Prevention of respiratory complications in patients at risk of adverse respiratory events by perioperative nitric oxide delivery during cardiac surgery under cardiopulmonary bypass: a single-center prospective randomized study

Introduction: Organoprotective effects of perioperative nitric oxide delivery towards the heart and kidneys have been demonstrated many times in cardiac surgery but information about its ability to prevent respiratory complications is extremely limited. Objective: This study aimed at evaluation of the efficacy and the safety of perioperative nitric oxide delivery for preventing respiratory complications during cardiac surgeries involving cardiopulmonary bypass in patients with an increased risk of adverse respiratory events and the identification of the risk factors towards postoperative acute respiratory. Methods: A prospective randomised controlled study included 132 cardiac surgical patients with increased risk of postoperative respiratory failure who were divided into two groups. The main group received nitric oxide at a concentration of 80 ppm throughout the operation and the first 6 hours at the postoperative period. The primary endpoint was the ratio of the partial pressure of oxygen in arterial blood to the fraction of inspired oxygen in 24 hours after the operation. Results: Patients receiving perioperative nitric oxide demonstrated significant improvements in oxygenation (paO2/FiO2 ratio, p < 0.001) in 24 hour post-surgery period that was associated with a decrease in pulmonary shunt fraction (p < 0.001), a decline of acute respiratory failure incidence (p = 0.042), and postoperative pneumonia (p = 0.013). Delivery of nitric oxide did not entail an increase in methemoglobin concentration above 5% and nitrogen dioxide above 3 ppm. In 24 h after surgery, revealed cases of acute respiratory failure were associated with blood transfusion (p = 0.033), as well as an excess of cardiopulmonary bypass duration of more than 97 min and mechanical ventilator duration of more than 628 min. Conclusion: Perioperative delivery of 80 ppm nitric oxide in cardiac surgeries involving cardiopulmonary bypass is safe and effective since it results in improved pulmonary oxygenating function and decreased pulmonary complications. In patients with an increased risk of adverse respiratory events, identified risk factors of acute respiratory failure include blood transfusion, prolonged cardiopulmonary bypass, and extended mechanical ventilation.