severely hypoxemic, and younger ECMO-treated patients had, however, a lower mortality.

Protocol for venoarterial ExtraCorporeal Membrane Oxygenation to reduce morbidity and mortality following bilateral lung TransPlantation: the ECMOToP randomised controlled trial.

INTRODUCTION: Lung transplantation (LTx) aims at improving survival and quality of life for patients with end-stage lung diseases. Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is used as intraoperative support for LTx, despite no precise guidelines for its initiation. We aim to evaluate two strategies of VA-ECMO initiation in the perioperative period in patients with obstructive or restrictive lung disease requiring bilateral LTx. In the control 'on-demand' arm, high haemodynamic and respiratory needs will dictate VA-ECMO initiation; in the experimental 'systematic' arm, VA-ECMO will be pre-emptively initiated. We hypothesise a 'systematic' strategy will increase the number of ventilatory-free days at day 28. METHODS AND ANALYSIS: We designed a multicentre randomised controlled trial in parallel groups. Adult patients with obstructive or restrictive lung disease requiring bilateral LTx, without a formal indication for pre-emptive VA-ECMO before LTx, will be included. Patients with preoperative pulmonary hypertension with haemodynamic collapse, ECMO as a bridge to transplantation, severe hypoxaemia or hypercarbia will be secondarily excluded. In the systematic group, VA-ECMO will be systematically implanted before the first pulmonary artery cross-clamp. In the on-demand group, VA-ECMO will be implanted intraoperatively if haemodynamic or respiratory indices meet preplanned criteria. Non-inclusion, secondary exclusion and VA-ECMO initiation criteria were validated by a Delphi process among investigators. Postoperative weaning of ECMO and mechanical ventilation will be managed according to best practice guidelines. The number of ventilator-free days at 28 days (primary endpoint) will be compared between the two groups in the intention-to-treat population. Secondary endpoints encompass organ failure occurrence, day 28, day 90 and year 1 vital status, and adverse events. ETHICS AND DISSEMINATION: The sponsor is the Assistance Publique-Hôpitaux de Paris. The ECMOToP protocol version 2.1 was approved by Comité de Protection des Personnes Ile de France VIII. Results will be published in international peer-reviewed medical journals. TRIAL REGISTRATION NUMBER: NCT05664204.

Cardiopulmonary bypass during a second-lung implantation improves postoperative oxygenation after sequential double-lung transplantation.

OBJECTIVES: During sequential double-lung transplantation (DLT), the newly implanted first lung receives the entire cardiac output during the implantation of the second one. This may be responsible for the increased hydrostatic pressure that causes severe interstitial and alveolar edema that can lead to allograft dysfunction. The authors tested the hypothesis that CPB started after first graft implantation and before second recipient lung removal should improve post-transplantation oxygenation and clinical outcomes. DESIGN: Observational during 2 consecutive 1-year periods. SETTING: University hospital. PARTICIPANTS: Nine consecutive patients undergoing sequential DLT with CPB started after first graft implantation and before second recipient lung removal were compared to controls, who were 10 consecutive patients who underwent sequential DLT but without CPB the year before. MEASUREMENTS AND MAIN RESULTS: Oxygenation after transplantation was assessed. The use of CPB during the implantation of the second lung was associated with an increased mean postoperative ratio of PaO2 to the fraction of inspired oxygen at 1 hour (363±51 v 240±113, p = 0.01) and 6 hours (430±111 v 280±103, p = 0.03). The mean duration of CPB was 111±19 min. The occurrence of primary graft dysfunction and the need for extracorporeal membrane oxygenation tended to be lower, but did not reach significance. Similarly, mortality rate was comparable between both groups, as was the rate of blood transfusions. CONCLUSIONS: The authors' results suggest that the use of CPB started after first graft implantation and before second recipient lung removal appears to benefit oxygenation and reduces the occurrence of severe pulmonary edema in the first transplanted lung.

Prognostic value of respiratory compliance course on mortality in COVID-19 patients with vv-ECMO.

