Response to Prone Position in COVID-19 and Non-COVID-19 Patients with Severe ARDS Supported by vvECMO

BACKGROUND

For moderate to severe acute respiratory distress syndrome (ARDS), lung-protective ventilation combined with prolonged and repeated prone position (PP) is recommended. For the most severe patients for whom this strategy failed, venovenous extracorporeal membrane oxygenation (vv-ECMO) allows a reduction in ventilation-induced lung injury and improves survival. Some aggregated data have suggested a benefit regarding survival in pursuing PP during vv-ECMO. The combination of PP and vv-ECMO has been also documented in COVID-19 studies, although there is scarce evidence concerning respiratory mechanics and gas exchange response. The main objective was to compare the physiological response of the first PP during vv-ECMO in two cohorts of patients (COVID-19-related ARDS and non-COVID-19 ARDS) regarding respiratory system compliance (C_RS) and oxygenation changes.

METHODS

This was a single-center, retrospective, and ambispective cohort study in the ECMO center of Marseille, France. ECMO was indicated according to the EOLIA trial criteria.

RESULTS

A total of 85 patients were included, 60 in the non-COVID-19 ARDS group and 25 in the COVID-19-related ARDS group. Lung injuries of the COVID-19 cohort exhibited significantly higher severity with a lower C_RS at baseline. Concerning the main objective, the first PP during vv-ECMO was not associated with a change in C_RS or other variation in respiratory mechanic variables in both cohorts. By contrast, oxygenation was improved only in the non-COVID-19 ARDS group after a return to the supine position. Mean arterial pressure was higher during PP as compared with a return to the supine position in the COVID-19 group.

CONCLUSION

We found distinct physiological responses to the first PP in vv-ECMO-supported ARDS patients according to the COVID-19 etiology. This could be due to higher severity at baseline or specificity of the disease. Further investigations are warranted.

Venovenous extracorporeal membrane oxygenation support in patients with COVID-19 respiratory failure: A multicenter study

Objective

The COVID-19 pandemic presents a high mortality rate amongst patients who develop severe acute respiratory distress syndrome (ARDS). The purpose of this study was to evaluate the outcomes of venovenous extracorporeal membrane oxygenation (VV-ECMO) in COVID-19-related ARDS and identify the patients who benefit the most from this procedure.

Methods

Adult patients with COVID-19 and severe ARDS requiring VV-ECMO support at 4 academic institutions between March and October 2020 were included. Data were collected through retrospective chart reviews. Bivariate and multivariable analyses were performed with the primary outcome of in-hospital mortality.

Results

Fifty-one consecutive patients underwent VV-ECMO with a mean age of 50.4 years; 64.7% were men. Survival to hospital discharge was 62.8%. Median intensive care unit and hospitalization duration were 27.4 days (interquartile range [IQR], 17-37 days) and 34.5 days (IQR, 23-43 days), respectively. Survivors and nonsurvivors had a median ECMO cannulation time of 11 days (IQR, 8-18) and 17 days (IQR, 12-25 days). The average postdecannulation length of stay was 17.5 days (IQR, 12.4-25 days) for survivors and 0 days for nonsurvivors (IQR, 0-6 days). Only 1 nonsurvivor was able to be decannulated. Clinical characteristics associated with mortality between nonsurviors and survivors included increasing age (P = .0048), hemorrhagic stroke (P = .0014), and postoperative dialysis (P = .0013) were associated with mortality in a bivariate model and retained statistical significance in a multivariable model.

Conclusions

This multicenter study confirms the effectiveness of VV-ECMO in selected critically ill patients with COVID-19-related severe ARDS. The survival of these patients is comparable to non-COVID-19-related ARDS.

Successful prone positioning after recent caesarean section in severe ARDS with postpartum pulmonary haemorrhage

A 35-year-old Thai women (gravida 3, para 0) at 36 weeks and five days of gestation was admitted to a delivery room due to premature rupture of membrane. She was diagnosed with Escherichia coli with extended-spectrum beta-lactamase (ESBL) chorioamnionitis and septic shock leading to signs of fetal distress. She underwent emergency caesarean section. Post-operatively, the patient developed severe acute respiratory distress syndrome (ARDS), disseminated intravascular coagulation (DIC), massive pulmonary haemorrhage, and intra-abdominal bleeding. Lung protective strategy and recruitment manoeuvres were applied; however, her oxygenation and haemodynamic parameters worsened. Twenty consecutive hours of prone positioning was performed as a rescue procedure to improve patient's oxygenation and allow the patient to undertake surgical re-exploration for abdominal compartment syndrome management safely. Neither high ventilator setting nor re-positioning was needed after the second operation.

