Methods
Study participants and data collection
This is a retrospective cohort study of 88 critically ill patients, with confirmed COVID-19 infection, admitted in the ICU at Tongji Hospital in Wuhan, China. The study was approved by the Institutional Review Board of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology (Wuhan, China).
In January 2020, Tongji Hospital was urgently reconstructed and assigned by the Chinese government as a hospital designated for severely or critically ill COVID-19 patients. All patients were diagnosed according to the Guidelines of diagnosis and management of COVID-19 (6th edition, in Chinese), released by the National Health Commission of China-WHO interim guidance 6. Critically ill cases were defined based on the following criteria: if respiratory failure occurred and mechanical ventilation was required; if shock occurred; if the infection was complicated with organ failure, requiring monitoring and treatment in the ICU. Information on the dynamic changes in the laboratory variables was collected in the ICU. The study endpoint for this special group of patients was the 28-day mortality in the ICU. According to the survival times, these patients were subdivided into three groups, including the\(\leq\)7 days, 8–14 days, and >14 days groups.
Diagnosis and principles of management
Acute respiratory distress syndrome (ARDS), acute kidney injury, sepsis, shock, acute liver injury, and acute cardiac injury were defined according to the interim guidance of WHO for SARS-CoV-27. All patients received standard intensive medical treatment in the ICU. The standard medications included but were not limited to oxygen support, nutritional support, antiviral therapy, corticosteroid therapy, antibiotics, vasopressors, blood component transfusion, continuous renal replacement therapy (CRRT), and Chinese traditional medicine. Additionally, patients underwent routine blood tests, coagulation and biochemical tests, and chest computed tomography. Supplemental oxygen therapy was given to patients with hypoxaemia immediately. If standard oxygen therapy failed, mechanical ventilation was considered; high flow nasal catheter oxygen or non-invasive ventilation was used. If no improvement was seen within 1h of non-invasive mechanical ventilation, invasive mechanical ventilation was provided. Experienced experts recommended extracorporeal membrane pulmonary oxygenation (ECMO) based on their evaluation of the patient’s condition. If the patient gave a history of seasonal or local influenza, empirical therapy was considered.
Clinical laboratory measurements
Initial clinical laboratory investigation included a complete blood count, serum biochemical tests (including liver and renal function tests and levels of creatine kinase[CK], lactate dehydrogenase [LDH], and electrolytes), coagulation profile, and levels of serum cytokines, including interleukin (IL)-6, IL-10,and tumour necrosis factor (TNF)-α. Arterial blood gas tests were performed within 30 min.
Statistical analysis
All statistical analyses were performed using the Graph Pad Prism (version 7.0 for Windows, Graph Pad Software, La Jolla, California). Continuous variables of the three groups were expressed as mean ± standard deviation (SD) and compared by one-way ANOVA or non-parametric Kruskal-Wallis tests, and categorical variables of the three groups were expressed as numbers (percentages) and compared by χ2 test or Fisher’s exact test. A two- tailed P value <0.05 was considered statistically significant.