Rationale: ACE2 (angiotensin-converting enzyme 2), the entry receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is expressed in type 2 alveolar epithelial cells (AT2) that may play key roles in postinjury repair. An imbalance between ACE2 and ACE has also been hypothesized to contribute to lung injury. Objectives: To characterize the expression and distribution of ACE2 and ACE and to compare AT2 with endothelial cell expression in coronavirus disease (COVID-19)–related or –unrelated acute respiratory distress syndrome (ARDS) and controls. Methods: Lung tissue stainings (using multiplex immunofluorescence) and serum concentrations of ACEs were determined retrospectively in two different cohorts of patients. AT2 and endothelial cells were stained in lung tissue for ProSPC (pro-surfactant protein C) and CD31, respectively. Measurements and Main Results: Pulmonary ACE2 expression was increased in patients with COVID-19–related and –unrelated ARDS (0.06% of tissue area and 0.12% vs. 0.006% for control subjects; P = 0.013 and P < 0.0001, respectively). ACE2 was upregulated in endothelial cells (0.32% and 0.53% vs. 0.01%; P = 0.009 and P < 0.0001) but not in AT2 cells (0.13% and 0.08% vs. 0.03%; P = 0.94 and P = 0.44). Pulmonary expression of ACE was decreased in both COVID-19–related and –unrelated ARDS (P = 0.057 and P = 0.032). Similar increases in ACE2 and decreases in ACE were observed in sera of COVID-19 (P = 0.0054 and P < 0.0001) and non–COVID-19 ARDS (P < 0.0001 and P = 0.016). In addition, AT2 cells were decreased in patients with COVID-19–related ARDS compared with COVID-19–unrelated ARDS (1.395% vs. 2.94%, P = 0.0033). Conclusions: ACE2 is upregulated in lung tissue and serum of both COVID-19–related and –unrelated ARDS, whereas a loss of AT2 cells is selectively observed in COVID-19–related ARDS.

Background: The severity of coronavirus disease 2019 (COVID-19) is highly variable between individuals, ranging from asymptomatic infection to critical disease with acute respiratory distress syndrome requiring mechanical ventilation. Such variability stresses the need for novel biomarkers associated with disease outcome. As SARS-CoV-2 infection causes a kidney proximal tubule dysfunction with urinary loss of uric acid, we hypothesized that low serum levels of uric acid (hypouricemia) may be associated with severity and outcome of COVID-19. Methods: In a retrospective study using two independent cohorts, we investigated and validated the prevalence, kinetics and clinical correlates of hypouricemia among patients hospitalized with COVID-19 to a large academic hospital in Brussels, Belgium. Survival analyses using Cox regression and a competing risk approach assessed the time to mechanical ventilation and/or death. Confocal microscopy assessed the expression of urate transporter URAT1 in kidney proximal tubule cells from patients who died from COVID-19. Results: The discovery and validation cohorts included 192 and 325 patients hospitalized with COVID-19, respectively. Out of the 517 patients, 274 (53%) had severe and 92 (18%) critical COVID-19. In both cohorts, the prevalence of hypouricemia increased from 6% upon admission to 20% within the first days of hospitalization for COVID-19, contrasting with a very rare occurrence (< 1%) before hospitalization for COVID-19. During a median (interquartile range) follow-up of 148 days (50–168), 61 (12%) patients required mechanical ventilation and 93 (18%) died. In both cohorts considered separately and in pooled analyses, low serum levels of uric acid were strongly associated with disease severity (linear trend, P < 0.001) and with progression to death and respiratory failure requiring mechanical ventilation in Cox (adjusted hazard ratio 5.3, 95% confidence interval 3.6–7.8, P < 0.001) or competing risks (adjusted hazard ratio 20.8, 95% confidence interval 10.4–41.4, P < 0.001) models. At the structural level, kidneys from patients with COVID-19 showed a major reduction in urate transporter URAT1 expression in the brush border of proximal tubules. Conclusions: Among patients with COVID-19 requiring hospitalization, low serum levels of uric acid are common and associate with disease severity and with progression to respiratory failure requiring invasive mechanical ventilation.

Objectives: Approximately half of the patients undergoing lung biopsy for nonresolving acute respiratory distress syndrome exhibit another histologic pattern than diffuse alveolar damage, with some of the pathologies characterized by a potential response to corticosteroids. This study aimed to assess whether open lung biopsy performed in the ICU for nonresolving acute respiratory distress syndrome was able to identify steroid-sensitive diseases and whether patients with a steroid-sensitive pathology experienced different clinical courses and outcomes. Design: Retrospective analysis. Setting: One 22-bed mixed ICU within a tertiary medical center. Patients: Patients age greater than or equal to 16 years old who met the Berlin definition for acute respiratory distress syndrome and underwent open lung biopsy from January 2007 to January 2017. Interventions: None. Measurements and Main Results: During the study period, 695 patients diagnosed with acute respiratory distress syndrome were identified, 51 (7%) of whom underwent open lung biopsy. An alternative diagnosis to diffuse alveolar damage was found in 29 patients (57%), and a steroid-sensitive pathology was identified in 19 (37%). In-hospital and 180-day mortality rates were 55% and 61%, respectively. There was a significant difference in hospital mortality and 180-day mortality rates between patients with steroid-sensitive pathology and those with steroid-resistant pathology (37% vs 65%; p < 0.045 and 37% vs 75%; p < 0.007, respectively). We did not identify any variable that could reliably predict a steroid-sensitive histologic pattern before open lung biopsy. Conclusions: Open lung biopsy was able to identify a steroid-sensitive pathology in a significant proportion of nonresolving acute respiratory distress syndrome patients. These patients had a better outcome, with lower hospital mortality and 180-day mortality.

Volatile anesthetic agents, such as sevoflurane, are increasingly used for long-term sedation in intensive care units worldwide, with improved clinical outcomes reported in recent studies due to favorable pharmacological properties. Despite possible renal toxicity related to the production of plasma inorganic fluoride and concerns related to reversible impairment of renal concentrating abilities, renal injury associated with sevoflurane sedation has rarely been reported in the intensive care unit setting. We hereby report 3 cases of nephrogenic diabetes insipidus associated with prolonged sevoflurane sedation using the AnaConDa device and review the possible mechanisms of renal toxicity.