The Role of Rescue Therapies in the Treatment of Severe ARDS

ARDS is characterized by a non-cardiogenic pulmonary edema with bilateral chest radiograph opacities and hypoxemia refractory to oxygen therapy. It is a common cause of admission to the ICU due to hypoxemic respiratory failure requiring mechanical ventilation. Corticosteroids are not recommended in ARDS patients. Rescue therapies alleviate hypoxemia in patients unable to maintain reasonable oxygenation: recruitment maneuvers, prone positioning, inhaled nitric oxide, high-frequency oscillatory ventilation, and extracorporeal membrane oxygenation improve oxygenation, but their impact on mortality remains unproven. Restrictive fluid management seems to be a favorable strategy with no significant reduction in 60-d mortality. Future studies are needed to clarify the efficacy of these therapies on outcomes in patients with severe ARDS, and institution of these therapies may be considered on a case-by-case basis.

Early severe acute respiratory distress syndrome: What's going on? Part I: pathophysiology

Severe acute respiratory distress syndrome (ARDS, PaO₂/FiO₂ < 100 on PEEP ≥ 5 cm H₂O) is treated using controlled mechanical ventilation (CMV), recently combined with muscle relaxation for 48 h and prone positioning. While the amplitude of tidal volume appears set < 6 mL kg⁻¹, the level of positive end-expiratory pressure (PEEP) remains controversial. This overview summarizes several salient points, namely: a) ARDS is an oxygenation defect: consolidation/ difuse alveolar damage is reversed by PEEP and/or prone positioning, at least during the early phase of ARDS b) ARDS is a dynamic disease and partially iatrogenic. This implies that the management of the ventilator may be a life-saver by reducing the duration of mechanical ventilation, or detrimental by extending this duration, leading into critical care-acquired diseases. Indeed, a high PEEP (10-24 cm H₂O) appears to be a life-saver in the context of early severe diffuse ARDS; c) tidal volume and plateau pressure cannot be identical for all patients; d) the only remaining rationale for CMV and muscle relaxation is to suppress patient-ventilator asynchrony and to lower VO2, during the acute cardio-ventilatory distress. Therefore, in early severe diffuse ARDS, this review argues for a combination of a high PEEP (preferably titrated on transpulmonary pressure) with spontaneous ventilation + pressure support (or newer modes of ventilation). However, conditionalities are stringent: upfront circulatory optimization, upright positioning, lowered VO₂, lowered acidotic and hypercapnic drives, sedation without ventilatory depression and without lowered muscular tone. As these propositions require evidence-based demonstration, the accepted practice remains, in 2016, controlled mechanical ventilation, muscle relaxation, and prone position.

Early severe acute respiratory distress syndrome: What's going on? Part II: controlled vs. spontaneous ventilation?

The second part of this overview on early severe ARDS delineates the pros and cons of the following: a) controlled mechanical ventilation (CMV: lowered oxygen consumption and perfect patient-to-ventilator synchrony), to be used during acute cardio-ventilatory distress in order to "buy time" and correct circulatory insufficiency and metabolic defects (acidosis, etc.); b) spontaneous ventilation (SV: improved venous return, lowered intrathoracic pressure, absence of muscle atrophy). Given a stabilized early severe ARDS, as soon as the overall clinical situation improves, spontaneous ventilation will be used with the following stringent conditionalities: upfront circulatory optimization, upright positioning, lowered VO2, lowered acidotic and hypercapnic drives, sedation without ventilatory depression and without lowered muscular tone, as well as high PEEP (titrated on transpulmonary pressure, or as a second best: "trial"-PEEP) with spontaneous ventilation + pressure support (or newer modes of ventilation). As these propositions require evidence-based demonstration, the reader is reminded that the accepted practice remains, in 2016, controlled mechanical ventilation, muscle relaxation and prone position.