Background. Hemolysis is a pathological condition accompanied by the release of hemoglobin (Hbf) into the plasma, which has adverse effects. Intravascular hemolysis occurs in various diseases, and also complicates the postoperative period of surgical interventions using cardiopulmonary bypass. Objective. In an animal experiment, to study the effect of inhalation of nitric oxide (NO) on the cell-free hemoglobin (Hbf) concentration. Methods. The study included 10 pigs, which were randomized into two groups: control (n = 5) and experimental (n = 5). After induction of anesthesia and tracheal intubation, intravascular hemolysis was simulated in all animals by intravenous administration of Hbf. After modeling hemolysis, the animals of the experimental group were inhaled with NO at a dosage of 80 ppm. Animals from the control group did not receive NO. The dynamics of Hbf and methemoglobin were evaluated for 6 hours. Then euthanasia was performed. Results. The Hbf level in the experimental group was statistically significantly lower compared to the control group after 30 minutes (1.2 (1; 1.3) g/l vs. 1.7 (1.6; 1.9) g/l, p = 0.047), 60 minutes (0.9 (0.9; 1) g/l vs. 1.24 (1.2; 1.5) g/l, p = 0.046) and 90 minutes (0.7 (0.7; 0.8) g/l vs. 0.94 (0.9; 1.2) g/l, p = 0.035) after administration of Hbf. The level of methemoglobin in the experimental group was statistically significantly higher than in the control group throughout the study, but did not reach a toxic concentration of 5 %. Conclusion. Inhalation of NO at a dosage of 80 ppm reduces the level of Hbf. Inhalation of NO at a dosage of 80 ppm increases the level of methemoglobin within safe values.