Abstract 82

Background. Severe meconium aspiration syndrome (MAS) usually requires aggressive treatment and is frequently complicated by fatal pulmonary artery hypertension. We tested the hypothesis that the postnatal adaptation of the pulmonary and ductal hemodynamics is disturbed also in the milder forms of MAS.

Subjects. 17 infants with moderate MAS and 16 healthy control infants were studied.

Measurements. The presence and direction of ductus arteriosus shunting, peak ductal aortopulmonary pressure gradient (APPG), and left pulmonary artery flow velocity integral (LPA FVI), as well as left ventricular output (LVO) were estimated with Doppler ultrasound at 2, 12, 24, 48 and 72 hours of age.

Results. The rate of ductal closure was similar in the two groups, but still infants with MAS had more frequently (p=0.03) bidirectional ductal shunting at 12 hours of life. Similarly, during the first 12 hours APPG in infants with MAS was significantly lower (p<0.001) and increased more slowly (p=0.04). LPA FVI values were lower (p=0.003) in infants with MAS than controls during the first three days of life. No differences in LVO or mean arterial pressure were found between the study groups.

Conclusions. Infants with MAS, also with milder forms of the disease, have a delayed postnatal adaptation of the pulmonary circulation. Thus, all infants with MAS need careful cardiovascular monitoring during postnatal transition.