BACKGROUND: COVID-19-associated acute respiratory distress syndrome (ARDS) supported by veno-venous extra-corporal membrane oxygenation (vv-ECMO) results in a high in-hospital mortality rate of more than 35%. However, after cannulation, no prognostic factor has been described to guide the management of these patients. The objective was to assess the association between static respiratory compliance over the first 10 days post-vv-ECMO implantation on 180-day mortality. RESULTS: In this multicentric retrospective study in three ECMO referral centers, all patients with COVID-19-associated ARDS supported by vv-ECMO were included from 03/01/2020 to 12/31/2021. Patients were ventilated with ultra-protective settings targeting a driving pressure lower than 15 cmH2O. 122 patients were included. Median age was 59 IQR (52-64), 83 (68%) were male, with a median body mass index of 33 (28-37) kg/m2. Delay between first symptoms to vv-ECMO implantation was 16 (10-21) days. Six-month death was 48%. Over the first ten days, compliance increased in 180 day survivors [from 18 (12-25) to 20 (15-27) mL/cmH2O] compared to non-survivors [from 12 (9-20) to 10 (8-14) mL/cmH2O, p interaction < 0.0001]. A time varying multivariable Cox model found age, history of chronic lung disease, compliance from day one to day ten and sweep gas flow from day one to day ten as independent factors associated with 180-day mortality. CONCLUSIONS: In COVID-19-associated ARDS, static respiratory compliance course over the first ten days post-vv-ECMO implantation is associated with 180-day mortality. This new information may provide crucial information on the patient's prognosis for intensivists.

Prediction of survival after a lung transplant at 1 year (SALTO cohort) using information available at different key time points.

OBJECTIVES: A lung transplant is the final treatment option for end-stage lung disease. We evaluated the individual risk of 1-year mortality at each stage of the lung transplant process. METHODS: This study was a retrospective analysis of patients undergoing bilateral lung transplants between January 2014 and December 2019 in 3 French academic centres. Patients were randomly divided into development and validation cohorts. Three multivariable logistic regression models of 1-year mortality were applied (i) at recipient registration, (ii) the graft allocation and (iii) after the operation. The 1-year mortality was predicted for individual patients assigned to 3 risk groups at time points A to C. RESULTS: The study population consisted of 478 patients with a mean (standard deviation) age of 49.0 (14.3) years. The 1-year mortality rate was 23.0%. There were no significant differences in patient characteristics between the development (n = 319) and validation (n = 159) cohorts. The models analysed recipient, donor and intraoperative variables. The discriminatory power (area under the receiver operating characteristic curve) was 0.67 (0.62-0.73), 0.70 (0.63-0.77) and 0.82 (0.77-0.88), respectively, in the development cohort and 0.74 (0.64-0.85), 0.76 (0.66-0.86) and 0.87 (0.79 - 0.95), respectively, in the validation cohort. Survival rates were significantly different among the low- (< 15%), intermediate- (15%-45%) and high-risk (> 45%) groups in both cohorts. CONCLUSIONS: Risk prediction models allow estimation of the 1-year mortality risk of individual patients during the lung transplant process. These models may help caregivers identify high-risk patients at times A to C and reduce the risk at subsequent time points.

Effect of non-invasive ventilation after extubation in critically ill patients with obesity in France: a multicentre, unblinded, pragmatic randomised clinical trial.

