OBJECTIVEMeconium aspiration syndrome (MAS) is a disease of the term and near-term infant that is associated with considerable respiratory morbidity. The purpose of this study was to investigate effects of inhaled nitric oxide (iNO) in oxygenation and outcome of newborns with MAS.

METHODSEligible patients diagnosed as severe MAS admitted consecutively to the neonatal intensive care unit (NICU) of Hebei Children's Hospital from January 2004 to June 2006 were included in the study. The patients with an oxygenation index (OI) > or = 15 were randomized in a nonblinded manner to receive either iNO (NO group, n = 21) or no NO (control group, n = 25). Patients with an OI > or = 15 after enrollment were treated with iNO at 15 ppm initially. The response to iNO was assessed according to the increase in arterial PaO(2) and oxygen saturation (SpO(2)) after exposure to the starting concentration for 60 minutes. A response of 10 mm Hg (1 mm Hg = 0.133 kPa) increase in PaO(2) and a 10% increase in SpO(2) was assessed responsive to iNO. All patients were treated in the same neonatal unit and received the same standard therapy throughout the study period. Arterial blood gas tensions, pulmonary arterial pressure and systemic arterial blood pressures were recorded at baseline, 1 hour, and 24 hours in all patients. Methemoglobin levels were obtained at 12 - 24 hours after inhaled NO treatment. Parameters of fraction of inspired oxygen (FiO(2)), OI, mortality, ventilation time, and incidence of intraventricular hemorrhage (IVH, grade III-IV) were recorded. Informed consent was obtained from parents before enrollment. The protocol and the informed consent forms were approved by the ethic committee of the hospital before patient enrollment.

RESULTSThere was no significant difference in gestational age, birth weight, gender ratio, age at admission in hours, c-section delivery between the two groups, and no significant difference was found in respiratory mechanics parameters between the two groups at baseline. The duration of iNO was 34.90 +/- 16.41 hours. At the beginning of the treatment, no significant differences were detected in the OI and PAP between the two groups. One hour later, OI and PAP of NO group decreased significantly (OI, F = 35.27, P < 0.01, PAP, F = 24.30, P < 0.01), while in control group the difference was not found until 24 hours (OI, F = 20.16, P < 0.01, PAP, F = 101.22, P < 0.01). There were significant differences in PAP at 1, 24 hours between the two groups (1 h, t = 2.41, P < 0.05; 24 h, t = 3.11, P < 0.01). The methemoglobin levels were normal. Compared to the controls, hospital stay (t = 2.86, P < 0.05), duration of the need for oxygen supplement (t = 2.53, P < 0.05) and ventilation time were shorter (t = 2.41, P < 0.05), whereas mortality (chi(2) = 0.21, P > 0.05) and incidence of IVH (chi(2) = 0.00, P > 0.05) were not significantly different between the groups.

CONCLUSIONSiNO could effectively improve the oxygenation and shorten the ventilation time and hospital stay without augmentation of risk of IVH and pneumothorax in these neonatal patients.