The influence of various technologies for the use of gaseous nitric oxide on the functional and morphological state of the lungs, markers of myocardial damage and clinical outcomes in cardiosurgical interventions with cardiopulmonary bypass

Abstract

The aim of the study was to evaluate the impact of various technologies for the use of gaseous nitric oxide on the state of the lungs and heart during heart valve surgery under cardiopulmonary bypass (CPB).Methods. The study included 93 patients of both sexes. All patients underwent heart valve surgery and combined surgical interventions under CPB. The patients were divided into 4 groups. Group 1 (control, n = 30) used the standard protocol for anesthetic and perfusion management. Group 2 (n = 30) received inhalation of nitric oxide (20 ppm) within 3 days before surgery, as well as before and after CPB. Group 3 (n = 30) inhaled nitric oxide (40 ppm) throughout surgery with the medication delivered through inspiratory part of the ventilator and combined with perfusion of the pulmonary artery and reduced volume ventilation during CPB. Group 4 (n = 33) received nitric oxide (40 ppm) via oxygenator of the heart-lung machine. We assessed changes in the functional parameters of the lungs at different phases of surgery, performed a morphological examination of the lungs in the initial phase (before CPB), at the peak of ischemia, and after reperfusion. The state of the myocardium after surgery was assessed by troponin I (cTnI) activity at the beginning of the operation, after transfer to the ICU, at 12, 24 and 48 hours after the surgery. Myocardial damage index (MDI) was calculated according to the following formula: MDI = TnIlate / TnIearly. The clinical outcomes of the surgeries were evaluated.Results. There were no statistically significant differences in the functional state of the lungs with various options for inhalation delivery and administration via the CPB circuit. The most intact indicators of the functional state of the lungs were seen in patients of Group 3 who received inhaled nitric oxide throughout surgery and combined mechanical ventilation with the addition of nitric oxide and perfusion of the pulmonary artery during CPB. Morphological examination of the lungs showed that inhalation of nitric oxide before CPB does not prevent the development of morphological disorders. Morphological changes found in Group 3 were the smallest. The supply of nitric oxide into the CPB circuit statistically significantly improved the restoration of pulmonary blood flow during reperfusion. The cTnI level statistically significantly increased in all groups of patients, however, it was statistically significantly lower in Groups 2, 3, and 4 compared with Group 1 at the end of surgery, in Groups 3 and 4 compared with Groups 1 and 2 after 12 and 24 hours, and in Group 3 after 48 hours. The most favorable changes in the MDI were seen in Group 3; statistically significantly lower MDI was registered 12 and 48 hours after surgery in this group compared with Groups 1, 2, and 4. A lower complication rate, a shorter duration of ventilation and stay in the ICU were observed in Groups 3 and 4.Conclusion. Nitric oxide has a protective effect on the lungs and heart when used during anesthesia and cardiopulmonary bypass in heart valve surgery. It preserves the lung function and morphology and statistically significantly reduces cTnI level and myocardial damage index in the postoperative period. The extent of the protective effect depends on the nitric oxide exposure time and is most pronounced when nitric oxide is used throughout the surgery, including during CPB.