3-nitrotyrosine and Meconium-Aspiration-Syndrome

Current neonatal resuscitation guidelines recommend tracheal suctioning of nonvigorous neonates born through meconium-stained amniotic fluid.. We evaluated the effect of tracheal suctioning at birth in 29 lambs with asphyxia induced by cord occlusion and meconium aspiration during gasping.. Tracheal suctioning at birth (n = 15) decreased amount of meconium in distal airways (53 ± 29 particles/mm(2) lung area) compared to no suction (499 ± 109 particles/mm(2); n = 14; P < 0.001). Three lambs in the suction group had cardiac arrest during suctioning, requiring chest compressions and epinephrine. Onset of ventilation was delayed in the suction group (146 ± 11 vs. 47 ± 3 s in no-suction group; P = 0.005). There was no difference in pulmonary blood flow, carotid blood flow, and pulmonary or systemic blood pressure between the two groups. Left atrial pressure was significantly higher in the suction group. Tracheal suctioning resulted in higher Pao2/FiO2 levels (122 ± 21 vs. 78 ± 10 mm Hg) and ventilator efficiency index (0.3 ± 0.05 vs.0.16 ± 0.03). Two lambs in the no-suction group required inhaled nitric oxide. Lung 3-nitrotyrosine levels were higher in the suction group (0.65 ± 0.03 ng/µg protein) compared with the no-suction group (0.47 ± 0.06).. Tracheal suctioning improves oxygenation and ventilation. Suctioning does not improve pulmonary/systemic hemodynamics or oxidative stress in an ovine model of acute meconium aspiration with asphyxia.

Topics: Analysis of Variance; Animals; Animals, Newborn; Asphyxia Neonatorum; Fluorescence; Hemodynamics; Luminescent Measurements; Meconium Aspiration Syndrome; Microspheres; Pulmonary Gas Exchange; Resuscitation; Sheep; Sheep Diseases; Suction; Trachea; Tyrosine

Meconium aspiration syndrome (MAS) is meconium-induced respiratory failure of newborns associated with activation of inflammatory and oxidative pathways. For severe MAS, exogenous surfactant treatment is used which improves respiratory functions but does not treat the inflammation. Oxidative process can lead to later surfactant inactivation; hence, surfactant combination with antioxidative agent may enhance the therapeutic effect. Young New Zealand rabbits were instilled by meconium suspension and treated by surfactant alone, N-acetylcysteine (NAC) alone or by their combination and oxygen-ventilated for 5 h. Blood samples were taken before and 30 min after meconium application and 30 min, 1, 3 and 5 h after the treatment for evaluating of oxidative damage, total leukocyte count, leukocyte differential count and respiratory parameters. Leukocyte differential was assessed also in bronchoalveolar lavage fluid. NAC alone had only mild therapeutic effect on MAS. However, the combination of NAC and surfactant facilitated rapid onset of therapeutic effect in respiratory parameters (oxygenation index, PaO(2)/FiO(2)) compared to surfactant alone and was the only treatment which prevented neutrophil migration into the lungs, oxidative damage and lung edema. Moreover, NAC suppressed IL-8 and IL-beta formation and thus seems to be favorable agent for improving surfactant therapy in MAS.

Topics: Acetylcysteine; Animals; Animals, Newborn; Bronchoalveolar Lavage Fluid; Cell Migration Assays, Leukocyte; Cytokines; Drug Evaluation, Preclinical; Drug Therapy, Combination; Edema; Expectorants; Leukocyte Count; Lung; Meconium Aspiration Syndrome; Pilot Projects; Pulmonary Surfactants; Rabbits; Random Allocation; Respiratory Function Tests; Thiobarbituric Acid Reactive Substances; Tyrosine