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).

The outbreak of COVID-19 and its global pandemic has posed a threat to public health. On December 7, 2022, the National Health Commission (NHC) of China issued an announcement on further optimization of public health control measures. Since then, the rapid spread and breakthrough of SARS-CoV-2 infections have been observed in the majority of China, caused by the more infectious and less virulent Omicron variant of SARS-Cov-2. Consequently, the proportion of surgical patients with current or previous SARS-CoV-2 infections will inevitably increase within a relatively narrow time window.

It has been reported that a history of SARS-CoV-2 infection is associated with a transiently elevated risk of postoperative complications. The longer the time interval between infection and surgery, the lower the risk of postoperative complications. An updated recommendation suggested postponing surgery for at least seven weeks following SARS-CoV-2 infection, thereby reducing the risk of postoperative complications and 30-day mortality to baseline levels (similar to those without a history of SARS-CoV-2 infection).

COVID-19 infection significantly affects respiratory functions by massively disrupting pulmonary oxygenation and activating the synthesis of proinflammatory cytokines, inducing severe oxidative stress, enhanced vascular permeability, and endothelial dysfunction which has rendered researchers and clinicians to depend on prophylactic treatment due to the unavailability of proper disease management approaches. Inhaled nitric oxide gas (NO) has shown antiviral activity against Coronavirus during the 2003 SARS outbreak. Previous studies have indicated that nitric oxide (NO) application appears to be significant concerning the antiviral activities, antioxidant, and anti-inflammatory properties in relieving disease-related symptoms. Inhaled nitric oxide had been widely used during the Covid-19 pandemic. In the scoping and systemic reviews, it was demonstrated that nitric oxide inhalation was effective in improving oxygenation, cardiopulmonary function, and fastening virus clearance. The investigators designed this study to assess whether inhaled NO reduces postoperative pulmonary complications in patients with a COVID-19 infection history 7 weeks prior to surgery.

Here, the investigators propose a randomized clinical trial aimed to improve postoperative outcomes in patients with an increased risk of postoperative pulmonary complications after COVID-19 infection.

Control group: the institutional standard of care will be delivered. Treatment group: In addition to standard therapy, the subjects will receive inhalation of NO. Inspired NO/N2 will be delivered at 80 parts per million (ppm) after anesthesia induction and intubation and last until the end of surgery and leave the operating room. The physician will follow their own institutional weaning protocols. In the absence of institutional protocols, NO will be reduced in a step-wise fashion starting from 40 ppm to 20, 10, 5, 3, 2, and 1 ppm. If hypoxemia (SpO2 < 93%) or acute hypotension (systolic blood pressure < 90 mmHg) occurs during weaning, NO should be increased to a prior higher concentration.

Safety: prolonged treatment with inhaled NO can lead to increased methemoglobin levels. Blood levels of methemoglobin will be monitored via a non-invasive CO-oximeter or MetHb levels in the blood. If methemoglobin levels rise above 5% at any point in the study, inhaled NO concentration will be halved.

Inclusion Criteria:

1. ≥ 18 years old
2. Planned for surgery under general anesthesia
3. With a history of COVID-19 infection within 7 weeks prior to surgery.

Exclusion Criteria:

1. Physician makes a decision that trial involvement is not in the patient's best interest or any condition that does not allow the protocol to be followed safely
2. ASA ≥ IV, life expectancy< 24 h.
3. Pregnant or lactating women.
4. Severe liver disease (Child-Pugh score ≥ 12).
5. Patients with severe respiratory failure need mechanical ventilation support or ECMO life support before the operation.
6. Severe renal dysfunction (eGFRC≤30 ml/min/1.73m2) or receiving continuous renal replacement therapy, hemodialysis, and peritoneal dialysis.
7. Having received or participated in other clinical trials within the previous month.

Individual participant data that underline the results reported in this article, after deidentification.

beginning 12 months

Investigators who provide a methodologically sound proposal and whose proposed use of data has been approved by the steering of INORDINATE identified for individual participant data meta-analysis. Proposals should be directed to corresponding author of the publication. To gain access, data requestors will need to sign a data access agreement.