BACKGROUND: Non-invasive ventilation (NIV) and oxygen therapy (high-flow nasal oxygen [HFNO] or standard oxygen) following extubation have never been compared in critically ill patients with obesity. We aimed to compare NIV (alternating with HFNO or standard oxygen) and oxygen therapy (HFNO or standard oxygen) following extubation of critically ill patients with obesity. METHODS: In this multicentre, parallel group, pragmatic randomised controlled trial, conducted in 39 intensive care units in France, critically ill patients with obesity undergoing extubation were randomly assigned (1:1) to either the NIV group or the oxygen therapy group. Two randomisations were performed: first, randomisation to either NIV or oxygen therapy, and second, randomisation to either HFNO or standard oxygen (also 1:1), which was nested within the first randomisation. Blinding of the randomisation was not possible, but the statistician was masked to group assignment. The primary outcome was treatment failure within 3 days after extubation, a composite of reintubation for mechanical ventilation, switch to the other study treatment, or premature discontinuation of study treatment. The primary outcome was analysed by intention to treat. Effect of medical and surgical status was assessed. The reintubation within 3 days was analysed by intention to treat and after a post-hoc crossover analysis. This study is registered with ClinicalTrials.gov, number NCT04014920. FINDINGS: From Oct 2, 2019, to July 17, 2021, of the 1650 screened patients, 981 were enrolled. Treatment failure occurred in 66 (13·5%) of 490 patients in the NIV group and in 130 (26·5%) of 491 patients in the oxygen-therapy group (relative risk 0·43; 95% CI 0·31-0·60, p<0·0001). Medical or surgical status did not modify the effect of NIV group on the treatment-failure rate. Reintubation within 3 days after extubation was similar in the non-invasive ventilation group and in the oxygen therapy group in the intention-to-treat analysis (48 (10%) of 490 patients and 59 (12%) of 491 patients, p=0·26) and lower in the NIV group than in the oxygen-therapy group in the post-hoc cross-over (51 (9%) of 560 patients and 56 (13%) of 421 patients, p=0·037) analysis. No severe adverse events were reported. INTERPRETATION: Among critically ill adults with obesity undergoing extubation, the use of NIV was effective to reduce treatment-failure within 3 days. Our results are relevant to clinical practice, supporting the use of NIV after extubation of critically ill patients with obesity. However, most of the difference in the primary outcome was due to patients in the oxygen therapy group switching to NIV, and more evidence is needed to conclude that an NIV strategy leads to improved patient-centred outcomes. FUNDING: French Ministry of Health.

Doppler resistive index to reflect regulation of renal vascular tone during sepsis and acute kidney injury.

INTRODUCTION: Renal resistive index (RI), determined by Doppler ultrasonography, directly reveals and quantifies modifications in renal vascular resistance. The aim of this study was to evaluate if mean arterial pressure (MAP) is determinant of renal RI in septic, critically ill patients suffering or not from acute kidney injury (AKI). METHODS: This prospective observational study included 96 patients. AKI was defined according to RIFLE criteria and transient or persistent AKI according to renal recovery within 3 days. RESULTS: Median renal RIs were 0.72 (0.68-0.75) in patients without AKI and 0.76 (0.72-0.80) in patients with AKI (P = 0.001). RIs were 0.75 (0.72-0.79) in transient AKI and 0.77 (0.70-0.80) in persistent AKI (P = 0.84). RI did not differ in patients given norepinephrine infusion and was not correlated with norepinephrine dose. RI was correlated with MAP (ρ = -0.47; P = 0.002), PaO2/FiO2 ratio (ρ = -0.33; P = 0.04) and age (ρ = 0.35; P = 0.015) only in patients without AKI. CONCLUSIONS: A poor correlation between renal RI and MAP, age, or PaO2/FiO2 ratio was found in septic and critically ill patients without AKI compared to patients with AKI. These findings suggest that determinants of RI are multiple. Renal circulatory response to sepsis estimated by Doppler ultrasonography cannot reliably be predicted simply from changes in systemic hemodynamics. As many factors influence its value, the interest in a single RI measurement at ICU admission to determine optimal MAP remains uncertain.

Clinical review: Update on neurally adjusted ventilatory assist--report of a round-table conference.

Conventional mechanical ventilators rely on pneumatic pressure and flow sensors and controllers to detect breaths. New modes of mechanical ventilation have been developed to better match the assistance delivered by the ventilator to the patient's needs. Among these modes, neurally adjusted ventilatory assist (NAVA) delivers a pressure that is directly proportional to the integral of the electrical activity of the diaphragm recorded continuously through an esophageal probe. In clinical settings, NAVA has been chiefly compared with pressure-support ventilation, one of the most popular modes used during the weaning phase, which delivers a constant pressure from breath to breath. Comparisons with proportional-assist ventilation, which has numerous similarities, are lacking. Because of the constant level of assistance, pressure-support ventilation reduces the natural variability of the breathing pattern and can be associated with asynchrony and/or overinflation. The ability of NAVA to circumvent these limitations has been addressed in clinical studies and is discussed in this report. Although the underlying concept is fascinating, several important questions regarding the clinical applications of NAVA remain unanswered. Among these questions, determining the optimal NAVA settings according to the patient's ventilatory needs and/or acceptable level of work of breathing is a key issue. In this report, based on an investigator-initiated round table, we review the most recent literature on this topic and discuss the theoretical advantages and disadvantages of NAVA compared with other modes, as well as the risks and limitations of NAVA.

