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We examined the effects of maternal magnesium sulphate (MgSO4) and ritodrine treatments on the autonomic cardiovascular control in preterm neonates with respiratory distress syndrome during the first 2 days of life. Serial measurements of heart rate (HR), blood pressure (BP) and respirogram were performed during the first 2 days of life in 28 preterm infants below 33 weeks of gestation with antenatal exposure to MgSO4 (n = 13) or ritodrine (n = 15), and in 12 nonexposed preterm controls. Spectral analysis was used for the quantification of HR and BP variability. Although antenatal MgSO4 exposure had no effect on HR or the systolic, diastolic or mean BP, it was associated with significant decreased beat-to-beat changes in BP. In contrast, ritodrine exposure had no consistent effects on the autonomic cardiovascular control during the first 2 days of life. Our data suggest that maternal MgSO4 treatment decreases the neonatal high frequency changes in BP. This early vascular stabilizing effect of antenatal MgSO4 exposure may contribute to a lowered risk of cerebral vascular catastrophes, in the vulnerable areas of the brain, among the preterm infants with respiratory distress syndrome.

Objective: To determine the course of systolic pulmonary artery pressure (PAP) in association with ductal shunting and cardiac output (CO) in preterm neonates., Design: During the acute phase of respiratory distress syndrome (RDS) with and without surfactant treatment, serial Doppler ultrasound examinations were performed at the ages of 2, 12, 24, 48, and 72 hours in 51 neonates with RDS and 21 healthy, preterm controls. Twenty-eight of the distressed neonates received two or four doses of synthetic exogenous surfactant at intervals of 12 hours. Measurements of hemodynamic variables in these neonates were performed before and after 8 hours following surfactant treatments. PAP was estimated by the Doppler method from the maximal tricuspid regurgitant flow velocity. Doppler ultrasound was also used to determine simultaneously CO, and the direction and magnitude of the ductal shunting., Results: The PAP was initially at the same level, but remained significantly higher in distressed than in healthy, preterm control neonates between the ages of 12 to 48 hours. The systolic systemic arterial blood pressures did not differ between the distressed and control neonates, but increased gradually during the study period. Consequently, the ratio of systolic pulmonary and systemic pressure was also higher in neonates with RDS than in controls during the first day of life. Bidirectional ductal shunting disappeared in all neonates studied after 2 days of life. Significant left-to-right shunting through the ductus arteriosus persisted more frequently in distressed neonates, especially those with surfactant treatment, than in control neonates during the study period, and more often caused the need for medical or surgical closure. Doppler-derived CO remained stable throughout the study in the distressed neonates, being significantly higher in surfactant-treated neonates than nontreated distressed neonates or healthy controls at 72 hours of life., Conclusions: The data of the present study confirms that the postnatal decrease in PAP is delayed in acute RDS. Further, significant patent ductus arteriosus shunting persists longer in RDS and may contribute to elevated CO during the resolution of the disease.

Severe prematurity is a prime factor causing perinatal mortality or morbidity. In Finland 1% of babies are born before 32 completed weeks of pregnancy and 0.9% are delivered with a birth weight of 1500 g or less. Since transport of a baby in utero is preferable to transporting a neonate, approximately 85% of infants below 1000 g and 90% of infants between 1000 to 1499 g are delivered in departments with facilities for neonatal intensive care. The rate of caesarean delivery is approximately 50% in pregnancies between 26 and 28 weeks, while the overall caesarean section rate is 15%. Deaths of low birth weight babies account for 66% of the total perinatal mortality and those of very low birth weight babies 46%. Intrauterine deaths constitute two thirds and neonatal deaths one third of perinatal mortality among very low birth weight babies. In Turku, neonatal survival rate for infants of 500 to 749 g was 61.5% and for infants of 750 to 999 g, 77.3%. In Turku respiratory distress syndrome is one of main complications of prematurity that has led to death in 11.2% of infants in recent years. Of the survivors, 85% have been healthy at the age of two years. The incidence of the bronchopulmonary dysplasia among very low birth weight infants has been 19.7%. In recent years, the incidence of severe brain haemorrhage has been 32% among infants with a birth weight below 1000 g.