Effects of antenatal magnesium sulfate therapy on cerebral and systemic hemodynamics in preterm newborns.

OBJECTIVES: To investigate whether antenatal magnesium sulfate (MgSO(4)) exposure has an influence on cerebral blood flow and systemic hemodynamics in preterm infants during the first few days of life.
DESIGN: Prospective case-control study.
SETTING: University affiliated referral hospital. POPULATION: A total of 48 women who delivered preterm (30-34 weeks) and their offspring.
METHODS: Mothers and newborns were divided into two groups based on maternal exposure to MgSO(4) (n = 28) or not (n = 20). Cerebral blood flow velocity measurements were obtained from the neonatal anterior cerebral artery and right and left middle cerebral arteries. MAIN OUTCOME MEASURES: Neonatal Doppler examinations of the brain circulation, heart rate, systemic blood pressure and echocardiographic assessment of ductus arteriosus shunting during the first week of life.
RESULTS: Maternal MgSO(4) had a significant lowering effect on neonatal cerebral blood flow. Peak systolic velocity was significantly lower in anterior cerebral artery and right and left middle cerebral arteries (p = 0.031, 0.027 and 0.039, respectively), as was end-diastolic velocity (p = 0.035, 0.012 and 0.025, respectively) and mean velocity (p = 0.036, 0.024 and 0.003, respectively). The resistance index and relative vascular resistance in the three cerebral arteries showed no significant difference between the two studied groups.
CONCLUSION: Antenatal MgSO(4) exposure before preterm birth has potent systemic vascular effects in the preterm offspring, which is reflected in decreased neonatal cerebral perfusion during the critical first few days of life. This is associated with an increased incidence of patent ductus arteriosus, which may require operative intervention.