High-resolution Free-breathing late gadolinium enhancement Cardiovascular magnetic resonance to diagnose myocardial injuries following COVID-19 infection.

PURPOSE: High-resolution free-breathing late gadolinium enhancement (HR-LGE) was shown valuable for the diagnosis of acute coronary syndromes with non-obstructed coronary arteries. The method may be useful to detect COVID-related myocardial injuries but is hampered by prolonged acquisition times. We aimed to introduce an accelerated HR-LGE technique for the diagnosis of COVID-related myocardial injuries. METHOD: An undersampled navigator-gated HR-LGE (acquired resolution of 1.25 mm3) sequence combined with advanced patch-based low-rank reconstruction was developed and validated in a phantom and in 23 patients with structural heart disease (test cohort; 15 men; 55 ± 16 years). Twenty patients with laboratory-confirmed COVID-19 infection associated with troponin rise (COVID cohort; 15 men; 46 ± 24 years) prospectively underwent cardiovascular magnetic resonance (CMR) with the proposed sequence in our center. Image sharpness, quality, signal intensity differences and diagnostic value of free-breathing HR-LGE were compared against conventional breath-held low-resolution LGE (LR-LGE, voxel size 1.8x1.4x6mm). RESULTS: Structures sharpness in the phantom showed no differences with the fully sampled image up to an undersampling factor of x3.8 (P > 0.5). In patients (N = 43), this acceleration allowed for acquisition times of 7min21s ± 1min12s at 1.25 mm3 resolution. Compared with LR-LGE, HR-LGE showed higher image quality (P = 0.03) and comparable signal intensity differences (P > 0.5). In patients with structural heart disease, all LGE-positive segments on LR-LGE were also detected on HR-LGE (80/391) with 21 additional enhanced segments visible only on HR-LGE (101/391, P < 0.001). In 4 patients with COVID-19 history, HR-LGE was definitely positive while LR-LGE was either definitely negative (1 microinfarction and 1 myocarditis) or inconclusive (2 myocarditis). CONCLUSIONS: Undersampled free-breathing isotropic HR-LGE can detect additional areas of late enhancement as compared to conventional breath-held LR-LGE. In patients with history of COVID-19 infection associated with troponin rise, the method allows for detailed characterization of myocardial injuries in acceptable scan times and without the need for repeated breath holds.

Characterization of acute kidney injury in critically ill patients with severe coronavirus disease 2019.

BACKGROUND: Coronavirus disease 2019 (COVID-19)-associated acute kidney injury (AKI) frequency, severity and characterization in critically ill patients has not been reported. METHODS: Single-centre cohort performed from 3 March 2020 to 14 April 2020 in four intensive care units in Bordeaux University Hospital, France. All patients with COVID-19 and pulmonary severity criteria were included. AKI was defined using Kidney Disease: Improving Global Outcomes (KDIGO) criteria. A systematic urinary analysis was performed. The incidence, severity, clinical presentation, biological characterization (transient versus persistent AKI; proteinuria, haematuria and glycosuria) and short-term outcomes were evaluated. RESULTS: Seventy-one patients were included, with basal serum creatinine (SCr) of 69 ± 21 µmol/L. At admission, AKI was present in 8/71 (11%) patients. Median [interquartile range (IQR)] follow-up was 17 (12-23) days. AKI developed in a total of 57/71 (80%) patients, with 35% Stage 1, 35% Stage 2 and 30% Stage 3 AKI; 10/57 (18%) required renal replacement therapy (RRT). Transient AKI was present in only 4/55 (7%) patients and persistent AKI was observed in 51/55 (93%). Patients with persistent AKI developed a median (IQR) urine protein/creatinine of 82 (54-140) (mg/mmol) with an albuminuria/proteinuria ratio of 0.23 ± 20, indicating predominant tubulointerstitial injury. Only two (4%) patients had glycosuria. At Day 7 after onset of AKI, six (11%) patients remained dependent on RRT, nine (16%) had SCr >200 µmol/L and four (7%) had died. Day 7 and Day 14 renal recovery occurred in 28% and 52%, respectively. CONCLUSION: Severe COVID-19-associated AKI is frequent, persistent, severe and characterized by an almost exclusive tubulointerstitial injury without glycosuria.