Inhaled NO in Surgical Patients With Recent COVID-19 Infection

The aim of this study is to evaluate the effect of perioperative inhalation of NO on reducing the incidence of postoperative pulmonary complications in patients with recent COVID-19 infection, and to evaluate whether inhaled NO can improve the prognosis of patients. The investigators will enroll 660 surgical patients who was infected with SARS-CoV-2 within 42days (7 weeks ) prior to planed surgery under general anesthesia. Patients will be randomized to receive either inhaled nitric oxide (per protocol) or a placebo. Perioperative standards of care will be the institution's own protocols (such as ventilation strategies and use and dose of anesthetics, analgesia and fluid management, etc).