Effect of inhalation of nebulized NO donor substance on acute hypoxic lung injury in newborn piglets.

Background: Birth asphyxia may result in multiple organ dysfunction such as lung injury. Inhalation of nebulized nitric oxide precursor can selectively reduce pulmonary hypertension. However, it is unknown whether such precursors can alleviate lung injury induced by hypoxia. We evaluated the effect of inhalation of nebulized nitroglycerine and sodium nitroprusside on acute hypoxic lung injury in newborn piglets.

Methods: Acute hypoxic lung injury was induced by inspiring 10% O2 for 1 hour. Twenty-four anaesthetized and mechanically ventilated piglets (5-7 days old) were randomly divided into four groups: (1) group S, not hypoxic; (2) group C, nebulized saline after hypoxia; (3) group NTG, nebulized nitroglycerine after hypoxia; (4) group SNP, nebulized sodium nitroprusside after hypoxia. Respiratory dynamic compliance and resistance of respiratory system were recorded at baseline, 0.5 hour and 1 hour of hypoxia; then 0.5 hour, 1 hour, 3 hours and 5 hours following hypoxia. After nebulization, arterial blood was collected for measuring methaemoglobin and nitrate/nitrite levels. Right lung tissue, wet-dry ratio and myeloperoxidase level were determined. White blood cell count (WBC), total surfactant phospholipids (TPL) and disaturated phosphatidyl choline (DSPC) of the bronchoalveolar lavage fluid (BALF) were calculated. Left lungs were used for examining pathological changes.

Results: No significant difference was observed in respiratory dynamic compliance, resistance of respiratory system, wet-dry ratio, levels of methaemoglobin and nitrate/nitrite after nebulization, TPL or DSPC/TPL among four groups. WBC in BALF in groups NTG and SNP significantly decreased as compared with group C: similarly for myeloperoxidase level in lung tissue. Lung histological findings showed infiltration of neutrophils in groups NTG and SNP decreased significantly as compared with group C.

Conclusion: Inhalation of nebulized nitroglycerine or sodium nitroprusside can alleviate the infiltration of neutrophils, while it affects neither the metabolism of phospholipids nor water content in the lungs.